Toshibumi Kinoshita

Assessment of Lacunar Hemorrhage Associated With Hypertensive Stroke by Echo-Planar Gradient-Echo T2*-Weighted MRI

BACKGROUND AND PURPOSE Echo-planar gradient-echo T2*-weighted MR imaging (GRE-EPI) may detect hypointense lesions representing microhemorrhages with high sensitivity. The aim of this study was to evaluate the effectiveness of GRE-EPI for detecting old lacunar hemorrhages in hypertensive patients with stroke. METHODS GRE-EPI was performed with a 1.5-T MRI system in 198 hypertensive patients with stroke (130 patients with hemorrhagic stroke and 68 patients with multiple lacunar stroke) and 66 age-matched healthy elderly individuals. RESULTS Concomitant hypointense foci were found in 84 (66%) patients with hemorrhagic stroke, 46 (68%) patients with multiple lacunar stroke, and 3 (5%) healthy elderly individuals. These hypointense foci were noted in the lentiform nucleus in 61 (47%) patients with hemorrhagic stroke, in the caudate nucleus in 9 (7%) patients, in the thalamus in 54 (42%) patients, in the corticosubcortical region in 57 (44%) patients, in the brain stem in 40 (34%) patients, and in the cerebellum in 32 (25%) patients. CONCLUSIONS GRE-EPI is effective for the detection of lacunar hemorrhages induced by hypertension.

Usefulness of diffusion tensor imaging of white matter in alzheimer disease and vascular dementia

Purpose: To evaluate the usefulness of diffusion tensor imaging in detecting the water diffusivity caused by neuropathological change in Alzheimer disease and vascular dementia. Material and Methods: Twenty patients with Alzheimer disease, 20 with vascular dementia, and 10 control subjects were examined. Diffusion tensor imaging applied diffusion gradient encoding in six non‐collinear directions. Fractional anisotropy values were compared in the genu and splenium of the corpus callosum, and anterior and posterior white matter among the three groups. Results: In the patients with Alzheimer disease, fractional anisotropy values of the posterior white matter were significantly lower than those of controls. In patients with vascular dementia, fractional anisotropy values of the anterior white matter tended to be lower than those of the posterior white matter (P=0.07). Conclusion: Diffusion tensor imaging reflects the neuropathological changes in the white matter, and may be useful in the diagnosis of Alzheimer disease and vascular dementia.

Interindividual Variations of Cerebral Blood Flow, Oxygen Delivery, and Metabolism in Relation to Hemoglobin Concentration Measured by Positron Emission Tomography in Humans

Regional cerebral blood flow (CBF) and oxygen metabolism can be measured by positron emission tomography (PET) with 15O-labeled compounds. Hemoglobin (Hb) concentration of blood, a primary determinant of arterial oxygen content (CaO2), influences cerebral circulation. We investigated interindividual variations of CBF, cerebral blood volume (CBV), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) in relation to Hb concentration in healthy human volunteers (n=17) and in patients with unilateral steno-occlusive disease (n=44). For the patients, data obtained only from the contralateral hemisphere (normal side) were analyzed. The CBF and OEF were inversely correlated with Hb concentration, but CMRO2 was independent of Hb concentration. Oxygen delivery defined as a product of CaO2 and CBF (CaO2 CBF) increased with a rise of Hb concentration. The analysis with a simple oxygen model showed that oxygen diffusion parameter (L) was constant over the range of Hb concentration, indicating that a homeostatic mechanism controlling CBF is necessary to maintain CMRO2. The current findings provide important knowledge to understand the control mechanism of cerebral circulation and to interpret the 15O PET data in clinical practice.

CT features of retroperitoneal neurilemmoma

PURPOSE The aim of this study was to characterize the CT features of retroperitoneal neurilemmoma. METHODS The CT findings were reviewed in seven patients with retroperitoneal neurilemmoma. RESULTS All of the tumours were well-demarcated round or oval masses. In five cases, heterogeneous contrast enhancement was noted after contrast medium administration. Areas of minimal enhancement reflected diffuse edema in one tumour. Areas without definite enhancement represented prominent cyst formation in three tumours. There were three cases with tumour calcification (two with punctate calcification and one with mottled calcification). CONCLUSION CT findings may suggest the diagnosis of retroperitoneal neurilemmoma preoperatively.

CT-guided transthoracic needle biopsy using a puncture site-down positioning technique.

OBJECTIVE We have developed a new CT-guided technique using puncture site-down positioning during the biopsy. The goal of our study was to determine the efficacy and safety of this technique for biopsy of lung lesions compared with the standard technique. MATERIALS AND METHODS Medical records of 236 patients who underwent CT-guided transthoracic needle biopsy were retrospectively evaluated. This study included 89 cases that were biopsied using the standard technique (group A) and 147 cases that were biopsied using the puncture site-down positioning technique (group B). A 20-gauge automated cutting needle without coaxial technique was used in all patients. Medical records were reviewed for lesion size and location, biopsy results, and complications. RESULTS When using the standard technique, the sensitivity for malignant lesions was 96.1%; the sensitivity for benign lesions, 92.1%; and diagnostic accuracy, 94.4%. Thirty-seven patients (41.6%) had pneumothorax, with 16 (18.0%) requiring chest tube placement. When using the puncture site-down positioning technique, the sensitivity for malignant lesions was 95.4%; the sensitivity for benign lesions, 93.3%; and diagnostic accuracy, 94.6%. Nineteen patients (12.9%) had pneumothorax, with four (2.7%) requiring chest tube placement. Other complications were minimal. CONCLUSION CT-guided transthoracic needle biopsy using the puncture site-down positioning technique is an effective and safe procedure with a high diagnostic accuracy and low complication rate. This new technique is especially useful in reducing the rate of pneumothorax.

Angiomyoma of the lower extremity: MR findings

A healthy 61-year-old woman with no antecedent trauma presented with a 10-year history of a slowly growing, painless mass in the right planta. She could not comfortably wear her right shoe. She did not complain of tenderness. The mass was elastic and hard, and was located in the subcutaneous tissue. The overlying skin was not thinned or discolored. Laboratory investigation disclosed no abnormality. MR imaging showed a welldemarcated subcutaneous soft tissue mass beneath the medial compartment of the plantar muscle (Figs. 1–3). On T1-weighted MR images, curvilinear lesions of signal loss were noted within the mass, which was iso-intense with muscle (Fig. 1). The soft tissue mass had heterogeneous high signal intensity on T2weighted MR images (Fig. 2). After administration of contrast agent, homogeneous contrast enhancement was evident within the mass on T1weighted images (Fig. 3). The excised tumor was a sharply circumscribed, whitish hard mass, 3 cm in diameter. Histological examination revealed numerous tortuous vascular channels with proliferation of spindle-shaped cells showing an interlacing band-like pattern (Fig. 4A). Admixed with these findings, fibrous components and edematous stroma were observed (Fig. 4B). Immunohistochemical staining for α smooth muscle actin was positive in the spindle-shaped cells. The pathological diagnosis was the solid type of angiomyoma. Fifteen months after surgery there was no recurrence.

Low-grade fibromyxoid sarcoma of the small bowel mesentery: computed tomography and magnetic resonance imaging findings

Low-grade fibromyxoid sarcoma (LGFMS) is a rare tumor that commonly arises in the lower extremities but rarely in the mesentery. We report computed tomography (CT) and magnetic resonance imaging (MRI) findings of LGFMS of the small bowel mesentery. On CT, the mass was composed of two components. One component, on its right side, appeared to have isointense attenuation relative to muscle, whereas the other component, on its left side, appeared to have low attenuation. On MRI the mass on the right side showed hypointensity similar to muscle on both T1-and T2-weighted images as well as mostly slight enhancement on contrast-enhanced T1-weighted images. On the other hand, the mass on the left side showed relative hypointensity on T1-weighted images and hyperintensity on T2-weighted images as well as intense enhancement on contrast-enhanced T1-weighted images, suggesting that the tumor contained myxoid tissue. The myxoid area of LGFMS may have a tendency to reveal intense enhancement on contrast-enhanced images.

Late-presenting posterior transdiaphragmatic (Bochdalek) hernia in adults: prevalence and MDCT characteristics.

Purpose The objective of our study was to determine the prevalence of posterior transdiaphragmatic hernia in a large normal adult population. We also performed volume measurements and described its characteristics and sequential changes. Materials and Methods We prospectively evaluated 3107 chest computed tomography screenings obtained at our center between September 2005 and March 2006. The images were analyzed by experienced radiologists, who focused on the distribution, size, content, and sequential changes of the diaphragmatic hernia. Volumetric measurement was used to evaluate the size of the hernia. We also performed a chart review for each case and recorded the sex, age, symptoms, and clinical history. Results A total of 525 hernias were identified in 396 of 3107 persons, representing an incidence of 12.7%. Age ranges were 36 to 86 years and average was 62.8 years. The prevalence of the posterior diaphragmatic hernias in the 50s, 60s, and 70s age groups was 10.5% (168/1596), 13.7% (137/1003), and 20.3% (80/394), respectively. All persons were asymptomatic. In 93.7% (492/525) of the hernias, only fat was observed, whereas kidney involvement was observed in 5.5% (29/525). Protruded hernia content extended along the diaphragm, thoracoabdominal wall, and in the intermediate position between these 2 structures in 53.7%, 32.8%, and 13.5% of the hernias, respectively. No significant sequential changes were observed (P=0.082) during our follow-up period (12 to 27 mo). Conclusions Incidentally observed posterior transdiaphragmatic hernias are a common finding on multidetector-row computed tomography, occurring in up to 20% of persons by age 70 years.

Curvilinear T1 hyperintense lesions representing cortical necrosis after cerebral infarction

Curvilinear T1 hyperintense lesions in the cerebral cortex in patients with subacute infarction were investigated for: (1) the presence or absence of T2* hypointensity and (2) correlations with neuropathologic findings. Thirty-six consecutive patients with subacute to chronic embolic infarction, in whom curvilinear hyperintense lesions in the infarcted cortex were seen on T1-weighted images, underwent echo-planar gradient-echo (GRE-EPI) T2*-weighted imaging. GRE-EPI T2*-weighted imaging revealed no evidence of hemorrhage within the curvilinear T1 hyperintense lesions of the cerebral cortex in all of the patients. In 11 of the 36 patients, focal hypointense lesions were seen in the depth of infarcted gyri on GRE-EPI T2*-weighted images. In the remaining 25 patients, no T2* hypointensities were seen in the infarct zone. Pathological correlation was performed in a patient with middle cerebral artery infarction and curvilinear hyperintense lesions on postmortem T1-weighted images. In the autopsied brain, curvilinear T1 hyperintense lesions corresponded to necrosis of all the cortical layers on histological examination. These data suggest that curvilinear hyperintense lesions in the cerebral cortex on T1-weighted images during the subacute to chronic period of cerebral infarction may not represent hemorrhage.

MR imaging findings of parotid tumors with pathologic diagnostic clues:A pictorial essay

This pictorial essay depicts MR features of benign and malignant parotid tumors. Increased T2 signal intensity is suggestive of pleomorphic adenoma. Tumors with relatively low signal intensity on T2-weighted images are more likely to be malignant even when they are well-demarcated. Fat suppression technique improves the ability to define the boundaries of neoplatic or inflammatory lesions.