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Biomedical subjects

A H Matsumoto

Publications and source records attributed to A H Matsumoto.

At least 19 recordsLinked to original sources
PubMed2005

Contrast-enhanced MR angiography at 1.5 T after implantation of platinum stents: in vitro and in vivo comparison with conventional stent designs.

OBJECTIVE: The objective of our study was to evaluate the in vitro and in vivo 3D contrast-enhanced MR angiography characteristics of a new platinum-based balloon-expandable stent system and compare this system with a variety of competing metallic stents. MATERIALS AND METHODS: All experiments were performed on 1.5-T scanners. In vitro experiments were performed using 10 stents implanted into a custom-built phantom. Different orientations of the stents along the magnetic field and multiple flip angles were examined. In addition, 19 patients underwent contrast-enhanced MR angiography after the implantation of 36 stents, including four patients with six platinum stents. Angiographic correlation was available for all 19 patients, and luminal patency and stent-induced artifacts were assessed quantitatively. RESULTS: Of the tested balloon-expandable stents, only the platinum-based stents created artifact causing luminal narrowing of 30% or less. All other balloon-expandable stents induced larger artifacts that resulted in higher degrees of narrowing. Thus, if patent, the platinum-based stents allow significant in-stent stenosis to be ruled out reliably. Selected nitinol- or tantalum-based self-expandable stents also are suitable in this regard. CONCLUSION: Of the tested devices, platinum-based stents are the only type of currently available balloon-expandable stent that creates 30% or less artifact-induced apparent stenosis and thus are suitable for MR angiography.

Aged↗
PubMed2004

Primary sarcoma of the distal abdominal aorta: CT angiography findings.

Primary aortic angiosarcomas are extremely rare. Clinically and radiographically, they mimic atherosclerosis and atheroembolic disease. For a definitive diagnosis, histologic evaluation of the tumor or of peripheral emboli is required. The imaging findings are frequently nonspecific and in most published cases did not allow a definitive preoperative diagnosis. This is the first report of the computed tomographic angiographic findings of a primary intimal abdominal aortic sarcoma and a review of previously described imaging findings in these tumors.

Aorta, Abdominal↗
PubMed2001

Uterine fibroid embolization: assessment of treatment response using perfusion-weighted extraslice spin tagging (EST) magnetic resonance imaging.

In this pilot study, we demonstrate the feasibility of using an arterial spin tagging technique, Extraslice Spin Tagging (EST), to assess tumor perfusion before and after uterine fibroid embolization (UFE) and correlate the changes in perfusion with fibroid size reduction. We followed two patient volunteers over a six-month period. The perfusion-weighted image intensity decreased immediately after UFE. The size of the tumor decreased by 14% immediately after UFE and continued to decrease over a six-month period to 84%. The imaging methods presented allow for rapid measurement of tumor volume and the evaluation of perfusion of the tumor without the need for intravenous administration of gadolinium compounds. J. Magn. Reson. Imaging 2001;13:982-986.

Adult↗
PubMed2001

Dr. Gary J. Becker young investigator award: comparison of small-diameter type 1 collagen stent-grafts and PTFE stent-grafts in a canine model--work in progress.

PURPOSE: To report an in-progress experiment in a canine model in which two types of small-diameter stent-grafts-one constructed of polytetrafluoroethylene (PTFE) and the other of a new, type 1 collagen material-were compared regarding vessel patency, intimal hyperplasia formation, and tissue reaction. MATERIALS AND METHODS: Six mongrel dogs weighing 30-35 kg were used. Stent-grafts of 4-mm diameter and 20-mm length were constructed with use of balloon-expandable stainless-steel stents wrapped with either PTFE or a new type 1 collagen graft. Stent-grafts were placed in deep femoral arteries bilaterally (PTFE on one side, collagen on the other). Animals were followed for 2 weeks (n = 2), 6 weeks (n = 2), or 12 weeks (n = 2). Percent stenosis based on angiographic findings as well as thickness and area of neointimal hyperplasia were compared at each time point and compared with use of the Student t test. RESULTS: All devices were patent in the immediate postimplantation period. Five of six collagen stent-grafts and five of six PTFE implants were patent at follow-up. In-stent stenosis was undetectable angiographically in all five patent collagen stent-grafts. All five patent PTFE stent-grafts showed demonstrable in-stent stenosis (10%-60%), indicating a trend toward improved patency in collagen stent-grafts versus PTFE stent-grafts (P = .07). Neointimal hyperplasia was absent at 2 weeks in the collagen stent-grafts. Neointimal thickness increased to a maximum of 360 microm at 12 weeks in the collagen stent-grafts. For PTFE stent-grafts, neointimal hyperplasia was present in all samples and reached a maximum of 770 microm at 12 weeks (P = .03). CONCLUSIONS: Even in small-diameter vessels, type 1 collagen stent-grafts demonstrate excellent patency rates and favorable histologic findings. The type 1 collagen stent-graft technology merits further developmental efforts in preclinical models.

Animals↗
PubMed2001

Gadolinium contrast agents: their role in vascular and nonvascular diagnostic angiography and interventions.

Gadolinium-based contrast agents can be used for diagnostic and interventional angiographic procedures to reduce contrast-related nephrotoxicity or in patients with a history of severe allergic reaction to iodine-containing contrast material. These agents are best used in conjunction with CO(2) to complete nondiagnostic CO(2) angiograms and to monitor the progress of a percutaneous intervention. However, the total volume of gadolinium that can be administered, the reduced quality of gadolinium digital subtraction angiography images, and the increased cost of the gadolinium-based agents can limit their use.

Contrast Media↗
PubMed2001

Angiographic evaluation and treatment of transplant renal artery stenosis.

Transplant renal artery stenosis is an uncommon but important complication of renal transplantation. It is a potentially reversible cause of patient morbidity and allograft dysfunction, which can present both early and late in the post-transplant period. Although transplant renal artery stenosis can be detected using noninvasive imaging, definitive diagnosis and percutaneous treatment typically require the use of invasive angiographic techniques. In experienced hands, these studies can be performed safely, effectively and with a low risk of contrast induced nephrotoxicity when alternative contrast agents are used.

Algorithms↗
PubMed2001

Safety of CO(2)- and gadodiamide-enhanced angiography for the evaluation and percutaneous treatment of renal artery stenosis in patients with chronic renal insufficiency.

OBJECTIVE: The objective of our study was to evaluate the safety of CO(2) and gadodiamide angiography for diagnosing and percutaneously treating renal artery stenosis in patients with chronic renal insufficiency and presumed ischemic nephropathy. SUBJECTS AND METHODS: One hundred forty-six consecutive patients with chronic renal insufficiency (serum creatinine > 1.5 mg/dL) were examined for renal artery stenosis using CO(2) and gadodiamide as the angiographic contrast agents. If renal artery stenosis was detected, percutaneous balloon angioplasty with or without stenting was performed. In patients for whom 48-hr creatinine levels were available, we performed an analysis to determine the incidence of contrast-involved nephropathy (increase in serum creatinine of 0.5 mg/dL at 48 hr without identifiable cause). Major complications were reported up to 1 week, and mortality was reported up to 30 days after the procedure. RESULTS: Ninety-five patients had serum creatinine levels available at 48 hr. An increase in creatinine of greater than 0.5 mg/dL at 48 hr occurred in three patients (3.2%), presumably caused by CO(2), by gadodiamide, or by both. Neither diabetes nor the degree of preexisting chronic renal insufficiency was a predictor of worsening renal function 48 hr after the procedure. The volumes of CO(2) and gadodiamide used for diagnostic studies alone versus the volume used for interventional studies was not significantly different (for CO(2), p = 0.09; for gadodiamide, p = 0.30). Eleven major complications occurred in eight patients (5.5%). Two deaths (1.4%) occurred within 30 days. One death was due to cholesterol embolization and the other was not believed to be related to the procedure. CONCLUSION: Angiography and percutaneous treatment of renal artery stenosis in patients with chronic renal insufficiency and suspected ischemic nephropathy can be performed relatively safely using CO(2) and gadodiamide as angiographic contrast agents without an increased risk of complications. Contrast-induced nephropathy potentially occurred in 3.2% of patients. Neither the degree of underlying renal insufficiency nor diabetes was a risk factor for predicting a greater likelihood of renal function worsening at 48 hr of follow-up. The volumes of CO(2) and gadodiamide used in this study did not result in an increased risk of contrast-involved nephropathy.

Adult↗
PubMed2000

Lower extremity arteriography with use of iodinated contrast material or gadodiamide to supplement CO2 angiography in patients with renal insufficiency.

PURPOSE: To determine if the use of nonionic contrast material, as compared to the use of gadodiamide to supplement carbon dioxide angiography in patients with peripheral vascular disease (PVD) and chronic renal insufficiency (CRI), results in significant worsening of renal function. MATERIALS AND METHODS: Lower extremity angiographic procedures (diagnostic and diagnostic/intervention) were performed in 40 patients with CRI (baseline serum creatinine [Cr] > 1.5 mg/dL) using CO2 alone or CO2 supplemented with the use of either nonionic contrast material or gadodiamide (up to 0.4 mmol/kg). Serum creatinine levels were obtained before the procedure and at 48 hours after the procedure. The peak Cr level was also determined for patients with a significant (> 0.5 mg/dL) Cr elevation. RESULTS: Forty-two lower extremity angiographic procedures (19 diagnostic and 23 diagnostic/interventions) were performed in 40 consecutive patients from August 1997 to October 1998, with a mean preprocedure Cr of 2.2 mg/dL and a mean postprocedure Cr of 2.4 mg/dL. Twenty-five of the 40 patients (63%) had diabetes mellitus. Fifteen procedures, including six interventions, were performed utilizing CO2 and nonionic contrast material in 15 patients. Six of these 15 patients (40%) demonstrated a Cr increase > 0.5 mg/dL at 48 hours. Seven procedures, including two interventions, were performed with CO2 alone in seven patients. No patients in this group demonstrated an increase in serum creatinine of greater than 0.5 mg/dL at 48 hours. Twenty procedures, including 15 interventions, were performed with CO2 and gadodiamide in 18 patients. In one of these 20 procedures (5%) there was an increase in Cr > 0.5 mg/dL at 48 hours The difference in worsening renal function for the nonionic contrast group (six of 15) compared with the CO2/gadodiamide group (one of 20) was statistically significant (P = .03). When comparing the use of CO2 and nonionic contrast material versus CO2 alone and with gadodiamide (six of 15 versus one of 27), the difference is also statistically significant (P < .01). The average volume of supplemental contrast material was similar in the nonionic contrast material and gadodiamide groups, as was the average volume of supplemental nonionic contrast material in the six patients with an increased Cr. CONCLUSION: The use of small volumes of nonionic contrast material to supplement CO2 angiography in patients with PVD and CRI can be associated with a significant increased risk of worsening renal function when compared to angiography performed with CO2 alone or CO2 and gadodiamide.

Aged↗
PubMed2000

Feasibility of gadodiamide compared with dilute iodinated contrast material for imaging of the abdominal aorta and renal arteries.

PURPOSE: To determine the quality of digital abdominal angiograms obtained with use of full-strength, intra-arterial gadodiamide compared with similar volumes of half-strength iodinated contrast material for evaluating the abdominal aorta and renal vessels. MATERIALS AND METHODS: Twenty-five consecutive patients underwent digital subtraction arteriography of the abdominal aorta performed with equal volumes (32 mL) of either half-strength (300 mg/mL iodine) iodinated contrast material or full strength gadodiamide (0.11-0.25 mmol/kg) to evaluate the abdominal aorta and renal arteries. The contrast agent used was not known to the image readers. The abdominal aorta, left and right renal main renal artery, and first and second order segmental branches were graded separately as diagnostic or nondiagnostic by four angiographers. RESULTS: Images of the abdominal aorta were diagnostic 100% of the time for iodine and gadodiamide, 76% and 80% diagnostic for iodine and gadodiamide in the left main renal artery, respectively; and 100% and 80% diagnostic for iodine and gadodiamide in the right main renal artery, respectively. The first order segmental branches of the right and left renal arteries were graded diagnostic 72% and 56% of the time, respectively, for dilute iodinated contrast material, and 40% and 28% of the time, respectively, for gadodiamide. The second order segmental branches of the right and left kidney were graded diagnostic 24% of the time for iodinated contrast and 8% and 4% of the time, respectively, for gadodiamide. CONCLUSION: Full-strength, intra-arterial gadodiamide at doses smaller than 0.3 mmol/kg can produce diagnostic images of the abdominal aorta and main renal arteries. However, images of the intrarenal branches are usually not diagnostic.

Adult↗
PubMed1999

Perfusion of the kidney using extraslice spin tagging (EST) magnetic resonance imaging.

This study was undertaken to determine whether extraslice spin tagging (EST) perfusion-weighted magnetic resonance imaging is suitable for screening persons for renal perfusion deficits. Six normal and seven patient volunteers with suspected decreased renal perfusion due to renal vascular disease were imaged. X-ray angiograms were also obtained on all patients. The normalized EST signal intensity showed a linear correlation with respect to the percent stenosis measured from the X-ray angiograms. This demonstrates the potential utility of using EST for the evaluation of kidney perfusion, which was done without the need for exogenous MR contrast agents. EST is fast and less expensive than contrast-based methods. These features make EST a candidate for routine screening of patients for renal vascular disease and for the assessment of angiographically equivocal renal artery stenoses. J. Magn. Reson. Imaging 1999;10:886-891.

Adult↗
PubMed1999

Use of fibrin sealant to reduce bleeding after needle liver biopsy in an anticoagulated canine model: work in progress.

PURPOSE: Needle biopsy of the liver is a common diagnostic procedure. Although relatively safe, bleeding remains a potential complication and may occur more frequently in patients with coagulopathy. The purpose of this study was to evaluate the utility of a fibrin sealant in preventing bleeding after a 15-gauge needle biopsy of the liver in a canine model heparinized to simulate coagulopathy. MATERIALS AND METHODS: Fibrin sealant was delivered to biopsy tract sites in eight dogs anticoagulated with heparin (activated clotting time 387 seconds +/- 94) using the same sheath system that was employed to obtain the biopsy specimen. RESULTS: The results demonstrated complete hemostasis in the sealant-plugged tracts as compared to controls. Continuous bleeding was observed in none of the fibrin sealant-treated sites, compared with all of the control biopsy sites (P = .0078). CONCLUSION: These results demonstrate the high degree of efficacy of fibrin sealant delivered through a sheath system in plugging liver biopsy tracts and eliminating bleeding in a severely coagulopathic animal model. This indicates that fibrin sealant use in cutting needle biopsies can reduce major and minor complications associated with the procedure.

Animals↗
PubMed1999

Effect of Health Care Financing Administration regulation on radiology fellowship training.

RATIONALE AND OBJECTIVES: The purpose of this study was to assess the effect of Health Care Financing Administration (HCFA) regulations on radiology fellowship training. MATERIALS AND METHODS: Surveys were sent to 157 fellowship program directors in body imaging and vascular/ interventional radiology. Questions addressed program accreditation status, faculty supervision of fellows, and any change in faculty supervision of fellows in response to HCFA's revised plan for Medicare Part B reimbursement. RESULTS: Eighty of 157 (51%) surveys were returned. Thirty (37%) respondents indicated supervision of fellows had changed after institution of the new HCFA rules in July 1996. Vascular/interventional program directors (n = 25, 49%) were more likely to have changed their practice than body imaging program directors (n = 5, 17%). Nearly all respondents (29 of 30, 97%) indicating a change stated supervision had increased. Twenty-seven (33%) respondents also indicated faculty supervision was beyond that necessary for patient care and house staff education; most of these respondents (21 of 27, 78%) stated the new HCFA regulations were responsible. Many program directors also expressed concern the HCFA regulations might prevent fellows from obtaining sufficient experience to effectively learn independent clinical decision-making. CONCLUSION: HCFA regulations intended to address attending physician billing practices at teaching institutions may have had the unintended effect of substantively altering the training of radiology fellows.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed1999

Renal insufficiency: usefulness of gadodiamide-enhanced renal angiography to supplement CO2-enhanced renal angiography for diagnosis and percutaneous treatment.

PURPOSE: To determine whether gadodiamide is a safe and useful angiographic contrast agent for help in diagnosis and percutaneous treatment of renal artery stenosis in patients with renal insufficiency. MATERIALS AND METHODS: Diagnostic renal angiography and percutaneous renal interventions were performed by using gadodiamide (total dose, 0.3 mmol/kg) and CO2 as intraarterial contrast agents in 25 procedures in 24 patients with renal insufficiency. Serum creatinine levels were obtained within 24 hours before and at 24 and 48 hours after the procedure. Increases in serum creatinine of more than 44 mumol/L were considered clinically important. Gadodiamide-enhanced angiograms were compared with CO2-enhanced angiograms. RESULTS: In 23 (92%) of 25 procedures, there was no increase in serum creatinine level at 48 hours. One patient with acute and chronic rejection of a renal transplant and one with evidence of cholesterol embolization had a clinically important increase in serum creatinine level at 48 hours. No marked increase in creatinine level was observed in patients with relatively low baseline levels (n = 19). Gadodiamide-enhanced angiograms appeared to be better than CO2-enhanced angiograms for help in identifying renal artery occlusions, visualizing renal vessels incompletely filled with CO2, and determining the progress of intervention. CONCLUSION: Gadodiamide appears to be a safe and useful intraarterial contrast agent in patients with renal insufficiency and can be used to supplement or confirm CO2-enhanced angiographic findings.

Acute Disease↗