Takanori Kikuchi

Alteration of rCBF in Alzheimer's disease patients with delusions of theft

We investigated the neural substrate of the delusion of theft in patients with Alzheimers disease (AD). Nine AD patients with only one type of delusion (delusions of theft) and nine age, cognitive function-matched AD patients without any type of delusions were selected from 334 consecutive outpatients of Ehime University Hospital. All subjects underwent 99mTc-HMPAO SPECT scanning, and SPECT images were analyzed by Statistical Parametric Mapping (SPM). AD patients with delusions of theft showed significant hypoperfusion in the right medial posterior parietal region compared to patients without delusions. Our data suggest that attention impairment or lack of awareness of illness caused by right parietal dysfunction might play a role in producing the delusion of theft.

Heterogeneity of cerebral blood flow in frontotemporal lobar degeneration and Alzheimer’s disease

This study was designed to quantify the heterogeneity on cerebral blood flow single-photon emission tomography (SPET) images in frontotemporal lobar degeneration (FTLD) and Alzheimer’s disease (AD) using a three-dimensional fractal analysis. Twenty-one FTLD patients, 21 AD patients and 11 healthy controls underwent technetium-99m hexamethylpropylene amine oxime SPET scanning. Patients with FTLD and AD matched for sex, age and the severity of dementia as estimated with the Clinical Dementia Rating and were determined to be in the early stage of illness. We delineated the SPET images using a 35% cut-off and a 50% cut-off of the maximal voxel radioactivity and measured the number of voxels included in the contours of two different cut-offs. The fractal dimension (FD) was calculated by relating the logarithms of the cut-offs and the numbers of voxels, and it was defined as the heterogeneity of the cerebral perfusion. We divided the SPET images into two sets, anterior and posterior, with equal numbers of coronal SPET slices. We calculated total FD, anterior FD and posterior FD for total, anterior and posterior SPET images. Anterior FDs for FTLD and AD were 1.55±0.34 and 1.24±0.19 (P=0.0002). The ratios of anterior to posterior FD for FTLD and AD were 1.81±0.41 and 1.32±0.14 (P<0.0001). Use of the anterior FD and the ratio of anterior to posterior FD separated FTLD patients from AD patients and controls with a sensitivity of 85.7% and a specificity of 93.8%. Anterior FD and the ratio of anterior to posterior FD may be useful in distinguishing FTLD from AD.

Ischemic “memory image” in acute myocardial infarctio of123I-BMIPP after reperfusion therapy: A comparison with99mTc-pyrophosphate and201Tl dual-isotope SPECT

Ischemic “memory image” is a phenomenon of123I-15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) in which an area at risk of acute myocardial infarction (AMI), could be detected as a defect in a couple of weeks even after successful reperfusion therapy.The purpose of this study was to clarify the incidence of the ischemic “memory image” of123I-BMIPP in patients with AMI by comparing99mTc-PYP and201Tl dual-isotope SPECT.Materials consisted of 14 patients with successfully reperfused AMI and 20 patients with old myocardial infarction (OMI). All AMI patients underwent PYP/Tl dual-isotope SPECT within 1 week after the onset of AMI, and BMIPP SPECT was performed within 1 week after the PYP/Tl dual-isotope SPECT. The extent and severity of the defect of BMIPP and Tl were visually scored into four grades: 0=no defect to 3=large or severe defect. These scores were compared.PYP positive AMI lesions were concordant with BMIPP defects (13/14). In AMI, both the extent and severity scores of BMIPP were higher than201Tl (p<0.001). Differences (BMIPP-Tl) of extent and severity scores were greater in AMI than in OMI (p<0.001).In conclusion, the ischemic “memory image” obtained by means of the BMIPP is a common phenomenon (13/14) in AMI, and helpful in evaluating the area at risk.

Utility of 99mTc-HM-PAO SPECT hippocampal image to diagnose early stages of Alzheimer's disease using semiquantitative analysis

Objective: Examination of the utility of 99mTc-hexamethylpropylene amine oxide (99mTc-HM-PAO) SPECT hippocampal image to diagnose early stages of Alzheimer’s disease (AD) using semiquantitative analysis. Subjects: 10 early-stage AD patients and 8 normal sex-matched elderly controls. Setting: Outpatient division of the Ehime University Hospital. Method: We performed 99mTc-HM-PAO SPECT perfusion imaging in each subject. A semiquantitative method of assessing regional variation was used. The regions of interest for temporal regions were set at images parallel to the long axis of the hippocampal formation which were reconstructed at 30Results: The regional cerebral blood flow ratio of the bilateral medial temporal lobe at the hippocampal image was significantly lower in the AD subjects than in the normally aged controls without any other differences in ordinary transaxial images. Conclusion: This study suggests that 99mTc-HM-PAO SPECT hippocampal images might be a helpful tool for the diagnosis of very-early-stage AD.

Thallium-201 scintigraphy in bone and soft-tissue tumors: a comparison of dynamic, early and delayed scans

Objective: It has been reported that delayed scan of thallium-201 (201Tl) scintigraphy is useful for differentiating malignant tumors from benign lesions and for evaluating treatment response. However, physiological muscle uptake which usually increases in delayed scans, often makes it difficult to evaluate201T1 uptake and its washout in bone and soft-tissue tumors. The purpose of this study was to evaluate whether the delayed scan is necessary and whether a dynamic scan is useful in the evaluation of bone and soft-tissue tumors.Methods: We studied 175 cases of bone and soft-tissue tumors (malignant 45, benign 130). Dynamic scans were acquired every 5 seconds for 10 minutes after201T1 injection, and time activity curves (TACs) were generated by adaptive smoothing methods. Early and delayed scans were acquired at 10–15 minutes and 2 hours after injection.20lTl images were visually interpreted and the radioactivity count ratio (T/N) of tumors to normal tissues and washout rate [WR = (early T/N - delayed T/N)/early T/N] were denned.Results: When there were no201T1 uptake in dynamic (n = 67) and early scans (n = 68), no tumor uptake was also appreciated in delayed scans, and all but two cases of negative scans were benign. In 107 lesions, although there were significant differences in T/Ns between malignant and benign lesions both on early scans (2.84 ± 1.45 vs. 2.05 ± 1.13, p < 0.05) and delayed scans (2.17 ± 1.03 vs. 1.58 ± 0.64, p < 0.05), there was a substantial overlap. The T/Ns decreased in delayed scans (i.e., WR > 0) in 100 of 107 cases due to increase of surrounding muscle uptake, and there was no difference in WR between malignant tumors and benign lesions (0.21 ± 0.14 vs. 0.19 ± 0.14).Conclusions: For evaluating bone and soft-tissue tumors, delayed scan had little clinical usefulness and it may be time consuming. Dynamic scan would be useful for demonstrating the differences between tumor blood flow and201Tl uptake in tumors.

Two cases of pediatric bone disease (eosinophilic granuloma and Brodie's abscess) showing similar scintigraphic and radiographic findings.

Two 9-year-old patients with femoral bone lesions were referred to the authors’ institution within a few days of each other. Both showed similar radiographic, magnetic resonance imaging, and scintigraphic findings. The radiographs showed osteolytic lesions in the right femoral diaphyses, and gadolinium-DTPA–enhanced magnetic resonance imaging revealed inhomogeneous enhancement. Tc-99m HMDP showed marked linear accumulation with relatively low central uptake in the right femoral shafts, and Tl-201 scintigraphy showed considerable uptake corresponding to the area seen with Tc-99m HMDP. Histologic analysis confirmed eosinophilic granuloma in the first patient and Brodie’s abscess in the second. The radiographic and scintigraphic findings in Brodie’s abscess may be similar to those in eosinophilic granuloma.

Tc-99m PMT hepatobiliary scintigraphy in the differential diagnosis of extrahepatic metastases and hepatocellular carcinoma.

Purpose The authors evaluated the utility of hepatobiliary scintigraphy for tissue characterization of extrahepatic metastases from hepatocellular carcinoma (HCC) using Tc-99m N-pyrydoxyl-5-methyltriptophane (Tc-99m PMT). Methods We examined 13 patients with HCC (29 extrahepatic metastases and 3 benign bone lesions) and 5 patients with other cancers (15 extrahepatic metastases). Thirty minutes to 6 hours after intravenous administration of Tc-99m PMT, planar (all 47 lesions) and SPECT (42 lesions) images were obtained. Accumulation of Tc-99m PMT in the lesion was evaluated visually by comparing bone scintigraphy, computed tomography, magnetic resonance imaging, or all of these. Results Findings were positive in 12 of 13 patients with HCC and extrahepatic metastases (16 of 29 on planar imaging and 21 of 26 on SPECT). Findings in all three benign bone lesions and 15 metastatic lesions from non-HCC primary lesions were negative (0 of 18 on planar imaging, 0 of 16 on SPECT). There were no false-positive findings in these lesions. Lesion-by-lesion sensitivity, specificity, accuracy, and positive and negative predictive values were 55%, 100%, 72%, 100%, and 58% by planar imaging and 81%, 100%, 88%, 100%, and 76% by SPECT, respectively. Conclusions Because of the high specificity and reasonable sensitivity, Tc-99m PMT appears to be useful for the differential diagnosis of extrahepatic metastases from HCC. SPECT improves the detectability of small or faint accumulation in metastases from HCC.

Kinetic parameter estimation from compartment models using a genetic algorithm.

Kinetic parameters were estimated from a three-compartment fluorodeoxyglucose model with three rate constants using a genetic algorithm. The performance of the genetic algorithm was investigated by simulation studies, in which brain time-activity data (TAD) were generated using cited mean values of rate constants and the plasma TAD obtained from positron emission tomographic studies. The accuracy of kinetic parameter estimation using the genetic algorithm was compared with that using the non-linear least-squares (NLSQ) method. The margin of error in the parameters estimated using the genetic algorithm tended to be smaller than that obtained by the NLSQ method. Although not statistically significant at a noise level of 5% in the brain TAD, the difference between the two methods became significant for all parameters at a noise level of 15% or higher. Our results suggest that the genetic algorithm is a promising means of estimating kinetic parameters from compartment models, because it is more robust against statistical noise than the NLSQ method and it can be rendered highly parallel for processing.

Accumulation of Tc-99m HMDP in ovarian serous papillary adenocarcinoma reflecting ongoing calcification.

In a 64-year-old woman who had ovarian serous papillary adenocarcinoma, Tc-99m HMDP bone scintigraphy showed avid accumulation in the primary tumor and its peritoneal metastases. Histologic analysis revealed psammoma bodies within the papillary growth of tumor cells. Serial computed tomographic (CT) scans showed ongoing dense calcifications corresponding to the uptake revealed by bone scintigraphy.

Twenty-four-hour Tl-201 delayed scan underestimates myocardial viability in patients with acute myocardial infarction after percutaneous transluminal coronary angioplasty.

BackgroundMyocardial viability in area at risk of acute myocardial infarction (AMI) after reperfusion therapy may be underestimated by the 24-hour images due to reverse redistribution (r-RD).MethodsSubjects were 37 AMI patients in whom Tc-99m pyrophosphate (PYP)/Tl-201 dualisotope SPECT was positive. The 24-hour delayed scan was performed with only a Tl window. One month later, follow up rest Tl SPECT was performed to evaluate myocardial viability. In early (at PYP/Tl-201 dual-isotope SPECT), 24-hour, and one month follow up Tl studies, Tl uptake in the area of AMI was scored into four grades: 3 as normal to 0 as severely reduced. The scores were evaluated.ResultsAmong the 37 AMI lesions, there were 16 r-RD, 3 RD, 16 fixed defect (FD) and 2 normal (positive PYP and normal Tl). Mean Tl scores were early; 1.4±1.1, 24-hr; 0.9±0.9 and one month; 1.3±1.1. The 24-hour Tl score was lower than the early and one month Tl scores (p<0.01).ConclusionReverse redistribution is frequently observed in an area at risk where PYP SPECT was positive. Nuclear medicine physicians should be aware of the existence of frequent r-RD in Tl scan to avoid the underestimation of myocardial viability in the acute phase after PTCA.