Yasuo Kuwabara

High [18F]-fluorodeoxyglucose uptake in abdominal abscesses: a PET study.

We report two cases of abdominal abscess displaying high uptake of [18F]fluorodeoxyglycose (FDG) by positron emission tomography (PET). Abdominal abscesses should be considered in the differential diagnosis of abdominal masses showing high FDG uptake in PET studies.

FDG-PET in infectious lesions: The detection and assessment of lesion activity

The usefulness of FDG-PET in the detection of infectious foci and the assessment of lesion activity was evaluated. The study covered 24 patients with 25 FDG-PET studies, including lesions of bacterial, tuberculous and fungal origins. The FDG uptake was determined by the lesion to muscle ratio (LMR) on the static images. The time activity curves (TACs) were classified into four patterns based on both the existence of an initial peak and a slope thereafter. A high FDG uptake was observed in 23 of 25 lesions (92%). Two lesions, in which no abnormal uptake was noted, included one in the healing stage and the other consisting of a cavity with a thin wall. The acute active lesions showed higher LMRs than the chronic active or healing lesions (mean ± SD: 9.8 ± 3.6, 3.6 ±1.8 and 4.3 ± 1.7, respectively, p < 0.05), and they could be approximately distinguished by an LMR of 6. The patterns of the TACs in acute or chronic active lesions were either an increase without an initial peak or a plateau, while those in the healing lesions demonstrated predominantly an increase with an initial sharp peak. Our results indicated that FDG-PET is clinically useful in the detection of the infection of miscellaneous microorganisms as well as in the assessment of lesion activity.

The usefulness of FDG positron emission tomography for the detection of mediastinal lymph node metastases in patients with non-small cell lung cancer : a comparative study with X-ray computed tomography

We evaluated the usefulness of fluorine-18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) in the detection of mediastinal lymph node metastases in patients with non-small cell lung cancer and then compared the findings with the results of X-ray CT by region based on the histological diagnoses. We examined 29 patients with non-small cell lung cancer. One hundred and thirty-two mediastinal lymph nodes were surgically removed and the histological diagnoses were confirmed. FDG PET images, including 146 mediastinal regions, were visually analysed and the mediastinal lymph nodes were scored as positive when the FDG uptake was higher than that in the other mediastinal structures. On the X-ray CT scans, any mediastinal lymph nodes with a diameter of 10 mm or larger were scored as positive. All three examinations were successfully performed on 71 regions. For FDG PET, we found a sensitivity of 76%, a specificity of 98% and an accuracy of 93%. On the other hand, for X-ray CT a sensitivity of 65%, a specificity of 87% and an accuracy of 82% were observed. A significant difference was observed in respect of both specificity and accuracy (P<0.05). Based on the above findings, FDG PET is suggested to be superior to X-ray CT when used for the detection of mediastinal lymph node metastases in patients with non-small cell lung cancer.

A comparative study of thallium-201 SPET, carbon-11 methionine PET and fluorine-18 fluorodeoxyglucose PET for the differentiation of astrocytic tumours

Abstract. Thallium-201, carbon-11 methionine (MET) and fluorine-18 fluorodeoxyglucose (FDG) have all been used to assess brain tumours. The aim of this study was to determine which of these tracers are of use for evaluating the histological grade and the extent of astrocytoma. 201Tl single-photon emission tomography (SPET), MET positron emission tomography (PET) and FDG PET were all performed in 23 patients (13 men, 10 women) with newly diagnosed astrocytic tumours [seven with astrocytoma (grade II), ten with anaplastic astrocytoma (grade III) and six with glioblastoma (grade IV)]. The 201Tl uptake of the tumours was evaluated by a lesion-to-normal region count ratio. Both MET and FDG uptake of the tumours was evaluated by a semiquantitative analysis using the standardized uptake value. 201Tl uptake was found to increase in rank order with histological grade and was significantly different among the three groups (grade II: 1.51±0.36; grade III: 2.58±1.50; grade IV: 7.65±3.84). MET uptake in grade II (1.49±0.44) was also significantly lower than that in both grade III (3.29±1.44) and grade IV (3.20±0.92). FDG uptake was not significantly different among the three groups (grade II: 2.90±0.45; grade III: 3.86±1.56; grade IV: 3.57±0.83). No significant correlation was observed between 201Tl uptake and either MET uptake or FDG uptake. In most patients, the extent of the increased MET uptake was the largest while that of the increased FDG uptake was the smallest. In patients with positive 201Tl uptake, the extent of the 201Tl uptake was equal to or smaller than that of gadolinium enhancement. For evaluation of histological grade of astrocytic tumours. 201Tl is therefore considered to be useful though the 201Tl uptake in some grade III astrocytomas was not different from that in grade II astrocytomas. MET was found to be highly useful for detecting astrocytomas, for differentiating between benign and malignant astrocytomas, and for evaluating the extent of astrocytomas; however, it was not sufficiently useful permit evaluation of the histological grade. FDG was not found to be useful either for evaluating the histological grade or for differentiating between benign and malignant astrocytomas.

Cerebral blood flow and oxygen metabolism in patients with vascular dementia of the Binswanger type.

We performed clinical and neuroradiologic studies, including positron emission tomography, in five patients with vascular dementia of the Binswanger type. The clinical features of these cases consisted of slowly progressive dementia, together with vascular risk factors such as hypertension and often a history of minor stroke, and characteristic white matter lesions on brain computed tomograms or magnetic resonance images. Digital subtraction angiography of the cervical and intracranial arteries demonstrated no occlusive lesion in any patient. Both cerebral blood flow and the cerebral metabolic rate for oxygen were markedly reduced in the white matter (54-77% of control values), and both were decreased in the parietal (73% of control), frontal (74-80%), and temporal (74-83%) cortices, where no abnormalities were detected by brain computed tomography or magnetic resonance imaging. We conclude that vascular dementia of the Binswanger type may be caused by disconnection between the cerebral cortex and subcortical structures due to ischemic damage in the white matter.

Leukoaraiosis and dementia in hypertensive patients.

Background and Purpose: Although our previous study demonstrated that dementia of the Binswanger type may be a disconnection dementia caused by leukoaraiosis, some hypertensive patients with marked leukoaraiosis do not develop dementia. The goal of the present study is to elucidate the pathophysiology of nondemented hypertensive patients with leukoaraiosis. Methods: We performed clinical and neuroradiological studies, including positron emission tomography, in eight hypertensive patients with leukoaraiosis. Results: Four patients were demented, and two among the other four who were not demented at the first examination developed dementia during the follow-up period. Digital subtraction angiography of the cervical and intracranial arteries demonstrated stenotic lesions in only one patient. Cerebral blood flow and oxygen metabolism in patients with dementia were markedly reduced in the white matter (59–67% of control values). In contrast, cerebral blood flow in the white matter of patients without dementia was reduced less markedly (74% of control), oxygen extraction fraction in the white matter was significantly increased (130% of control), and oxygen metabolism remained at almost-normal levels not only in the white matter but also in the cortical area. Conclusions: Hypertension-caused arteriosclerotic changes of the long penetrating medullary arteries may cause misery perfusion and later ischemic damage in the periventricular white matter. Preserved oxygen metabolism in hypertensive patients with leukoaraiosis may represent the early stage of vascular dementia of the Binswanger type.

A Multicenter Validation of Regional Cerebral Blood Flow Quantitation Using [123I]Iodoamphetamine and Single Photon Emission Computed Tomography

Recently, two methods have been proposed for regional cerebral blood flow (rCBF) quantitation using [123I]iodoamphetamine (IMP) and single-photon emission computed tomography (SPECT). The table look-up (TLU) method has been shown to provide both rCBF and volume of distribution, Vd, images from two SPECT scans, while a single-scan autoradiographic (ARG) technique provided rCBF using a fixed and assumed Vd. In both methods, a single blood sample was referred to calibrate the previously determined standard input function The present multicenter project was designed to evaluate the accuracy of both methods for use as clinical investigative tools. Ten independent institutions performed [123I]IMP-SPECT studies according to both methods in 76 subjects (10 normal volunteers, 32 patients with cerebrovascular disease, and 34 patients with other diseases). Calculated rCBF values were compared with those obtained by the following reference methods available in the participating institutions; [15O] H2O positron emission tomography (PET) (five institutions), [133Xe]SPECT (four institutions), and the [123I]IMP microsphere method (three institutions). Both ARG and TLU methods provided rCBF values that were significantly correlated with those measured by the [15O] H2O PET technique (p < 0.001 for all subjects; overall regression equation, y = 15.14 + 0.54×) and those measured by the [123I]IMP-microsphere method (p < 0.001 for all subjects; y = 2.0 + 0.80×). Significant correlation (p < 0.05) was observed in 18 of 24 subjects studied with the [133Xe] SPECT reference technique (overall regression equation, y = 15.0 + 0.55×). Mean cortical gray matter rCBF in a group of normal subject was 43.9 ± 3.3 and 43.4 ± 2.0 ml/min/100 g for the ARG and TLU methods, respectively. Regional Vd of [123I]IMP estimated by the TLU method was 45 ml/ml ± 20% in the normal cortical region. Close agreement between ARG and TLU rCBF values was observed (y = −3.21 + 1.07×, r = 0.97), confirming the validity of assuming a fixed Vd in the ARG method. Results of this study demonstrate that both the ARG and TLU methods accurately and reliably estimate rCBF in a variety of clinical settings.

Clinical impact of whole body FDG-PET on the staging and therapeutic decision making for malignant lymphoma

Objectives: The aim of this study is to evaluate the clinical impact of whole-body FDG-PET for the pre-therapeutic evaluation of malignant lymphoma and compared to that of 67Ga-scintigraphy when added to non-RI examinations. Methods: We examined 46 patients with malignant lymphoma including 42 newly diagnosed cases and 4 relapsed cases. Whole-body FDG-PET was started 63 minutes after the administration of FDG with ECATEXACT HR+. The clinical stage of each patient was determined based on the results of a non-RI examination (consisting of physical examination, CT, gastrointestinal studies and bone marrow aspiration), 67Ga planar images and FDG-PET. Discrepant findings were verified based on the response to treatment and the findings of a follow-up examination more than 6 months after treatment. Finally, 152 nodal regions and 19 extranodal tissues were found to be involved by disease. Results: In the 152 nodal lesions, FDG-PET detected 54 nodal lesions in addition to 98 lesions detected by non-RI examinations, whereas 67Ga-scintigraphy detected 14 additional lesions. The sensitivity of non-RI, non-RI+67Ga and non-RI+FDG was 64.5%, 73.7% and 100.0%, respectively. In 19 extranodal lesions, FDG-PET detected 5 extranodal lesions in addition to 13 lesions detected by non-RI examinations, whereas 67Ga-scintigraphy detected 1 additional lesion. The sensitivity of non-RI, non-RI+67Ga and non-RI+FDG was 68.4%, 73.7% and 94.7%, respectively. When combining the FDG-PET findings with the non-RI findings, the improvement of the detectability was much higher than that when 67Ga findings were combined to the non-RI findings. For the staging of lymphoma, the non-RI and non-RI+67Ga findings accurately diagnosed 76.1% and 80.4%, respectively, whereas the non-RI+FDG findings accurately diagnosed 82.6%. Finally, FDG-PET resulted in changes in the clinical management of 8 patients (17.4%). Conclusions: FDG-PET offers more information in addition to the findings of conventional diagnostic methods than 67Ga-scintigraphy in order to accurately detect malignant lymphoma. FDG-PET can therefore play an important role in therapeutic decision making on lymphoma.

A clinical evaluation of FDG-PET to assess the response in radiation therapy for bronchogenic carcinoma

The clinical usefulness of FDG-PET in the prediction and assessment of response to radiation therapy in patients with bronchogenic carcinoma was evaluated. Thirty patients with untreated bronchogenic carcinoma were included in the study. All patients received FDG-PET before the initiation of radiation therapy, while 20 also received it after completing the therapy. The tumor to muscle ratio (TMR) was used as an index of the FDG uptake. The tumor response to therapy was classified as either a partial response (PR, n = 21) or no change (NC, n = 9) according to changes in the tumor size. Prognosis was made 6 months after the initiation of therapy, and was classified as either relapse (n = 19) or non-relapse (n = 9). The FDG uptakes both before and after therapy were compared with tumor response and prognosis. A high FDG uptake was noted in all 30 lesions before therapy. No significant differences in the uptake before therapy was observed according to the histological types nor T factors (UICC). The lesions with a higher uptake (TMR more than 7) responded better to therapy than those with a lower uptake (p < 0.05). The decrease in the uptake after therapy tended to be more prominent in the PR group than in the NC group. The rate of relapse was higher in lesions with a higher uptake before therapy (TMR more than 10) than in those with a lower uptake. The relapse group also showed a higher uptake after therapy than the non-relapse group. In addition, all 6 lesions showing a higher uptake (TMR more than 5) after therapy eventually relapsed (p < 0.05). Two lesions demonstrating a lower uptake both before and after therapy did not relapse, although no tumor regression due to the therapy was observed. These results indicate that FDG-PET plays a complementary role in both predicting and assessing the therapeutic response and prognosis in patients with bronchogenic carcinoma.

Can Transcranial Doppler Really Detect Reduced Cerebral Perfusion States

BACKGROUND AND PURPOSE This study was designed to determine whether transcranial Doppler ultrasonography (TCD) may detect reduced perfusion states of the brain in patients with hypertension or diabetes mellitus with suspected cerebral atherosclerosis and arteriolosclerosis. METHODS We determined blood flow velocity with TCD in the middle cerebral artery and cerebrovascular vasodilator responses to carbon dioxide in 22 patients with or without carotid artery occlusive disease and minor stroke; we compared the results with the measurements of cerebral blood flow and oxygen metabolism by positron emission tomography (PET). RESULTS Blood flow velocity measured by TCD correlated with ipsilateral cerebral blood flow measured by PET in frontal, temporal, and striatal regions and throughout the entire hemisphere (P < .05 to P < .005). Relative changes in blood flow velocity and calculated cerebrovascular resistance tested by carbon dioxide inhalation both correlated closely with regional mean transit time (calculated as the ratio of cerebral blood volume divided by cerebral blood flow) in frontal, striatal, temporal, parietal, and occipital regions and also in the entire hemisphere (P < .05 to P < .0001). TCD variables did not correlate with hemispheric measurements of oxygen metabolism by PET. CONCLUSIONS Although TCD is not useful in assessing impairments of cerebral metabolism, it is useful for detecting abnormalities of cerebral hemodynamics among patients with risk factors for cerebrovascular disease.