Kiyohiko Sakamoto

Decreased Incidence of Thymic Lymphoma in AKR Mice as a Result of Chronic, Fractionated Low-Dose Total-Body X Irradiation

We have investigated whether low-dose total-body X irradiation could suppress the development of lymphoma in AKR mice. Male mice were irradiated with 5 cGy three times a week or 15 cGy two times a week from 11 weeks of age for 40 weeks. The incidences of lymphoma were 80.5% in sham-irradiated mice, 67.5% in mice irradiated with 5 cGy three times a week and 48.6% in mice irradiated with 15 cGy twice a week. Incidence of lymphoma was significantly reduced by irradiation with 15 cGy twice a week (P = 0.006). The mean survival time was significantly prolonged from 283 +/- 3 days in control mice to 316 +/- 10 days in mice irradiated with 15 cGy twice a week (P = 0.008) and to 309 +/- 14 days in mice irradiated with 5 cGy three times a week (P = 0.040). Because about 80% of male AKR mice die of lymphoma, it is likely that the prolonged life span observed in the irradiated mice is due to the reduced incidence of lymphoma.

MR findings in Tay-Sachs disease.

OBJECTIVE MR and CT findings in two patients of Tay-Sachs disease are reported. MATERIALS AND METHODS In two patients of Tay-Sachs disease, MR and CT studies were conducted in the early phase (11 and 10 months of age, respectively) and one was followed-up with MR in the late phase at the age of 5 years and 8 months. Six MR studies on this disease (including 3 other cases documented in the literature) were reviewed and correlated with the pathological phases of this disease. RESULTS MRI findings drastically changed during the phases of disease process in one case. In the early phase, T2-weighted MR images demonstrated hyperintensity in both basal ganglia and thalamus. MR images obtained in the late phase demonstrated markedly advanced brain atrophy and diffuse white matter lesions, which were hyperintense on the T2-weighted images. T1-weighted images exhibited hyperintensity in the basal ganglia, thalamus, and along the cortical layer of the cerebrum, which appeared to by hypointense on T2-weighted images. CONCLUSION MR was apparently superior to CT in clearly delineating lesions of this disease. These abnormal signal intensities in the late phase may reflect the pathological findings, marked accumulation of GM2 ganglioside in the basal ganglia and thalamus and along the cerebral gray matter.

MR imaging of multiple sclerosis simulating brain tumor

Multiple sclerosis may sometimes present as a mass lesion that is indistinguishable from brain tumor both clinically and radiologically. We describe two cases of multiple sclerosis simulating brain tumor on computed tomography (CT) scans and magnetic resonance (MR) images, one of which was proved and another was suggestive to be demyelinating disease by biopsy. Steroid therapy produced regression of the lesions of MR images and CT scans. Our cases and others in the literature suggest strategies for detecting multiple sclerosis presenting as a mass lesion.

Prostacyclin Production in Cultured Endothelial Cells is Highly Sensitive to Low Doses of Ionizing Radiation

In an attempt to detect if low doses of ionizing radiation affect the physiological function of blood vessels, the effect of prostacyclin production was examined using cultured endothelial cells. Irradiation with 5 cGy suppressed the production to 53% of the levels in unirradiated control cells. The PGI2 production decreased with an increase in the dose, showing a maximal decrease at 100 cGy without further decrease at 200 cGy. The suppressive effect lasted for 15 min after irradiation and disappeared later. Preincubation with alpha-tocopherol abrogated the suppressive effect completely, although preincubation with ascorbic acid showed little effect. These results suggest that low dose irradiation inhibits the prostacyclin production by changing the cellular membranes transiently.

Phase Ia study of a hypoxic cell sensitizer doranidazole (PR-350) in combination with conventional radiotherapy.

A phase Ia study of a 2-nitroimidazole nucleoside analog radiosensitizer doranidazole was conducted to evaluate its toxicity and pharmacokinetics in patients undergoing conventional external beam radiotherapy. Twenty-nine patients, aged 40-74 years, with a WHO performance status of 0-2 and with adequate organ functions, were entered in the study. Single administration of doranidazole was investigated first with 13 patients and then a course of five consecutive daily administrations was tested in 16 patients. Doranidazole was given i.v. 25 min before irradiation. Doranidazole doses of 400, 800, 1300 and 2000 mg/m2 were evaluated in the former study, and daily doses of 800, 1300 and 2000 mg/m2 were investigated in the latter study. All patients tolerated doranidazole administration. Although a transient decrease in the 24-h creatinine clearance rate was observed in five patients (one in the single administration study and four in the repeat administration study), this was not considered to be the dose-limiting toxicity. Other toxicities (hematological and gastrointestinal), which may not be related to doranidazole administration, were also mild and were not dose limiting. No neurotoxicity was observed. The average maximum concentration, area under the time-concentration curve and half-life of doranidazole in serum were 172-194 μg/ml, 502-582 μg·h/l and 4.2-4.6 h, respectively, at 2000 mg/m2. At the tested doses, administration of doranidaozle was tolerable and achieved serum concentrations at which reasonable radiosensitization could be expected. A phase Ib/II study to evaluate the feasibility and efficacy of up to 30 repeat administrations seems to be warranted.

CT and MR imaging of craniopharyngioma

Abstract. We reviewed imaging findings of CT and MR imaging in 20 cases of surgically confirmed craniopharyngioma in an attempt to determine their relation to patterns of tumor extent. The relationship between these patterns and the frequency of preoperative CT diagnosis and MR imaging diagnosis according to the surgical diagnosis were determined. The CT technique was superior to MR imaging in the detection of calcification. The MR imaging technique was superior to CT for determining tumor extent and provided valuable information about the relationships of the tumor to surrounding structures. Thus, CT and MR imaging have complementary roles in the diagnosis of craniopharyngiomas. In cases of possible craniopharyngioma, noncontrast sagittal T1-weighted images may enable the identification of the normal pituitary, possibly leading to the correct diagnosis.

Multisegmental anomaly of the inferior vena cava with thrombosis of the left inferior vena cava

We present a rare case of an extensive venous thrombosis associated with a multisegmental anomaly of the inferior vena cava (IVC), double IVCs, a hypoplastic right IVC, an aneurysm arising at the distal portion of the right IVC, and a severe stenosis between the prerenal and the hepatic segments of the IVC.

MR findings of avulsive cortical irregularity of the distal femur.

Avulsive cortical irrgularity, a benign condition occurring only among children and adolescents, has been known to simulate malignancy not only radiologically but also microscopically. Therefore, in addition to plain radiographs, further studies including by magnetic resonance (MR) imaging may occasionally be required. MR images of seven cases of avulsive cortical irregularity of the femur were reviewed. In all cases, the lesion appeared hypointense on T1-weighted images and hyperintense on T2-weighted images, with a dark rim on both sequences at or near the sites of the bony attachment of the medial head of the gastrocnemius muscle. In all cases, bilateral involvement was demonstrated by plain radiography, computed tomography, and/or MR imaging. The authors suggest that avulsive cortical irregularity involves both femora much more frequently than has been reported previously.

MRI of anterior spinal artery syndrome of the cervical spinal cord

SummaryCervical spinal cord lesions in the anterior spinal artery syndrome were delineated on magnetic resonance images (MRI) in four patients. The lesion was always seen anteriorly in the cervical cord. On T2-weighted images, the lesions appeared hyperintense relative to the normal spinal cord, while on T1-weighted images, two chronic lesions appeared hypointense, with local atrophy of the cord. In one case, repeated T1-weighted images showed no signal abnormality 4 days after the ictus, but the lesion became hypointense 18 days later, when contrast enhancement was also recognized after injection of Gd-DTPA; this sequence of intensity changes was similar to that of cerebral infarction. The extent of the lesion seen MRI correlated closely with neurological findings in all cases. Although the findings may not be specific, MRI is now the modality of choice for confirming the diagnosis in patients suspected of having an anterior spinal artery syndrome.

Radiotherapy for malignant fistula to other tract

Radiotherapy was applied to 14 esophageal carcinomas with respiratory tract fistulas using various treatment regimes. Closure of the fistulas was observed in four cases after irradiation at a daily dose of 1.5 GY. The period of closure was transient in two cases but long‐term in the other two. One long‐term closure case underwent low‐dose rate telecobalt therapy (LDRT)(1 GY per hour, 7 GY per day; a total dose of 28 GY) as a boost. His cancer has been well controlled and he is still alive without recurrence at 74 months after fistula formation.