Integrating artificial intelligence and natural language processing for computer-assisted reporting and report understanding in nuclear cardiology.

Garcia EV
Natural language processing (NLP) offers many opportunities in Nuclear Cardiology. These opportunities include applications in converting nuclear cardiology imaging reports to digital searchable information that may be used as Big Data for machine learning and registries. Another major NLP application is, with the support of AI, in automatically translating MPI image features directly into nuclear cardiology reports. This review describes the symbiotic relationship between AI and NLP in that NLP is being used to facilitate AI applications and, AI techniques are being used to facilitate NLP. This article reviews the fundamentals of NLP and describes various conventional and AI techniques that have been applied in imaging. Key nuclear cardiology applications are reviewed such as conversion of MPI free-text reports to digital documents as well as direct conversion of MPI images into structured medical reports.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 20 Jun 2022; epub ahead of print

Performance of visual, manual, and automatic coronary calcium scoring of cardiac N-ammonia PET/low dose CT.

Dobrolinska MM, Lazarenko SV, van der Zant FM, Does L, ... Slart RHJA, Knol RJJ
Background
Coronary artery calcium is a well-known predictor of major adverse cardiac events and is usually scored manually from dedicated, ECG-triggered calcium scoring CT (CSCT) scans. In clinical practice, a myocardial perfusion PET scan is accompanied by a non-ECG triggered low dose CT (LDCT) scan. In this study, we investigated the accuracy of patients\' cardiovascular risk categorisation based on manual, visual, and automatic AI calcium scoring using the LDCT scan.
Methods
We retrospectively enrolled 213 patients. Each patient received a ¹³N-ammonia PET scan, an LDCT scan, and a CSCT scan as the gold standard. All LDCT and CSCT scans were scored manually, visually, and automatically. For the manual scoring, we used vendor recommended software (Syngo.via, Siemens). For visual scoring a 6-points risk scale was used (0; 1-10; 11-100; 101-400; 401-100; > 1 000 Agatston score). The automatic scoring was performed with deep learning software (Syngo.via, Siemens). All manual and automatic Agatston scores were converted to the 6-point risk scale. Manual CSCT scoring was used as a reference.
Results
The agreement of manual and automatic LDCT scoring with the reference was low [weighted kappa 0.59 (95% CI 0.53-0.65); 0.50 (95% CI 0.44-0.56), respectively], but the agreement of visual LDCT scoring was strong [0.82 (95% CI 0.77-0.86)].
Conclusions
Compared with the gold standard manual CSCT scoring, visual LDCT scoring outperformed manual LDCT and automatic LDCT scoring.

© 2022. The Author(s).

J Nucl Cardiol: 16 Jun 2022; epub ahead of print

The prognostic and diagnostic implications of surveillance serial myocardial perfusion imaging in asymptomatic renal transplant candidates.

Tottleben J, Howland J, Rofael M, Co MLF, Torres A, Doukky R
Background
The utility of serial SPECT myocardial perfusion imaging (MPI) for CAD surveillance in asymptomatic ESRD patients awaiting kidney transplantation (KT) is uncertain.
Methods and results
We retrospectively investigated 700 asymptomatic KT candidates with ≥ 2 pre-transplant SPECT-MPIs (mean interval, 20 ± 13 months). Worsening MPI was defined as total perfusion deficit increase (ΔTPD) > 5%. High clinical risk was defined as ≥ 3 AHA/ACC KT risk factors. The primary outcome was major adverse cardiac events (MACE) of cardiac death or myocardial infarction. The initial MPI was normal in 462 (66%) subjects. On repeat MPI, ΔTPD > 5% was observed in 82 (12%) subjects, and the incidence increased with increasing time gap between MPIs (P = .006). During a mean follow-up of 16 ± 8 months, there were 119 (17%) MACEs. In the entire cohort, ΔTPD > 5% was not significantly associated with MACE (HR = 1.38; P = .210). ΔTPD > 5% was associated with increased MACE rate among patients with normal initial MPI (HR = 2.30; P = .005), but not among those with abnormal initial MPI (P = .260). There was a significant interaction between ΔTPD > 5% and initial MPI normalcy status in predicting MACE (interaction P = .018), such that the predictive value of ΔTPD is dependent on the initial MPI normalcy. Among subjects with normal initial MPI, ΔTPD > 5% was significantly associated with MACE only if the sum of KT risk factors was ≥ 3 (HR = 2.26; P = .016). Among 123 patients who underwent coronary angiography, ΔTPD > 5% was associated with a higher prevalence of obstructive CAD when the initial MPI was normal and the sum of KT risk factors was ≥ 3.
Conclusion
Among patients with ESRD waitlisted for KT, new/worsening MPI abnormalities are expected. On serial surveillance, ΔTPD > 5% is associated with MACE and obstructive CAD among those with a normal initial MPI and ≥ 3 AHA/ACC KT risk factors.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 15 Jun 2022; epub ahead of print

Automated nonlinear registration of coronary PET to CT angiography using pseudo-CT generated from PET with generative adversarial networks.

Singh A, Kwiecinski J, Cadet S, Killekar A, ... Dey D, Slomka PJ
Background
Coronary ¹⁸F-sodium-fluoride (¹⁸F-NaF) positron emission tomography (PET) showed promise in imaging coronary artery disease activity. Currently image processing remains subjective due to the need for manual registration of PET and computed tomography (CT) angiography data. We aimed to develop a novel fully automated method to register coronary ¹⁸F-NaF PET to CT angiography using pseudo-CT generated by generative adversarial networks (GAN).
Methods
A total of 169 patients, 139 in the training and 30 in the testing sets were considered for generation of pseudo-CT from non-attenuation corrected (NAC) PET using GAN. Non-rigid registration was used to register pseudo-CT to CT angiography and the resulting transformation was used to align PET with CT angiography. We compared translations, maximal standard uptake value (SUV_max) and target to background ratio (TBR_max) at the location of plaques, obtained after observer and automated alignment.
Results
Automatic end-to-end registration was performed for 30 patients with 88 coronary vessels and took 27.5 seconds per patient. Difference in displacement motion vectors between GAN-based and observer-based registration in the x-, y-, and z-directions was 0.8 ± 3.0, 0.7 ± 3.0, and 1.7 ± 3.9 mm, respectively. TBR_max had a coefficient of repeatability (CR) of 0.31, mean bias of 0.03 and narrow limits of agreement (LOA) (95% LOA: - 0.29 to 0.33). SUV_max had CR of 0.26, mean bias of 0 and narrow LOA (95% LOA: - 0.26 to 0.26).
Conclusion
Pseudo-CT generated by GAN are perfectly registered to PET can be used to facilitate quick and fully automated registration of PET and CT angiography.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 14 Jun 2022; epub ahead of print

Deep-learning-based methods of attenuation correction for SPECT and PET.

Chen X, Liu C
Attenuation correction (AC) is essential for quantitative analysis and clinical diagnosis of single-photon emission computed tomography (SPECT) and positron emission tomography (PET). In clinical practice, computed tomography (CT) is utilized to generate attenuation maps (μ-maps) for AC of hybrid SPECT/CT and PET/CT scanners. However, CT-based AC methods frequently produce artifacts due to CT artifacts and misregistration of SPECT-CT and PET-CT scans. Segmentation-based AC methods using magnetic resonance imaging (MRI) for PET/MRI scanners are inaccurate and complicated since MRI does not contain direct information of photon attenuation. Computational AC methods for SPECT and PET estimate attenuation coefficients directly from raw emission data, but suffer from low accuracy, cross-talk artifacts, high computational complexity, and high noise level. The recently evolving deep-learning-based methods have shown promising results in AC of SPECT and PET, which can be generally divided into two categories: indirect and direct strategies. Indirect AC strategies apply neural networks to transform emission, transmission, or MR images into synthetic μ-maps or CT images which are then incorporated into AC reconstruction. Direct AC strategies skip the intermediate steps of generating μ-maps or CT images and predict AC SPECT or PET images from non-attenuation-correction (NAC) SPECT or PET images directly. These deep-learning-based AC methods show comparable and even superior performance to non-deep-learning methods. In this article, we first discussed the principles and limitations of non-deep-learning AC methods, and then reviewed the status and prospects of deep-learning-based methods for AC of SPECT and PET.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 09 Jun 2022; epub ahead of print

Texture analysis of SPECT myocardial perfusion provides prognostic value for dilated cardiomyopathy.

Wang C, Ma Y, Liu Y, Li L, ... Li D, Zhou W
Background
Texture analysis (TA) has demonstrated clinical values in extracting information, quantifying inhomogeneity, evaluating treatment outcomes, and predicting long-term prognosis for cardiac diseases. The aim of this study was to explore whether TA of SPECT myocardial perfusion could contribute to improving the prognosis of dilated cardiomyopathy (DCM) patients.
Methods
Eighty-eight patients were recruited in our study between 2009 and 2020 who were diagnosed with DCM and underwent single-photon emission tomography myocardial perfusion imaging (SPECT MPI). Forty TA features were obtained from quantitative analysis of SPECT imaging in subjects with myocardial perfusion at rest. All patients were divided into two groups: the all-cause death group and the survival group. The prognostic value of texture parameters was assessed by Cox regression and Kaplan-Meier analysis.
Results
Twenty-five all-cause deaths (28.4%) were observed during the follow-up (39.2±28.7 months). Compared with the survival group, NT-proBNP and total perfusion deficit (TPD) were higher and left ventricular ejection fraction (LVEF) was lower in the all-cause death group. In addition, 26 out of 40 texture parameters were significantly different between the two groups. Univariate Cox regression analysis revealed that NT-proBNP, LVEF, and 25 texture parameters were significantly associated with all-cause death. The multivariate Cox regression analysis showed that low gray-level emphasis (LGLE) (P = 0.010, HR = 4.698, 95% CI 1.457-15.145) and long-run low gray-level emphasis (LRLGE) (P =0.002, HR = 6.085, 95% CI 1.906-19.422) were independent predictors of the survival outcome. When added to clinical parameters, LVEF, TPD, and TA parameters, including LGLE and LRLGE, were incrementally associated with all-cause death (global chi-square statistic of 26.246 vs. 33.521; P = 0.028, global chi-square statistic of 26.246 vs. 34.711; P = 0.004).
Conclusion
TA based on gated SPECT MPI could discover independent prognostic predictors of all-cause death in medically treated patients with DCM. Moreover, TA parameters, including LGLE and LRLGE, independent of the total perfusion deficit of the cardiac myocardium, appeared to provide incremental prognostic value for DCM patients.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 08 Jun 2022; epub ahead of print

Machine learning to predict abnormal myocardial perfusion from pre-test features.

Miller RJH, Hauser MT, Sharir T, Einstein AJ, ... Berman DS, Slomka PJ
Background
Accurately predicting which patients will have abnormal perfusion on MPI based on pre-test clinical information may help physicians make test selection decisions. We developed and validated a machine learning (ML) model for predicting abnormal perfusion using pre-test features.
Methods
We included consecutive patients who underwent SPECT MPI, with 20,418 patients from a multi-center (5 sites) international registry in the training population and 9019 patients (from 2 separate sites) in the external testing population. The ML (extreme gradient boosting) model utilized 30 pre-test features to predict the presence of abnormal myocardial perfusion by expert visual interpretation.
Results
In external testing, the ML model had higher prediction performance for abnormal perfusion (area under receiver-operating characteristic curve [AUC] 0.762, 95% CI 0.750-0.774) compared to the clinical CAD consortium (AUC 0.689) basic CAD consortium (AUC 0.657), and updated Diamond-Forrester models (AUC 0.658, p < 0.001 for all). Calibration (validation of the continuous risk prediction) was superior for the ML model (Brier score 0.149) compared to the other models (Brier score 0.165 to 0.198, all p < 0.001).
Conclusion
ML can predict abnormal myocardial perfusion using readily available pre-test information. This model could be used to help guide physician decisions regarding non-invasive test selection.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 07 Jun 2022; epub ahead of print

Phenotype-based management of coronary microvascular dysfunction.

Ang DTY, Berry C, Kaski JC
40-70% of patients undergoing invasive coronary angiography with signs and symptoms of ischemia are found to have no obstructive coronary artery disease (INOCA). When this heterogeneous group undergo coronary function testing, approximately two-thirds have demonstrable coronary microvascular dysfunction (CMD), which is independently associated with adverse prognosis. There are four distinct phenotypes, or subgroups, each with unique pathophysiological mechanisms and responses to therapies. The clinical phenotypes are microvascular angina, vasospastic angina, mixed (microvascular and vasospastic), and non-cardiac symptoms (reclassification as non-INOCA). The Coronary Vasomotor Disorders International Study Group (COVADIS) have proposed standardized criteria for diagnosis. There is growing awareness of these conditions among clinicians and within guidelines. Testing for CMD can be done using invasive or non-invasive modalities. The CorMicA study advocates the concept of \'functional angiography\' to guide stratified medical therapy. Therapies broadly fall into two categories: those that modulate cardiovascular risk and those to alleviate angina. Management should be tailored to the individual, with periodic reassessment for efficacy. Phenotype-based management is a worthy endeavor for both patients and clinicians, aligning with the concept of \'precision medicine\' to improve prognosis, symptom burden, and quality of life. Here, we present a contemporary approach to the phenotype-based management of patients with INOCA.

© 2022. The Author(s).

J Nucl Cardiol: 07 Jun 2022; epub ahead of print

Quantitative single photon emission computed tomography derived standardized uptake values on 99mTc-PYP scan in patients with suspected ATTR cardiac amyloidosis.

Avalon JC, Fuqua J, Deskins S, Miller T, ... Sengupta PP, Hamirani YS
Technetium-99 pyrophosphate scintigraphy (99mTc-PYP) provides qualitative and semiquantitative diagnosis of ATTR cardiac amyloidosis (ATTR-CA) using the Perugini scoring system and heart/contralateral heart ratio (H/CL) on planar imaging. Standardized uptake values (SUV) with quantitative single photon emission computed tomography (xSPECT/CT) can offer superior diagnostic accuracy and quantification through precise myocardial contouring that enhances assessment of ATTR-CA burden. We examined the correlation of xSPECT/CT SUVs with Perugini score and H/CL ratio. We also assessed SUV correlation with cardiac magnetic resonance (CMR), echocardiographic, and baseline clinical characteristics. Retrospective review of 78 patients with suspected ATTR-CA that underwent 99mTc-PYP scintigraphy with xSPECT/CT. Patients were grouped off Perugini score (Grade 0-1 and Grade 2-3), H/CL ratio (≥ 1.5 and < 1.5). Two cohorts were also created: myocardium SUV_max > 1.88 and ≤ 1.88 at 1-hour based off an AUC curve with 1.88 showing the greatest sensitivity and specificity. Cardiac SUV retention index was calculated as [SUV_max myocardium/SUV_max vertebrae] × SUV_max paraspinal muscle. Primary outcome was myocardium SUV_max at 1-hour correlation with Perugini grades, H/CL ratio, CMR, and echocardiographic data. Higher Perugini Grades corresponded with higher myocardium SUV_max values, especially when comparing Perugini Grade 3 to Grade 2 and 1 (3.03 ± 2.1 vs 0.59 ± 0.97 and 0.09 ± 0.2, P < 0.001). Additionally, patients with H/CL ≥ 1.5 had significantly higher myocardium SUV_max compared to patients with H/CL ≤ 1.5 (2.92 ± 2.18 vs 0.35 ± 0.60, P < 0.01). Myocardium SUV_max at 1-hour strongly correlated with ECV (r = 0.91, P = 0.001), pre-contrast T1 map values (r = 0.66, P = 0.037), and left ventricle mass index (r = 0.80, P = 0.002) on CMR. SUVs derived from 99mTc-PYP scintigraphy with xSPECT/CT provides a discriminatory and quantitative method to diagnose and assess ATTR-CA burden. These findings strongly correlate with CMR.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 02 Jun 2022; epub ahead of print

Cardiac amyloidosis in Latin America: Gaps and opportunities to increase awareness of the disease. Findings from the AMILO-LATAM research group.

Mut F, Carvajal I, Camilletti J, Erriest J, Alexanderson E, Grossman GB
Background
Cardiac amyloidosis (CA) is an under-diagnosed disease presenting as a restrictive cardiomyopathy with high morbidity and mortality. Wild-type transthyretin amyloid cardiomyopathy (ATTR-CM) is mostly seen in elderly patients, with increasing prevalence as life expectancy is growing. New diagnostic imaging techniques and treatments allow for a better prognosis, but lack of clinical awareness delays timely diagnosis and appropriate management. Our purpose was to investigate the knowledge of clinicians regarding ATTR-CM and to assess the availability of imaging resources in the Latin-American region.
Methods and results
Two online surveys were distributed among clinicians and nuclear medicine professionals, respectively: one asking about awareness of CA in different clinical scenarios, and the other about the availability of diagnostic resources and studies performed. 406 responses were received for the first survey and 82 for the second, representing 17 and 14 countries, respectively. A significant lack of awareness was identified among clinicians, although appropriate diagnostic resources are generally available. Survey data showed that very few patients are evaluated for ATTR-CM in most Latin-American countries.
Conclusions
The surveys demonstrated the need for educational programs and other measures to increase clinical awareness and early detection of CA, so patients receive timely treatment and management of the disease.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 31 May 2022; epub ahead of print

Invasive evaluation of coronary microvascular dysfunction.

Travieso A, Jeronimo-Baza A, Faria D, Shabbir A, Mejia-Rentería H, Escaned J
Coronary microvascular dysfunction (CMD) is a prevalent cause of ischemic heart disease and is associated with poorer quality of life and worse patient outcomes. Both functional and structural abnormalities of the microcirculation can generate ischemia in the absence of epicardial stenosis or worsen concomitant obstructive coronary artery disease (CAD). The invasive assessment of CMD allows for the evaluation of the entirety of the coronary vascular tree, from the large epicardial vessels to the microcirculation, and enables the study of vasomotor function through vasoreactivity testing. The standard evaluation of CMD includes vasomotor assessment with acetylcholine, as well as flow- and resistance-derived indices calculated with either thermodilution or Doppler guidewires. Tailored treatment based upon the information gathered from the invasive evaluation of CMD has been demonstrated to reduce the burden of angina; therefore, a thorough understanding of these procedures is warranted with the aim of improving the quality of life of the patient. This review summarizes the most widespread approaches for the invasive evaluation of CMD, with a focus on patients with ischemia and non-obstructive CAD.

© 2022. The Author(s).

J Nucl Cardiol: 26 May 2022; epub ahead of print

Deep learning prediction of quantitative coronary angiography values using myocardial perfusion images with a CZT camera.

Arvidsson I, Davidsson A, Overgaard NC, Pagonis C, ... Heyden A, Ochoa-Figueroa M
Purpose
Evaluate the prediction of quantitative coronary angiography (QCA) values from MPI, by means of deep learning.
Methods
546 patients (67% men) undergoing stress 99mTc-tetrofosmin MPI in a CZT camera in the upright and supine position were included (1092 MPIs). Patients were divided into two groups: ICA group included 271 patients who performed an ICA within 6 months of MPI and a control group with 275 patients with low pre-test probability for CAD and a normal MPI. QCA analyses were performed using radiologic software and verified by an expert reader. Left ventricular myocardium was segmented using clinical nuclear cardiology software and verified by an expert reader. A deep learning model was trained using a double cross-validation scheme such that all data could be used as test data as well.
Results
Area under the receiver-operating characteristic curve for the prediction of QCA, with > 50% narrowing of the artery, by deep learning for the external test cohort: per patient 85% [95% confidence interval (CI) 84%-87%] and per vessel; LAD 74% (CI 72%-76%), RCA 85% (CI 83%-86%), LCx 81% (CI 78%-84%), and average 80% (CI 77%-83%).
Conclusion
Deep learning can predict the presence of different QCA percentages of coronary artery stenosis from MPIs.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 24 May 2022; epub ahead of print

Statistical methods for validation of predictive models.

Diniz MA
Predictive models are widely used in clinical practice. Despite of the increasing number of published AI systems, recent systematic reviews have identified lack of statistical rigor in the development and validation of predictive models. This work reviewed the current literature for predictive performance measures and resampling methods. Furthermore, common pitfalls were discussed.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 24 May 2022; epub ahead of print

Amyloid myopathy: expanding the clinical spectrum of transthyretin amyloidosis-case report and literature review.

Ungericht M, Wanschitz J, Kroiss AS, Röcken C, ... Loescher WN, Poelzl G
We identified two patients with transthyretin (ATTR) amyloid myopathy (one ATTR variant amyloidosis, ATTRv; one wild-type ATTR amyloidosis, ATTRwt). Myopathy was the initial manifestation in ATTRwt, whereas it followed neuropathy and cardiomyopathy in ATTRv. The ATTRwt patient showed muscular tracer uptake on ^99mTc-DPD planar scintigraphy at the time of initial diagnosis, consistent with ATTR amyloid myopathy. The ATTRv patient underwent heart transplantation because of progressive heart failure. Within the next two years, progressive myopathic symptoms and extracardiac tracer uptake on ^99mTc-DPD planar scintigraphy were documented, attributable to ATTR amyloid myopathy. Interstitial amyloid deposits were confirmed by muscle biopsy in both patients, with a particularly high amyloid burden in the adipose tissue. This case report highlights the frequent concomitant presence of cardiac ATTR amyloidosis and ATTR amyloid myopathy. ATTR amyloid myopathy may precede cardiac manifestation in ATTRwt or occur after heart transplantation in ATTRv. Due to the high diagnostic accuracy of ^99mTc-DPD scintigraphy for detecting ATTR amyloid myopathy and the emergence of novel therapeutics, it is important to increase the awareness of its presence.

© 2022. The Author(s).

J Nucl Cardiol: 17 May 2022; epub ahead of print

Echocardiographic indices of left ventricular function and filling pressure are not related to blood pool activity on pyrophosphate scintigraphy.

Asif T, Gupta A, Murthi M, Soman P, Singh V, Malhotra S
Background
Pyrophosphate (PYP) imaging has a high diagnostic accuracy for transthyretin cardiac amyloidosis (ATTR-CA). Indeterminate findings are often reported due to persistent blood pool activity, presumed to be from low cardiac output. We evaluated the relationship between blood pool activity on PYP imaging and echocardiographic indices of cardiac function.
Methods
Clinical and imaging data of 189 patients referred for PYP scintigraphy were evaluated. All patients underwent planar imaging and SPECT (diagnostic standard). Among those with a negative PYP SPECT, persistent left ventricular blood pool activity on planar images was inferred by a visual score ≥2 or a heart-to-contralateral (HCL) ratio ≥ 1.5. Absence of blood pool activity was inferred when both visual score was < 2 and HCL was < 1.5. Left ventricular ejection fraction (LVEF), global longitudinal strain (GLS), stroke volume index (SVi), and left atrial pressure (LAP) were calculated from standard transthoracic echocardiograms.
Results
ATTR-CA was present in 43 (23%) patients. Among those with a negative PYP SPECT, 11 patients had significant blood pool activity. Patients with ATTR-CA had a lower LVEF, SVi, and GLS, with a higher LAP, compared to those without ATTR-CA. Among those without ATTR-CA, there were no significant differences in these parameters.
Conclusion
Approximately 8% of patients with a negative PYP SPECT have significant blood pool activity. Measures of cardiac function are not different among those with and without blood pool activity. PYP SPECT should be routinely performed in all patients to avoid false image interpretation.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 16 May 2022; epub ahead of print

Quantitative Tc-DPD-SPECT/CT assessment of cardiac amyloidosis.

Kessler L, Fragoso Costa P, Kersting D, Jentzen W, ... Papathanasiou M, Rischpler C
Introduction
Transthyretin (ATTR) amyloidosis is responsible for the majority of cardiac amyloidosis (CA) cases and can be reliably diagnosed with bone scintigraphy and the visual Perugini score. We aimed to implement a quantification method of cardiac amyloid deposits in patients with suspected cardiac amyloidosis and to compare performance to visual scoring.
Methods and materials
136 patients received ^99mTc-DPD-bone scintigraphy including SPECT/CT of the thorax in case of suspicion of cardiac amyloidosis. Imaging phantom studies were performed to determine the scaling factor for standardized uptake value (SUV) quantification from SPECT/CT. Myocardial tracer uptake was quantified in a whole heart volume of interest.
Results
Forty-five patients were diagnosed with CA. A strong relationship between cardiac SUVmax and Perugini score was found (Spearman r 0.75, p < 0.0001). Additionally, tracer uptake in bone decreased with increasing cardiac SUVmax and Perugini score (p < 0.0001). ROC analysis revealed good performance of the SUVmax for the detection of ATTR-CA with AUC of 0.96 ± 0.02 (p < 0.0001) with sensitivity 98.7% and specificity 87.2%.
Conclusion
We demonstrate an accessible and accurate quantitative SPECT approach in CA. Quantitative assessment of the cardiac tracer uptake may improve diagnostic accuracy and risk classification. This method may enable monitoring and assessment of therapy response in patients with ATTR amyloidosis.

© 2022. The Author(s).

J Nucl Cardiol: 13 May 2022; epub ahead of print

Definition and epidemiology of coronary microvascular disease.

Bradley C, Berry C
Ischemic heart disease remains one of the leading causes of death and disability worldwide. However, most patients referred for a noninvasive computed tomography coronary angiogram (CTA) or invasive coronary angiogram for the investigation of angina do not have obstructive coronary artery disease (CAD). Approximately two in five referred patients have coronary microvascular disease (CMD) as a primary diagnosis and, in addition, CMD also associates with CAD and myocardial disease (dual pathology). CMD underpins excess morbidity, impaired quality of life, significant health resource utilization, and adverse cardiovascular events. However, CMD often passes undiagnosed and the onward management of these patients is uncertain and heterogeneous. International standardized diagnostic criteria allow for the accurate diagnosis of CMD, ensuring an often overlooked patient population can be diagnosed and stratified for targeted medical therapy. Key to this is assessing coronary microvascular function-including coronary flow reserve, coronary microvascular resistance, and coronary microvascular spasm. This can be done by invasive methods (intracoronary temperature-pressure wire, intracoronary Doppler flow-pressure wire, intracoronary provocation testing) and non-invasive methods [positron emission tomography (PET), cardiac magnetic resonance imaging (CMR), transthoracic Doppler echocardiography (TTDE), cardiac computed tomography (CT)]. Coronary CTA is insensitive for CMD. Functional coronary angiography represents the combination of CAD imaging and invasive diagnostic procedures.

© 2022. The Author(s).

J Nucl Cardiol: 09 May 2022; epub ahead of print

Artificial intelligence for disease diagnosis and risk prediction in nuclear cardiology.

Miller RJH, Huang C, Liang JX, Slomka PJ
Artificial intelligence (AI) techniques have emerged as a highly efficient approach to accurately and rapidly interpret diagnostic imaging and may play a vital role in nuclear cardiology. In nuclear cardiology, there are many clinical, stress, and imaging variables potentially available, which need to be optimally integrated to predict the presence of obstructive coronary artery disease (CAD) or predict the risk of cardiovascular events. In spite of clinical awareness of a large number of potential variables, it is difficult for physicians to integrate multiple features consistently and objectively. Machine learning (ML) is particularly well suited to integrating this vast array of information to provide patient-specific predictions. Deep learning (DL), a branch of ML characterized by a multi-layered convolutional model architecture, can extract information directly from images and identify latent image features associated with a specific prediction. This review will discuss the latest AI applications to disease diagnosis and risk prediction in nuclear cardiology with a focus on potential clinical applications.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 04 May 2022; epub ahead of print

Increasing angular sampling through deep learning for stationary cardiac SPECT image reconstruction.

Xie H, Thorn S, Chen X, Zhou B, ... Sinusas AJ, Liu C
Background
The GE Discovery NM (DNM) 530c/570c are dedicated cardiac SPECT scanners with 19 detector modules designed for stationary imaging. This study aims to incorporate additional projection angular sampling to improve reconstruction quality. A deep learning method is also proposed to generate synthetic dense-view image volumes from few-view counterparts.
Methods
By moving the detector array, a total of four projection angle sets were acquired and combined for image reconstructions. A deep neural network is proposed to generate synthetic four-angle images with 76 ([Formula: see text]) projections from corresponding one-angle images with 19 projections. Simulated data, pig, physical phantom, and human studies were used for network training and evaluation. Reconstruction results were quantitatively evaluated using representative image metrics. The myocardial perfusion defect size of different subjects was quantified using an FDA-cleared clinical software.
Results
Multi-angle reconstructions and network results have higher image resolution, improved uniformity on normal myocardium, more accurate defect quantification, and superior quantitative values on all the testing data. As validated against cardiac catheterization and diagnostic results, deep learning results showed improved image quality with better defect contrast on human studies.
Conclusion
Increasing angular sampling can substantially improve image quality on DNM, and deep learning can be implemented to improve reconstruction quality in case of stationary imaging.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 04 May 2022; epub ahead of print

Time-related aortic inflammatory response, as assessed with F-FDG PET/CT, in patients hospitalized with severely or critical COVID-19: the COVAIR study.

Vlachopoulos C, Terentes-Printzios D, Katsaounou P, Solomou E, ... Tsioufis K, Anagnostopoulos C
Aim
Arterial involvement has been implicated in the coronavirus disease of 2019 (COVID-19). Fluorine 18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging is a valuable tool for the assessment of aortic inflammation and is a predictor of outcome. We sought to prospectively assess the presence of aortic inflammation and its time-dependent trend in patients with COVID-19.
Methods
Between November 2020 and May 2021, in this pilot, case-control study, we recruited 20 patients with severe or critical COVID-19 (mean age of 59 ± 12 years), while 10 age and sex-matched individuals served as the control group. Aortic inflammation was assessed by measuring ¹⁸F-FDG uptake in PET/CT performed 20-120 days post-admission. Global aortic target to background ratio (GLA-TBR) was calculated as the sum of TBRs of ascending and descending aorta, aortic arch, and abdominal aorta divided by 4. Index aortic segment TBR (IAS-TBR) was designated as the aortic segment with the highest TBR.
Results
There was no significant difference in aortic ¹⁸F-FDG PET/CT uptake between patients and controls (GLA-TBR: 1.46 [1.40-1.57] vs. 1.43 [1.32-1.70], respectively, P = 0.422 and IAS-TBR: 1.60 [1.50-1.67] vs. 1.50 [1.42-1.61], respectively, P = 0.155). There was a moderate correlation between aortic TBR values (both GLA and IAS) and time distance from admission to ¹⁸F-FDG PET-CT scan (Spearman\'s rho = - 0.528, P = 0.017 and Spearman\'s rho = - 0.480, p = 0.032, respectively). Patients who were scanned less than or equal to 60 days from admission (n = 11) had significantly higher GLA-TBR values compared to patients that were examined more than 60 days post-admission (GLA-TBR: 1.53 [1.42-1.60] vs. 1.40 [1.33-1.45], respectively, P = 0.016 and IAS-TBR: 1.64 [1.51-1.74] vs. 1.52 [1.46-1.60], respectively, P = 0.038). There was a significant difference in IAS- TBR between patients scanned ≤ 60 days and controls (1.64 [1.51-1.74] vs. 1.50 [1.41-1.61], P = 0.036).
Conclusion
This is the first study suggesting that aortic inflammation, as assessed by ¹⁸F-FDG PET/CT imaging, is increased in the early post COVID phase in patients with severe or critical COVID-19 and largely resolves over time. Our findings may have important implications for the understanding of the course of the disease and for improving our preventive and therapeutic strategies.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 02 May 2022; epub ahead of print

A longitudinal pilot study to assess temporal changes in coronary arterial F-sodium fluoride uptake.

Kitagawa T, Sasaki K, Fujii Y, Tatsugami F, ... Hirokawa Y, Nakano Y
Purpose
How coronary arterial ¹⁸F-sodium fluoride (¹⁸F-NaF) uptake on positron emission tomography changes over the long term and what clinical factors impact the changes remain unclear. We sought to investigate the topics in this study.
Methods
We retrospectively studied 15 patients with ≥1 coronary atherosclerotic lesion/s detected on cardiac computed tomography who underwent baseline and follow-up (interval of >3 years) ¹⁸F-NaF positron emission tomography/computed tomography scans. Focal ¹⁸F-NaF uptake in each lesion was quantified using maximum tissue-to-background ratio (TBR_max). The temporal change in TBR_max was assessed using a ratio of follow-up to baseline TBR_max (R-TBR_max).
Results
A total of 51 lesions were analyzed. Mean R-TBR_max was 0.96 ± 0.21. CT-based lesion features (location, obstructive stenosis, plaque types, features of high-risk plaque) did not correlate with an increase in R-TBR_max. In multivariate analysis, baseline TBR_max significantly correlated with higher follow-up TBR_max (β = 0.57, P < 0.0001), and the presence of diabetes mellitus significantly correlated with both higher follow-up TBR_max (β = 0.34, P = 0.001) and elevated R-TBR_max (β = 0.40, P = 0.003).
Conclusion
Higher coronary arterial ¹⁸F-NaF uptake is likely to remain continuously high. Diabetes mellitus affects the long-term increase in coronary arterial ¹⁸F-NaF uptake.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 29 Apr 2022; epub ahead of print

Rest/stress myocardial perfusion imaging by positron emission tomography with F-Flurpiridaz: A feasibility study in mice.

Bengs S, Warnock GI, Portmann A, Mikail N, ... Gebhard C, Haider A
Background
Myocardial perfusion imaging by positron emission tomography (PET-MPI) is the current gold standard for quantification of myocardial blood flow. ¹⁸F-flurpiridaz was recently introduced as a valid alternative to currently used PET-MPI probes. Nonetheless, optimum scan duration and time interval for image analysis are currently unknown. Further, it is unclear whether rest/stress PET-MPI with ¹⁸F-flurpiridaz is feasible in mice.
Methods
Rest/stress PET-MPI was performed with ¹⁸F-flurpiridaz (0.6-3.0 MBq) in 27 mice aged 7-8 months. Regadenoson (0.1 µg/g) was used for induction of vasodilator stress. Kinetic modeling was performed using a metabolite-corrected arterial input function. Image-derived myocardial ¹⁸F-flurpiridaz uptake was assessed for different time intervals by placing a volume of interest in the left ventricular myocardium.
Results
Tracer kinetics were best described by a two-tissue compartment model. K₁ ranged from 6.7 to 20.0 mL·cm^-3·min^-1, while myocardial volumes of distribution (V_T) were between 34.6 and 83.6 mL·cm^-3. Of note, myocardial ¹⁸F-flurpiridaz uptake (%ID/g) was significantly correlated with K₁ at rest and following pharmacological vasodilation for all time intervals assessed. However, while Spearman\'s coefficients (r_s) ranged between 0.478 and 0.681, R² values were generally low. In contrast, an excellent correlation of myocardial ¹⁸F-flurpiridaz uptake with V_T was obtained, particularly when employing the averaged myocardial uptake from 20 to 40 min post tracer injection (R² ≥ 0.98). Notably, K₁ and V_T were similarly sensitive to pharmacological vasodilation induction. Further, mean stress-to-rest ratios of K₁, V_T, and %ID/g ¹⁸F-flurpiridaz were virtually identical, suggesting that %ID/g ¹⁸F-flurpiridaz can be used to estimate coronary flow reserve (CFR) in mice.
Conclusion
Our findings suggest that a simplified assessment of relative myocardial perfusion and CFR, based on image-derived tracer uptake, is feasible with ¹⁸F-flurpiridaz in mice, enabling high-throughput mechanistic CFR studies in rodents.

© 2022. The Author(s).

J Nucl Cardiol: 28 Apr 2022; epub ahead of print

Development and validation of ischemia risk scores.

Miller RJH, Rozanski A, Slomka PJ, Han D, ... Thomson LEJ, Berman DS
Background
The likelihood of ischemia on myocardial perfusion imaging is central to physician decisions regarding test selection, but dedicated risk scores are lacking. We derived and validated two novel ischemia risk scores to support physician decision making.
Methods
Risk scores were derived using 15,186 patients and validated with 2,995 patients from a different center. Logistic regression was used to assess associations with ischemia to derive point-based and calculated ischemia scores. Predictive performance for ischemia was assessed using area under the receiver operating characteristic curve (AUC) and compared with the CAD consortium basic and clinical models.
Results
During derivation, the calculated ischemia risk score (0.801) had higher AUC compared to the point-based score (0.786, p < 0.001). During validation, the calculated ischemia score (0.716, 95% CI 0.684- 0.748) had higher AUC compared to the point-based ischemia score (0.699, 95% CI 0.666- 0.732, p = 0.016) and the clinical CAD model (AUC 0.667, 95% CI 0.633- 0.701, p = 0.002). Calibration for both ischemia scores was good in both populations (Brier score  < 0.100).
Conclusions
We developed two novel risk scores for predicting probability of ischemia on MPI which demonstrated high accuracy during model derivation and in external testing. These scores could support physician decisions regarding diagnostic testing strategies.

© 2022. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.

J Nucl Cardiol: 28 Apr 2022; epub ahead of print

Evaluation of balloon pulmonary angioplasty using lung perfusion SPECT in patients with chronic thromboembolic pulmonary hypertension.

Hashimoto H, Oka T, Nakanishi R, Mizumura S, ... Ota K, Ikeda T
Background
The aim of this study was to evaluate the effect of balloon pulmonary angioplasty (BPA) using lung perfusion single-photon emission computed tomography (SPECT) in patients with chronic thromboembolic pulmonary hypertension (CTEPH).
Methods and results
20 consecutive patients (64 ± 15 years) who were diagnosed with CTEPH and underwent BPA were included in this study. All patients underwent lung perfusion SPECT before and after BPA. The relationship between functional %volume of the lung calculated from the lung perfusion SPECT (FVL-LPSPECT), and other clinical parameters before and after BPA was assessed using the Wilcoxon signed-rank test. The correlation between each parameter and mean pulmonary artery pressure (mPAP) using the Spearman\'s correlation was performed. To determine predictors of mPAP for evaluating treatment effectiveness, significant parameters were included in multiple regression analysis. After BPA, world health organization functional classification, six-minute walk distance (6MWD), mPAP, and FVL-LPSPECT significantly improved. FVL-LPSPECT (r = - 0.728, P < 0.001) and 6MWD (r = - 0.571, P = 0.009) were significant correlation of mPAP. In the multiple regression analysis, FVL-LPSPECT was the most significant predictor of improvement in mPAP after BPA (P < 0.001).
Conclusions
This study demonstrated that the lung perfusion SPECT could be a potential measurement of the effectiveness of BPA in patients with CTEPH.

© 2022. The Author(s).

J Nucl Cardiol: 26 Apr 2022; epub ahead of print

Cross-vender, cross-tracer, and cross-protocol deep transfer learning for attenuation map generation of cardiac SPECT.

Chen X, Hendrik Pretorius P, Zhou B, Liu H, ... King MA, Liu C
It has been proved feasible to generate attenuation maps (μ-maps) from cardiac SPECT using deep learning. However, this assumed that the training and testing datasets were acquired using the same scanner, tracer, and protocol. We investigated a robust generation of CT-derived μ-maps from cardiac SPECT acquired by different scanners, tracers, and protocols from the training data. We first pre-trained a network using 120 studies injected with ^99mTc-tetrofosmin acquired from a GE 850 SPECT/CT with 360-degree gantry rotation, which was then fine-tuned and tested using 80 studies injected with ^99mTc-sestamibi acquired from a Philips BrightView SPECT/CT with 180-degree gantry rotation. The error between ground-truth and predicted μ-maps by transfer learning was 5.13 ± 7.02%, as compared to 8.24 ± 5.01% by direct transition without fine-tuning and 6.45 ± 5.75% by limited-sample training. The error between ground-truth and reconstructed images with predicted μ-maps by transfer learning was 1.11 ± 1.57%, as compared to 1.72 ± 1.63% by direct transition and 1.68 ± 1.21% by limited-sample training. It is feasible to apply a network pre-trained by a large amount of data from one scanner to data acquired by another scanner using different tracers and protocols, with proper transfer learning.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 26 Apr 2022; epub ahead of print

Incidental cardiac uptake of Tc-diphosphonates is predictive of poor outcome: data from 9616 bone scintigraphies.

Salvalaggio A, Cipriani A, Righetto S, Artioli P, ... Cecchin D, Briani C
Background
Bone scintigraphy (BS) is highly diagnostic for amyloid transthyretin (ATTR) cardiomyopathy. Prevalence and prognostic value of BS cardiac uptake is not well established. Our aim was to assess the prevalence of subclinical cardiac ATTR amyloidosis in patients undergoing [^99mTc]MDP/DPD scintigraphy and to define their phenotype and prognosis.
Methods and results
BS scans performed for any clinical indications from 2009 to 2020 were reviewed. Patients were stratified according to Perugini visual score of cardiac uptake. Follow-up data were collected. Among 9616 BS scans, 0.7% (n = 67) showed cardiac uptake. In 47 (70%) patients, Perugini score was 1 and in 20 (30%) patients uptake was ≥ 2, suggesting cardiac ATTR amyloidosis. Forty subjects (61%) died during the follow-up (mean 47 ± 30 months). Compared with patients with Perugini score 1, those Perugini score ≥ 2 showed increased death rate (P = .018). Two (2/67) subjects were investigated for TTR gene mutations resulting negative.
Conclusions
In patients undergoing BS for different clinical indications, cardiac uptake suggesting cardiac ATTR amyloidosis is a rare, but still neglected finding, thus preventing possible diagnosis of ATTR cardiomyopathy. Importantly, cardiac uptake negatively affects the survival. Physicians should be aware of this rare, but crucial finding for timely diagnosis and treatment.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 18 Apr 2022; epub ahead of print

External validation of the CRAX2MACE model.

Hijazi W, Leslie W, Filipchuk N, Choo R, ... Slomka PJ, Miller RJH
Background
Single-photon emission computed tomography (SPECT) myocardial perfusion is frequently used to predict risk of major adverse cardiovascular events (MACE). We performed an external validation of the CRAX2MACE score, developed to estimate 2-year risk of MACE in patients with suspected coronary artery disease (CAD).
Methods
Patients who underwent clinically indicated SPECT with available follow-up for MACE were included (N = 2,985). The prediction performance for MACE (revascularization, myocardial infarction, or death) within 2 years for CRAX2MACE was compared with stress and ischemic total perfusion deficit (TPD) using area under the receiver operating characteristic curve (AUC). Calibration was assessed with calibration plots, Brier score, and the Hosmer-Lemeshow test.
Results
MACE occurred within 2 years in 243 (8.1%) patients. The AUC for CRAX2MACE (0.710, 95% CI 0.677-0.743) was significantly higher compared to stress TPD (AUC 0.669, 95% CI 0.632-0.706, P = .010) and ischemic TPD (AUC 0.664, 95% CI 0.627-0.700, P < .001). The model had acceptable goodness-of-fit (P = .103) and was well-calibrated with Brier score of 0.071.
Conclusion
CRAX2MACE had higher predictive performance for 2-year MACE than quantitative perfusion in an external population. The current model is simple to use and could be implemented to assist physicians when estimating patient risk.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 13 Apr 2022; epub ahead of print

Optimization of the left ventricle ejection fraction estimate obtained during cardiac adenosine stress Rubidium-PET scanning: impact of different reconstruction protocols.

Lassen ML, Wissenberg M, Byrne C, Kjaer A, Hasbak P
Background
Left ventricular ejection fraction (LVEF) estimation using adenosine stress myocardial perfusion imaging (MPI) can be challenging. The short half-life of adenosine and the guideline-recommended adenosine infusion stop during Rubidium-82 acquisition protocol may affect the accuracy and repeatability of the LVEF measures.
Methods
This study comprised 25 healthy volunteers (median age 23 years) who underwent repeat myocardial perfusion imaging (MPI) sessions employing Rubidium-82 PET/CT. A guideline-recommended reconstruction protocol was used for both rest and adenosine stress MPI (150-360 s post-radiotracer injection, standard_recon). For the stress MPI protocol, two additional reconstruction protocols were considered; one was employing 60 seconds data (150-210 seconds, short_fixed) and the other a dynamic frame window based on the bolus arrival of Rubidium-82 in the heart until 210 seconds (x-210 seconds, short_individual). We report rest and stress LVEF, the LVEF reserve, and the LVEF reserve repeatability.
Results
Differences in the LVEF assessments were observed between the guideline recommended and alternative reconstruction protocol (LVEF stress MPI: standard_recon = 68 ± 7%, short_fixed = 71 ± 7% (P = .08), short_individual = 72 ± 7% (P = .04)), and the LVEF reserve was reduced for the guideline-recommended protocol (standard_recon = 7.8 ± 3.5, short_fixed = 10.1 ± 3.7, short_individual = 10.5 ± 3.6, all P < .001). The best repeatability measures were obtained for the short_individual protocol (repeatability: standard_recon = 45.3%, short_fixed = 41.2%, short_individual = 31.7%).
Conclusion
We recommend using the short_individual reconstruction protocol for improved LVEF repeatability and reserve assessment. Alternatively, in centers with limited technical support we recommend the use of the short_fixed protocol.

© 2022. The Author(s).

J Nucl Cardiol: 12 Apr 2022; epub ahead of print

Associations between coronary/aortic F-sodium fluoride uptake and pro-atherosclerosis factors in patients with multivessel coronary artery disease.

Wen W, Gao M, Yun M, Meng J, ... Zhang X, Li X
Background
¹⁸F-NaF PET/CT is a novel approach to detect and quantify microcalcification in atherosclerosis. We aimed to explore the underlying systematic vascular osteogenesis in the coronary artery and aorta in patients with multivessel coronary artery disease (CAD).
Methods
Patients with multivessel CAD prospectively underwent ¹⁸F-NaF PET/CT. The coronary microcalcification activity (CMA) and aortic microcalcification activity (AMA) were calculated based on both the volume and intensity of ¹⁸F-NaF PET activity. Peri-coronary adipose tissue (PCAT) density was measured in adipose tissue surrounding the coronary arteries and the ¹⁸F-NaF tissue-to-blood ratio (TBR) was measured in the coronary arteries.
Results
100 patients with multivessel CAD were prospectively recruited. The CMA was significantly associated with the AMA (r = 0.70; P < .001). After multivariable adjustment, the CMA was associated with the AMA (Beta = 0.445 per SD increase; P < .001). The coronary TBR was also significantly associated with the PCAT density (r = 0.56; P < .001). The PCAT density was independently associated with the coronary TBR after adjusting confounding factors.
Conclusions
Coronary ¹⁸F-NaF uptake was significantly associated with the PCAT density. There was a significant relationship between the coronary and the aortic ¹⁸F-NaF uptake. It might indicate an underlying systematic vascular osteogenesis in patients with multivessel CAD.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 12 Apr 2022; epub ahead of print

Diagnostic performance of IQ·SPECT with high-speed scanning: A preliminary quality control study in obese patients.

Werner RA, Martinez RB, Marcus C, Kruse MJ, ... Javadi MS, Rowe SP
Background
IQ·SPECT is a recently introduced collimator design for myocardial perfusion imaging (MPI). Little data exist on use of this collimator type in obese patients, particularly Class 2 or 3 [body mass index (BMI) > 35 kg/m²].
Methods
Two consecutive rest-stress MPI scans were prospectively acquired using a conventional collimator and IQ·SPECT (acquisition times of 20 and 7 minutes, respectively) in 20 patients with a BMI of >30 kg/m². Assigned by two blinded, independent readers, image quality (on a 5-point scale) and metrics of myocardial perfusion [summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS)] were compared. Software-based left ventricular ejection fraction (EF) was also correlated.
Results
Mean BMI was 39.6 ± 7.6 kg/m². Class 2 or 3 obesity was present in 12 patients (BMI, 44.1 ± 6.8 kg/m²). Gated/non-gated images from IQ·SPECT revealed fair to good quality scores (median ≥ 3.25), which were inferior to the conventional collimator (median ≥ 4.0; P ≤ 0.01). Significant correlative indices were achieved when comparing IQ·SPECT and conventional collimators for EF values (r = 0.86, P < 0.01), SSS (r = 0.75, P < 0.0001) and SRS (r = 0.60, P < 0.005), but not for SDS (r = 0.15).
Conclusion
IQ·SPECT was comparable to conventional SPECT in obese patients. The reduced acquisition time of IQ·SPECT may allow for improved throughput with no loss in diagnostic accuracy.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 06 Apr 2022; epub ahead of print

Simultaneous assessment of myocardial perfusion and adrenergic innervation in patients with heart failure by low-dose dual-isotope CZT SPECT imaging.

Assante R, D\'Antonio A, Mannarino T, Nappi C, ... Cuocolo A, Acampa W
Background
In patients with heart failure (HF) sequential imaging studies have demonstrated a relationship between myocardial perfusion and adrenergic innervation. We evaluated the feasibility of a simultaneous low-dose dual-isotope ¹²³I/^99mTc-acquisition protocol using a cadmium-zinc-telluride (CZT) single-photon emission computed tomography (SPECT) camera.
Methods and results
Thirty-six patients with HF underwent simultaneous low-dose ¹²³I-metaiodobenzylguanidine (MIBG)/^99mTc-sestamibi gated CZT-SPECT cardiac imaging. Perfusion and innervation total defect sizes and perfusion/innervation mismatch size (defined by ¹²³I-MIBG defect size minus ^99mTc-sestamibi defect size) were expressed as percentages of the total left ventricular (LV) surface area. LV ejection fraction (EF) significantly correlated with perfusion defect size (P < .005), innervation defect size (P < .005), and early (P < .05) and late (P < .01) ¹²³I-MIBG heart-to-mediastinum (H/M) ratio. In addition, late H/M ratio was independently associated with reduced LVEF (P < .05). Although there was a significant relationship (P < .001) between perfusion and innervation defect size, innervation defect size was larger than perfusion defect size (P < .001). At multivariable linear regression analysis, ¹²³I-MIBG washout rate (WR) correlated with perfusion/innervation mismatch (P < .05).
Conclusions
In patients with HF, a simultaneous low-dose dual-isotope ¹²³I/^99mTc-acquisition protocol is feasible and could have important clinical implications.

© 2022. The Author(s).

J Nucl Cardiol: 04 Apr 2022; epub ahead of print

Cardiac imaging for the assessment of patients being evaluated for kidney transplantation.

Kassab K, Doukky R
Cardiac risk assessment before kidney transplantation has become widely accepted. However, the optimal patient selection and screening tool for cardiac assessment remain controversial. Clinicians face several challenges in this process, including the ever-growing pre-transplant population, aging transplant candidates, increasing prevalence of coronary artery disease, and scarcity of donor organs. Optimizing the cardiovascular risk profile in kidney transplant candidates is necessary to better appropriate limited donor organs and improve patient outcomes. Increasing waiting times from the initial evaluation for transplant candidacy to the actual transplant raises questions regarding re-testing and re-stratification of risk. In this review, we summarize and discuss the current literature on cardiac evaluation prior to kidney transplantation. We also propose simple evidence-based evaluation algorithms for initial and follow-up CAD surveillance in patients being wait-listed for kidney transplantation.

© 2021. American Society of Nuclear Cardiology.

J Nucl Cardiol: 31 Mar 2022; 29:543-557

A quick glance at selected topics in this issue.

Bhambhvani P, Hage FG, Iskandrian AE
\"A quick glance at selected topics in this issue\" aims to highlight contents of the Journal and provide a quick review to the readers.

© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.

J Nucl Cardiol: 31 Mar 2022; 29:392-394