Acute renal failure after arteriography with a gadolinium-based contrast agent.
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Acute Kidney Injury↗
Biomedical subjects
E K Yucel
Publications and source records attributed to E K Yucel.
A new generation endovascular graft for repair of abdominal aortic aneurysms.
BACKGROUND: Several endovascular grafts are currently being evaluated for repair of abdominal aortic aneurysms (AAA). The goals of our study were twofold. First was to develop a new endovascular graft with several advantages over previous devices: (1) smaller size (16 fr), (2) recapturability (the device can be partially deployed and then recaptured and moved to a new location or entirely removed if needed), and (3) accuracy and ease of placement. Our second goal was to develop an animal model in which a full-scale prototype of the device could be tested. METHODS: Our final endovascular graft prototype was developed after extensive in-vitro testing, and trials of earlier prototypes in dog, pig, and female sheep models. Uncastrated male sheep, 75 to 100 kg, were chosen as the animal model in which to test the device. These animals had infrarenal aortas that were comparable to that of small humans, with diameters of 12 to 15 mm. Two models were used: (1) native infrarenal aorta, and (2) artificial infrarenal aneurysm. Pre-implant and postimplant angiography and intravascular ultrasound were used to evaluate graft placement, and were repeated prior to euthanasia and necropsy. RESULTS: The final prototype was implanted in 22 animals. Sixteen animals had the device placed in their native infrarenal aorta. Three animals were sacrificed immediately after implantation, and 6 more were euthanized after 2 weeks (n = 2), 6 weeks (n = 2), and 3 to 4 months (n = 2). In 7 animals the device is still in place. All procedures were successful. Pathology confirmed complete exclusion of the aorta and thrombosis of all lumbar branches covered by the graft. There was no evidence of graft malposition, migration, or perigraft leak, and no evidence of significant vessel injury on histology. Six animals had artificial aneurysms surgically created and then repaired with the device. A technical error resulted in a failure in 1 case; the remaining aneurysms were all successfully excluded. CONCLUSIONS: We report the development of a new endovascular prosthesis for the repair of AAA. Newer design features provide for smaller delivery size (16 fr), facilitate accurate placement, and provide the option when the device is partially deployed to recapture and reposition the device if necessary. In addition, we have developed an animal model in which this device, and future endovascular aortic devices, can be tested.
Animals↗
MR imaging of soft tissues adjacent to orthopaedic hardware: techniques to minimize susceptibility artefact.
This article demonstrates and compares imaging of orthopaedic hardware (fixation plates, screws, Kischner wire and prostheses) using gradient-echo, spin-echo and fast spin-echo sequences. It describes simple techniques which minimize susceptibility artefact induced by these components at magnetic resonance (MR) imaging, allowing visualization of adjacent soft tissues. The article emphasizes the importance of selecting the appropriate imaging plane in order to avoid hardware distortion of slice select gradients, emphasizes the importance of selecting frequency encoding gradient axes in order to orientate the long axis of the artefact away from the tissue of interest and, finally, compares the marked susceptibility artefact observed adjacent to hardware using gradient-echo with the artefact reduction achieved by using fast spin-echo sequences.
Artifacts↗
T2-weighted MR imaging of the liver: optimization of hybrid-RARE sequences.
The objectives of this study were to optimize T2-weighted hybrid-RARE pulse sequences for clinical MR imaging of the liver, and to compare them to the conventional spin-echo (CSE) sequence. Specifically, the ranges of the echo train length (ETL) and the effective echo time (TEeff) were investigated to optimize image quality and liver-spleen contrast, in healthy volunteers. A total of thirteen volunteers were scanned at 1.5 Tesla with an extensive array of hybrid-RARE scans. The images were analyzed quantitatively with respect to CNR (contrast-to-noise ratio of spleen vs. liver), SNR (signal to noise ratio of the spleen), SIR (signal intensity ratio of liver and spleen) and CDR (contrast difference ratio between the spleen and liver). The images were also analyzed qualitatively with respect to image sharpness, vascular artifacts, ghosting, chemical shift, and truncations. Results of quantitative analysis indicated that CDR and SIR of hybrid-RARE at higher ETL (> 13) were consistently better than both the reference CSE and the lower ETL sequences (p < 0.05) at all TEeff. SNR was slightly inferior for all hybrid-RARE sequences than for the CSE sequence. Image quality for hybrid-RARE sequences with ETL > 13 proved to be consistently better than that for the CSE (TE = 90 ms) with respect to imaging sharpness, vascular artifacts and ghosting artifacts (p < 0.05). In conclusion, the optimized hybrid-RARE sequences with ETL greater than or equal to 13 are capable of producing sharp and relatively artifact free images with the advantage of a much greater acquisition time efficiency.
Adult↗
Aortic root abscess with fistula formation.
Aortic root abscess is a common complication of aortic valve endocarditis. However, aortic root abscess and formation of a fistula from the aortic root to the right ventricular outflow tract in the setting of a native aortic valve and previous repair of an aortic dissection with a Dacron graft is an uncommon event. Transesophageal echocardiography is superior to transthoracic echocardiography for the diagnosis of aortic root abscess. To our knowledge, no studies have compared the diagnostic value of cardiac MRI with transesophageal echocardiography for this condition.
Abscess↗
MR urography: evaluation of a three-dimensional fast spin-echo technique in patients with hydronephrosis.
OBJECTIVE: The purpose of this study was to evaluate a respiratory-triggered three-dimensional (3D) fast spin-echo technique for MR urography in patients with urinary tract dilatation. SUBJECTS AND METHODS: Using a respiratory-triggered 3D fast spin-echo technique for MR urography, we obtained MR urograms in 24 patients with hydronephrosis. Images were separately reviewed by two radiologists who evaluated the images for quality, presence of, degree of, level of, and cause of urinary tract dilatation. Findings were compared with all available clinical, imaging, surgical, and pathologic data, which served as the standard of reference. Sensitivity, specificity, positive predictive value, and negative predictive value of MR urograms were calculated for each reviewer to reveal urinary tract dilatation. For each reviewer, we calculated agreement between MR urography and the standard of reference using kappa analysis. We also calculated interobserver agreement for the presence of degree of, level of, and cause of urinary tract dilatation. RESULTS: Technically adequate MR urograms were obtained in all patients. For detection of urinary tract dilatation by MR urography, the sensitivity was 100%; specificity was 96%; positive predictive value was 96%; and negative predictive value was 100%. The kappa values for the degree of dilatation seen on the MR urograms were 0.57 (moderate) and 0.43 (moderate); for the level of obstruction, 0.74 (substantial) and 0.55 (moderate); and for the cause of obstruction, 0.66 (moderate) and 0.66 (moderate). Interobserver agreement for seeing dilatation on MR urograms was 1.0 (perfect agreement); degree of dilatation, 0.48 (moderate); level of dilatation, 0.60 (moderate); and cause of dilatation, 0.74 (substantial). CONCLUSION: MR urography using a respiratory-triggered 3D fast spin-echo technique can produce high-resolution images of the urinary tract by which reviewers can achieve a high sensitivity (100%) and specificity (96%) for the detection of urinary tract dilatation. On MR urograms, reviewers also identified the cause of obstruction in most patients: 92% (reviewer 1) and 88% (reviewer 2).
Adult↗
Improved contrast of enhancing brain lesions using contrast-enhanced T1-weighted fast spin-echo MR imaging.
OBJECTIVE: The purpose of this study was to evaluate the ability of T1-weighted fast spin-echo MR sequences to provide improved contrast-to-noise ratios for contrast-enhanced lesions during acquisition times shorter than those used for conventional T1-weighted spin-echo MR sequences. SUBJECTS AND METHODS: We compared contrast-to-noise ratios of 32 enhancing brain lesions in 25 patients on T1-weighted spin-echo (546/10 [TR/TE]; two excitations; acquisition time, 4 min 12 sec) and on fast spin-echo (546/10 [TR/effective TE]; echo-train length, 4; echo spacing, 10 msec; two excitations; acquisition time, 1 min 45 sec) MR images obtained at 1.5 T after i.v. administration of 0.10 mmol/kg gadopentetate dimeglumine. RESULTS: The contrast-enhanced T1-weighted fast spin-echo MR images showed approximately a 12% reduction in the signal-to-noise ratios of the background white matter without an accompanying reduction in the signal-to-noise ratios of the enhancing lesions or CSF when compared with the contrast-enhanced T1-weighted spin-echo MR images. The contrast-enhanced T1-weighted fast spin-echo MR images provided a 23% improvement in the contrast-to-noise ratios of enhancing lesions over the contrast-enhanced T1-weighted spin-echo images (p < .001). CONCLUSION: Contrast-enhanced T1-weighted fast spin-echo MR imaging showed a statistically significant improvement in contrast-to-noise ratios at much shorter scan times than those used in conventional contrast-enhanced T1-weighted spin-echo MR imaging.
Adult↗
Evaluation of renal artery stenosis with dynamic gadolinium-enhanced MR angiography.
OBJECTIVE: The purpose of this study was to compare dynamic gadolinium-enhanced three-dimensional spoiled gradient-recalled MR angiography with conventional arteriography in the evaluation of proximal renal artery stenosis (RAS). MATERIALS AND METHODS: MR angiography and conventional arteriographic examinations of 30 patients evaluated for RAS were analyzed retrospectively. Three-dimensional MR angiography was performed with an RF spoiled gradient-recalled imaging sequence acquired during the dynamic i.v. injection of gadolinium (0.2-0.3 mmol/kg), MR data and conventional arteriograms were independently evaluated for the number and location of renal arteries and the degree and location of stenoses. The patients had a mean age of 70 years old and a mean serum creatinine level of 2.9 mg/dl, reflecting a population in whom atherosclerotic RAS was the primary concern. RESULTS: Gadolinium-enhanced MR angiography revealed 100% of main renal arteries. For RAS of 50% or greater occlusion, the technique was 100% sensitive and 71% specific; the negative predictive value was 100%. The technique was 100% sensitive and 71% specific for RAS of 75% or greater occlusion. CONCLUSION: Dynamic gadolinium-enhanced three-dimensional spoiled gradient-recalled MR angiography has a high sensitivity for revealing proximal RAS and is a quick and reliable technique for obtaining helpful anatomic information.
Aged↗
Iliac artery stenosis measurements: comparison of two-dimensional time-of-flight and three-dimensional dynamic gadolinium-enhanced MR angiography.
OBJECTIVE: We compared our ability to make iliac artery measurements on two-dimensional (2D) time-of-flight (TOF) and three-dimensional dynamic gadolinium-enhanced MR angiography with conventional angiography. SUBJECTS AND METHODS: Fifteen patients with lower extremity vascular disease underwent pelvic MR angiography. Parameters of the cardiac-gated axial 2D TOF sequence included a TR/TE of 24/7 msec and a 50 degrees flip angle. Parameters for the three-dimensional MR angiography sequence, in which we obtained 32 coronal 3-mm slices with fat suppression, included a TR/TE of 32/5 msec and a 40 degrees flip angle during infusion of 40 ml of gadolinium-chelated contrast material. Patients then underwent conventional angiography of the iliac arteries. Maximum stenosis in the common iliac, external iliac, and common femoral arteries was then measured. Measurements of stenosis were compared by repeated measures of analysis of variance. Sensitivity and specificity were calculated for identification of greater than or equal to 50% stenosis and less than 50% stenosis. RESULTS: For all vessels studied, we found no significant difference in measurements obtained from the gadolinium-enhanced MR angiography technique and those obtained from conventional angiography (p > .05). However, significantly different stenotic measurements were obtained from the 2D TOF MR angiography sequence and conventional angiography. In the external iliac arteries, 2D TOF MR angiography exaggerated stenoses most substantially. Gadolinium-enhanced MR angiography achieved 100% sensitivity and specificity. CONCLUSION: Dynamic gadolinium-enhanced MR angiography was more accurate than 2D TOF MR angiography when measuring degree of stenosis in the iliac arteries.
Adult↗
Black blood MR angiography using multislab three-dimensional TI-weighted turbo spin-echo technique: imaging of intracranial circulation.
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Adult↗
A comparison of whole-body turboSTIR MR imaging and planar 99mTc-methylene diphosphonate scintigraphy in the examination of patients with suspected skeletal metastases.
OBJECTIVE: This study was undertaken to compare whole-body turbo short inversion time inversion recovery MR imaging and 99mTc-methylene diphosphonate planar scintigraphy in the examination of patients with suspected skeletal metastases. SUBJECTS AND METHODS: Twenty-five patients with known or suspected skeletal metastatic disease underwent both whole-body turbo short inversion time inversion recovery MR imaging and whole-body 99mTc-methylene diphosphonate scintigraphy. RESULTS: MR imaging revealed metastases at 57 of 175 possible sites (sensitivity, 96.5%, specificity, 100%; positive predictive value, 100%). Scintigraphy revealed metastases at 43 of 175 possible sites (sensitivity, 72%; specificity, 98%; positive predictive value, 95%) (McNemar test, 0.01; p = .016). Discrepancies in skeletal evaluation by whole-body MR imaging and scintigraphy were observed in six (24%) of 25 patients. Soft-tissue abnormalities were identified in 13 (52%) of 25 patients with MR imaging alone. CONCLUSION: Preliminary results suggest that whole-body MR imaging is an effective method of examining patients with suspected skeletal metastases, with better sensitivity than conventional planar 99mTc-methylene diphosphonate scintigraphy.
Adult↗
MR urography.
Developments of MR imaging of static fluid has led to the emergence of MR urography (MRU) as a potential imaging technique of the urinary system. MRU has been shown to be highly sensitive in the diagnosis of urinary obstruction, defining the severity of dilatation, the site, and in the majority of cases, the cause of obstruction. At the current level of resolution, however, MR cannot consistently demonstrate nonobstructive or small obstructing calculi. Demonstration of perinephric and periuretic edema in obstruction helps in the differentiation of acute from nonacute urinary obstruction. MRU has shown potential in the work-up of urinary disease for which intravenous urography used to be performed, without the hazards of intravenous contrast administration.
Humans↗
Multisection T1-weighted hybrid-RARE: a pulse sequence for MR imaging of the entire liver during suspended respiration.
It is shown that the maximum average-data-collection-speed (ADCS) of multisection 2D hybrid-RARE sequences is independent of TR and TEeff, and a monotonically increasing function of echo-train-length (ETL). This result was used in the design of an optimized T1-weighted hybrid-RARE sequence that produces 20 images of the abdomen in 31 s divided into four breath-hold periods. The resulting ADCS is 58 lines in k-space per second. Twenty-four subjects (2 healthy volunteers and 22 patients) were imaged with a protocol that also included: (a) breath-hold T1-weighted FLASH which acquires data at 34 lines in k-space per second (49 s scan time), and (b) T1-weighted conventional spin-echo (9:44 minutes scan time) with respiratory compensation. The experiments show that this T1-weighted-hybrid-RARE sequence has: (1) a level of T1 weighting that is comparable with the conventional sequences, (2) very low vulnerability to susceptibility artifacts, (3) high data acquisition efficiency, and (4) higher SNR than T1-weighted-FLASH. In conclusion, the T1-weighted-hybrid-RARE sequence described herein is an efficacious and reproducible technique for rapid imaging of the upper abdomen during suspended respiration.
Adult↗
Magnetic resonance cholangiography: comparison with endoscopic retrograde cholangiopancreatography.
BACKGROUND & AIMS: Magnetic resonance cholangiography (MRC) is a noninvasive diagnostic modality capable of producing high-quality images of the biliary tree. The purpose of this study was to determine in a prospective, blinded fashion the sensitivity and specificity of three-dimensional fast spin-echo (3D FSE) MRC for the evaluation of biliary tract abnormalities. METHODS: Forty-six patients referred for elective direct cholangiography (45 endoscopic retrograde cholangiopancreatography and 1 percutaneous transhepatic cholangiography) were studied prospectively with 3D FSE MRC during a 1-year period. All images were interpreted blindly by two radiologists. The presence of dilatation, strictures, and intraductal abnormalities was recorded. Sensitivity and specificity of 3D FSE MRC were determined using findings on direct cholangiography as the gold standard. RESULTS: MRC images of diagnostic quality were obtained in 44 (95.7%) of the patients. Sensitivity for the detection of bile duct dilatation (n = 27), biliary strictures (n = 10), and intraductal abnormalities (n = 7) was 96.3%, 90%, and 100%, respectively. In addition, the MRC showed 16 of 17 patients with normal bile ducts (specificity, 94.1%). CONCLUSIONS: MRC has a very high sensitivity and specificity in the evaluation of the biliary tract. Based on these data, we believe that the efficacy of MRC using 3D FSE is sufficient to warrant its use in the routine diagnosis of biliary tract disease.
Adolescent↗
MR cholangiopancreatography after unsuccessful or incomplete ERCP.
PURPOSE: To assess the value of magnetic resonance (MR) cholangiopancreatography in patients in whom endoscopic retrograde cholangiopancreatography (ERCP) was unsuccessful or did not completely delineate ductal abnormalities. MATERIALS AND METHODS: MR cholangiopancreatography was performed in 37 consecutive patients because ERCP was unsuccessful (n = 20), postsurgical biliary-enteric anatomy was present (n = 10), or evidence of complete pancreatic duct obstruction was found ar ERCP (n = 7). RESULTS: MR cholangiopancreatography was successful in all patients. Eleven patients had normal MR findings and required no further intervention. Eight patients has abnormalities that were detected with MR but were followed up clinically. Eleven patients subsequently underwent laparotomy, three underwent therapeutic percutaneous transhepatic cholangiography (PTC), two underwent diagnostic (PTC), and one underwent ultrasound-guided biopsy. CONCLUSIONS: MR cholangiopancreatography plays an important role in the care of patients in whom ERCP is unsuccessful or incomplete and when technical difficulties can be anticipated.
Bile Duct Diseases↗
MR angiography, the Health Care Financing Administration, and Laetrile.
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Centers for Medicare and Medicaid Services, U.S.↗
Follow-up sonographic examinations at 3 and 6 months for patients with a diagnosis of deep vein thrombosis.
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Anticoagulants↗
Magnetic resonance cholangiopancreatography of the biliary ducts: techniques, clinical applications, and limitations.
Magnetic resonance cholangiopancreatography (MRCP) is a noninvasive method capable of generating images of the biliary tree that resemble those provided by direct invasive cholangiographic techniques. MRCP is based on the ability of heavily T2-weighted sequences to obtain images in which static fluid in the bile ducts appears bright against a dark background. MRCP allows display of both cross-sectional and projectional information without the need for contrast media injection. Because the projectional images resemble those of direct cholangiography, they are readily accepted by gastroenterologists and surgeons. Although the exact role of MRCP for the evaluation of the biliary system has not been fully defined, continued advances in both technique and experience have begun to clarify the potential uses of MRCP in the workup of biliary diseases. This review will discuss these developing clinical roles and their implications for patient management as well as the imaging principles, techniques, limitations, and artifacts of MRCP.
Artifacts↗