Biomedical subjects

Tohru Shiga

Publications and source records attributed to Tohru Shiga.

21 records · Page 2Linked to original sources

PubMed2002

Image fusion between 18FDG-PET and MRI/CT for radiotherapy planning of oropharyngeal and nasopharyngeal carcinomas.

PURPOSE: Accurate diagnosis of tumor extent is important in three-dimensional conformal radiotherapy. This study reports the use of image fusion between (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (18FDG-PET) and magnetic resonance imaging/computed tomography (MRI/CT) for better targets delineation in radiotherapy planning of head-and-neck cancers. METHODS AND MATERIALS: The subjects consisted of 12 patients with oropharyngeal carcinoma and 9 patients with nasopharyngeal carcinoma (NPC) who were treated with radical radiotherapy between July 1999 and February 2001. Image fusion between 18FDG-PET and MRI/CT was performed using an automatic multimodality image registration algorithm, which used the brain as an internal reference for registration. Gross tumor volume (GTV) was determined based on clinical examination and 18FDG uptake on the fusion images. Clinical target volume (CTV) was determined following the usual pattern of lymph node spread for each disease entity along with the clinical presentation of each patient. RESULTS: Except for 3 cases with superficial tumors, all the other primary tumors were detected by 18FDG-PET. The GTV volumes for primary tumors were not changed by image fusion in 19 cases (89%), increased by 49% in one NPC, and decreased by 45% in another NPC. Normal tissue sparing was more easily performed based on clearer GTV and CTV determination on the fusion images. In particular, parotid sparing became possible in 15 patients (71%) whose upper neck areas near the parotid glands were tumor-free by 18FDG-PET. Within a mean follow-up period of 18 months, no recurrence occurred in the areas defined as CTV, which was treated prophylactically, except for 1 patient who experienced nodal recurrence in the CTV and simultaneous primary site recurrence. CONCLUSION: This preliminary study showed that image fusion between 18FDG-PET and MRI/CT was useful in GTV and CTV determination in conformal RT, thus sparing normal tissues.

Adult↗

PubMed2002

The effect of scatter correction on 123I-IMP brain perfusion SPET with the triple energy window method in normal subjects using SPM analysis.

Scatter correction (SC) using the triple energy window method (TEW) has recently been applied for brain perfusion single-photon emission tomography (SPET). The aim of this study was to investigate the effect of scatter correction using TEW on N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) SPET in normal subjects. The study population consisted of 15 right-handed normal subjects. SPET data were acquired from 20 min to 40 min after the injection of 167 MBq of IMP, using a triple-head gamma camera. Images were reconstructed with and without SC. 3D T1-weighted magnetic resonance (MR) images were also obtained with a 1.5-Tesla scanner. First, IMP images with and without SC were co-registered to the 3D MRI. Second, the two co-registered IMP images were normalised using SPM96. A t statistic image for the contrast condition effect was constructed. We investigated areas using a voxel-level threshold of 0.001, with a corrected threshold of 0.05. Compared with results obtained without SC, the IMP distribution with SC was significantly decreased in the peripheral areas of the cerebellum, the cortex and the ventricle, and also in the lateral occipital cortex and the base of the temporal lobe. On the other hand, the IMP distribution with SC was significantly increased in the anterior and posterior cingulate cortex, the insular cortex and the medial part of the thalamus. It is concluded that differences in the IMP distribution with and without SC exist not only in the peripheral areas of the cerebellum, the cortex and the ventricle but also in the occipital lobe, the base of the temporal lobe, the insular cortex, the medial part of the thalamus, and the anterior and posterior cingulate cortex. This needs to be recognised for adequate interpretation of IMP brain perfusion SPET after scatter correction.

Adult↗

PubMed2002

Human brain region response to distention or cold stimulation of the bladder: a positron emission tomography study.

PURPOSE: Several kinds of perceptions, including distention and coldness, arise from the bladder. Information on bladder fullness conveyed by mechanoreceptors within the bladder wall contributes to the basic micturition reflex via the bulbospinal reflex pathway, whereas cold stimulation of the bladder is processed differently. To elucidate the human brain mechanisms of voluntary urine storage and bladder cold perception we performed positron emission tomography scanning to examine brain regions activated by bladder distention or cold stimulation. MATERIALS AND METHODS: A total of 17 right-handed healthy male volunteers were catheterized via the urethra for bladder infusion. Subjects were divided into 2 groups for 2 types of positron emission tomography, namely the bladder distention group-11 who were 24 to 41 years old and the intravesical ice water group-6 who were 24 to 38 years old. Data were analyzed by the statistical parametric mapping procedure. RESULTS: Significant brain activation during maximum urine storage (bladder distention) were found in the pons, midbrain periaqueductal gray, anterior insula, putamen, thalamus and anterior cingulate gyrus. On the other hand, intravesical ice water instillation significantly activated several regions in frontal and parietal lobes, amygdala-hippocampus area and crus cerebri ventral border. Distribution of the activated regions after intravesical instillation of ice water overlapped none of those observed after bladder distention. CONCLUSIONS: Our data show that the brainstem as well as more rostral regions are involved in voluntary urine storage and these regions are functionally separated from those associated with bladder cold perception in healthy individuals.

Adult↗