An alternative method for radioactivity measurement in quantitative bone SPECT/CT imaging.

Bone scintigraphy with combined single-photon emission computed tomography (SPECT) and computed tomography (CT) has become widely used for the detection of bone metastases. However, calculation of the semi-quantitative standardized uptake value (SUV) requires measurement of the pre- and post-injection radioactivity of the radiopharmaceutical. This study aimed to compare measured and fixed input radioactivity values for quantitative SPECT/CT bone imaging to examine whether the fixed measurement method of radiopharmaceutical radioactivity could be used as an alternative method. Four different methods were used to quantify the Tc-99m hydroxymethylene diphosphonate input radioactivity: (A) measured pre- and post-injection radioactivity values; (B) measured pre-injection and fixed post-injection radioactivity values; (C) fixed pre-injection and measured post-injection radioactivity values; (D) fixed pre- and post-injection radioactivity values. All SPECT/CT acquisitions were analyzed using bone SPECT analysis software, and the semi-quantitative parameters (SUVpeak and SUVmean) were recorded and compared for each analytical method. Two semi-quantitative parameters showed significant differences between analytical methods A and B, A and D, and C and D. However, an additional subgroup analysis performed on patients whose median post-injection measured radioactivity value was <1.5 MBq showed no significant differences in parameters between all analytical methods. Measurement of the radiopharmaceutical radioactivity can be an alternative method because it reduces the volume of radioactivity post-injection. The simplified fixed measurement method of radiopharmaceutical radioactivity can be used as an alternative method in cases when measuring the radioactivity in quantitative bone SPECT/CT imaging is missed.

Accuracy of washout rate analysis for thallium-201 single-photon emission computed tomography myocardial perfusion imaging using cadmium zinc telluride detectors: A phantom study.

OBJECTIVE: The aim of this study was to assess the accuracy of washout rate (WOR) analysis for thallium-201 chloride (201Tl) single-photon emission computed tomography myocardial perfusion imaging data acquired using cadmium zinc telluride detectors and a myocardial phantom. METHODS: A myocardial phantom was injected with 10.5 MBq 201Tl, and 10-min acquisitions were performed at 0, 24, 46, and 62 h to accommodate natural radioactive decay over time. Global myocardial WOR (global-WOR) and regional WOR (regional-WOR, left anterior descending artery [LAD], right coronary artery [RCA], and left circumflex artery [LCX]) were analyzed between 0 and 24 h (infarction model), 0 and 46 h (ischemia model), and 0 and 62 h (normal model), respectively. We compared the calculated radioactive decay-rate as a reference standard and phantom imaging WOR (phantom-WOR). RESULTS: Decay-rate versus phantom-WOR were 20.4% vs. 20.8% (global-WOR), 21.3% (LAD), 21.2% (RCA), and 19.7% (LCX) for the infarction model; 35.4% vs. 35.6% (global-WOR), 35.5% (LAD), 36.2% (RCA), and 35.2% (LCX) for the ischemia model; and 44.5% vs. 45.1% (global-WOR), 45.4% (LAD), 44.7% (RCA), and 43.5% (LCX) for the normal model. CONCLUSION: WOR analysis for 201Tl single-photon emission computed tomography myocardial perfusion imaging using cadmium zinc telluride detectors is a reliable analysis method.

An Exploratory Study of Washout Rate Analysis for Thallium-201 Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging Using Cadmium Zinc Telluride Detectors.

The aim of this study was to assess the washout rate (WOR) for thallium-201-chloride single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) using cadmium zinc telluride detectors for SPECT (CZT SPECT) versus conventional Anger-type SPECT (conventional SPECT). A total of 52 Japanese patients were examined using CZT SPECT and conventional SPECT, and the global WORs were compared. Additionally, the MPI WORs were compared for patients with a normal MPI versus those in whom MPI reflected the patients' multivessel disease (MVD) MPI. Washout rates were similar when approximated by CZT SPECT versus conventional SPECT 12.59 ± 2.26%/h vs 12.57 ± 2.27%/h ( P = .997), respectively. The WOR values for CZT SPECT versus conventional SPECT were 13.42%/h (1.53%/h) vs 13.93%/h (1.24%/h) ( P = .337), respectively, for 7 normal MPI patients, and 10.64 ± 2.20%/h vs 10.84 ± 2.26%/h ( P = .848), respectively, for 7 MVD-MPI patients. The WOR values for normal MPI versus MVD-MPI patients for CZT SPECT were 13.42 ± 1.53%/h vs 10.64 ± 2.20%/h ( P = .025), respectively. Thallium-201-chloride WOR values obtained with high-efficiency CZT SPECT, which enabled significantly reduced imaging times and use of a low-dose protocol, were similar to those obtained with conventional SPECT.

Optimal thallium-201 dose in cadmium-zinc-telluride SPECT myocardial perfusion imaging.

BACKGROUND: We aimed to determine the optimal thallium 201 chloride (thallium-201) dose using a novel ultrafast cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors (D-SPECT). METHODS AND RESULTS: The optimal thallium-201 dose for obtaining left ventricular (LV) myocardial counts was determined from a phantom study. Consecutive 292 patients underwent stress myocardial perfusion imaging with a thallium-201 injection. Stress test comprised exercise or pharmacological (adenosine) provocation. We calculated an optimal thallium-201 dose that resulted in better LV myocardial counts during 6 minutes of acquisition time. We corrected the respective values according to the patient's age, sex, body mass index (BMI), and type of stress test. The lowest thallium-201 dose for obtaining acceptable imaging was 1.2 million counts. Radiopharmaceutical doses showed a positive correlation with the patient's age (P < .001), sex (P = .012), BMI (P < .001), and type of stress test (P < .001). Multivariate analysis revealed that the patient's BMI and the type of stress test were statistically significant factors for determining the correct radiopharmaceutical dose (P < .001 for both). CONCLUSIONS: For clinical use of the CZT SPECT system, the optimal individual thallium-201 doses can be determined based on the patient's BMI and type of stress test.

Comparison of conventional and cadmium-zinc-telluride single-photon emission computed tomography for analysis of thallium-201 myocardial perfusion imaging: an exploratory study in normal databases for different ethnicities.

The aim of this study was to clarify the differences in thallium-201-chloride (thallium-201) myocardial perfusion imaging (MPI) scans evaluated by conventional anger-type single-photon emission computed tomography (conventional SPECT) versus cadmium-zinc-telluride SPECT (CZT SPECT) imaging in normal databases for different ethnic groups. MPI scans from 81 consecutive Japanese patients were examined using conventional SPECT and CZT SPECT and analyzed with the pre-installed quantitative perfusion SPECT (QPS) software. We compared the summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) for the two SPECT devices. For a normal MPI reference, we usually use Japanese databases for MPI created by the Japanese Society of Nuclear Medicine, which can be used with conventional SPECT but not with CZT SPECT. In this study, we used new Japanese normal databases constructed in our institution to compare conventional and CZT SPECT. Compared with conventional SPECT, CZT SPECT showed lower SSS (p < 0.001), SRS (p = 0.001), and SDS (p = 0.189) using the pre-installed SPECT database. In contrast, CZT SPECT showed no significant difference from conventional SPECT in QPS analysis using the normal databases from our institution. Myocardial perfusion analyses by CZT SPECT should be evaluated using normal databases based on the ethnic group being evaluated.

Non-contrast coronary artery wall and plaque imaging using inversion-recovery prepared steady-state free precession.

BACKGROUND: The objective of this study was to investigate whether three-dimensional (3D) single inversion-recovery prepared steady-state free precession (IR-SSFP) could characterize the coronary artery wall. METHODS: IR-SSFP was scanned on a 1.5-T MR scanner with a five element cardiac coil. One hundred and twenty-one subjects with known or suspected coronary artery disease who had undergone X-ray coronary angiography (XCA) underwent coronary artery wall imaging using IR-SSFP sequences. In each coronary segment, the detection of the coronary wall was categorized, and contrast (signal of plaque minus signal of blood in the aorta divided by the signal of plaque plus signal of blood in the aorta) was calculated. RESULTS: 422 of 517 segments (82%) were successfully visualized, and the detection scores tended to be higher at the proximal coronary artery when compared with other segments of the coronary artery. High contrast (contrast≥0.75) areas were observed in 62 of 218 segments with ≥50% coronary artery stenosis by XCA but also in 25 of 299 segments without ≥50% coronary stenosis. CONCLUSIONS: IR-SSFP provided good visualization of the coronary wall. This approach represents a promising noninvasive strategy for the assessment of the coronary artery wall.

Separate pulmonary artery and vein magnetic resonance angiography by use of an arterial spin labeling method.

A separate pulmonary vein (PV) is difficult to depict with the commonly used bright-blood magnetic resonance angiography method. Until now, no study has described the depiction of peripheral PVs without the artery. Our purpose in this study was to develop an arterial spin labeling (ASL)-based magnetic resonance angiography sequence to depict the pulmonary artery (PA) and vein separately. We developed such a sequence by using two inversion recovery pulses. The first pulse was non-selective, and the second pulse was selective and was applied to the aorta and heart. All studies were conducted on a 1.5-T clinical magnetic resonance system with six different inversion times for seven healthy volunteers. For evaluation, we categorized the inversion times by using visual scoring. Then, we used the magnitude image to evaluate the PA, and we used the real image to evaluate the PV. For the PA, an inversion time of 300 ms had the lowest score (1.43), and the score changed with increasing times; an inversion time of 1,100 ms had the highest score (3.85). For the PV, an inversion time of 300 ms had the highest score (2.68), and the score decreased with increasing times. The results indicated that the PA and vein could be depicted separately by the use of an ASL-based magnetic resonance angiography method. The optimal inversion times for the PV and artery were 300 and 1,100 ms, respectively.

[Lumbar spinal nerve roots imaging using balanced sequence with inversion recovery (IR) pulse].

We devised a method for visualizing the distal portion of lumbar spinal nerve roots in the direction of the long axis using a three-dimensional balanced sequence with inversion recovery pulse, and we established the imaging parameters. This pulse sequence was used with the following parameters: 260 mm field of view, 4.8 ms repetition time, 2.4 ms echo time, 90 degree flip angle, 1.5 mm slice thickness (0.75 mm overlap), and low-high radial k-space profile order. We assessed the signal intensity and contrast for the phantom and healthy volunteer images with different inversion times (TI). Moreover, we evaluated this method by using the optimal TI in clinical cases. The optimal TI obtained from the phantom and human studies was 600 ms. In clinical cases, this method with 600 ms of TI provided the best definition in images of abnormal pathway and compression of the lumbar spinal nerve roots. Our imaging method makes it possible to clearly and noninvasively visualize the lumbar spinal nerve roots.

[Furanocoumarins contents and cytochrome P450 3A (CYP3A) inhibitory activities of various processed fruit peel products: outflow of 6',7'-Dihydroxybergamottin during processing treatment of peel].

Furanocoumarins (FCs) such as bergamottin (BG) and 6',7'-dihydroxybergamottin (DHBG) contained in grapefruits are known to be cytochrome P450 3A4 (CYP3A4) inhibitors. These are contained in larger quantity in peel than in pulp, and therefore, processed peel products possibly have strong CYP3A4 inhibitory activity. The CYP3A4 inhibitory potency of these processed peel products, however, remains to be elucidated. The FC content and CYP3A inhibitory activities of various processed fruit peel products were investigated. CYP3A inhibitory activities of crystallized grapefruit peel, grapefruit marmalade, lemon peel and bitter orange slice were close to that of 100% grapefruit juice, while the activities of yuzu slice, pomelo (buntan) marmalade and crystallized iyokan peel were very weak, 1/8-1/20 of 100% grapefruit juice. The maximum BG content was 5.6 µg/g in lemon peel. The maximum DHBG content was 7.2 µg/g in crystallized grapefruit peel, about 1/30 that of raw peel. Grapefruit marmalade and crystallized grapefruit peel contained similar amounts of FCs to 100% grapefruit juice, but FCs were not detected in pomelo (buntan) marmalade or crystallized iyokan peel. Good correlation (r=0.78) was observed between the FC contents of these peel products and those CYP3A inhibitory activities. Preparation of homemade grapefruit marmalade and crystallized peel revealed that considerably lower DHBG content in these products and lower CYP3A inhibitory activity than anticipated were attributable to outflow of DHBG to broth during boiling of the raw peel.

[Studies of three-dimensional cardiac late gadolinium enhancement MRI at 3.0 Tesla].

Cardiac late Gadolinium enhancement MR imaging has been shown to allow assessment of myocardial viability in patients with ischemic heart disease. The current standard approach is a 3D inversion recovery sequence at 1.5 Tesla. The aims of this study were to evaluate the technique feasibility and clinical utility of MR viability imaging at 3.0 Tesla in patients with myocardial infarction and cardiomyopathy. In phantom and volunteer studies, the inversion time required to suppress the signal of interests and tissues was prolonged at 3.0 Tesla. In the clinical study, the average inversion time to suppress the signal of myocardium at 3.0 Tesla with respect to MR viability imaging at 1.5 Tesla was at 15 min after the administration of contrast agent (304.0+/-29.2 at 3.0 Tesla vs. 283.9+/-20.9 at 1.5 Tesla). The contrast between infarction and viable myocardium was equal at both field strengths (4.06+/-1.30 at 3.0 Tesla vs. 4.42+/-1.85 at 1.5 Tesla). Even at this early stage, MR viability imaging at 3.0 Tesla provides high quality images in patients with myocardial infarction. The inversion time is significantly prolonged at 3.0 Tesla. The contrast between infarction and viable myocardium at 3.0 Tesla are equal to 1.5 Tesla. Further investigation is needed for this technical improvement, for clinical evaluation, and for limitations.

[Studies of free breathing three-dimensional heart delayed enhancement MRI under resting respiration using KING].

Heart delayed enhancement magnetic resonance imaging(MRI)is an attempt to obtain intense image contrast using the null-point of normal myocardium, which changes with time. Imaging is generally conducted under breath-hold, but, if the retrospective gating method is used, it is necessary to shorten the imaging time and to fill the center of the k-space with the data in the early phase of imaging. In the present study, we examined free breathing three-dimensional heart delayed enhancement MRI(3D/KING method)using k-space inspired navigator gating(KING). In the 3D/KING, since respiratory artifact decreases by combining with the fat suppression technique and the gating window can be set widely, the imaging time was shortened in comparison with the conventional 3D method. In 3D/KING/isotropic(iso), on the other hand, the respiratory artifact was decreased by transverse imaging. The mean end time of imaging by the 3D/KING method(n=10)and the 3D/KING/iso(n=5)was 3.05+/-0.69 and 4.59+/-0.74 minutes, respectively. Moreover, the signal intensity ratio(SIR)of abnormal myocardium versus normal myocardium in the 3D/KING method was low in comparison with that in the breath-hold method. However, the capability to detect lesions was similar, and good images were obtained from the patients showing poor breath-hold. In the 3D/KING/iso, heart delayed enhancement MRI from multiple directions could be conducted in a single imaging by using the image reconstitution method.