真鍋 治

OBJECTIVE: Application of the electrocardiographically (ECG) gated positron emission tomography (PET) technique with (11)C-hydroxyephedrine (HED) would allow the simultaneous assessment of cardiac sympathetic and contractile functions. However, there are uncertainties regarding the diagnostic accuracy of left ventricular (LV) volume measurements using ECG-gated HED-PET. The purpose of this study was to clarify the minimal requirement of count statistics to measure LV volumes with ECG-gated HED-PET and to investigate the reliability of the measurements. METHODS: Five healthy volunteers and 11 patients with heart failure underwent a 40-min list-mode PET scan after an injection of HED (197 ± 35 MBq). The list-mode data were histogrammed into multiple sets of acquisition periods at 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, 12.0 Mcount/bin and reconstructed into corresponding gated images using an iterative algorithm. The LV end-diastolic volume (LVEDV), the LV end-systolic volume (LVESV), and the LV ejection fraction (LVEF) were calculated in each acquisition period. These values were compared with those obtained by cardiac magnetic resonance imaging (MRI). Possible effects of HED retention on the accuracy of the volume measurements were investigated. RESULTS: Collecting less than 4.0 Mcount/bin resulted in noisy cardiac images. The lower counts resulted in underestimation in the volume measurements. Reasonably accurate volume measurements required equal to or greater than 6.0 Mcount/bin. This corresponded to 7.0 ± 1.9 min (range, 4.0-10.3 min) for the acquisition period. Volumetric results using the 6.0 Mcount/bin data highly correlated with cardiac MRI (LVEDV: r = 0.85, p < 0.0001; LVESV: r = 0.89, p < 0.0001; LVEF: r = 0.77, p < 0.01). The HED retention did not affect the volumetric results compared to the MRI volumetry. CONCLUSIONS: The volumetric accuracy with ECG-gated HED-PET was affected by the count statistics rather than the HED retention. LV volume measurements were feasible with 10-min acquisition period for most of the patients. This technique allows the simultaneous assessment of cardiac sympathetic and contractile functions without the need for an additional injection or scanning time, thus reducing overall costs for diagnostic imaging.

OBJECTIVE: It is sometimes difficult to assess I-131 lung uptake at the initial I-131 therapy because of strong artifacts from I-131 uptake in the thyroid bed. The aim of this study was to analyze the lung uptake at the second I-131 therapy for lung metastasis in patients who did not have lung uptake at the initial therapy from differentiated thyroid carcinoma (DTC). Then, we also analyzed the relationship between the initial lung uptake and short-term outcome after I-131 therapies. METHODS: This study included 62 DTC patients with lung metastasis. The patients were classified into 2 groups according to the lung uptake at the initial I-131 therapy such as patients with lung uptake (positive uptake group n = 31) and those without lung uptake (negative uptake group n = 31). The lung uptake was analyzed at the second therapy in both groups. The short-term outcome was also analyzed based on the CT findings of lung metastasis size and serum thyroglobulin level between the two groups. RESULTS: The positive uptake group showed positive lung uptake at the second therapy in 23 patients (74 %), whereas none of negative uptake group showed any lung uptake at the second therapy (P < 0.01). The positive uptake group significantly decreased in the size of lung metastasis from the initial therapy to the second therapy (20.0 ± 11.7 to 16.6 ± 9.6 mm, P < 0.01) with further decrease after the second therapy (P < 0.05). The serum thyroglobulin level was also significantly decreased from the initial therapy to the second therapy (4348 ± 7011 to 2931 ± 4484 ng/ml, P < 0.05). In contrast, the negative uptake group significantly increased in the size of lung metastasis from the initial therapy to the second therapy (17.3 ± 12.2 to 19.9 ± 14.3 mm, P < 0.01) with further increase after the second therapy (P < 0.01). CONCLUSION: No patients without lung uptake at the initial I-131 therapy showed lung uptake at the second therapy, or showed treatment effect. Therefore, second I-131 therapy for these patients with initially negative lung uptake should be considered cautiously.

BACKGROUND: Fractional flow reserve (FFR) measured on catheterization is now widely used for the diagnosis of functional myocardial ischemia in patients with coronary artery disease (CAD). FFR, however, is invasive and carries potential procedural complications. Therefore, the aim of this study was to compare the diagnostic capability in functionally significant stenosis identified on FFR, between cardiac magnetic resonance myocardial perfusion imaging (CMR-MPI), single-photon emission computed tomography MPI (SPECT-MPI), and dobutamine stress echocardiography (DSE) in patients with CAD. METHODS AND RESULTS: A total of 25 patients who had at least 1 angiographic stenosis ≥50% on coronary angiography was studied. CMR-MPI, SPECT-MPI and DSE were done before FFR measurement. FFR was measured in all 3 major epicardial coronary arteries. Out of 71 vascular territories excluding 4 territories due to inadequate imaging, 29 (41%) had FFR <0.80. The sensitivity of CMR-MPI was significantly higher than that of SPECT-MPI and DSE (P=0.02 and P=0.001, respectively). The area under the receiver operating characteristic curve (AUC) for CMR-MPI (AUC, 0.92) was significantly greater than for SPECT-MPI (AUC, 0.73; P=0.006) and DSE (AUC, 0.69; P<0.001). CONCLUSIONS: CMR-MPI performed well in the detection of functionally significant stenosis defined according to FFR, and had the highest diagnostic sensitivity among the 3 modalities tested in patients with CAD.

BACKGROUND: 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)-computed tomography (CT) has been an essential modality in oncology. We propose a semi-automated algorithm to objectively determine liver standardized uptake value (SUV), which is used as a threshold for tumor delineation. METHODS: A large spherical volume of interest (VOI) was placed manually to roughly enclose the right lobe (RL) of the liver. For each voxel in this VOI, a coefficient of variation of voxel values (CVv) was calculated for neighboring voxels within a radius of d/2. The voxel with the minimum CVv was then selected, where a 30-mm spherical VOI was placed at that voxel in accordance with PERCIST criteria. Two nuclear medicine physicians independently defined 30-mm VOIs manually on 124 studies in 62 patients to generate the standard values, against which the results from the new method were compared. RESULTS: The semi-automated method was successful in determining the liver SUV that was consistent between the two physicians in all the studies (d = 80 mm). The liver SUV threshold (mean +3 SD within 30-mm VOI) determined by the new semi-automated method (3.12±0.61) was not statistically different from those determined by the manual method (Physician-1: 3.14±0.58, Physician-2: 3.15±0.58). The semi-automated method produced tumor volumes that were not statistically different from those by experts' manual operation. Furthermore, the volume change in the two sequential studies had no statistical difference between semi-automated and manual methods. CONCLUSIONS: Our semi-automated method could define the liver SUV robustly as the threshold value used for tumor volume measurements according to PERCIST. The method could avoid possible subjective bias of manual liver VOI placement and is thus expected to improve clinical performance of volume-based parameters for prediction of cancer treatment response.

PURPOSE: Cardiac involvement in sarcoidosis is one of the leading causes of death associated with abnormalities of the conduction system. (18)F-FDG PET is useful for detecting inflammatory lesions in cardiac sarcoidosis. However, the relationship between ECG abnormalities and focal (18)F-FDG uptake has not been studied. The aim of this study was to evaluate the relationship between electrocardiogram (ECG) abnormalities and the location of elevated myocardial (18)F-FDG uptake in patients with sarcoidosis. METHODS: Included in the study were 50 patients (56.3 ± 14.9 years old) with histologically proven sarcoidosis with suspected cardiac involvement based on ECG or echocardiography. All patients had fasted for at least 6 h and were given unfractionated heparin (50 IU/kg) intravenously to reduce the physiological (18)F-FDG uptake in the myocardium. The left ventricle (LV) wall was divided into 17 segments by visual analysis. Obvious accumulation in each segment was defined as positive. RESULTS: Of the 50 patients, 33 showed some ECG abnormalities, including atrioventricular (AV) block in 13. Patients with abnormal ECG findings had a higher number of regions with (18)F-FDG uptake than patients without ECG abnormality (3.48 ± 2.73 vs. 1.41 ± 2.09 regions, p = 0.0051). Among ECG abnormalities, the predictor for interventricular septum wall (18)F-FDG involvement was AV block (p = 0.0025). CONCLUSION: Patients with ECG abnormalities showed a higher number of abnormal (18)F-FDG myocardial uptake regions than patients without ECG abnormalities. In particular, focal (18)F-FDG uptake in the interventricular septum in cardiac sarcoidosis was associated with AV block. Therefore, determination of regional (18)F-FDG distribution might contribute to patient management in cardiac sarcoidosis.

PURPOSE: To investigate the specific imaging findings of multidetector row CT (MDCT) and PET/CT with(18)F-FDG in cardiac dominant diffuse large B-cell lymphoma (DLBCL) in comparison with other cardiac tumours. METHODS: Five patients with DLBCL and 12 patients with other cardiac tumours including pericardial tumours were retrospectively reviewed. Among the patients with other cardiac tumours, seven had metastatic tumours, three had benign tumours, and two had other malignant cardiac tumours. The location of the cardiac mass, the encasement of the coronary artery surrounded by the mass, and pericardial effusion were evaluated using MDCT. The disease activity of the cardiac tumour was also evaluated by PET/CT. RESULTS: Four of the five DLBCL patients had primarily right-sided cardiac lesions, which was seen significantly more frequently in DLBCL than in other cardiac tumours (p = 0.028). All cardiac DLBCL lesions were located around the atrioventricular groove and encased the coronary arteries. ECG-gated cardiac MDCT showed that there was no apparent stenosis of the coronary arteries. Large amounts of pericardial effusion were seen in all DLBCL patients. PET/CT revealed significantly higher FDG uptake in DLBCL than in other cardiac malignant tumours, with no overlap (p = 0.0007). CONCLUSION: The combination of a right-sided cardiac mass with a large pericardial effusion and no apparent stenosis of the encased coronary artery revealed by MDCT and a high maximum standard uptake value were the specific findings in cardiac dominant DLBCL.

UNLABELLED: The metabolic activity of the primary tumor is an important variable in (18)F-FDG PET interpretation for presurgical staging, because this activity is likely to affect the possibility of detection of malignant involvement in lymph nodes (LNs). The purpose of this study was to reevaluate the diagnostic accuracy of (18)F-FDG PET/CT for the presurgical staging of esophageal squamous cell carcinoma (SCC) in correlation with the (18)F-FDG avidity of the primary lesions. METHODS: One hundred fifty-six patients (mean age ± SD, 61.4 ± 8.0 y) underwent (18)F-FDG PET/CT before surgical esophagectomy and LN dissection. LN metastasis was identified using the fusion of PET and CT images with increased (18)F-FDG uptake greater than the background activity of the adjacent structures. The results of the patients' (18)F-FDG PET/CT examinations for LN involvement were compared with the histopathologic results to investigate the diagnostic accuracy of (18)F-FDG PET/CT for tumor staging. In addition, we examined the correlation between the diagnostic accuracy of (18)F-FDG PET/CT for LN involvement and the (18)F-FDG avidity of the primary lesions, to investigate the effect of tumor aggressiveness on the diagnosis of LN metastasis. RESULTS: The diagnostic accuracy of (18)F-FDG PET/CT for LN metastasis showed a low sensitivity, ranging from 29.3% to 53.3%, whereas the specificity was higher than 89.8% in regional thoracic nodes and in remote areas of the cervical and abdominal regions. The (18)F-FDG uptake of the primary lesions positively correlated with that of the metastatic LNs in the thoracic field (R = 0.52, P < 0.05). As a result, our receiver-operating-characteristic analyses demonstrated an area under the curve value of 0.73, with the optimal cutoff value at a maximum standardized uptake value of 3.3 in patients with mid to high (18)F-FDG avidity in the primary lesions (maximum standardized uptake value ≥ 5). CONCLUSION: This study showed that the avidity of the primary esophageal SCCs affected the detectability of lymph nodal metastases. If primary lesions of esophageal SCC present with a low (18)F-FDG uptake, PET/CT may have a limited role for initial staging because of low sensitivity to detect lymph node metastases.