Background We previously validated the use of a data-driven cardiac respiratory-motion (RM) correction method (REGAT) applicable to CZT SPECT myocardial perfusion imaging (MPI). In this study, we adapted the same process used with REGAT for RM to generate data-driven cardiac contraction triggers and corresponding cardiac contraction-gated SPECT studies (GSPECT-DD). We aimed to study its feasibility and compare its performances to GSPECT studies generated with ECG monitor-based triggers (GSPECT-ECG). Methods We included seven non-consecutive randomly chosen patients addressed for 1-day 99m Tc-Tetrofosmin stress/rest MPI acquired with multi-pinhole CZT SPECT. We studied the degree of agreement between GSPECT-DD and GSPECT-ECG for the classification of acquired images into the 16 categories of mean cardiac cycle, and compared between the two methods the cine image quality and global LV systolic function of reconstructed studies. Results We found almost perfect agreement between cardiac contraction triggers generated with data-driven and ECG monitor-based methods. As compared to GSPECT-ECG, GSPECT-DD provided comparable and well-correlated LV global systolic function parameters and similar cine image quality at both stress and rest. Conclusions Data-driven cardiac contraction gating using REGAT is feasible with low-dose and high-dose MPI CZT SPECT. It provides GSPECT-DD studies comparable to GSPECT-ECG.

Although substantial progress has been made in recent decades in reducing mortality and performing optimal revascularization in patients with myocardial infarction, ischaemic heart disease, including acute coronary syndrome, remains the leading cause of mortality worldwide. One of the remaining challenges is to better detect, prevent and treat extended myocardial damage despite angiographically optimal revascularization. Several indices are available in clinical practice to evaluate myocardial damage, infarct size and potential myocardial recovery. These indices are divided into two categories: non-invasive, generally performed after revascularization; and invasive, performed during the revascularization procedure. They allow the clinician to detect patients at risk and may help us to tailor the medical therapy and discharge strategy according to myocardial damage. Because of the number of indices, it is difficult to properly evaluate new therapeutics or to adopt one index that will provide sufficient data to better evaluate and understand the part of the coronary vasculature that is not seen - the microcirculation or so-called "black box". The aim of this review is to describe the non-invasive and invasive indices used to describe the microcirculation and their ability to predict clinical impact, and current dedicated therapeutics that may help to reduce microvascular damage and improve clinical outcomes.

Background We previously reported the clinical feasibility and positive impact on image characteristics of a data-driven cardiac respiratory motion (RM) correction method (REGAT) applicable to CZT SPECT myocardial perfusion imaging (MPI). Here, we evaluate its impact on the extent and severity of myocardial perfusion defects (MPD). Methods We included 25 patients having a 1-day 99m Tc-Tetrofosmin stress/rest MPI acquired with multi-pinhole CZT SPECT. Acquisitions were processed with REGAT to generate mean RM gated SPECT. These were summed either after (R-SPECT) or without realignment (NR-SPECT). We noted the maximal cardiac RM shift in the 3 axes of the left ventricle (LV). Both visual and semi-quantitative analyses of myocardial tracer uptake were realized. Studies were classified as having an impact on the extent/severity of MPD with REGAT if ≥1 segment presented a severity score changing by ≥1 level between NR-SPECT and R-SPECT. An impact on the extent of MPD was considered present if at least 1 segment shifted from normal (score = 0) to abnormal (score different from 0) or inversely. Results Cardiac RM was >10 mm in 55% of studies. With visual and semi-quantitative analyses, an impact on the extent/severity MPD was observed in 14% of all studies (7/49) and 60% of studies with cardiac RM >15 mm. An impact on the extent of MPD was observed in 5 of the 7 upper listed studies. All studies presenting an impact on MPD had RM in the anterior to inferior LV axis >10 mm. Conclusions A substantial number of MPI studies presented significant cardiac RM. Cardiac RM compensation showed a frequent impact on the extent/severity of MPD.

In 2019, the Journal of Nuclear Cardiology published excellent articles pertaining to imaging in patients with cardiovascular disease. In this review, we will summarize a selection of these articles to provide a concise review of the main advancements that have recently occurred in the field and provide the reader with an opportunity to review a wide selection of articles. In the first article of this 2-part series, we focused on publications dealing with positron emission tomography, computed tomography, and magnetic resonance. This review will place emphasis on myocardial perfusion imaging using single-photon emission computed tomography summarizing advances in the field including in diagnosis and prognosis, non-perfusion variables, safety of testing, imaging in patients with heart failure and renal disease.

BACKGROUND:We developed a data-driven respiratory motion (RM) correction method (REGAT program) for multiple-pinhole detector CZT SPECT. We verified its clinical feasibility with myocardial perfusion imaging (MPI) and studied its impact on image characteristics.METHODS:This retrospective study included 18 patients having stress/rest 99mTc-Tetrofosmin MPI SPECT. List mode was acquired on CZT SPECT and processed with REGAT. REGAT generates reconstructed RM-gated volumes that are summed either without realignment (NR-SPECT) or after realignment (R-SPECT). For both stress and rest, we calculated the maximal RM in the 3 axis, and image characteristics of both R-SPECT and NR-SPECT: minimum left ventricular (LV) cavity counts (LV-Min), maximum LV myocardial counts (LV-Max), LV contrast, and FWHM of both anterior (FWHM-ant) and inferior (FWHM-inf) LV myocardial walls.RESULTS:At both stress and rest, cranio-caudal motion was the dominant axial movement and REGAT had a positive impact on image characteristics as reflected by variations between R-SPECT and NR-SPECT in LV-Min, LV-Max, FWHM-ant, FWHM-inf, and contrast. These latter were well correlated to the amplitude of cranio-caudal motion at both stress and rest.CONCLUSIONS:Data-driven RM correction of MPI acquired with CZT SPECT is clinically feasible and easily applicable. It presents interesting impact on image characteristics.

We previously developed a data-driven (DD) respiratory-motion (RM) correction method for conventional SPECT gamma-cameras (REGAT) and adapted it to the new CZT camera (Discovery NM 530c). We recently reported that RM correction with REGAT applied to CZT myocardial perfusion SPECT imaging (MPI) is clinically feasible and impacts substantially myocardial perfusion defects. In this evaluation, we study whether REGAT applied to MPI (Discovery NM 530c) is capable of generating a data-driven (DD) cardiac gating signal allowing the generation of valid global left ventricular (LV) function parameters (EDV: end diastolic volume; ESV: end systolic volume; EF: ejection fraction). Were included 7 patients addressed for stress/rest MPI. All patients had prone stress MPI (2 MBq/Kg 99mTc-Tetrofosmin) and rest MPI 3-hours later (6 MBq/Kg). All acquisitions were made on Discovery NM 530c. Each acquisition was processed with REGAT to generate a dynamic SPECT acquisition study. The latter was processed to generate a DD cardiac gating signal and generate a mean DD cardiac GSPECT study (GSPECT-DD). In parallel, a mean ECG cardiac GSPECT study was generated using the ECG trigger signal provided by traditional ECG monitor (GSPECT-M). The 2 generated cardiac GSPECT studies were reconstructed on Xeleris workstation and processed with Emory Cardiac Toolbox (ECT). LV EDV, ESV and EF were compared between cardiac GSPECT-DD and GSPECT-M. Stress LV EVD, ESV, and EF were 91±24mL, 29±13ml, and 68±10% vs 95±23ml, 29±12ml, and 70±11% with GSPECT-DD vs GSPECTM respectively (P:NS). Rest LV EDV, ESV, and EF were 97±21ml, 32±10ml, and 67±6% vs 101±21ml, 31±10ml, and 69±6% with GSPECT-DD vs GSPECT-M respectively (P:NS). Data-driven cardiac gating of MPI with Discovery NM 530c processed with REGAT is clinically feasible. It provides LV global systolic function parameters similar to those provided by the traditional clinically used ECG monitor gating.

In this issue of the journal, Sciagrà et al. report on the use of 13 N-ammonia ( 13 NH 3 ) to recognize transmural perfusion abnormalities in patients with hypertrophic cardiomyopathy (HCM) [1].The authors developed a method to quantify absolute blood flow in the subendocardial and subepicardial layers.This paper comes after a series of studies using 15 Owater (H 2 15 O) with cardiac positron emission tomography (PET) to split mean transmural myocardial perfusion into two layers (subendocardial and subepicardial) and conducted in patients having normal or increased left ventricular (LV) myocardial wall thickness: HCM, coronary artery disease (CAD), aortic stenosis and healthy controls [2-6].The study by Sciagrà et al. is of particular interest because it broadens the scope of application of cardiac PET to the use of a more widely available myocardial perfusion PET radiotracer 13 NH 3 for splitting mean transmural absolute myocardial wall perfusion into subendocardial and subepicardial components.This study provides the opportunity to raise some interesting points concerning cardiac PET and its potential for exploring new frontiers by splitting mean myocardial wall quantitative parameters into two layers.

1798 Objectives We previously developed an LED video device and a data-driven (nuclear medicine images) method to generate respiratory-motion (RM) curves. These 2 systems are used to deal with RM in nuclear medicine using our processing software (REGAT). Here, we evaluate how RM curves generated by 3 methods compare between them: video, data-driven and respiratory belt monitor. Methods Were included 5 patients having stress (3.7 MBq/Kg 99mTc-Tetrofosmin) then rest supine SPECT MPI 3-hours later (11 MBq/Kg). After rest MPI acquisition, video and belt devices were installed. The video device consisted of a red light LED mounted on a small black plate and clipped to an ECG patch in the epigastric area and a consumer device video webcam camera focusing on the LED (WebCam Pro Philips SPC 1330 NC PC Camera). The Respiratory Monitor Belt consisted of a commercially available device (Vernier Software & Technology). Then, 3 successive dynamic planar acquisitions in the RAO view (3 phases) were acquired on a dual-head Symbia-T2 SPECT/CT. Concomitant to each acquired phase, a video and a belt-RM curve were acquired. Video was processed to generate a RM curve. Dynamic acquisitions were processed with REGAT to generate data-driven RM curves. Results Mean±SD of linear correlations between data-driven RM curves vs belt-RM curves and video-RM curves were 0.87±0.04, 0.89±0.04 for phase 1, 0.86±0.07 and 0.85±0.07 for phase 2, and 0.86±0.07 and 0.86±0.07 for phase 3, respectively. Mean±SD of linear correlations between belt-RM curves vs video-RM curves were 0.96±0.02 for phase 1, 0.95±0.03 for phase 2, and 0.94±0.05 for phase 3. Conclusions In MPI studies using 99mTc-Tetrofosmin, data-driven RM curves generated with REGAT, video-RM curves and belt-RM curves are very highly correlated. Each of these 3 methods may be used alternatively to deal with RM.

132 Objectives Recently, we adapted our data-driven respiratory-motion (RM) correction method (REGAT) to multi-pinhole Discovery NM 530c and reported its clinically feasibility and positive impact on image quality with myocardial perfusion SPECT (MPI). Here, we evaluate whether RM correction with REGAT impacts the extent/severity of MPI defects with Discovery NM 530c . Methods Were included 25 patients. All had stress (n=25 pts) then rest MPI at 3-hours (n=24 pts). All acquisitions were made on Discovery NM 530c and processed with REGAT. It generated RM gated volumes which were summed either with no realignment (NR SPECT) or after realignment (R SPECT). These NR and R SPECT studies (n=49) were compared and classified as presenting an impact (Gr 1) or no impact (Gr 2) on severity/extent MPI defects: impact present if ≥ 1 segment presented a modification ≥ 1 score (17 segments; 5 point scoring). Were noted the maximal RM in the 3 axis of reoriented LV: anterior/inferior (A-I), septal/lateral (S-L) and basal-apical (B-A). Was also calculated variation of LV myocardial counts (LV-Max, %) between both R and NR SPECT. Maximal RM of LV and variation of LV-Max were compared between Gr 1 and 2. Results A-I, S-L and B-A movements were 9.7±4.6 mm, 1.8±1.1 mm, 3±2.3 mm. Variation in LV-Max was 2.75±3.61 %. Gr 1 consisted of 7/49 studies (14%). In Gr 1 versus Gr 2, variations in LV-Max were 3.7±7.9 % vs 2.6±2.4% (NS) and A_I movement were 15.7±3.5 mm vs 8.7±4 mm (P 10 mm, 7/27 presented an impact on MPI defects. Conclusions Data-driven RM correction of MPI with Discovery NM 530c appears to impact MPI defects in a substantial number of studies. Its incidence is particularly related to the magnitude of RM. Research Support No support

The field of PET is founded upon a principle of imaging positron-emitting tracers, but it has been supported by a continually evolving technological framework. We have seen advancements, which continue through today, toward increased sensitivity, finer resolution, larger fields of view, and faster processing. This ambitious drive forward has been a constructive feature of our identity and has laid a foundation for a wide breadth of practice. PET as a field has expanded from its origins in brain imaging to become an established clinical modality that reaches a plethora of applications across medicine.

1731 Objectives We previously developed a data-driven respiratory-motion (RM) correction method for conventional SPECT. Discovery NM 530c is characterized by true 3D acquisition, 5 times higher sensitivity and 2 times better spatial resolution. This renders it more suitable for data-driven RM detection with higher expected benefit from RM correction. In this study, we adapted our RM correction method to Discovery NM 530c and verified its clinical applicability to myocardial perfusion SPECT imaging (MPI). Methods Were included 14 pts addressed for prone stress/rest MPI SPECT 99mTc-Tetrofosmin on Discovery NM 530c: 2 MBq/Kg and 5-min list mode for stress vs 6 MBq/Kg and 3-min for rest. Processing consisted in generating a dynamic SPECT study, a data-driven RM curve, and a mean RM GSPECT study. The mean reconstructed RM GSPECT was summed both without realignment and after realignment. Were noted maximal RM in the cranio-caudal (CC), left-right arm (LA-RA) and ventral-dorsal (V-D) axis, and for both realigned and non-realigned summed SPECT each of minimum left ventricular cavity counts (LV-Min), maximum LV myocardial counts (LV-Max), FWHM of anterior LV myocardial wall (FWHM-ant). Variation of these parameters (%) was also calculated. Results CC, LA-RA and V-D were 11±6, 2±2, 1±1 mm for stress and 11±4, 2±2, 2±2 for rest, respectively. CC was > 10 mm in 9/14 pts at stress and rest. Variations in LV-Min, LV-Max, FWHM-ant between non-realigned and realigned summed SPECT were -3±3 %, 21±15 % and 7±6 % at stress and -5±4 %, 27±17 % and 10±6 % at rest, respectively. CC was linearly well correlated to variations in LV-Min (stress: r=0.7, P Conclusions Data-driven RM correction of MPI SPECT with Discovery NM 530c is clinically feasible and easily applicable. It presents interesting impact on image characteristics.

1823 Objectives Attenuation correction (AC) of myocardial perfusion SPECT allows better quantification of cardiac tracer uptake. In normal patients, the apical left ventricular (LV) tracer uptake with SPECT-AC is variable with frequently observed reduced relative tracer uptake. In this study, we aimed to determine in normal patients the factors influencing the level of LV apical tracer uptake with SPECT-AC. Methods Our study included 100 consecutive patients with no previously known CAD addressed for myocardial perfusion scintigraphy (Myoview-Tc99m) and having clinically and electrically negative stress tests (exercise, dipyridamole, combined) and normal filtered back-projection (FBP) stress MPI (without AC). All patients had SPECT/CT MPI acquisitions (Myoview-Tc99m, Symbia, Siemens) allowing the reconstruction of both FBP (non-AC) and SPECT-AC. These were processed with QPS software and allowed the quantification of LV apical uptake (segment 17): seg17_FBP and seg17_AC. Stepwise regression analysis was used to determine the factors influencing the level of seg17_AC uptake: age, sex, weight, height, type of stress test, LV axis angle in the sagittal plane (angle_S, in degrees), LV axis angle in the transaxial plane (angle_T, in degrees), exercise work level (watts), maximal stress heart rate expressed as percent of age-predicted maximal heart rate, presence of coronary calcification on the CT part used for attenuation correction, and seg17_FBP. Results Seg17_AC was much lower than seg17_FBP: 68±7% (minimum=53%; maximum=87%) versus 83±6% (minimum=72%; maximum=96%) (P Conclusions The level of apical LV tracer uptake with SPECT-AC depends on both its level on FBP and the angle of the LV in the sagittal plane

1159 Objectives Gated blood pool SPECT radionuclide angiography (GSPECT RNA) is interesting for the evaluation of cardiac function. We previously validated the use of QBS software (Cedars Sinai) for the quantification of left ventricular (LV) and right ventricular (RV) function. This was done with filtered backprojection reconstruction (FBP). We aimed to study the performance of QBS for the quantification LV and RV function when using FBP as compared to iterative reconstruction with resolution recovery (3D-Flash, Siemens). Methods Our study included 37 patient addressed for LV and RV function evaluation with planar (planarLAO) and GSPECT RNA. Studies were acquired on a two-headed gamma-camera (Symbia, Siemens). PlanarLAO were processed with the NXT program (Vision, GEMS) and provided planarLAO LVEF and RVEF. GSPECT RNA were reconstructed using FBP and 3D-Flash and then processed with QBS. Results provided with the maximal activity threshold method (MAT) of QBS were noted: LV and RV end diastolic volumes, end systolic volumes and stroke volumes (SV), as well as LVEF and RVEF. For comparison of the performance of FBP versus 3D-Flash, planarLAO LVEF and RVEF were considered gold standard. And for RV and LV volumes, we hypothesized that the best reconstruction method would be the one providing the highest correlation between RV-SV and LV-SV. Results LVEF provided by planarLAO (61±9%) is highly correlated to LVEF measured with QBS-FBP (72±17%, r=0.81; P Conclusions QBS performances seem better when using 3D-Flash than FBP for both LV and RV EF and volume measurements

1681 Objectives Cardiac radionuclide angiography (RNA) is realized without considering respiratory (resp) motion. This deteriorates image quality and may impact negatively on the measurement of left ventricular ejection fraction (LVEF). We previously developed and validated the use of REGAT processing program with myocardial perfusion scintigraphy. It corrects for resp motion. We aimed to study the impact of the magnitude of cardiac resp motion on LVEF. Methods ECG gated RNA studies (LAO view)of 10 pts addressed for rest LVEF measurements were used (RNA-ref). Dynamic planar ECG gated RNA studies (6000 frames, 50 ms/frame) were generated using the RNA-ref by imposing a resp movement simulation (translation in the Y axis, sinusoidal model). Maximum resp movement curves of respectively 1, 2, 3, 4, and 5 cm were simulated. These simulated RNA were processed with REGAT program. It allows the generation of ECG gated RNA not corrected for resp motion (RNA-noncorr), RNA corrected for resp motion after realignment (RNA-corr-real), and RNA limited to end expiratory bin (RNA-corr-EE). LVEF were calculated for the RNA-ref (n=10) and compared to LVEF of simulated RNA using the NXT program (GE Healthcare). Results Mean±SD of LVEF was 63±6% for the RNA-ref. For 1, 2, 3, 4, and 5 cm movements, mean±SD of LVEF were respectively 62±6.7%, 61±7.3%, 58±7.1%, 52±7.1%, and 47±9.8% for RNA-noncorr, 62±7%, 62±7%, 62±6.8%, 62±6.9%, and 62±5.9% for RNA-corr-real, and 63±6.4%, 62±6.1%, 63±6.7%, 63±6.6%, and 62±6.8% for RNA-corr-EE. Mean±SD of the difference between RNA-noncorr and RNA-ref increased with the magnitude of resp motion: -1.3±1.6%, -2.2±1.9%, -5.6±3.2%, -11.3±3.5%, and -16.2±4.8% respectively. For RNA-corr-real and RNA-corr-EE, these were low and independent of resp motion magnitude: all Conclusions Resp gating of RNA is beneficial. It successfully removes the variability in the measurement of LVEF related to resp motion. At this step, clinical studies are warranted