IQ-SPECT for thallium-201 myocardial perfusion imaging: effect of normal databases on quantification

OBJECTIVE

Although IQ-single-photon emission computed tomography (SPECT) provides rapid acquisition and attenuation-corrected images, the unique technology may create characteristic distribution different from the conventional imaging. This study aimed to compare the diagnostic performance of IQ-SPECT using Japanese normal databases (NDBs) with that of the conventional SPECT for thallium-201 (²⁰¹Tl) myocardial perfusion imaging (MPI).

METHODS

A total of 36 patients underwent 1-day ²⁰¹Tl adenosine stress-rest MPI. Images were acquired with IQ-SPECT at approximately one-quarter of the standard time of conventional SPECT. Projection data acquired with the IQ-SPECT system were reconstructed via an ordered subset conjugate gradient minimizer method with or without scatter and attenuation correction (SCAC). Projection data obtained using the conventional SPECT were reconstructed via a filtered back projection method without SCAC. The summed stress score (SSS) was calculated using NDBs created by the Japanese Society of Nuclear Medicine working group, and scores were compared between IQ-SPECT and conventional SPECT using the acquisition condition-matched NDBs. The diagnostic performance of the methods for the detection of coronary artery disease was also compared.

RESULTS

SSSs were 6.6 ± 8.2 for the conventional SPECT, 6.6 ± 9.4 for IQ-SPECT without SCAC, and 6.5 ± 9.7 for IQ-SPECT with SCAC (p = n.s. for each comparison). The SSS showed a strong positive correlation between conventional SPECT and IQ-SPECT (r = 0.921 and p < 0.0001), and the correlation between IQ-SPECT with and without SCAC was also good (r = 0.907 and p < 0.0001). Regarding diagnostic performance, the sensitivity, specificity, and accuracy were 80.8, 78.9, and 79.4%, respectively, for the conventional SPECT; 80.8, 80.3, and 82.0%, respectively, for IQ-SPECT without SCAC; and 88.5, 86.8, and 87.3%, respectively, for IQ-SPECT with SCAC, respectively. The area under the curve obtained via receiver operating characteristic analysis were 0.77, 0.80, and 0.86 for conventional SPECT, IQ-SPECT without SCAC, and IQ-SPECT with SCAC, respectively (p = n.s. for each comparison).

CONCLUSIONS

When appropriate NDBs were used, the diagnostic performance of ²⁰¹Tl IQ-SPECT was comparable with that of the conventional system regardless of different characteristics of myocardial accumulation in the conventional system.

Comparison of phase dyssynchrony analysis using gated myocardial perfusion imaging with four software programs: Based on the Japanese Society of Nuclear Medicine working group normal database

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.

Comparison of diagnostic performance of four software packages for phase dyssynchrony analysis in gated myocardial perfusion SPECT

Background

Phase analysis of gated myocardial perfusion single-photon emission computed tomography (SPECT) for assessment of left ventricular (LV) dyssynchrony was investigated using the following dedicated software packages: Corridor4DM (4DM), cardioREPO (cREPO), Emory Cardiac Toolbox (ECTb), and quantitative gated SPECT (QGS). The purpose of this study was to evaluate the normal values of 95% histogram bandwidth, phase standard deviation (SD), and entropy and to compare the diagnostic performance of the four software packages. A total of 122 patients with normal myocardial perfusion and cardiac function (58.9 ± 12.3 years, 60 women, ejection fraction (EF) 74.3 ± 5.7%, and end-diastolic volume (EDV) 83.5 ± 3.6 mL) and 34 patients with suspected LV dyssynchrony (64.1 ± 12.2 years, 9 women, EF 52.0 ± 18.0%, and EDV 145.0 ± 6.8 mL) who underwent Tc-99m methoxy-isobutyl-isonitrile/tetrofosmin gated SPECT were retrospectively evaluated. Dyssynchrony indices of the 95% histogram bandwidth, phase SD, and entropy were computed with the four software programs. Diagnostic performance of LV phase dyssynchrony assessments was determined by receiver operator characteristic (ROC) analysis. The area under the ROC curve (AUC) was used to compare the software programs. The optimal cutoff point was determined by ROC curve based on the Youden index.

Results

The average of normal bandwidth significantly differed among the four software programs except in the comparison of 4DM and ECTb. Moreover, the normal phase SD significantly differed among the four software programs except in the comparison of cREPO and ECTb. The software programs showed high correlation levels for bandwidth, phase SD, and entropy (r ≥ 0.73, p < 0.001). ROC AUCs of bandwidth, phase SD, and entropy were ≥0.850, ≥0.858, and ≥0.900, respectively. Moreover, the ROC AUCs of bandwidth, phase SD, and entropy did not significantly differ among the four software programs. Optimal cutoff points for phase parameters were 24°–42° for bandwidth, 8.6°–15.3° for phase SD, and 31–48% for entropy.

Conclusions

Although the optimal cutoff value for determining LV phase dyssynchrony by ROC analysis varied depending on the use of the different software programs, all software programs can be used reliably for phase dyssynchrony analysis.

Innovative exercise device for the abdominal trunk muscles: An early validation study

BACKGROUND

Exercise is one of the few treatments that provide significant improvements in chronic low back pain (CLBP). We developed an innovative exercise device for abdominal trunk muscles. This device can be used in a sitting or standing position and contains a built-in system to measure abdominal trunk muscle strength. We examined whether subjects can adequately use the device to perform the exercises and measure their abdominal trunk muscle strength.

METHODS

We collected data on the body height, body weight, body mass index, and girth of 30 healthy male volunteers, and measured their grip power and trunk extensor muscle strength using a dynamometer. The volunteers performed a sit-up test as an indicator of trunk flexor muscle strength, and we measured their abdominal muscle strength using the device. We then evaluated the correlations between abdominal trunk muscle strength and anthropometric parameters as well as the strength of other muscles. In subsequent tests, 5 of the 30 subjects participated in two positron emission tomography (PET) series consisting of examinations after a resting period (control study) and during exercise (exercise study). For the exercise study, the subjects performed 2 sets of exercises for 20 minutes using the device before and after an injection of 18F-fluorodeoxyglucose (FDG). PET-computed tomography images were obtained 60 minutes after FDG injection in each study. We compared the skeletal muscle metabolism of the participants in both studies using the standardized uptake value.

RESULTS

The muscle strength measured by the device and the 30-second sit-up frequency were correlated. FDG accumulation within the diaphragm and abdominal rectus muscles was significantly higher in the exercise study.

CONCLUSION

Our innovative exercise device facilitates a coordinated contraction of the abdominal trunk muscles at the anterior aspect and the roof of the core, and enables subjects to measure the strength of these muscles.

Evaluation of cytological radiation damage to lymphocytes after I-131 metaiodobenzylguanidine therapy by the cytokinesis-blocked micronucleus assay

OBJECTIVE

The purpose of this study was to evaluate the degree of cytological radiation damage to lymphocytes occurring after I-131 metaiodobenzylguanidine (MIBG) therapy as determined by the cytokinesis-blocked micronucleus assay. The chromosomal damage to lymphocytes induced by I-131 in vivo should result in augmentation of the number of cells with micronuclei.

METHODS

We studied 15 patients with pheochromocytoma (14/15) or ganglioneuroma (1/15), who were treated initially with 7.4 GBq of I-131-MIBG. Isolated lymphocytes collected from patients 10 days after the therapy were harvested and treated according to the cytokinesis-blocked method of Fenech and Morley. Serial blood samples were obtained periodically only from two patients for 2 years after therapy. Micronucleus number of micronuclei per 500 binucleated cells was scored by visual inspection. As controls, lymphocytes from the same patients before the therapy were also studied. In an in vitro study, lymphocytes from eight normal volunteers were exposed to doses varying from 0.5 to 2 Gy and studied with the same method.

RESULTS

The mean number (mean ± SD) of micronuclei after treatment was significantly increased (p < 0.001) as compared to control subjects (49.4 ± 8.2 vs. 11.3 ± 6.4). Internal radiation absorbed doses estimated for the 15 patients were 1.6 ± 0.3 Gy in this external irradiation study. The frequency of micronuclei post-administration of I-131-MIBG gradually decreased to near baseline (i.e., pre-therapy) levels by 2 years.

CONCLUSIONS

The relatively low frequency of lymphocyte micronuclei induced by I-131-MIBG in vivo and reversal of the increasing frequency of lymphocyte micronuclei after therapy suggest that the short-term non-stochastic damage induced by this therapy with 7.4 GBq of I-131-MIBG in pheochromocytoma or ganglioneuroma patients is limited and reversible.

Optimization of the filter parameters in (99m)Tc myocardial perfusion SPECT studies: the formulation of flowchart

Myocardial perfusion single photon emission computed tomography (SPECT) is typically subject to a variation in image quality due to the use of different acquisition protocols, image reconstruction parameters and image display settings by each institution. One of the principal image reconstruction parameters is the Butterworth filter cut-off frequency, a parameter strongly affecting the quality of myocardial images. The objective of this study was to formulate a flowchart for the determination of the optimal parameters of the Butterworth filter for filtered back projection (FBP), ordered subset expectation maximization (OSEM) and collimator-detector response compensation OSEM (CDR-OSEM) methods using the evaluation system of the myocardial image based on technical grounds phantom. SPECT studies were acquired for seven simulated defects where the average counts of the normal myocardial components of 45° left anterior oblique projections were approximately 10-120 counts/pixel. These SPECT images were then reconstructed by FBP, OSEM and CDR-OSEM methods. Visual and quantitative assessment of short axis images were performed for the defect and normal parts. Finally, we formulated a flowchart indicating the optimal image processing procedure for SPECT images. Correlation between normal myocardial counts and the optimal cut-off frequency could be represented as a regression expression, which had high or medium coefficient of determination. We formulated the flowchart in order to optimize the image reconstruction parameters based on a comprehensive assessment, which enabled us to perform objectively processing. Furthermore, the usefulness of image reconstruction using the flowchart was demonstrated by a clinical case.

Diagnosis and treatment of bone metastasis: comprehensive guideline of the Japanese Society of Medical Oncology, Japanese Orthopedic Association, Japanese Urological Association, and Japanese Society for Radiation Oncology

Diagnosis and treatment of bone metastasis requires various types of measures, specialists and caregivers. To provide better diagnosis and treatment, a multidisciplinary team approach is required. The members of this multidisciplinary team include doctors of primary cancers, radiologists, pathologists, orthopaedists, radiotherapists, clinical oncologists, palliative caregivers, rehabilitation doctors, dentists, nurses, pharmacists, physical therapists, occupational therapists, medical social workers, etc. Medical evidence was extracted from published articles describing meta-analyses or randomised controlled trials concerning patients with bone metastases mainly from 2003 to 2013, and a guideline was developed according to the Medical Information Network Distribution Service Handbook for Clinical Practice Guideline Development 2014. Multidisciplinary team meetings are helpful in diagnosis and treatment. Clinical benefits such as physical or psychological palliation obtained using the multidisciplinary team approaches are apparent. We established a guideline describing each specialty field, to improve understanding of the different fields among the specialists, who can further provide appropriate treatment, and to improve patients’ outcomes.

Changes in muscle activity after performing the FIFA 11+ programme part 2 for 4 weeks

Changes in muscle activity were evaluated by positron emission tomography-computed tomography (PET-CT) after performing part 2 of the Fédération Internationale de Football Association's 11+ programme (11+) for 4 weeks. Eleven males performed part 2 of the 11+ for 20 min before and after 37 MBq of (18)F-fluorodeoxyglucose (FDG) was injected intravenously. PET-CT images were obtained 50 min after FDG injection. The participants were then instructed to perform part 2 of the 11+ 3 times per week for 4 consecutive weeks, after which another set of PET-CT images was obtained following the same procedure. Regions of interest were defined within 30 muscles. The standardised uptake value (SUV) of FDG by muscle tissue per unit volume was calculated, and FDG accumulation was compared between pre- and post-training PET-CT results. Performing part 2 of the 11+ for 4 weeks increased mean SUV in the sartorius, semimembranosus, biceps femoris, abductor hallucis, and flexor hallucis brevis muscles (P < 0.05). In conclusion, routinely performing part 2 of the 11+ for 4 weeks increased glucose uptake related to muscle activity in the hamstrings and hallux muscles. We speculate that there is some possibility of this change of muscle activity contributing to a decrease in sports-related injuries.

In Vivo Differences between Two Optical Isomers of Radioiodinated o-iodo-trans-decalinvesamicol for Use as a Radioligand for the Vesicular Acetylcholine Transporter

PURPOSE

To develop a superior VAChT imaging probe for SPECT, radiolabeled (-)-OIDV and (+)-OIDV were isolated and investigated for differences in their binding affinity and selectivity to VAChT, as well as their in vivo activities.

PROCEDURES

Radioiodinated o-iodo-trans-decalinvesamicol ([125I]OIDV) has a high binding affinity for vesicular acetylcholine transporter (VAChT) both in vitro and in vivo. Racemic [125I]OIDV was separated into its two optical isomers (-)-[125I]OIDV and (+)-[125I]OIDV by HPLC. To investigate VAChT binding affinity (Ki) of two OIDV isomers, in vitro binding assays were performed. In vivo biodistribution study of each [125I]OIDV isomer in blood, brain regions and major organs of rats was performed at 2,30 and 60 min post-injection. In vivo blocking study were performed to reveal the binding selectivity of two [125I]OIDV isomers to VAChT in vivo. Ex vivo autoradiography were performed to reveal the regional brain distribution of two [125I]OIDV isomers and (-)-[123I]OIDV for SPECT at 60 min postinjection.

RESULTS

VAChT binding affinity (Ki) of (-)-[125I]OIDV and (+)-[125I]OIDV was 22.1 nM and 79.0 nM, respectively. At 2 min post-injection, accumulation of (-)-[125I]OIDV was the same as that of (+)-[125I]OIDV. However, (+)-[125I]OIDV clearance from the brain was faster than (-)-[125I]OIDV. At 30 min post-injection, accumulation of (-)-[125I]OIDV (0.62 ± 0.10%ID/g) was higher than (+)-[125I]OIDV (0.46 ± 0.07%ID/g) in the cortex. Inhibition of OIDV binding showed that (-)-[125I]OIDV was selectively accumulated in regions known to express VAChT in the rat brain, and ex vivo autoradiography further confirmed these results showing similar accumulation of (-)-[125I]OIDV in these regions. Furthermore, (-)-[123I]OIDV for SPECT showed the same regional brain distribution as (-)-[125I]OIDV.

CONCLUSION

These results suggest that radioiodinated (-)-OIDV may be a potentially useful tool for studying presynaptic cholinergic neurons in the brain.

Simultaneous acquisition of (99m)Tc- and (123)I-labeled radiotracers using a preclinical SPECT scanner with CZT detectors

OBJECTIVE

Simultaneous acquisition of (99m)Tc and (123)I was evaluated using a preclinical SPECT scanner with cadmium zinc telluride (CZT)-based detectors.

METHODS

10-ml cylindrical syringes contained about 37 MBq (99m)Tc-tetrofosmin ((99m)Tc-TF) or 37 MBq (123)I-15-(p-iodophenyl)-3R,S-methyl pentadecanoic acid ((123)I-BMIPP) were used to assess the relationship between these SPECT radioactive counts and radioactivity. Two 10-ml syringes contained 100 or 300 MBq (99m)Tc-TF and 100 MBq (123)I-BMIPP to assess the influence of (99m)Tc upscatter and (123)I downscatter, respectively. A rat-sized cylindrical phantom also contained both 100 or 300 MBq (99m)Tc-TF and 100 MBq (123)I-BMIPP. The two 10-ml syringes and phantom were scanned using a pinhole collimator for rats. Myocardial infarction model rats were examined using 300 MBq (99m)Tc-TF and 100 MBq (123)I-BMIPP. Two 1-ml syringes contained 105 MBq (99m)Tc-labeled hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) and 35 MBq (123)I-labeled N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane ((123)I-FP-CIT). The two 1-ml syringes were scanned using a pinhole collimator for mice. Normal mice were examined using 105 MBq (99m)Tc-HMPAO and 35 MBq (123)I-FP-CIT.

RESULTS

The relationship between SPECT radioactive counts and radioactivity was excellent. Downscatter contamination of (123)I-BMIPP exhibited fewer radioactive counts for 300 MBq (99m)Tc-TF without scatter correction (SC) in 125-150 keV. There was no upscatter contamination of (99m)Tc-TF in 150-175 keV. In the rat-sized phantom, the radioactive count ratio decreased to 4.0 % for 300 MBq (99m)Tc-TF without SC in 125-150 keV. In the rats, myocardial images and radioactive counts of (99m)Tc-TF with the dual tracer were identical to those of the (99m)Tc-TF single injection. Downscatter contamination of (123)I-FP-CIT was 4.2 % without SC in 125-150 keV. In the first injection of (99m)Tc-HMPAO and second injection of (123)I-FP-CIT, brain images and radioactive counts of (99m)Tc-HMPAO with the dual tracer in normal mice also were the similar to those of the (99m)Tc-HMPAO single injection. In the first injection of (123)I-FP-CIT and second injection of (99m)Tc-HMPAO, the brain images and radioactive counts with the dual tracer were not much different from those of the (123)I-FP-CIT single injection.

CONCLUSIONS

Dual-tracer imaging of (99m)Tc- and (123)I-labeled radiotracers is feasible in a preclinical SPECT scanner with CZT detector. When higher radioactivity of (99m)Tc-labeled radiotracers relative to (123)I-labeled radiotracers is applied, correction methods are not necessarily required for the quantification of (99m)Tc- and (123)I-labeled radiotracers when using a preclinical SPECT scanner with CZT detector.

Radioisotope Therapy of Japan: Future Perspective and Recommendations

In Japan, because of the rapid increase in the number of thyroid cancer patients and the recent severe shortage of radioisotope therapy wards, the prolonged waiting time for the admission to the radioisotope therapy wards has become a social problem. This situation is against one of the main purposes of the Cancer Control Promotion Plan of our nation, which is advocating an equal accessibility of medical care for the Japanese citizens. In 2015, diet discussions about the problems of radioisotope therapy took place and the prime minister stated that the promotion of radioisotope therapy is one of the most important issues in Japan, therefore further promotion of research and development is anticipated in this field. In this article, we have summarized the problems during radioisotope therapy, and have added our recommendations in the social and medical realizable countermeasures in future, according to the deep considerations of medical economy in Japan, an assumption of disease prevalence of thyroid cancer in the future, and the situations of foreign countries.

Effects of the belt electrode skeletal muscle electrical stimulation system on lower extremity skeletal muscle activity: Evaluation using positron emission tomography

BACKGROUND

Lower-extremity muscle weakness in athletes after lower limb trauma or surgery can hinder their return to sports, and the associated muscle atrophy may lead to deterioration in performance after returning to sports. Recently, belt electrode skeletal muscle electrical stimulation (B-SES) which can contract all the lower limb skeletal muscles simultaneously was developed. However, no study has evaluated skeletal muscle activity with B-SES. Since only superficial muscles as well as a limited number of muscles can be investigated using electromyography, we investigated whether positron emission tomography (PET) can evaluate the activity of all the skeletal muscles in the body simultaneously. The purpose of this study was to evaluate the effectiveness of the B-SES system using PET.

METHODS

Twelve healthy males (mean age, 24.3 years) were divided into two groups. The subjects in the control group remained in a sitting position for 10 min, and [(18)F] fluorodeoxyglucose (FDG) was intravenously injected. In the exercise group, subjects exercised using the B-SES system for 20 min daily for three consecutive days as a pre-test exercise. On the measurement day, they exercised for 10 min, received an injection of FDG, and exercised for another 10 min. PET-computed tomography images were obtained in each group 60 min after the FDG injection. Regions of interest were drawn in each lower-extremity muscle. We compared each skeletal muscle metabolism using the standardized uptake value.

RESULTS

In the exercise group, FDG accumulation in the gluteus maximus, gluteus medius, gluteus minimus, quadriceps femoris, sartorius, and hamstrings was significantly higher than the muscles in the control (P < 0.05).

CONCLUSION

Exercise with B-SES increased the skeletal muscle activity of the gluteal muscles as well as the most lower-extremity muscles simultaneously.

Triple-phase contrast-enhanced MRI for the prediction of preoperative chemotherapeutic effect in patients with osteosarcoma: comparison with (99m)Tc-MIBI scintigraphy

OBJECTIVE

This study aims to determine whether (99m)Tc-MIBI scintigraphy and triple-phase contrast-enhanced magnetic resonance imaging (TCE-MRI) performed during and after preoperative chemotherapy have the power to predict final chemotherapeutic effects in patients with osteosarcoma (OS).

MATERIALS AND METHODS

Seventeen patients underwent (99m)Tc-MIBI scintigraphy and TCE-MRI before and after the middle and last courses of preoperative chemotherapy. As for (99m)Tc-MIBI scintigraphy, an uptake ratio (UR) and a reduction rate of UR (ΔUR(MIBI)) were calculated. As for TCE-MRI, a ratio of contrast to background (CTB) was calculated in the whole tumor area (WA) at each phase on dynamic T1-weighted fat suppression images. Then a ratio of signal (R(WA)) was calculated by dividing CTB at triple-phase by CTB at pre-phase.

RESULTS

Nine and eight patients showed good and poor response in histopathologic evaluation. The sensitivity, specificity, and accuracy for the prediction of histopathological chemotherapeutic effect was 44, 100, 69% in R(WA) at the first phase, 100, 75, 88% in ΔUR(MIBI) after the middle course, 88, 100, 94% in R(WA) at the first phase, and 100, 75, 88% in ΔUR(MIBI) after the last course of the preoperative chemotherapy, respectively.

CONCLUSION

Both (99m)Tc-MIBI scintigrapy and TCE-MRI can predict the tumor response in patients with OS after the completion of the preoperative chemotherapy.

Correlation between apoptosis and left ventricular remodeling in subacute phase of myocardial ischemia and reperfusion

Background

To investigate whether an apoptotic process demonstrated by ^99mTc-annexin-V (^99mTc-AV) uptake correlates with left ventricular remodeling (LVR) after myocardial infarction, we assessed ^99mTc-AV uptake in rat model of myocardial ischemia and reperfusion.

Methods

The left coronary artery (LCA) of 15 rats was occluded for 20 to 30 min, followed by reperfusion. After 2 weeks, ^99mTc-AV was injected, and then 1 h later, ²⁰¹Tl was injected after reocclusion of the LCA. Dual-tracer autoradiography was performed to assess ^99mTc-AV uptake and the area at risk (AAR) by ²⁰¹Tl defect. ^99mTc-AV uptake ratio was calculated by dividing the count density of the AAR by that of the normally perfused area. In short-axis LV slices, LV cavity dilation index (DI) was calculated by dividing the area of LV cavity by that of the whole LV area. LV wall-thinning ratio (WTR) was calculated by dividing the LV wall thickness in the AAR by that of the normally perfused area.

Results

Significant ^99mTc-AV uptake in the AAR was observed in 10 rats. DI was significantly higher in rats with positive ^99mTc-AV uptake than in rats without uptake. WTR was smaller in rats with positive ^99mTc-AV uptake than in rats without uptake.

Conclusions

The data suggest ^99mTc-AV uptake in injured myocardium might correlate with LVR at 2 weeks after myocardial ischemia and reperfusion.

Synthesis and evaluation of a new vesamicol analog o-[(11)C]methyl-trans-decalinvesamicol as a PET ligand for the vesicular acetylcholine transporter

INTRODUCTION

We focused on the vesicle acetyl choline transporter (VAChT) as target for early diagnosis of Alzheimer's diseases because the dysfunction of the cholinergic nervous system is closely associated with the symptoms of AD, such as problem in recognition, memory, and learning. Due to its low binding affinity for the sigma receptors (σ-1 and σ-2), o-methyl-trans-decalinvesamicol (OMDV) demonstrated a high binding affinity and selectivity for vesicular acetyl choline transporter (VAChT). [(11)C]OMDV was prepared and investigated the potential as a new PET ligand for VAChT imaging through in vivo evaluation.

METHOD

[(11)C]OMDV was prepared by a palladium-promoted cross-coupling reaction using [(11)C]methyl iodide, with a radiochemical yield of 60-75%, a radiochemical purity of greater than 98%, and a specific activity of 5-10 TBq/mmol 30 min after EOB. In vivo biodistribution study of [(11)C]OMDV in blood, brain regions and major organs of rats was performed at 2, 10, 30 and 60 min post-injection. In vivo blocking study and PET-CT imaging study were performed to check the binding selectivity of [(11)C]OMDV for VAChT.

RESULTS

In vivo studies demonstrated [(11)C]OMDV passage through the blood-brain barrier (BBB) and accumulation in the rat brain. The regional brain accumulation of [(11)C]OMDV was significantly inhibited by co-administration of vesamicol. In contrast, brain accumulation of [(11)C]OMDV was not significantly altered by co-administration of (+)-pentazocine, a selective σ-1 receptor ligand, or (+)-3-(3-hydroxyphenyl)-N-propylpiperidine [(+)-3-PPP], a σ-1 and σ-2 receptor ligand. PET-CT imaging revealed inhibition of [(11)C]OMDV accumulation in the brain by co-administration of vesamicol.

CONCLUSION

[(11)C]OMDV selectively binds to VAChT with high affinity in the rat brain in vivo, and that [(11)C]OMDV may be utilized in the future as a specific VAChT ligand for PET imaging.

[The Optimal Reconstruction Parameters by Scatter and Attenuation Corrections Using Multi-focus Collimator System in Thallium-201 Myocardial Perfusion SPECT Study]

The aim of this study was to reveal the optimal reconstruction parameters of ordered subset conjugates gradient minimizer (OSCGM) by no correction (NC), attenuation correction (AC), and AC+scatter correction (ACSC) using IQ-single photon emission computed tomography (SPECT) system in thallium-201 myocardial perfusion SPECT. Myocardial phantom acquired two patterns, with or without defect. Myocardial images were performed 5-point scale visual score and quantitative evaluations using contrast, uptake, and uniformity about the subset and update (subset×iteration) of OSCGM and the full width at half maximum (FWHM) of Gaussian filter by three corrections. We decided on optimal reconstruction parameters of OSCGM by three corrections. The number of subsets to create suitable images were 3 or 5 for NC and AC, 2 or 3 for ACSC. The updates to create suitable images were 30 or 40 for NC, 40 or 60 for AC, and 30 for ACSC. Furthermore, the FWHM of Gaussian filters were 9.6 mm or 12 mm for NC and ACSC, 7.2 mm or 9.6 mm for AC. In conclusion, the following optimal reconstruction parameters of OSCGM were decided; NC: subset 5, iteration 8 and FWHM 9.6 mm, AC: subset 5, iteration 8 and FWHM 7.2 mm, ACSC: subset 3, iteration 10 and FWHM 9.6 mm.

Development and validation of a direct-comparison method for cardiac (123)I-metaiodobenzylguanidine washout rates derived from late 3-hour and 4-hour imaging

PURPOSE

The washout rate (WR) has been used in (123)I-metaiodobenzylguanidine (MIBG) imaging to evaluate cardiac sympathetic innervation. However, WR varies depending on the time between the early and late MIBG scans. Late scans are performed at either 3 or 4 hours after injection of MIBG. The aim of this study was to directly compare the WR at 3 hours (WR3h) with the WR at 4 hours (WR4h).

METHODS

We hypothesized that the cardiac count would reduce linearly between the 3-hour and 4-hour scans. A linear regression model for cardiac counts at two time-points was generated. We enrolled a total of 96 patients who underwent planar (123)I-MIBG scintigraphy early (15 min) and during the late phase at both 3 and 4 hours. Patients were randomly divided into two groups: a model-creation group (group 1) and a clinical validation group (group 2). Cardiac counts at 15 minutes (countearly), 3 hours (count3h) and 4 hours (count4h) were measured. Cardiac count4h was mathematically estimated using the linear regression model from countearly and count3h.

RESULTS

In group 1, the actual cardiac count4h/countearly was highly significantly correlated with count3h/countearly (r = 0.979). In group 2, the average estimated count4h was 92.8 ± 31.9, and there was no significant difference between this value and the actual count4h (91.9 ± 31.9). Bland-Altman analysis revealed a small bias of -0.9 with 95 % limits of agreement of -6.2 and +4.3. WR4h calculated using the estimated cardiac count4h was comparable to the actual WR4h (24.3 ± 9.6 % vs. 25.1 ± 9.7 %, p = ns). Bland-Altman analysis and the intraclass correlation coefficient showed that there was excellent agreement between the estimated and actual WR4h.

CONCLUSION

The linear regression model that we used accurately estimated cardiac count4h using countearly and count3h. Moreover, WR4h that was mathematically calculated using the estimated count4h was comparable to the actual WR4h.

Diagnostic Performance of Artificial Neural Network for Detecting Ischemia in Myocardial Perfusion Imaging

BACKGROUND

The purpose of this study was to apply an artificial neural network (ANN) in patients with coronary artery disease (CAD) and to characterize its diagnostic ability compared with conventional visual and quantitative methods in myocardial perfusion imaging (MPI).

METHODS AND RESULTS

A total of 106 patients with CAD were studied with MPI, including multiple vessel disease (49%), history of myocardial infarction (27%) and coronary intervention (30%). The ANN detected abnormal areas with a probability of stress defect and ischemia. The consensus diagnosis based on expert interpretation and coronary stenosis was used as the gold standard. The left ventricular ANN value was higher in the stress-defect group than in the no-defect group (0.92±0.11 vs. 0.25±0.32, P<0.0001) and higher in the ischemia group than in the no-ischemia group (0.70±0.40 vs. 0.004±0.032, P<0.0001). Receiver-operating characteristics curve analysis showed comparable diagnostic accuracy between ANN and the scoring methods (0.971 vs. 0.980 for stress defect, and 0.882 vs. 0.937 for ischemia, both P=NS). The relationship between the ANN and defect scores was non-linear, with the ANN rapidly increased in ranges of summed stress score of 2-7 and summed defect score of 2-4.

CONCLUSIONS

Although the diagnostic ability of ANN was similar to that of conventional scoring methods, the ANN could provide a different viewpoint for judging abnormality, and thus is a promising method for evaluating abnormality in MPI.

Effect of postconditioning on dynamic expression of tenascin-C and left ventricular remodeling after myocardial ischemia and reperfusion

Background

Tenascin-C (TNC), an extracellular matrix glycoprotein, is expressed transiently in distinct areas in association with active tissue remodeling. This study aimed to explore how ischemic postconditioning (PC) affects myocardial expression of TNC and ventricular remodeling using ¹²⁵I-labeled anti-TNC antibody (¹²⁵I-TNC-Ab) in a rat model of ischemia and reperfusion.

Methods

In control rats (n = 27), the left coronary artery (LCA) was occluded for 30 min followed by reperfusion for 1, 3, 7, and 14 days. PC (n = 27) was performed just after the reperfusion. At the time of the study, ¹²⁵I-TNC-Ab (1.0 to 2.5 MBq) was injected. Six to 9 h later, to verify the area at risk, ^99mTc-MIBI (100 to 200 MBq) was injected intravenously just after the LCA reocclusion, with the rats sacrificed 1 min later. Dual tracer autoradiography was performed to assess ¹²⁵I-TNC-Ab uptake and area at risk. To examine the ventricular remodeling, echocardiography was performed 2 M after reperfusion in both groups.

Results

In control rats, ¹²⁵I-TNC-Ab uptake ratio at 1 day after reperfusion was 3.73 ± 0.71 and increased at 3 days (4.65 ± 0.87), followed by a significant reduction at 7 days (2.91 ± 0.55, P < 0.005 vs 3 days) and14 days (2.01 ± 0.17, P < 0.005 vs 1 and 3 days). PC attenuated the ¹²⁵I-TNC-Ab uptake throughout the reperfusion time from 1 to 14 days; 2.59 ± 0.59 at 1 day, P < 0.05: 3.10 ± 0.42 at 3 days, P < 0.005: 1.93 ± 0.37 at 7 days, P < 0.05: 1.40 ± 0.07 at 14 days, P < 0.001. In echocardiography, PC reduced the ventricular end-diastolic and systolic dimensions (1.00 ± 0.06 cm to 0.83 ± 0.14 cm (P < 0.05) and 0.90 ± 0.15 cm to 0.62 ± 0.19 cm (P < 0.05), respectively) and prevented a decline of ventricular percentage fractional shortening (10.5 ± 3.7 to 28.2 ± 10.7, P < 0.005).

Conclusions

These data indicate that ¹²⁵I-TNC-Ab imaging may be a way to monitor myocardial injury, the subsequent repair process, and its response to novel therapeutic interventions like PC by visualizing TNC expression.

Nuclear myocardial perfusion imaging using thallium-201 with a novel multifocal collimator SPECT/CT: IQ-SPECT versus conventional protocols in normal subjects

OBJECTIVE

A novel multifocal collimator, IQ-SPECT (Siemens) consists of SMARTZOOM, cardio-centric and 3D iterative SPECT reconstruction and makes it possible to perform MPI scans in a short time. The aims are to delineate the normal uptake in thallium-201 ((201)Tl) SPECT in each acquisition method and to compare the distribution between new and conventional protocol, especially in patients with normal imaging.

METHODS

Forty patients (eight women, mean age of 75 years) who underwent myocardial perfusion imaging were included in the study. All patients underwent one-day protocol perfusion scan after an adenosine-stress test and at rest after administering (201)Tl and showed normal results. Acquisition was performed on a Symbia T6 equipped with a conventional dual-headed gamma camera system (Siemens ECAM) and with a multifocal SMARTZOOM collimator. Imaging was performed with a conventional system followed by IQ-SPECT/computed tomography (CT). Reconstruction was performed with or without X-ray CT-derived attenuation correction (AC). Two nuclear physicians blinded to clinical information interpreted all myocardial perfusion images. A semi-quantitative myocardial perfusion was analyzed by a 17-segment model with a 5-point visual scoring. The uptake of each segment was measured and left ventricular functions were analyzed by QPS software.

RESULTS

IQ-SPECT provided good or excellent image quality. The quality of IQ-SPECT images without AC was similar to those of conventional LEHR study. Mid-inferior defect score (0.3 ± 0.5) in the conventional LEHR study was increased significantly in IQ-SPECT with AC (0 ± 0). IQ-SPECT with AC improved the mid-inferior decreased perfusion shown in conventional images. The apical tracer count in IQ-SPECT with AC was decreased compared to that in LEHR (0.1 ± 0.3 vs. 0.5 ± 0.7, p < 0.05). The left ventricular ejection fraction from IQ-SPECT was significantly higher than that from the LEHR collimator (p = 0.0009).

CONCLUSION

The images of IQ-SPECT acquired in a short time are equivalent to that of conventional LEHR. The results indicated that the IQ-SPECT system with AC is capable of correcting inferior artifacts with high image quality.

Draft guidelines regarding appropriate use of (131)I-MIBG radiotherapy for neuroendocrine tumors : Guideline Drafting Committee for Radiotherapy with (131)I-MIBG, Committee for Nuclear Oncology and Immunology, The Japanese Society of Nuclear Medicine

Since the 1980s when clinical therapeutic trials were initiated, (131)I-MIBG radiotherapy has been used in foreign countries for unresectable neuroendocrine tumors including malignant pheochromocytomas and neuroblastomas. In Japan, (131)I-MIBG radiotherapy has not been approved by the Ministry of Health, Labour and Welfare; however, personally imported (131)I-MIBG is now available for therapeutic purposes in a limited number of institutions. These updated draft guidelines aim to provide useful information concerning (131)I-MIBG radiotherapy, to help prevent side effects and protect physicians, nurses, other health care professionals, patients and their families from radiation exposure. The committee has also provided appendices on topics such as practical guidance for attending physicians, patient management, and referring physicians.