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Compressed sensing (CS) has been used to improve image quality in single-photon emission tomography (SPECT) imaging. However, the effects of CS on image quality parameters in myocardial perfusion imaging (MPI) have not been investigated in detail. This preliminary study aimed to compare the performance of CS-iterative reconstruction (CS-IR) with filtered back-projection (FBP) and maximum likelihood expectation maximization (ML-EM) on their ability to reduce the acquisition time of MPI. A digital phantom that mimicked the left ventricular myocardium was created. Projection images with 120 and 30 directions (360°), and with 60 and 15 directions (180°) were generated. The SPECT images were reconstructed using FBP, ML-EM, and CS-IR. The coefficient of variation (CV) for the uniformity of myocardial accumulation, septal wall thickness, and contrast ratio (Contrast) of the defect/normal lateral wall were calculated for evaluation. The simulation was performed ten times. The CV of CS-IR was lower than that of FBP and ML-EM in both 360° and 180° acquisitions. The septal wall thickness of CS-IR at the 360° acquisition was inferior to that of ML-EM, with a difference of 2.5 mm. Contrast did not differ between ML-EM and CS-IR for the 360° and 180° acquisitions. The CV for the quarter-acquisition time in CS-IR was lower than that for the full-acquisition time in the other reconstruction methods. CS-IR has the potential to reduce the acquisition time of MPI.

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BACKGROUND: Although coronary artery disease (CAD) is characterized by epicardial atherosclerosis and microvascular disease, the importance of evaluating microvascular dysfunction has not been sufficiently recognized in clinical practice. We estimated microvascular disease severity by assessing hyperemic microvascular resistance (MVR), as determined by absolute quantification of myocardial blood flow (MBF) with 13N-ammonia positron emission tomography-myocardial perfusion imaging (PET-MPI). METHODS: We retrospectively collected data for 23 CAD patients who underwent both stress/rest PET-MPI and invasive coronary angiography (CAG) with fractional flow reserve (FFR) measurement. Among 30 vessels for which FFR measurement was performed, 13 had a low FFR (FFR ≤0.75). For each patient, myocardial segments of a standard 17-segment model were assigned to the stenotic myocardial area perfused by the FFR-measured vessel and a reference normal-perfusion area based on PET-MPI and the coronary distribution on CAG. Hyperemic MVR was calculated by using the formula, hyperemic MVR = hyperemic mean blood pressure × FFR/hyperemic MBF of the stenotic vessel. RESULTS: A strong negative correlation was observed between hyperemic MVR and hyperemic MBF in the reference normal-perfusion area (R = -0.758, P<0.001). CONCLUSION: Microvascular disease severity in chronic CAD can be estimated by hyperemic MBF of the normal-perfusion area with 13N-ammonia PET-MPI.

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OBJECTIVE: The purpose of this study was to develop a novel myocardial phantom insert model that attaches to commercially available myocardial phantoms and simulates an ischemic area, using three-dimensional printing technology. METHODS: Ischemic inserts were designed to give four levels of absolute percent contrast (Low; 10%, Medium; 20%, High; 35%, and Defect; 100%) using CT images and computer-aided design software. The ischemic insert was composed of multiple slit structures to replicate myocardial ischemia. Myocardial phantom images with developed ischemic inserts were acquired using a SPECT/CT system and were then reconstructed using filtered back projection (FBP) and iterative reconstruction (IR) with various cutoff frequencies of a Butterworth filter. The performance and utility of ischemic inserts were evaluated according to percent contrast and 5-point scoring. RESULTS: The percent contrast and scoring results changed according to the ischemic insert type, cutoff frequency, and reconstruction method. The percent contrast of each insert obtained by FBP with 0.4 cycles/cm was 4.1% (Low), 15.7% (Medium), 17.4% (High), and 36.1% (Defect). Similarly, the percent contrast of each insert obtained by IR with 0.4 cycles/cm was 5.0% (Low), 17.0% (Medium), 21.9% (High), and 47.7% (Defect). CONCLUSIONS: We successfully developed an ischemic insert that attaches to a commercially available myocardial phantom by using CT imaging and 3D printing technology. Our proposed ischemic insert provided several abnormal perfusion patterns on myocardial SPECT images and may be useful for evaluating SPECT image quality.

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This study aimed to evaluate the effectiveness of a single computed tomography (CT) based attenuation correction method using thallium-201 chloride (201TlCl) in stress-rest myocardial perfusion imaging (MPI). The data of 106 patients who underwent MPI with single photon emission computed tomography (SPECT) using 201TlCl were retrospectively reviewed. MPI SPECT images were reconstructed using stress SPECT and stress CT (SIO), rest SPECT and rest CT (RIO), and rest SPECT and stress CT (RIA). The accuracy of alignment between the SPECT and CT images was evaluated with normalized cross-correlation (NCC) and visual examination. The summed rest score (SRS) was used to evaluate hypoperfusion at rest; washout rate (WO) was used to assess ischemia; and left ventricular ejection fraction (LVEF) was used to evaluate the left ventricle (LV) function. There was no significant difference in NCC and visual evaluation in all three dimensions. The SRS of both RIO and RIA (7.5 ± 7.7 and 7.7 ± 7.6, respectively) did not differ significantly. However, SRSs of RIO and RIA showed a strong correlation (r = 0.98). The WO was 39.0 ± 0.98% for both RIO and RIA, with a strong correlation between the two values (r = 1.00). LVEF was 61.1 ± 17.4% for RIO and 61.3 ± 17.4% for RIA, and a strong correlation was observed between the two values (r = 1.00). In conclusion, the single CT-based attenuation correction method with 201TlCl SPECT has an accuracy equivalent to that of the conventional two CT-based attenuation correction method.

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OBJECTIVES: The current management of coronary artery disease (CAD) relies on three major therapeutic options, namely medication, percutaneous coronary intervention (PCI), and coronary artery bypass grafting (CABG). However, severe CAD that is not indicated for PCI or CABG still bears a poor prognosis due to the lack of effective treatments. In 2006, extracorporeal cardiac shock wave (SW) therapy reported on human for the first time. This treatment resulted in better myocardial perfusion as evaluated by dipyridamole stress thallium scintigraphy, angina symptoms, and exercise tolerance. The aim of the present study was to investigate: myocardial perfusion images and evaluate the relationship between the ischemia improvement and symptom amelioration by SW therapy. METHODS: We treated ten patients (i.e., nine males and one female) with cardiac SW therapy who had CAD but not indicated for PCI or CABG and aged 63-89 years old. After the SW therapy, all patients were followed up for three months to evaluate any amelioration of the myocardial ischemia based on symptoms, adenosine stress thallium scintigraphy, transthoracic echocardiography, and blood biochemical examinations. RESULTS: The changes in various parameters were evaluated before and after cardiac SW therapy. The cardiac SW therapy resulted in a significant improvement in the symptoms as evaluated by the Canadian Cardiovascular Society [CCS] class score (P=0.016) and a tendency to improve in summed stress score (SSS) (P=0.068). However, no significant improvement was observed in the summed rest score (SRS), summed difference score (SDS), left ventricular wall motion score index (LVWMSI), N-terminal pro-brain natriuretic, and troponin I. The difference of CCS class score (ΔCCS) was significantly correlated with those of SSS (ΔSSS) and SDS (ΔSDS) (r=0.69, P=0.028 and r=0.70, P=0.025, respectively). There was no significant correlation between ΔCCS and other parameters. Furthermore, no significant difference was observed between the CCS improved and non-improved groups in terms of the baseline characteristics. CONCLUSION: The current study demonstrated the potential efficacy and safety of Cardiac SW therapy in CAD patients. As the findings indicated, symptom amelioration was associated with ischemia improvement by extracorporeal shock wave therapy for the CAD patients.

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Although single photon emission computed tomography-myocardial perfusion image (SPECT-MPI) and fractional flow reserve (FFR) derived from coronary computed tomographic angiography (CCTA) (FFRCT) have permitted functional assessment of coronary artery disease (CAD), the concordance between these modalities has not been well described. The aim of this study is to compare SPECT-MPI and anatomical stenosis by CCTA and invasive coronary angiography to FFRCT for assessing functional significance of CAD. We identified 62 patients with suspected CAD who underwent ≥64 slice coronary CTA and SPECT-MPI within 3 months. FFRCT was analyzed from CCTA data using the computational fluid dynamic techniques. The association between SPECT-MPI ischemia and FFRCT (≤0.80) was evaluated. Out of 62 patients, 186 vessels were evaluated. On a per-vessel analysis, accuracy, sensitivity and specificity of SPECT-MPI to predict FFRCT ≤ 0.80 was 74.2, 45.0 and 77.7%, respectively. The area under the curve (AUC) by receiver-operating characteristic curve analysis for SPECT-MPI demonstrated a modest performance for predicting FFRCT ≤ 0.80 (AUC 0.56). Among patients with suspected CAD who were assessed by non-invasive functional modalities, SPECT-MPI showed modest concordance with FFRCT.

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PURPOSE: Left ventricular (LV) phase dyssynchrony parameters based on gated myocardial perfusion imaging varied among software programs. The aim of this study was to determine normal ranges and factors affecting phase parameters. METHODS: Normal databases were derived from the Japanese Society of Nuclear Medicine working group (n = 69). The programs were Emory Cardiac Toolbox with SyncTool (ECTb), Quantitative Gated SPECT (QGS), Heart Function View (HFV), and cardioREPO (cREPO); parameters of phase standard deviation (PSD), 95% bandwidth, and entropy were compared with parameters with ECTb as a reference. RESULTS: PSD (degree) was 5.3 ± 3.3 for QGS (P < .0001), 5.4 ± 2.5 for HFV (P < .0001), and 10.3 ± 3.2 for cREPO (P = n. s.) compared with 11.5 ± 5.5 for ECTb. Phase bandwidth with three programs differed significantly from ECTb. Gender differences were significant for all programs, indicating larger variation in males. After adjustment of LV volumes between genders, the difference disappeared except for QGS. The phase parameters showed wider variations in patients with the lower ejection fraction (EF) and larger LV volumes, depending on software types. CONCLUSION: Based on normal ranges of phase dyssynchrony parameters in four software programs, dependency on genders, LV volume, and EF should be considered, indicating the need for careful comparison among different software programs.

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A 30-year-old man visited the emergency room for chest pain, dyspnea and fever. Despite increased serum cardiac enzymes, ST segment elevation and inferior wall akinesis in electrocardiography and echocardiography, no atherosclerosis was evident in the coronary angiography. However, radionuclide myocardial perfusion image at day 2 showed a persistent perfusion defect in the left ventricular (LV) inferior wall. At day 3, prominent myocardial edema and severe LV systolic dysfunction developed with signs of heart failure. In this case, fulminant myocarditis seemed to originate from the right coronary artery territory and simulated a ST segment elevation myocardial infarction without coronary artery obstruction. The pathogenesis of the localized perfusion defect was unlcear.

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PURPOSE: For good quality of myocardial perfusion images, an approximately 30 min to 1 hour of waiting time after radiopharmaceutical injection and ingestion of fatty meal are asked of the patients. The aim of this study was to investigate the shortening of waiting time after radiopharmaceutical injection and improvement of image quality using natural plant extracts that promote bile excretion. MATERIALS AND METHODS: Ten volunteers participated in protocol 1 (7 men, 3 women; mean age, 24.1+/-2.4 years) and protocol 2 (8 men, 2 women; mean age, 26.1+/-2.9 years), respectively. For the modified method of both protocols, subjects took natural plant extracts 15 minutes before the first injection of 99mTc MIBI without taking fatty meals. Control (Conventional) methods were performed with intake of a fatty meal 20 to 30 minutes after 99mTc MIBI injection. RESULTS: As the results of protocol 1 and 2, the ratio of myocardial to lung ratio were not different between modified and conventional method. Liver to lung ratio of modified method showed significantly lower value than that of conventional method. In modified method, myocardial to liver ratio was higher persistently. In protocol 2, natural plant extracts took before the first injection of 99mTc MIBI exerted accelerating effect of excretion of bile juice into intestine until the end of examination. CONCLUSION: These results represent that natural plant extracts for facilitation of bile excretion before injection of 99mTc MIBI may provide better quality of myocardial perfusion images without the need for preparations such as ingestion of fatty meal within the 2 hours compared with conventional method.

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