Observer variation study of the assessment and diagnosis of incidental colonic FDG uptake.

PURPOSE: The aim of this study was to evaluate the interpretations of incidental colonic 18F-FDG uptake made by 10 experienced readers and to more clearly identify the pattern of suspicious colonic FDG uptake. The potential contributions of delayed FDG-PET scanning and of immune fecal occult blood testing (FOBT) in making a diagnosis were also analyzed. MATERIALS AND METHODS: Visual interpretations by 10 readers were made for 147 FDG uptake sites from 126 PET scans (cancer, 38 sites; adenoma, 43 sites; and no abnormality, 66 sites) with colonic FDG uptake. Assessments for the early FDG-PET images were (1) FDG uptake pattern, (2) FDG uptake degree, and (3) likelihood of malignancy. For the delayed images, the assessments were (1) change in the FDG uptake position, (2) change in FDG uptake degree, and (3) likelihood of malignancy. The results of FOBT were analyzed independently of the visual interpretations. RESULTS: Interobserver agreement (κ) was 0.501 for assessing FDG uptake patterns, while agreement on assessing changes in uptake degree and changes in uptake position between early and delayed imaging were low (κ = 0.213-0.229). Logistic regression analysis indicated that 'FDG uptake patterns' and 'FDG uptake degree' were significantly related to decide on the suspicion of malignancy (p < 0.001) and the final result (p < 0.001). "Small localized" and "large irregular localized" types had a high probability of a lesion regardless of either (1) FDG uptake degree or (2) variation in the uptake between the early and the delayed image. The delayed image decreased false-positive cases for some FDG uptake patterns, but it had little impact on distinguishing clearly between "cancer or adenoma" and "normal". The addition of FOBT had little impact on the diagnosis. CONCLUSION: There was highest agreement among readers with respect to the recognition of specified colonic FDG uptake patterns, and this pattern recognition had the most influence on the diagnosis. "Small localized" and "large irregular localized" types had a high probability of a lesion. The addition of delayed imaging and of FOBT results to the early imaging did not have much impact on the diagnosis.

[Assessment of diagnostic criteria for FDG-PET cancer screening program according to the interpretation of FDG-PET and combined examination].

OBJECTIVE: The aim of this study is to establish the diagnostic criteria for FDG-PET cancer screening program of four kinds of organ (breast, thyroid, lung and colon/rectum) according to the interpretation of FDG-PET cancer screening program of the case with proved clinical outcome. METHODS: Among FDG-PET cancer screening examinations performed in two PET centers during 2003 to 2006, two hundreds of examinations with proved clinical outcome were evaluated. Interpretation of breast ultrasonography, thyroid ultrasonography, chest CT and fecal occult blood testing, which were regarded as combined examinations, were performed together with the interpretation of FDG-PET images. RESULTS: As a result of the interpretation, localized FDG accumulating site in all four organs should be recommended for further inspections. In addition, essential point for diagnosis was considered as follows; (1) check over the slight localized FDG accumulation with screening of breast region, (2) combine chest CT with FDG-PET for the evaluation of lung region and (3) check up the shift of FDG accumulation between early and delayed phase with screening of colon/rectum region. CONCLUSIONS: According to the interpretation results of this study, we establish diagnostic criteria of FDG-PET and combined examination of four kinds of organ.

[The development of new method for the assessment of perfusion reserve using split dose iodine-123-IMP SPECT: one-day protocol by modified ARG method].

Evaluation of the regional cerebrovascular reactivity (rCVR) to a cerebral vasodilatory stimulus is important in the investigation of patients with ischemic cerebrovascular disease. We devised a simplified one-day protocol technique using [123I]N-isopropyl-p-iodoamphetamine (IMP) autoradiography (ARG) with SPECT. To validate the accuracy of IMP-ARG for quantifying rCVR to acetazolamide, we compared rCVR measured using IMP-ARG with rCVR calculated using IMP split dose method of microsphere model. Twenty patients with chronic steno-occlusive disease in a unilateral major cerebral artery underwent 123I-SPECT. On rCBF SPECT image above 3.5 cm from OM line, large cortical regions of interest (ROI) was bilaterally determined for bilateral middle cerebral artery and anterior cerebral artery. Based on rCBF values in each ROI, rCVR to acetazolamide was calculated. Significant correlation was observed between rCVR values obtained using IMP-ARG and microsphere model IMP methods in the 80 ROIs examined in the 20 patients (r = 0.72; p < 0.001). The result demonstrated that [123I]IMP-ARG split dose method can quantify rCVR non-invasively in a short time.