Quantitative Assessment Using the Compartment Model for Detecting Regional Coronary Artery Disease by Dynamic Myocardial Perfusion Single-Photon Emission Computed Tomography.

BACKGROUND: This study aimed to quantitatively evaluate myocardial perfusion single-photon emission computed tomography (SPECT) using an original analysis tool in the compartment model for detecting regional significant coronary artery disease (CAD).Methods and Results: This study analyzed 41 patients (median age, 76 years) with suspected or known CAD who underwent both dynamic SPECT using 99 mTc-tetrofosmin and invasive coronary angiography. The quantitative analysis was performed using a single-tissue compartment model to evaluate the diagnostic performance of the myocardial flow reserve (MFR) for regional significant CAD, excluding infarcted territories. In the regional analysis, 114 vessels were assessed, of which 31 were diagnosed as significant coronary lesions (≥70% stenosis and/or fraction flow reserve ≤0.8). The MFR of regional significant CAD was significantly lower than that of non-significant CAD (1.11 [0.97-1.31] vs. 1.74 [1.30-2.27]; P<0.001). In the receiver operating characteristic curve analysis, the MFR displayed an area under the curve (AUC) of 0.81. While analyzing each coronary artery territory, the diagnostic performance of the MFR value in the left anterior descending (LAD) artery territory was found to be significantly higher than that found in qualitative assessment (AUC: 0.84 vs. 0.61). CONCLUSIONS: A quantitative analysis of dynamic SPECT data facilitated detecting regional CAD. For the LAD artery, the MFR displayed a higher diagnostic performance than the qualitative assessment of conventional myocardial perfusion SPECT.

Time-related study on external exposure dose of 2-deoxy-2-[F-18]fluoro-D-glucose PET for workers' safety.

Time-course study of individual dose equivalents of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography (18F-FDG PET) was conducted in different hospital workers, and the daily work duties were analyzed. For the measurements, a semiconductor dosimeter was used. The values at intervals of 1 min and 1 h, the monthly cumulative and daily cumulative doses, and trend graphs were acquired with dedicated software and displayed on the reader. The following radiation workers with duties involving maximum external exposure work were included: doctors making diagnoses (4.8 µSv/procedure), nurses removing injection needles (3.1 µSv/procedure), pharmacists performing quality control tests (2.9 µSv/procedure), nuclear medicine technologists assisting patient positioning (6.5 µSv/procedure), and cyclotron engineers performing daily checks (13.4 µSv/procedure). The results of analysis of daily work duties revealed the influencing factors of external exposure dose. To reduce the external exposure dose, investigators should shorten the patient's contact time with the 18F-FDG source or patient tracer.

Positron emission tomography/computed tomography detection of increased 18F-fluorodeoxyglucose uptake in the cardiac atria of patients with atrial fibrillation.

BACKGROUND: Direct evidence of inflammatory activity in the atria of patients with atrial fibrillation (AF) is scarce. We assessed the capability of positron-emission tomography/computed tomography (PET/CT) to diagnose AF based on fluorodeoxyglucose (FDG) uptake in the atrial wall. METHODS AND RESULTS: Among 8233 patients who underwent FDG-PET/CT as work-up for malignancies, we identified 180 consecutive patients with AF (2.2%). Of those, we selected 137 patients who had fasted >12 h before FDG injection for inclusion in the experimental group (88 men and 49 women; age: 72.7 ±â€¯8.9 years). Controls were 62 age- and sex-matched patients without AF. For visual analysis, we used a 4-point grading system. For quantitative analysis, we used the maximum standard uptake value (SUVmax) in the left (LA) and right atrial (RA) myocardium and the target-to-background ratio (TBR) of SUVmax to blood pool activity. The sensitivity, specificity, and positive-predictive value for detecting AF visually were 54.0%, 95.2%, and 96.1%, respectively; for quantitative analysis, the respective values were 65.7%, 75.8%, and 85.7%. Multivariable analysis of 11 clinical and imaging variables showed significant associations with RA SUVmax (odds ratio [OR]: 14.353, P = 0.026) and LA volume (OR: 1.371, P = 0.0001). The RA TBR was greater in cases with persistent AF than in those with paroxysmal AF (P < 0.0001). Pathological investigation of 4 autopsy hearts confirmed infiltration of extravascular macrophages and lymphocytes in the regions with FDG uptake. CONCLUSIONS: Higher atrial FDG uptake was associated with AF. PET/CT could be a useful tool for detecting local inflammation in the atria with AF.

Estimation of myocardial flow reserve utilizing an ultrafast cardiac SPECT: Comparison with coronary angiography, fractional flow reserve, and the SYNTAX score.

BACKGROUND: Quantitative assessment of myocardial flow reserve (MFR) by single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is challenging but may facilitate evaluation of multi-vessel coronary artery disease (CAD). METHODS: We enrolled 153 patients with suspected or known CAD, referred for pharmacological stress MPI. They underwent a 99mTc-perfusion stress/rest SPECT with an ultrafast cadmium-zinc-telluride (CZT) camera. Dynamic data were acquired and time-activity curves fitted to a 1-tissue compartment analysis with input function. K1 was assigned for stress and rest data. The MFR index (MFRi) was calculated as K1 stress/K1 at-rest. The findings were validated by invasive coronary angiography in 69 consecutive patients. RESULTS: The global MFRi was 1.46 (1.16-1.76), 1.33 (1.12-1.54), and 1.18 (1.01-1.35), for 1-vessel disease (VD), 2-VD, and 3-VD, respectively. In the 3-VD, global MFRi was lower than that in 0-VD (1.63 [1.22-2.04], P<0.0001) and 1-VD (P=0.003). Multivariate logistic regression analysis for 3-VD showed significant associations with smoking history (odds ratio [OR]: 4.4 [0.4-8.4]), left ventricular ejection fraction (OR: 61.6 [57.5-66.0]), and global MFRi (OR: 119.6 [111.5-127.7], P=0.002). A cut-off value of 1.3 yielded 93.3% sensitivity and 75.9% specificity for diagnosing 3-VD. Fractional flow reserve positively correlated with regional MFRi (r=0.62, P=0.008), and the SYNTAX score correlated negatively with global MFRi (r=0.567, P=0.0003). CONCLUSION: We developed and validated a clinically available method for MFR quantification by dynamic 99mTc-perfusion SPECT utilizing a CZT camera, which improves the detectability of multi-vessel CAD.

Diagnostic performance of a semiconductor gamma-camera system as studied by multicenter registry.

BACKGROUND: Despite the introduction of the novel cadmium-zinc-telluride (CZT) single-photon emission computed tomography (SPECT) in Japan; its diagnostic value in clinical practice remains largely unknown. METHODS: The Semiconductor SPECT Study group is a multicenter Japanese registry which registered 1000 patients to evaluate the diagnostic utility of the CZT camera system (Discovery NM530c; GE Healthcare, Haifa, Israel). The patients underwent stress myocardial SPECT and coronary angiography within a 3-month interval. A significant stenosis was defined as ≥75% diameter narrowing based on the American Heart Association classification. RESULTS: Technetium (99mTc) radiotracer (555-1110MBq) was used in 71% and thallium-201 (201Tl) (74-148MBq) in 29%. The scan times with 99mTc-radiotracer were 5-10min for stress and 3-10min for rest, whereas those with 201Tl were 5-9min for stress and 8-10min for rest. To detect individual coronary stenosis, the respective sensitivities, specificities, and accuracies were 74%, 85%, and 81% for left anterior descending coronary artery (LAD) stenosis, 76%, 89%, and 85% for left circumflex stenosis, and 72%, 86%, and 82% for right coronary artery stenosis. However, 66% sensitivity and 91% specificity for LAD stenosis were observed with 99mTc-radiotracer, whereas 88% sensitivity and 63% specificity were found with 201Tl. CONCLUSIONS: The novel CZT SPECT system facilitated a short scan time with reduced radiotracer dose, yielding an acceptable diagnostic performance for angiographical coronary artery disease, although the low sensitivity for LAD detection with 99mTc-radiotracer needs to be refined.

Dual radioisotopes simultaneous SPECT of (99m)Tc-tetrofosmin and (123)I-BMIPP using a semiconductor detector.

OBJECTIVES: The energy resolution of a cadmium-zinc-telluride (CZT) solid-state semiconductor detector is about 5%, and is superior to the resolution of the conventional Anger type detector which is 10%. Also, the window width of the high-energy part and of the low-energy part of a photo peak window can be changed separately. In this study, we used a semiconductor detector and examined the effects of changing energy window widths for (99m)Tc and (123)I simultaneous SPECT. METHODS: The energy "centerline" for (99m)Tc was set at 140.5 keV and that for (123)I at 159.0 keV. For (99m)Tc, the "low-energy-window width" was set to values that varied from 3% to 10% of 140.5 keV and the "high-energy-window width" were independently set to values that varied from 3% to 6% of 140.5 keV. For (123)I, the "low energy-window-width" varied from 3% to 6% of 159.0 keV and the high-energy-window width from 3% to 10% of 159 keV. In this study we imaged the cardiac phantom, using single or dual radionuclide, changing energy window width, and comparing SPECT counts as well as crosstalk ratio. RESULTS: The contamination to the (123)I window from (99m)Tc (the crosstalk) was only 1% or less with cutoffs of 4% at lower part and 6% at upper part of 159KeV. On the other hand, the crosstalk from (123)I photons into the (99m)Tc window mostly exceeded 20%. Therefore, in order to suppress the rate of contamination to 20% or less, (99m)Tc window cutoffs were set at 3% in upper part and 7% at lower part of 140.5 KeV. The semiconductor detector improves separation accuracy of the acquisition inherently at dual radionuclide imaging. In, this phantom study we simulated dual radionuclide simultaneous SPECT by (99m)Tc-tetrofosmin and (123)I-BMIPP. CONCLUSION: We suggest that dual radionuclide simultaneous SPECT of (99)mTc and (123)I using a CZT semiconductor detector is possible employing the recommended windows.

Performance of a semiconductor SPECT system: comparison with a conventional Anger-type SPECT instrument.

OBJECTIVE: The performance of a new single photon emission computed tomography (SPECT) scanner with a cadmium-zinc-telluride (CZT) solid-state semiconductor detector (Discovery NM 530c; D530c) was evaluated and compared to a conventional Anger-type SPECT with a dual-detector camera (Infinia). METHODS: Three different phantom studies were performed. Full width at half maximum (FWHM) was measured using line sources placed at different locations in a cylindrical phantom. Uniformity was measured using cylindrical phantoms with 3 different diameters (80, 120, and 160 mm). Spatial resolution was evaluated using hot-rod phantoms of various diameters (5, 9, 13, 16, and 20 mm). Three different myocardial phantom studies were also performed, acquiring projection data with and without defects, and evaluating the interference of liver and gallbladder radioactivity. In a clinical study, the D530c employed list-mode raw data acquisition with electrocardiogram (ECG)-gated acquisition over a 10-min period. From the 10-min projection data, 1-, 3-, 5-, 7- and 10-min SPECT images were reconstructed. RESULTS: The FWHM of the D503c was 1.73-3.48 mm (without water) and 3.88-6.64 mm (with water), whereas the FWHM of the Infinia was 8.17-12.63 mm (without water) and 15.48-16.28 mm (with water). Non-uniformity was larger for the D530c than for the Infinia. Truncation artifacts were also observed with the D530c in a Φ160 mm phantom. The contrast ratio, as defined by myocardial defect/non-defect ratio, was better for the D530c than for the Infinia, and the influence from liver and gallbladder radioactivities was less. Quantitative gated SPECT (QGS) software demonstrated significant differences between data captured over a 10-min period, relative to those acquired over periods of <5 min; there was no difference between ejection fractions calculated using data capture for periods ≥5 min (p < 0.05). CONCLUSIONS: The D530c is superior to the Infinia, with regard to both spatial resolution and sensitivity. In this study, these advantages were confirmed by the myocardial phantom and in a clinical setting, using the QGS software.