Toshi Hashimoto

Showa University, Shinagawa, Tōkyō, Japan

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Publications (11)8.18 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Although CT urography (CTU) is widely used for the evaluation of the entire urinary tract, the most important drawback is the radiation exposure. To evaluate the effect of a noise reduction filter (NRF) using a phantom and to quantitatively and qualitatively compare excretory phase (EP) images using a low noise index (NI) with those using a high NI and postprocessing NRF (pNRF). Each NI value was defined for a slice thickness of 5 mm, and reconstructed images with a slice thickness of 1.25 mm were assessed. Sixty patients who were at high risk of developing bladder tumors (BT) were divided into two groups according to whether their EP images were obtained using an NI of 9.88 (29 patients; group A) or an NI of 20 and pNRF (31 patients; group B). The CT dose index volume (CTDI(vol)) and the contrast-to-noise ratio (CNR) of the bladder with respect to the anterior pelvic fat were compared in both groups. Qualitative assessment of the urinary bladder for image noise, sharpness, streak artifacts, homogeneity, and the conspicuity of polypoid or sessile-shaped BTs with a short-axis diameter greater than 10 mm was performed using a 3-point scale. The phantom study showed noise reduction of approximately 40% and 76% dose reduction between group A and group B. CTDI(vol) demonstrated a 73% reduction in group B (4.6 ± 1.1 mGy) compared with group A (16.9 ± 3.4 mGy). The CNR value was not significantly different (P = 0.60) between group A (16.1 ± 5.1) and group B (16.6 ± 7.6). Although group A was superior (P < 0.01) to group B with regard to image noise, other qualitative analyses did not show significant differences. EP images using a high NI and pNRF were quantitatively and qualitatively comparable to those using a low NI, except with regard to image noise.
    Acta Radiologica 04/2011; 52(6):692-8. · 1.35 Impact Factor
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    ABSTRACT: We successfully created a percutaneous transhepatic portacaval shunt under ultrasonography (US) guidance in a 46-year-old man with refractory ascites. The shunt was created to salvage an attempt to create a transjugular intrahepatic portosystemic shunt (TIPS) that failed because of the elevated level of portal vein bifurcation due to alcoholic liver cirrhosis. Under US guidance, we simultaneously punctured the right branch of the portal vein and the inferior vena cava (IVC) using a two-step biliary drainage set. An Amplatz gooseneck snare was introduced transjugularly to retrieve the percutaneously inserted guidewire. The intrahepatic tract between the portal vein and the IVC was dilated using a balloon catheter, and a stent was placed in the tract. The patient showed complete resolution of ascites at discharge. We assume that our method is an alternative method for TIPS creation in patients with inadequate anatomical relations between the portal vein branches and the hepatic veins. This approach is thought to be feasible for patients with occluded or small hepatic veins.
    Japanese journal of radiology 08/2010; 28(7):542-6. · 0.73 Impact Factor
  • The Showa University Journal of Medical Sciences. 01/2009; 21(2):107-116.
  • The Showa University Journal of Medical Sciences. 01/2009; 21(2):85-93.
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    ABSTRACT: Positioning a stent graft (SG) that adapts to the anatomical shape of the aorta is important to prevent complications after SG procedures to treat aortic disease. The Gianturco Z-stent has several benefits, but its rigid structure prevents adaptation to flexure. We improved this stent and studied its ability to adapt in the clinical environment. We positioned SGs and inspected their adaptability to flexure in an aortic arch model. We examined several gap lengths and strut directions, and determined the distance generated between the stent and the aortic wall. We found that adaptation was quite satisfactory with a gap of more than 10 mm or when the struts faced the major flexure or the side of the model aorta. Based on these findings and to facilitate placement, we manufactured the unibody Z-stent with 10-mm gaps. The unibody Z-stent was applied to treat thoracic and thoracoabdominal aortic disease in seven patients. The SG was positioned from the femoral or iliac artery in five patients and from an anastomosed graft to the ascending aorta after median sternotomy and bypass of the arch branches in two patients. A minor endoleak developed in one patient. None of the other six patients developed complications or died during the procedure, although one patient died in the hospital due to cerebral infarction. The unibody Z-stent was applied as a SG that adapts to flexure of the aorta and was easy to apply. The frequency of complications was apparently decreased after clinical application of the unibody Z-stent in SG treatment for thoracic and thoracoabdominal aortic disease.
    Journal of Artificial Organs 02/2007; 10(3):165-70. · 1.39 Impact Factor
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    ABSTRACT: The purpose of our study was to assess the usefulness of dynamic MRI in distinguishing high-flow vascular malformations from low-flow vascular malformations, which do not need angiography for treatment. Between September 2001 and January 2003, 16 patients who underwent conventional and dynamic MRI had peripheral vascular malformations (six high- and 10 low-flow). The temporal resolution of dynamic MRI was 5 sec. Time intervals between beginning of enhancement of an arterial branch in the vicinity of a lesion in the same slice and the onset of enhancement in the lesion were calculated. We defined these time intervals as "artery-lesion enhancement time." Time intervals between the onset of enhancement in the lesion and the time of the maximal percentage of enhancement above baseline of the lesion within 120 sec were measured. We defined these time intervals as "contrast rise time" of the lesion. Diagnosis of the peripheral vascular malformations was based on angiographic or venographic findings. The mean artery-lesion enhancement time of the high-flow vascular malformations (3.3 sec [range, 0-5 sec]) was significantly shorter than that of the low-flow vascular malformations (8.8 sec [range, 0-20 sec]) (Mann-Whitney test, p < 0.05). The mean maximal lesion enhancement time of the high-flow vascular malformations (5.8 sec [range, 5-10 sec]) was significantly shorter than that of the low-flow vascular malformations (88.4 sec [range, 50-100 sec]) (Mann-Whitney test, p < 0.01). Dynamic MRI is useful for distinguishing high-flow from low-flow vascular malformations, especially when the contrast rise time of the lesion is measured.
    American Journal of Roentgenology 12/2005; 185(5):1131-7. · 2.74 Impact Factor
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    ABSTRACT: PURPOSE To establish MR imaging features that may distinguish hemangiomas from high-flow and low-flow vascular malformations (VMs). METHOD AND MATERIALS Twentyseven patients with peripheral vascular anomalies (5 hemangiomas, 6 high-flow VMs and 16 low-flow VMs) underwent conventional and dynamic MR imaging. The temporal resolution of the dynamic MR imaging was 5 sec. Enhancement was calculated by the formula: percentage enhancement = (signal intensity after enhancement – signal intensity before enhancement)/ signal intensity before enhancement ×100. Time intervals between onset of enhancement of the lesion and the maximal percentage enhancement of the lesion were measured and was defined as contrast rise time. Lesions were assessed for presence of flow voids, phleboliths and skin involvement on conventional MR images. Margins, internal homogeneity and signal intensity on T2-weighted images were compared on conventional MR images. RESULTS The mean contrast rise time for hemangiomas was 6.0 sec (range 0-10 sec). The mean contrast rise time for high-flow VMs was 4.2 sec (range 0-5 sec). The mean contrast rise time for low-flow VMs was 83.3 sec (range 50-105 sec). The mean contrast rise time for low-flow VMs was significantly longer than those for hemangiomas and high-flow VMs (Scheffe; P<0.01). There was no significant difference between hemangiomas and high-flow VMs. When compared with high-flow VMs, a significantly greater proportion of hemangiomas consisted of a defined margin (Scheffe; P<0.01), but they did not differ in internal homogeneity and signal intensity on T2-weighted images. Flow voids were observed in 1 hemangioma and 3 high-flow VMs. Phleboliths were seen in 4 low-flow VMs. Involved skin was noted in 4 high-flow VMs and 3 low-flow VMs. CONCLUSION The long contrast rise time separates low-flow VMs from the other lesions. The presence of defined margins and absence of skin involvement is suggestive of a hemangioma when compared with VMs. PURPOSE To establish MR imaging features that may distinguish hemangiomas from high-flow and low-flow vascular malformations (VMs). METHOD AND MATERIALS Twentyseven patients with peripheral vascular anomalies (5 hemangiomas, 6 high-flow VMs and 16 low-flow VMs) underwent conventional and dynamic MR imaging. The temporal resolution of the dynamic MR imaging was 5 sec. Enhancement was calculated by the formula: percentage enhancement = (signal intensity after enhancement – signal intensity before enhancement)/ signal intensity before enhancement ×100. Time intervals between onset of enhancement of the lesion and the maximal percentage enhancement of the lesion were measured and was defined as contrast rise time. Lesions were assessed for presence of flow voids, phleboliths and skin involvement on conventional MR images. Margins, internal homogeneity and signal intensity on T2-weighted images were compared on conventional MR images. RESULTS The mean contrast rise time for hemangiomas was 6.0 sec (range 0-10 sec). The mean contrast rise time for high-flow VMs was 4.2 sec (range 0-5 sec). The mean contrast rise time for low-flow VMs was 83.3 sec (range 50-105 sec). The mean contrast rise time for low-flow VMs was significantly longer than those for hemangiomas and high-flow VMs (Scheffe; P<0.01). There was no significant difference between hemangiomas and high-flow VMs. When compared with high-flow VMs, a significantly greater proportion of hemangiomas consisted of a defined margin (Scheffe; P<0.01), but they did not differ in internal homogeneity and signal intensity on T2-weighted images. Flow voids were observed in 1 hemangioma and 3 high-flow VMs. Phleboliths were seen in 4 low-flow VMs. Involved skin was noted in 4 high-flow VMs and 3 low-flow VMs. CONCLUSION The long contrast rise time separates low-flow VMs from the other lesions. The presence of defined margins and absence of skin involvement is suggestive of a hemangioma when compared with VMs.
    Radiological Society of North America 2005 Scientific Assembly and Annual Meeting; 11/2005
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    ABSTRACT: LEARNING OBJECTIVES (1) To understand categorization of vascular malformations (VMs) and hemangiomas. (2) To illustrate MR imaging features including dynamic MRI of VMs and hemangiomas. (3) To learn appropriate treatment for VMs and hemangiomas. (4) To recognize the pitfalls of VMs and hemangiomas. ABSTRACT Peripheral vascular lesions are common, particularly during childhood. However, physicians often confuse these lesions because the nomenclature for classifying these lesions is often used appropriately. Therefore, knowledge of the imaging and treatment of these patients is essential for radiologists. This exhibit demonstrates characteristic imaging findings and practical classification for treatment of vascular malformations (VMs) and hemangiomas using dynamic MRI. Thirty-four consecutive patients with peripheral VM (3 hemangiomas, 6 arteriovenous malformations, 2 lymphangiomas and 16 venous malformations, including Kasabach-Merritt syndrome and Klippel Traunauny syndrome) underwent dynamic MRI and conventional MRI. The dynamic MR images were continuously obtained every 5 sec for 120 sec. All hemangiomas and all arteriovenous malformations showed rapidly enhancement. All venous malformations showed gradual enhancement. All lymphangiomas did not show enhancement. Dynamic MR imaging is useful for classifying VMs and hemangiomas.
    Radiological Society of North America 2004 Scientific Assembly and Annual Meeting; 11/2004
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    ABSTRACT: Endotracheal expandable metallic stents have been shown to be useful in treating malignant tracheobronchial stenosis. We report two cases of early stent migration in the upper trachea after what appeared to be a successful stent placement. We conclude that care should be taken when placing Gianturco stents across short, extrinsic, stenotic lesions with smooth mucosa located in the upper trachea because they have a tendency to migrate.
    CardioVascular and Interventional Radiology 05/1997; 20(3):216-218. · 1.97 Impact Factor
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    ABSTRACT: PURPOSE/AIM (1) To review extra-pancreatic radiological findings in cases of patients with autoimmune pancreatitis were reviewed. (2)To correlate the radiological findings with clinical and pathological findings. CONTENT ORGANIZATION (1) Review of imaging findings;retroperitoneal fibrosis (periaortic soft tissue mass on CT), renal involvement (focal renal mass,multiple masses,or renomegaly), lymphadenopathy (periaorta,hepatic hilum, peripancreas, lessar omentum), pulmonary involvement (diffuse gallium uptake),and salivary gland involvement (acinar dilatation on sialogram). (2) Review of histopathological findings(lymphoplasmocytic infiltration). (3) Review of clinical findings. SUMMARY (1) Extra-pancreatic manifestations of autoimmune pancreatitis is a common findings. (2) Autoimmune pancreatitis is a multisystem fibrosclerosis that is pathologically characteristic of lymphoplasmocystic infiltration.
    Radiological Society of North America 2006 Scientific Assembly and Annual Meeting;
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    ABSTRACT: PURPOSE/AIM The purpose of this exhibit is: 1. To introduce characteristics of imaging from cone-beam CT in C-arm. 2. To learn required techniques and dealing with volume CT data for biopsy and percutaneous therapeutic procedures. 3. To show benefits and limitations of referring volume CT data with or without C-arm Fluoroscope during procedures. CONTENT ORGANIZATION A.Characteristics of imaging cubic reconstruction, high contrast structures, low contrast structures, artifacts, B. How to use volume data and C-arm Fluoroscope decision of puncture point, control and advancement of needle angle, prevent artifacts, C. Benefits and Limitations image quality, workstation, hardware, D. Future directions and summary SUMMARY 1.Although the poor soft tissues differentiation would be limitation for planning, cone-beam CT equipped with C-arm and flat panel detector can be a practical clinical tool that facilitates effective performance of CT guided procedures. 2.It is important to know difference between conventional and Cone-beam CT guidance. We will show how to handle volume data and C-arm fluoroscope during CT guided interventions.
    Radiological Society of North America 2006 Scientific Assembly and Annual Meeting;