ObjectiveRecent many studies have shown that whole body “diffusion-weighted imaging with background body signal suppression” (DWIBS) seems a beneficial tool having higher tumor detection sensitivity without ionizing radiation exposure for pediatric tumors. In this study, we evaluated the diagnostic performance of whole body DWIBS and 18F-FDG PET/CT for detecting lymph node and bone metastases in pediatric patients with neuroblastoma.MethodsSubjects in this retrospective study comprised 13 consecutive pediatric patients with neuroblastoma (7 males, 6 females; mean age, 2.9 ± 2.0 years old) who underwent both 18F-FDG PET/CT and whole-body DWIBS. All patients were diagnosed as neuroblastoma on the basis of pathological findings. Eight regions of lymph nodes and 17 segments of skeletons in all patients were evaluated. The images of 123I-MIBG scintigraphy/SPECT-CT, bone scintigraphy/SPECT, and CT were used to confirm the presence of lymph node and bone metastases. Two radiologists trained in nuclear medicine evaluated independently the uptake of lesions in 18F-FDG PET/CT and the signal-intensity of lesions in whole-body DWIBS visually. Interobserver difference was overcome through discussion to reach a consensus. The sensitivities, specificities, and overall accuracies of 18F-FDG PET/CT and whole-body DWIBS were compared using McNemer’s test. Positive predictive values (PPVs) and negative predictive values (NPVs) of both modalities were compared using Fisher’s exact test.ResultsThe total numbers of lymph node regions and bone segments which were confirmed to have metastasis in the total 13 patients were 19 and 75, respectively. The sensitivity, specificity, overall accuracy, PPV, and NPV of 18F-FDG PET/CT for detecting lymph node metastasis from pediatric neuroblastoma were 100, 98.7, 98.9, 95.0, and 100%, respectively, and those for detecting bone metastasis were 90.7, 73.1, 80.3, 70.1, and 91.9%, respectively. In contrast, the sensitivity, specificity, overall accuracy, PPV, and NPV of whole-body DWIBS for detecting bone metastasis from pediatric neuroblastoma were 94.7, 24.0, 53.0, 46.4 and 86.7%, respectively, whereas those for detecting lymph node metastasis were 94.7, 85.3, 87.2, 62.1, and 98.5%, respectively. The low specificity, overall accuracy, and PPV of whole-body DWIBS for detecting bone metastasis were due to a high incidence of false-positive findings (82/108, 75.9%). The specificity, overall accuracy, and PPV of whole-body DWIBS for detecting lymph node metastasis were also significantly lower than those of 18F-FDG PET/CT for detecting lymph node metastasis, although the difference between these 2 modalities was less than that for detecting bone metastasis.ConclusionThe specificity, overall accuracy, and PPV of whole-body DWIBS are significantly lower than those of 18F-FDG PET/CT because of a high incidence of false-positive findings particularly for detecting bone metastasis, whereas whole-body DWIBS shows a similar level of sensitivities for detecting lymph node and bone metastases to those of 18F-FD...

Objective: We compared the efficacies of Methods:We examined 11 patients (8 females and 3 males; mean age 6 standard deviation, 61.9 6 8.7 years) with DTC who had been suspected of having bone metastases after total thyroidectomy and were hospitalized to be given 131 I therapy. Bone metastases were verified either when positive findings were obtained on both 131 I scintigraphy and CT or when MRI findings were positive if MRI was performed. Results: Metastases were confirmed in 24 (13.6%) of 176 bone segments in 9 (81.8%) of the 11 patients. The sensitivities of Differentiated thyroid carcinoma (DTC) shows a relatively good prognosis compared with carcinomas of other organs, and the 10-year survival rate of DTC is .80% because of treatments such as total thyroidectomy and ablation of remnants with radioiodine.1 However, metastases of DTC develop in 7-23% of patients; the distant metastases occur commonly in the lungs, bones and brain, and the bones are the second most common site of metastases of DTC.2 Bone scintigraphy using 99m Tc-labelled phosphate compounds [ 99m Tc-methylene diphosphonate ( 99m Tc-MDP) or 99m Tchydroxymethylene diphosphonate ( 99m Tc-HMDP)] has been widely used for detecting and evaluating bone metastases of various kinds of carcinomas because of its overall high sensitivity and the easy evaluation of the entire skeleton.3 However, there were often false-positive cases in 99m Tc bone scintigraphy, because degenerative or inflammatory foci were often confused with metastatic lesions. The addition of single photon emission CT (SPECT) to planar acquisition of 99m Tc bone scintigraphy has been shown to exhibit a beneficial effect on the detection and evaluation of bone metastases. [4][5][6] Skeletal imaging by 18 F-fludeoxyglucose positron emission tomography ( 18 F-FDG PET)/CT has been shown to be useful in the detection of bone metastases of various carcinomas including DTC. 7 Previously, we compared the efficacies of 18 F-FDG PET and planar 99m Tc bone scintigraphy for the detection of bone metastases in patients with DTC. 8 We found that the specificity and the overall accuracy of 18 F-FDG PET for the detection of bone metastases in patients with DTC were

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Background: Before radioiodine therapy for Graves' disease, the estimated thyroidabsorbed dose is calculated based on various clinical parameters. However, the actual accumulation of iodine in the thyroid during radioiodine therapy is not determined. We validated the feasibility of post-therapeutic image-based thyroid dosimetry through quantitative single-photon emission computed tomography (SPECT) imaging and thyroid biokinetics and expanding the Medical Internal Radiation Dose Committee's (MIRD) voxel dosimetry guidelines. Methods: Forty-three patients with Graves' disease who underwent radioiodine therapy were chosen as subjects for this retrospective analysis. We acquired patients' SPECT images 24 h after oral administration. SPECT images were quantified using system volume sensitivity to calculate time-integrated activity coefficients on a voxel basis. Absorbed dose was obtained by convolving MIRD guideline voxel S values with time-integrated activity coefficients. To determine accuracy, we compared the results obtained using the post-therapeutic image-based absorbed-dose method (D ̅ image,PVC) with absorbed doses calculated using the method described by the European Association of Nuclear Medicine (pre-therapeutic method; D EANM). Results: Using image-based dosimetry as post-therapeutic dosimetry, we visualized the local accumulation and absorbed dose distribution of iodine in the thyroid. Furthermore, we determined a strong correlation (Pearson's correlation coefficient = 0.89) between both dosimetries, using the regression equation: D ̅ image,PVC = 0.94 × D EANM + 1.35. Conclusion: Post-therapeutic image-based doses absorbed in the thyroid resembled those of pre-therapeutic EANM method-based absorbed doses. Additionally, the post-therapeutic image-based method had the advantage of visualizing thyroid iodine distribution, thus determining local dose distributions at the time of treatment. From these points, we propose that post-therapeutic image-based dosimetry could provide an alternative to standard pre-therapeutic dosimetry to evaluate dose response.