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M R Prince

Publications and source records attributed to M R Prince.

At least 37 records · Page 2Linked to original sources
PubMed1999

Magnetic resonance imaging of the aorta and branch vessels.

Magnetic resonance imaging (MRI) can provide a comprehensive evaluation of the aorta and its major branches. T1-weighted spin-echo images and cine-MRI have long been known to be useful for the evaluation of congenital aortic anomalies, aortic aneurysms, and aortic dissections. Gadolinium (Gd)-enhanced three-dimensional magnetic resonance angiography (MRA) is a more recent development that affords better spatial resolution. This technique can be performed during an individual breath-hold and does not require electrocardiographic gating. The data from Gd-enhanced three-dimensional MRA, furthermore, can be used both for projectional angiographic viewing and for multiplanar reformation. In this article, MRI of the aorta and its major branches will be reviewed, with emphasis on the newer technique of Gd-enhanced three-dimensional MRA.

Aorta↗
PubMed1999

Polyclonal, nonspecific 111In-IgG scintigraphy in the evaluation of complicated osteomyelitis and septic arthritis.

BACKGROUND: In this investigation we tested the hypothesis that 111In-IgG scintigraphy can differentiate infectious from sterile inflammatory processes in patients with complicated osteomyelitis or septic arthritis. METHODS: A prospective university hospital based study was performed over 18 months. We studied 31 sites of suspected infection, in 25 adult patients, (age 18 to 74 years, 12 females and 13 males) referred with clinical presentations compatible with complicated osteomyelitis or septic arthritis and in whom proof of the infection was likely to be obtained. The clinical setting in these patients was previous trauma, recent surgery, peripheral vascular disease or adjacent soft tissue infection. Whole body scintigraphy was performed at 1-6, 18-24 and 42-48 hours after administration of 55 MBq of 111In-IgG and results were compared to radiographs, 99mTc-MDP skeletal scintigraphy, biopsy specimens (9 sites) or synovial fluid aspirates (4 sites) and clinical follow-up. RESULTS: Of the 31 sites evaluated, 68% (21/31) were interpreted as negative for abnormal tracer accumulation and 32% (10/31) were considered positive. In patients who underwent biopsy and/or synovial fluid aspiration, 6 of 7 sites were correctly interpreted as positive; sensitivity 86%. Five of 6 sites were correctly interpreted as negative; specificity 83%. When all patients were considered using clinical follow-up in addition to culture results, 9 of 10 sites were correctly interpreted as positive (sensitivity 90%) and 20 of 21 patients were correctly interpreted as negative (specificity 95%). CONCLUSIONS: 111In-IgG scintigraphy is useful for detection of musculoskeletal infection in patients in whom sterile inflammatory events simulate infectious processes.

Adolescent↗
PubMed1999

Pulmonary MR angiography.

Imaging of the pulmonary vasculature with "inflow" MR imaging is difficult both to perform and interpret. Over the last few years, however, a greater understanding of contrast-enhanced techniques and the availability of fast gradient performance have facilitated the development of high resolution breath-hold images with high contrast-to-noise ratios. Increasing clinical experience with these contrast-enhanced techniques suggests a likely role for MR angiography in investigating patients with a variety of pulmonary vasculature disorders, including pulmonary embolism, pulmonary hypertension and arterio-venous malformation.

Aged↗
PubMed1998

In vitro model of arterial stenosis: correlation of MR signal dephasing and trans-stenotic pressure gradients.

PURPOSE: Turbulent flow just distal to stenoses causes signal loss (dephasing) on magnetic resonance angiography (MRA). This study correlates dephasing with trans-stenotic pressure gradients in an in vitro model of arterial stenosis. MATERIALS AND METHODS: Three-dimensional (3D) phase contrast, 2D time-of-flight, and 3D spoiled gradient echo MRA with/without gadolinium and varied echo time were performed for a system consisting of a peristaltic perfusion pump and a silastic vessel with stenoses of varying caliber. Length and diameter of dephasing jets were measured, and volumes calculated at varying pressure gradients and echo times, then correlated with percentage cross-sectional area stenosis as measured by conventional angiography. RESULTS: Dephasing occurred in all sequences at pressure gradients of > or =4 mmHg (1 mmHg = 133 Pa) and stenoses of greater than 70%, and varied directly with pressure gradient. The dephasing was greatest for 3D phase contrast (PC). Gadolinium did not diminish dephasing. CONCLUSIONS: MRA signal dephasing at stenoses varies directly with pressure gradient. MRA may provide a non-invasive means for determining the hemodynamic significance of arterial stenoses.

Arterial Occlusive Diseases↗
PubMed1998

Arterial-phase three-dimensional gadolinium magnetic resonance angiography of the renal arteries. Strategies for timing and contrast media injection: original investigation.

RATIONALE AND OBJECTIVES: The authors review different imaging and contrast-media infusion strategies for arterial-phase three-dimensional (3D) gadolinium-enhanced magnetic resonance angiography (Gd-MRA). METHODS: The influence of physicochemical factors on the infusion of contrast media, including viscosity, flow rate, inline pressure, and cannula size, is assessed. The combination of manual or automated contrast-media administration with timing-dependent or -independent 3D Gd-MRA techniques is reviewed regarding the aspects of effectiveness, robustness, image quality, and costs. RESULTS: For effective bolus delivery with high flow rates, the type and temperature of the contrast media, the size of the cannula, and an immediate saline flush must be considered. Timing-dependent techniques based on a test bolus and using automated contrast-media infusion as well as timing independent techniques such as MR SmartPrep or multiphase 3D Gd-MRA by using a manual injection with a SmartSet tubing set, are all effective procedures for arterial phase 3D Gd-MRA. CONCLUSIONS: Manual contrast-media injection with a tubing set can be used for timing-independent MRA techniques. The multiphase 3D Gd-MRA approach seems to be favorable for different MR systems, robustness, and speed.

Contrast Media↗
PubMed1998

Optimizing three-dimensional gadolinium-enhanced magnetic resonance angiography. Original investigation.

RATIONALE AND OBJECTIVES: This primarily theoretical work examines three-dimensional gadolinium-enhanced magnetic resonance angiography f8p4Gd-MRA) with the goal of understanding how to achieve the best possible images with respect to signal to noise ratio (SNR) and k-space induced artifacts. Patient variables, contrast injection schemes, and pulse sequence parameters are considered for this purpose. METHODS: A theoretical analysis, including computer simulation, describes how contrast material injection profiles influence 3D Gd-MRA images, both in terms of intravascular signal and resultant artifacts. Further theoretical analysis of the spoiled gradient refocused pulse sequence describes how to maximize SNR. Clinical imaging complements computer modeling. RESULTS: Equations were derived relating contrast injection parameters and pulse sequence variables to SNR and artifacts. For present imaging equipment, administering contrast material over a duration of 60% to 80% of the total imaging time and using fractional echo techniques gives the best SNR without significantly sacrificing image quality. CONCLUSIONS: Three-dimensional Gd-MRA can be tailored to a specific clinical situation and imaging system through the use of proper breath-holding, bolus timing, Gd administration, and pulse sequence design.

Artifacts↗
PubMed1998

Gadolinium-enhanced magnetic resonance venography of the portal venous system prior to transjugular intrahepatic portosystemic shunts and liver transplantation. Original investigation.

RATIONALE AND OBJECTIVES: The accuracy of gadolinium-enhanced magnetic resonance venography (GdMRV) in identifying visceral venous abnormalities was assessed in patients before they underwent transjugular intrahepatic portosystemic shunt (TIPS) or orthotopic liver transplantation (OLT). METHODS: Twenty-seven patients with portal hypertension underwent GdMRV and transcatheter venography prior to OLT or TIPS. The gadolinium dose was 0.5 mL/kg (0.25 mmol/kg), administered by rapid hand injection. Coronal 3D spoiled gradient-echo GdMRV was performed in a single breath-hold. Four blinded reviewers retrospectively evaluated coronal maximum intensity projection (MIP) images, while two reviewers evaluated the MIPs and multiplanar reconstructions. Abnormalities that could affect transjugular intrahepatic portosystemic shunt or transplantation were noted and compared with the results of corresponding catheter venograms read by a separate blinded reviewer. RESULTS: Abnormalities were identified by GdMRV with a sensitivity and specificity of 83% and 97% for the right hepatic vein, 86% and 100% for the main portal vein (MPV), 42% and 99% for the right portal vein, 54% and 94% for the left portal vein, 61% and 96% for the superior mesenteric vein, and 74% and 91% for the splenic vein. Varices and shunts were correctly identified with a sensitivity of 96%. Multiplanar reconstruction increased MPV sensitivity to 100%. CONCLUSION: Vascular abnormalities that affect TIPS and OLT can be identified by GdMRV. Multiplanar reconstruction increased the accuracy to 100% for the MPV.

Catheterization, Central Venous↗
PubMed1998

Renal anatomic changes on magnetic resonance imaging and gadolinium-enhanced magnetic resonance angiography after renal revascularization. Original investigation.

RATIONALE AND OBJECTIVES: The anatomic and hemodynamic renal changes after renal arterial revascularization (RAR) were investigated. METHODS: Thirty-seven kidneys and 40 renal arteries were evaluated in 20 patients by using magnetic resonance imaging/magnetic resonance angiography (MRI/MRA) to assess pre- and post-RAR renal length and mass, parenchymal thickness, renal enhancement, renal artery caliber, poststenotic dilation, and signal dephasing on 3D phase contrast (PC). The kidneys and renal arteries were segregated into three groups. Group 1 included 16 patients who benefited from RAR (defined as clinical improvement based on decreased serum creatinine or fewer number of antihypertensive medications) in whom 26 renal arteries in 25 kidneys were studied. Intervention included renal artery endarterectomy (n = 20); aortorenal bypass (n = 3); renal artery reimplantation (n = 3); and percutaneous transluminal angioplasty (PTA; n = 1). A total of 27 interventions was performed, as PTA failed for one patient who subsequently underwent aortorenal bypass before reimaging. Group 2 included four patients who did not clinically benefit. A total of eight revascularized arteries were studied in seven kidneys. In group 3, six renal arteries in five kidneys from groups 1 and 2 without RAS/RAR were analyzed as an internal control. RESULTS: Technical success (defined as increased vessel caliber after intervention) was achieved in 33 of the 34 revascularized arteries. A statistically significant increase in renal length occurred regardless of clinical outcome (pre-RAR, 9.5 cm; post-RAR, 10.5 cm; P < 0.0001). Parenchymal thickness and renal mass, however, improved only in patients who benefited clinically from RAR. Parenchymal enhancement was unchanged in any of the groups studied. No significant morphologic changes were detected in the control group. CONCLUSIONS: Magnetic resonance imaging and Gd-MRA detect anatomic and hemodynamic changes that occur with renal revascularization.

Adult↗
PubMed1998

Magnetic resonance angiography with gadomer-17. An animal study original investigation.

RATIONALE AND OBJECTIVES: Our purpose was to investigate a "blood pool" contrast agent for abdominal and thoracic MR angiography by comparison with standard ionic and nonionic gadolinium-based contrast agents, which redistribute into the extracellular fluid compartment. METHODS: Abdominal and thoracic MR angiography was performed in three adult dogs using a three-dimensional spoiled gradient echo pulse sequence before and after intravenous administration of one of three gadolinium-based contrast agents (gadopentetate dimeglumine, gadobutrol, and gadomer-17). Each compound was tested at five different doses in all three dogs. Quantitative analysis of signal-to-noise ratio (SNR) was performed in the aorta, inferior vena cava (IVC), liver, spleen, kidney (medulla and cortex), fat, and muscle. RESULTS: Gadomer-17 improved visualization of vascular anatomy at doses of 0.025, 0.05, 0.1, and 0.2 mmol/kg with three-fold greater aorta SNR during the arterial phase and more than four-fold greater aorta and IVC SNR during the equilibrium phase, in comparison with gadopentetate dimeglumine and gadobutrol at equal doses. CONCLUSIONS: Gadomer-17 is a promising contrast agent for both arterial phase and equilibrium phase MR angiography.

Adipose Tissue↗
PubMed1998

Vascular complications of liver transplantation: evaluation with gadolinium-enhanced MR angiography.

PURPOSE: To evaluate use of gadolinium-enhanced magnetic resonance (MR) angiography in detection of vascular complications of liver transplantation. MATERIALS AND METHODS: Thirteen liver transplant recipients suspected to have vascular complications were evaluated with gadolinium-enhanced MR angiography by using a three-dimensional spoiled gradient-echo breath-hold technique during the arterial and venous phases of a high-dose (42 mL) bolus injection of gadolinium contrast material. Conventional angiography (n = 11) and surgery (n = 3) were used as the standard of reference. The transplant hepatic artery, celiac trunk, superior mesenteric artery, portal vein, superior mesenteric vein, splenic vein, hepatic veins, and inferior vena cava (IVC) were evaluated for thrombosis or stenosis by two radiologists. RESULTS: Ten vascular complications were identified with conventional angiography or surgery: transplant hepatic artery thrombosis (n = 3) or stenosis (n = 3), portal vein stenosis (n = 1) or occlusion (n = 2), and suprahepatic IVC stenosis (n = 1). All 10 complications were correctly diagnosed with MR angiography. There was agreement between results of MR angiography and conventional angiography or surgery in 58 of 62 vessels evaluated (94%). There was minor disagreement in four vessels (6%). CONCLUSION: Three-dimensional gadolinium-enhanced MR angiography may have the potential to enable accurate diagnosis of vascular complications of liver transplantation.

Adolescent↗
PubMed1998

Contrast-enhanced MR angiography: theory and optimization.

It is now possible to perform contrast arteriography safely and rapidly by taking advantage of gadolinium contrast agents and three-dimensional MR imaging. Although the development of this approach to arteriography is in its infancy, the image quality already rivals conventional arteriography. As we continue to develop this technique by taking advantage of more pulse sequence tricks, improving hardware, and improving contrast agents, the field of vascular imaging will undoubtedly be transformed. This article discusses the fundamental concepts underlying this approach to angiography.

Contrast Media↗
PubMed1998

Renal MR angiography.

Three-dimensional gadolinium MR angiography (3D-Gd-MRA) accurately visualizes the renal arteries with almost no degradation from inplane saturation or motion artifacts. The diagnostic accuracy for detecting and grading of renal artery stenosis, as well as the assessment of other vascular pathology, approaches that of conventional x-ray angiography. For the renovascular system, this technique requires precise contrast media bolus timing since multiple successively enhancing structures are present. Details on performing renal MR angiography, strategies for image analysis, and examples of common renal vascular pathology are reviewed. The 3D-Gd-MRA protocol can be easily combined with other MR imaging techniques to provide a comprehensive assessment of the hemodynamic and functional significance of renal artery stenosis.

Aneurysm↗
PubMed1997

Diagnosis of pulmonary embolism with magnetic resonance angiography.

BACKGROUND: Diagnosing pulmonary embolism may be difficult, because there is no reliable noninvasive imaging method. We compared a new noninvasive method, gadolinium-enhanced pulmonary magnetic resonance angiography, with standard pulmonary angiography for diagnosing pulmonary embolism. METHODS: A total of 30 consecutive patients with suspected pulmonary embolism underwent both standard pulmonary angiography and magnetic resonance angiography during the pulmonary arterial phase at the time of an intravenous bolus of gadolinium. All magnetic resonance images were reviewed for the presence or absence of pulmonary emboli by three independent reviewers who were unaware of the findings on standard angiograms. RESULTS: Pulmonary embolism was detected by standard pulmonary angiography in 8 of the 30 patients in whom pulmonary embolism was suspected. All 5 lobar emboli and 16 of 17 segmental emboli identified on standard angiograms were also identified on magnetic resonance images. Two of the three reviewers reported one false positive magnetic resonance angiogram each. As compared with standard pulmonary angiography, the three sets of readings had sensitivities of 100, 87, and 75 percent and specificities of 95, 100, and 95 percent, respectively. The interobserver correlation was good (k=0.57 to 0.83 for all vessels, 0.49 to 1.0 for main and lobar vessels, and 0.40 to 0.81 for segmental vessels). CONCLUSIONS: In this preliminary study, gadolinium-enhanced magnetic resonance angiography of the pulmonary arteries, as compared with conventional pulmonary angiography, had high sensitivity and specificity for the diagnosis of pulmonary embolism. This new technique shows promise as a noninvasive method of diagnosing pulmonary embolism without the need for ionizing radiation or iodinated contrast material.

Adult↗