Examination of Some Factors Affected Right-to-left Shunt Rate and the Normal Value of Right-to-left Shunt Rate in Lung Perfusion Scintigraphy.

PURPOSE: Diagnosis for right-to-left shunt was determined by the assessment of shunt-rate, which was obtained by using 99 mTc-macroaggregated albumin. However, it is difficult to diagnose right-to-left shunt, using the normal level of shunt-rate measured by using conventional methods. To solve this problem, we investigated ourselves the normal level of shunt-rate. METHOD: We researched 20 patients with pulmonary embolism, and they didn't have right-to-left shunt. We investigated three points for the normal level of shunt-rate. First, we examined the region of interest (ROI) area of the lungs to modify the upper level of gray scale. Second, we confirmed the difference between the whole visual field and body contour of the ROI area. Third, we examined the necessity whether we correct the background of whole body and the lungs. RESULT: We resulted three points. First, stable right-to-left shunt rate is got to set that the upper level of gray scale is 35%. Second, there is no significant difference between the whole visual field and body contour of the ROI area. Third, correcting background isn't needed to get right-to-left shunt rate. The normal level of the shunt-rate was 12.6±2.8% in the condition. CONCLUSION: We are able to decide the optimal condition for the normal level of shunt-rate. It is important to evaluate the normal level of the shunt-rate fixed on each factor in each hospital.

[Influence of Reconstruction FOV and Matrix Size on the Quantitative Accuracy of FDG-PET: Comparison between OSEM and Bayesian Penalized Likelihood].

PURPOSE: Field of view (FOV) and matrix size determine the pixel size of positron emission tomography (PET) images; however, the effect of any variation in these parameters on the quantitative accuracy is unclear. The FOV and matrix size of PET images are adjusted as per each clinical objective. Therefore, this study aimed to evaluate the quantitative accuracy of PET images under different FOV and matrix sizes. METHOD: A National Electrical Manufacturers Association (NEMA) body phantom set was filled with 18F-FDG solution, and imaging data were acquired for 30 min. Images were reconstructed using ordered subset expectation maximization (OSEM) and Bayesian penalized likelihood (BPL), both of which were combined with point spread function (PSF) and time of flight (TOF). In each reconstruction method, the image parameters were set to the following: FOV, 20-70 cm; matrix size, 128×128 to 384×384; and pixel size, 1-3 mm. The images were evaluated by physical assessment of the recovery coefficient (RC) and maximum standardized uptake value ratio (SUVmax ratio). RESULT: The RC of OSEM images was not affected by changes in FOV, whereas the RC of BPL images decreased in small spheres, when FOV was 20 and 30 cm. The SUVmax ratio of the OSEM images was not affected by the difference in pixel size. However, the SUVmax ratio of BPL images degraded in the 1-mm pixel size; this influence was observed only when the FOV was changed. Conclusion: BPL images reconstructed using a small FOV might degrade the quantitative accuracy of small spheres.

FDG PET for the assessment of myometrial infiltration in clinical stage I uterine corpus cancer.

OBJECTIVE: For surgical planning of uterine corpus cancer, prior knowledge of the depth of myometrial invasion is important. Curative tumour resection is possible in superficial invasion (stages IA and IB), while post-surgical chemotherapy or radiation therapy is required in deep invasion (stage IC). We evaluated the value of positron emission tomography with 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG PET) for estimating the myometrial invasion in uterine corpus cancer. METHODS: We studied 22 patients with clinical stage I uterine corpus cancer, who underwent FDG PET prior to surgery. Standardized uptake value (SUV; tracer activity per injected dose normalized to body weight) was calculated on the PET image. PET findings were compared with magnetic resonance imaging (MRI) and the surgical staging. RESULTS: The surgical stage was IA in five, IB in 11 and IC in six patients. SUVs in deep invasion (15.69+/-4.73, 8.83-21.84) were significantly higher than those in superficial invasion (9.09+/-3.29, 2.68-15.41) (P<0.005). Using 12.0 as a cut-off value of SUV for the differentiation of these two groups, PET results were correct in 19 patients but were incorrect in three patients. Although both PET and MRI provided correct staging in 14 patients, only MRI overestimated the myometrial invasion in four patients with stage IB and showed inconclusive findings in one patient with stage IC. Four of these five patients were post-menopausal. CONCLUSIONS: The cut-off value of SUV (=12.0) may be a useful index for the differentiation of superficial invasion and deep invasion. FDG PET may be feasible for predicting the myometrial infiltration of uterine corpus cancer, especially when uterine atrophy makes it difficult at MRI in post-menopausal patients.

[Measurement of radiation exposure to a PET institution driver from patients injected with FDG].

With the recent increase in FDG-PET examinations, concern has mounted regarding radiation exposure to hospital staff and the general public from patients injected with FDG. Because our PET institution is located 15 km from the hospital that provides these examinations, a driver has been designated to transport patients injected with FDG. This study was designed to measure the radiation dose to the driver from these patients (n=28) and to compare it with the estimated dose. A pocket dosimeter was used to measure radiation exposure to the driver. When the distances between the driver and patient were 1.1 m and 1.9 m, mean measured doses were 7.31 microSv and 2.26 microSv, respectively, while mean estimated doses were 8.61 microSv and 2.82 microSv, respectively, per trip. It was presumed that maximum radiation exposure per year was between 3.02 mSv (1.1 m) and 0.92 mSv (1.9 m). According to our data, the measured dose was 20% lower than the estimated dose. This discrepancy may be due to the difference between the volume source (measured dose) and point source (estimated dose).

[Physical property of emission data in simultaneous emission/transmission acquisition: evaluation for clinical application].

PURPOSE: Although simultaneous emission transmission acquisition (SET) is the ideal method for positron emission tomography (PET) because the same patient position can be used for both emission and transmission scans, the quality of PET images is subject to interference by the cross-contamination of each data. In recent years, segmented attenuation correction of transmission data has made it possible to exclude the contamination from emission data. In the present study using a phantom, the physical property of emission data in SET acquisition was evaluated in comparison with that in separate scan. METHODS: We measured scatter fraction, scatter projection, % random, and noise equivalent count rate in the sinogram. Next, we determined the acquisition time of the SET scan to obtain the same coefficient of variation as the separate scan in reconstructed images. RESULTS: In the evaluation of the strength of the line source, the physical property of emission data in the SET scan seemed inferior to that in separate scan, and SET scanning was not effective enough to reduce the acquisition time of PET examinations. CONCLUSION: SET scanning has the advantage that the same patient position can be used for emission and transmission data; however, further studies may be necessary to apply it to clinical examinations.

Imaging of gynecologic tumors: comparison of (11)C-choline PET with (18)F-FDG PET.

UNLABELLED: This study was designed to compare the value of PET using (11)C-choline with that of PET using (18)F-FDG for the diagnosis of gynecologic tumors. METHODS: We examined 21 patients, including 18 patients with untreated primary tumors and 3 patients with suspected recurrence of ovarian cancer. (11)C-choline PET and (18)F-FDG PET were performed within 2 wk of each other on each patient. The patients fasted for at least 5 h before the PET examinations, and PET was performed 5 min ((11)C-choline) and 60 min ((18)F-FDG) after injection of each tracer. PET images were corrected for the transmission data, and the reconstructed images were visually analyzed. Then, the standardized uptake value (SUV) was calculated for quantitative assessment of tumor uptake. PET results were compared with surgical histology or >6 mo of clinical observations. RESULTS: Of 18 untreated patients, (11)C-choline PET correctly detected primary tumors in 16 patients, whereas (18)F-FDG PET detected them in 14 patients. In 1 patient with small uterine cervical cancer and 1 diabetic patient with uterine corpus cancer, only (11)C-choline PET was true-positive. Both tracers were false-negative for atypical hyperplasia of the endometrium in 1 patient and were false-positive for pelvic inflammatory disease in 1 patient. For the diagnosis of recurrent ovarian cancer (n = 3), (11)C-choline PET and (18)F-FDG PET were true-positive in 1 patient, whereas neither tracer could detect cystic recurrent tumor and microscopic peritoneal disease in the other 2 patients. In the 15 patients with true-positive results for both tracers, tumor SUVs were significantly higher for (18)F-FDG than for (11)C-choline (9.14 +/- 3.78 vs. 4.61 +/- 1.61, P < 0.0001). In 2 patients with uterine cervical cancer, parailiac lymph node metastases were clearly visible on (18)F-FDG PET but were obscured by physiologic bowel uptake on (11)C-choline PET. CONCLUSION: The use of (11)C-choline PET is feasible for imaging of gynecologic tumors. Unlike (18)F-FDG PET, interpretation of the primary tumor on (11)C-choline PET is not hampered by urinary radioactivity; however, variable background activity in the intestine may interfere with the interpretation.

18F-FDG PET in the detection of extrahepatic metastases from hepatocellular carcinoma.

BACKGROUND: Positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (18F-FDG) is useful in detecting distant metastases from a variety of malignancies. However, its efficiency in detecting distant metastases from hepatocellular carcinoma (HCC) has not been investigated. The aim of this study was to evaluate the usefulness of 18F-FDG PET for the detection of extrahepatic metastases from HCC. METHODS: Nineteen patients suspected of having extrahepatic HCC underwent 18F-FDG PET. Fourteen patients (group A) had extrahepatic lesions, which were detected by conventional studies. In five patients (group B), conventional imaging showed no extra- or intrahepatic lesions, but the tumor marker levels were elevated. The PET results were compared with those obtained by histopathology or by clinical follow-up. RESULTS: The detection rate of 18F-FDG PET was 83% (24 of 29 metastases) for extrahepatic metastases larger than 1 cm in greatest diameter and 13% (1 of 8 metastases) for lesions less than or equal to 1 cm. PET revealed two bone metastases not depicted by bone scan, and detected the nodal metastasis and intestinal metastases inconclusive on computed tomography. Extrahepatic lesions were resected in 5 patients of group A on the basis of PET findings. In all patients of group B, PET results were true negative for extrahepatic metastases, but HCCs were detected in the liver within 4 months in 4 patients. These were no false-positive lesions in either group. CONCLUSIONS: This preliminary study suggested that 18F-FDG PET could provide additional information and contribute to the management of HCC patients suspected of having extrahepatic metastases.

Suggestion of one-hand type power-assisted wheelchair and driving control for persons with hemiplegia.

Elderly people and disabled people use the wheelchair as a transportation device. However, the manual wheelchair has a large physical burden in order to use own power, and the activity on the outdoors is difficult. Moreover, the electric wheelchair causes the fall of muscular power by operation with joy stick. We suggest the one-hand type power-assisted wheelchair for persons with hemiplegia. This paper describes the driving control of straight and revolution by one-hand. The simulation was performed about straight and revolution. The result showed the validity of driving control.

Early therapy monitoring with FDG-PET in aggressive non-Hodgkin's lymphoma and Hodgkin's lymphoma.

This study was designed to determine the value of 2-[fluorine-18]-fluoro-2-deoxy- d-glucose positron emission tomography (FDG-PET) in the early assessment of therapy response in lymphoma patients. We studied 20 patients with pathologically proven lymphoma, including 17 patients with aggressive non-Hodgkin's lymphoma and three patients with Hodgkin's lymphoma. All patients underwent whole-body FDG-PET imaging at baseline and after 1-2 cycles of chemotherapy. PET images were analysed visually and quantitatively by calculating the standardised uptake value (SUV). In each patient, we measured the SUV of the tumour demonstrating the highest FDG uptake at baseline study and the SUV of the same tumour after 1-2 cycles of therapy. The achievement of complete response was assessed on the basis of a combination of clinical findings and the results of conventional imaging modalities. Follow-up of progression-free survival (PFS) was obtained for the validation of PET data. Of the 20 patients, ten achieved complete remission at the completion of chemotherapy and the other ten did not respond to chemotherapy. Of the ten responders, four are still in remission (PFS 24-34 months) while the other six have relapsed (PFS 8-16 months). For the prediction of 24-month clinical outcome, visual analysis of PET after 1-2 cycles showed high sensitivity (87.5%) and accuracy (80%) but low specificity (50%). Comparison with the baseline SUVs revealed that the responders showed a significantly greater percent reduction in SUV after 1-2 cycles of therapy as compared with the non-responders (81.2%+/-9.5% vs 35.0%+/-20.2%, P<0.001). In addition, using 60% reduction as a cut-off value, the responders were clearly separated from the non-responders, with the exception of one non-responder. In conclusion, when performed early during chemotherapy, FDG-PET may be predictive of clinical outcome and allows differentiation of responders from non-responders in cases of aggressive lymphoma.