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Martin R Prince

Publications and source records attributed to Martin R Prince.

At least 37 records · Page 2Linked to original sources
PubMed2004

Blood pool MR angiography of aortic stent-graft endoleak.

OBJECTIVE: The purpose of our research was to investigate the value of a blood pool contrast agent in detecting endoleaks on MR angiography after endoluminal stent-graft repair of infrarenal aortic aneurysms. CONCLUSION: Blood pool MR angiography using Ferumoxytol reveals more aortic stent-graft endoleaks than does CT angiography and depicts more endoleaks 24 hr after administration than during the immediate arterial phase because of a 50-fold increase in the volume of enhancement in the aneurysmal sac outside the stent-graft.

Aged↗
PubMed2004

Decreased venous contamination on 3D gadolinium-enhanced bolus chase peripheral mr angiography using thigh compression.

OBJECTIVE: We evaluated the potential for improving bolus chase peripheral MR angiography in patients with fast arterial flow using thigh compression to prevent venous contamination. SUBJECTS AND METHODS: We performed bolus chase peripheral MR angiography in 32 consecutive patients in whom the travel time for a contrast agent to reach the popliteal artery trifurcation was less than 25 sec. Thigh compression was applied by a tourniquet (n = 13) or blood pressure cuff inflated to 60 mm Hg (n = 19). We compared the results with those of 36 consecutive patients who underwent angiography without thigh compression. The effect of thigh compression on arterial flow and tissue enhancement was assessed in patients with symmetric travel time in both legs by applying compression to one leg during the time-resolved 2D-projection MR angiography with 6 mL of gadolinium. On 3D bolus chase MR angiography, thigh compression was applied bilaterally. Venous contamination on the 3D images of the calf was graded as 0, none; 1, trace; 2, mild; 3, moderate; and 4, severe. Signal-to-noise ratio was measured in the popliteal artery. RESULTS: Thigh compression slowed the arterial travel time by a mean +/- SD of 4.7 +/- 2 sec (p < 0.001) with a blood pressure cuff and 3.1 +/- 1 sec (p < 0.001) with a tourniquet. Blood pressure cuffs reduced the score of venous contamination on the calf station from 1.9 to 0.4 (p < 0.05) for intermediate flow (contrast travel time, 20-25 sec) and from 2.5 to 0.9 (p < 0.05) for fast flow (< 20 sec). Thigh compression increased the popliteal artery signal-to-noise ratio (81 vs 52, p < 0.001). CONCLUSION: Thigh compression with blood pressure cuffs inflated to 60 mm Hg slows down arterial flow, increases arterial signal-to-noise ratio, and reduces venous contamination on 3D gadolinium-enhanced bolus chase peripheral MR angiography.

Aged↗
PubMed2003

Atherosclerotic disease distribution in carotid and vertebrobasilar arteries: clinical experience in 100 patients undergoing fluoro-triggered 3D Gd-MRA.

PURPOSE: To determine how often three-dimensional gadolinium-enhanced magnetic resonance angiography (3D Gd-MRA) shows disease outside of the standard two-dimensional time-of-flight magnetic resonance angiography (2D TOF-MRA) imaging volume. MATERIALS AND METHODS: One hundred consecutive patients with known or suspected cerebrovascular disease were examined using fluoro-triggered 3D Gd-MRA with a 1.5 Tesla scanner. All vessel segments from the aortic arch to the circle of Willis were independently evaluated for the presence of occlusive disease, ulceration, aneurysm, and anatomic variations by two radiologists blinded to clinical information. Branch vessel and circle of Willis visibility were also assessed. Kappa statistics were calculated to determine interobserver agreement. RESULTS: Interobserver agreement for the degree of stenosis was good to excellent (kappa = 0.83-1.0). Disagreement was more frequent in the cases of mild stenoses and was less frequent for stenoses > or = 50%. In 38% of the patients, 3D Gd-MRA demonstrated either ulcerated plaques in carotid arteries (N = 14) or stenosis > or = 50% in great vessel (N = 20) and/or vertebral artery (N = 38) origins, none of which can be readily evaluated on standard TOF-MRA. CONCLUSION: Fluoro-triggered 3D Gd-MRA provides a comprehensive evaluation of the carotid arteries including all vessel segments from the aortic arch to the circle of Willis.

Adult↗
PubMed2003

Quantitative evaluation of susceptibility and shielding effects of nitinol, platinum, cobalt-alloy, and stainless steel stents.

The purpose of this study is to quantitatively estimate the shielding and susceptibility effects of commonly used metallic stents on MR signal. Two experiments were performed using a 3D gradient echo sequence with short TE to image a stent phantom: 1) short TR and high flip angle (contrast enhanced MRA parameters), and 2) long TR (TR >> T(1)) and low flip angle. The factor characterizing susceptibility effects was estimated from the signal phase of the first experiment, and then the factor characterizing the shielding effects was derived from the second experiment. Susceptibility induced signal loss was negligible (<1%) for nonstainless-steel (nitinol, platinum, and cobalt-alloy) stents and totally destructive (100%) for the stainless steel stent. Signal loss due to RF shielding was 31-62% for nitinol stents, 14-50% for platinum stents, 50-77% for the cobalt-alloy stents (undetermined for the stainless steel stent), varied with stent orientation, diameter, and wall geometry. In summary, stents made of nitinol, platinum, and cobalt-alloy have negligible susceptibility effects but stents made of stainless steel may have complete dephasing. All stents have substantial shielding effects, which vary with composition, geometry, and orientation. Large platinum stents may have the smallest artifacts and are the best suited for postinterventional MR imaging.

Alloys↗
PubMed2003

Simultaneous multiple volume (SMV) acquisition algorithm for real-time navigator gating.

Navigator gating techniques can effectively reduce motion effects in MRI by accepting data only when the object is in a small range of positions at the cost of significantly prolonging scan time. A simultaneous multiple volume (SMV) algorithm is reported here that can substantially increase the scan efficiency while maintaining the effectiveness of motion suppression. This is achieved by acquiring different image volumes at different motion states. Initial experiments demonstrate that SMV can significantly increase the scan efficiency of navigator MRI.

Algorithms↗
PubMed2003

Gadodiamide administration causes spurious hypocalcemia.

PURPOSE: To evaluate the prevalence of spurious hypocalcemia after gadodiamide-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: Eight hundred ninety-six inpatients with available serum calcium data obtained before and after gadodiamide-enhanced MR imaging were identified. Changes in serum calcium measurements following gadodiamide administration in 1,049 MR imaging examinations performed in these patients were correlated with gadodiamide dose, renal function, and time between gadodiamide administration and phlebotomy. RESULTS: Following 42 gadodiamide-enhanced examinations, serum calcium measurements spuriously decreased by more than 2 mg/dL (0.5 mmol/L), resulting in laboratory reports of "critical" hypocalcemia (ie, calcium level < 6 mg/dL [1.5 mmol/L]) in 25 examinations. These reduced calcium measurements were correlated with serum creatinine level (r = 0.39, P <.001), gadodiamide dose (r = 0.37, P <.001), and time between gadodiamide injection and phlebotomy (r = -0.28, P <.001). Spurious reductions in calcium measurements after administration of 0.1 mmol of gadodiamide per kilogram of body weight were greater in patients with renal insufficiency (0.6 mg/dL [0.15 mmol/L] +/- 0.5 [0.125, SD]) than in those with normal renal function (0.14 mg/dL [0.035 mmol/L] +/- 0.4 [0.1]) (P <.001). After administration of more than 0.2 mmol/kg of gadodiamide, spurious calcium measurement decreases were greater in patients with renal insufficiency (2.4 mg/dL [0.6 mmol/L] +/- 3.6 [0.9]) than in those with normal renal function (0.4 mg/dL [0.1 mmol/L] +/- 0.7 [0.175]) (P <.001). Patients with renal insufficiency had spuriously low calcium measurements up to 4(1/2) days after gadodiamide administration. Seven patients were inappropriately treated with intravenous calcium and eleven with oral calcium in response to false-positive laboratory reports of critical hypocalcemia. No patient had characteristic symptoms of hypocalcemia or injuries attributed to the inappropriate medical treatment. CONCLUSION: Gadodiamide administration causes spurious hypocalcemia, particularly at doses of 0.2 mmol/kg or higher and in patients with renal insufficiency.

Calcium↗
PubMed2002

Automatic selection of mask and arterial phase images for temporally resolved MR digital subtraction angiography.

For time-resolved background-subtracted contrast-enhanced magnetic resonance angiography, the bright and sparse arterial signal allows unique identification of contrast bolus arrival in the arteries. This article presents an automatic filtering algorithm using such arterial characterization for selecting arterial phase images and mask images to generate an optimal summary arteriogram. A paired double-blinded comparison demonstrated that this automatic algorithm is as effective as the manual process.

Adult↗
PubMed2002

Bolus arterial-venous transit in the lower extremity and venous contamination in bolus chase three-dimensional magnetic resonance angiography.

RATIONALE AND OBJECTIVES: To investigate the phenomena and causes for undesired venous signal in the distal station of bolus chase 3D MRA. METHODS: Consecutive patients (in 8 months) undergoing peripheral MRA consisting of 2D projection MRA of the tibial trifurcation and 3D bolus chase MRA were retrospectively evaluated. Venous contamination in mid-calf in bolus chase 3D MRA was correlated to the arterial phase duration, the time between the contrast bolus arrival and venous return measured on time resolved 2D images. Statistical analyses were performed to identify the clinical parameters indicative of venous contamination. RESULTS: The arterial phase durations at the mid-calf were 49 +/- 8 seconds on 101 legs without venous signal in the bolus chase 3D MRA, 35 +/- 9 seconds on 13 legs with moderate venous signal, and 20 +/- 4 seconds on 40 legs with substantial venous signal; the differences were significant among different venous signal levels (P < 0.001 for all pairs). Legs with cellulitis had shorter arterial phase and more venous contamination than legs without cellulitis (P < 0.05). Patients with myocardial infarction had longer arterial phase and less venous contamination than patients without myocardial infarction (P < 0.01). CONCLUSION: Venous signal in the distal calf station of bolus chase 3D peripheral MRA is caused by fast arterial-venous transit. It is worse in legs with cellulitis and less in patients with a history of myocardial infarction.

Aged↗
PubMed2002

Postprocessing techniques for time-resolved contrast-enhanced MR angiography.

The purpose of this study was to improve dynamic two-dimensional projection magnetic resonance digital subtraction angiography by using remasking and filtering postprocessing techniques. Four methods were evaluated in 50 patients: default mask subtraction, remasked subtraction, filtering based on the SD, and linear filtering. The results demonstrated that postprocessing techniques such as linear filtering can reduce background motion artifacts and improve arterial contrast-to-noise ratio.

Adult↗
PubMed2002

Peripheral vascular disease: combined 3D bolus chase and dynamic 2D MR angiography compared with x-ray angiography for treatment planning.

PURPOSE: To compare combined three-dimensional (3D) and two-dimensional (2D) contrast material-enhanced magnetic resonance (MR) angiography with x-ray angiography for planning treatment of peripheral vascular disease. MATERIALS AND METHODS: Three radiologists retrospectively reviewed the pretreatment x-ray angiographic and MR angiographic studies obtained in 30 consecutive patients: 15 patients (15 limbs) evaluated for limb salvage and 15 patients (20 limbs) evaluated because of claudication. MR angiography included acquisition of 2D contrast-enhanced MR digital subtraction angiograms of the area from the adductor canal to the feet and 3D spoiled gradient-recalled-echo bolus chase MR angiograms obtained in three stations from the aorta to the middle portion of the calf. Each reader reviewed the x-ray and MR angiograms to determine the inflow and outflow segments for a hypothetical bypass graft placement. RESULTS: The three readers selected identical segments for inflow at MR angiography and x-ray angiography in 32, 32, and 35 of the 35 limbs evaluated (mean percentages of agreement [95% CI ]: 91% [77%, 98%], 91% [77%, 98%], and 95% [90%, 100%], respectively). The readers selected identical segments for outflow in 32, 32, and 34 of the 35 limbs evaluated (mean percentages of agreement [95% CI]: 91% [77%, 98%], 91% [77%, 98%], and 97% [85%, 100%], respectively). CONCLUSION: Preliminary data support the combining of 2D MR digital subtraction angiography with 3D bolus chase MR angiography to extend the utility of 3D MR angiography in treatment planning to include patients being evaluated for limb salvage, as well as those being evaluated for claudication.

Adult↗
PubMed2002

Contrast material travel times in patients undergoing peripheral MR angiography.

PURPOSE: To retrospectively review time-resolved two-dimensional projection magnetic resonance (MR) angiographic data to characterize the passage of gadolinium-based contrast material down the leg arteries in patients undergoing peripheral MR angiography. MATERIALS AND METHODS: Data of 87 consecutive standardized peripheral MR angiographic examinations were retrospectively reviewed to determine contrast material arrival times to the common femoral artery (CFA), the popliteal and tibial arteries, and the corresponding veins. Travel times were correlated with clinical data obtained with retrospective chart review and predictive multiparameter models developed with stepwise linear regression. RESULTS: The mean travel time of contrast material to the CFA was 24 seconds +/- 6 (SD), with additional 5 seconds +/- 2 to reach the popliteal artery and 7 seconds +/- 4 to reach the ankle artery. The mean time window of arterial enhancement was 49 seconds +/- 10 in the pelvis, 45 seconds +/- 10 in the thigh, and 35 seconds +/- 14 in the calf. The travel time to CFA was correlated with aortic aneurysm (r = 0.41; P <.001), increasing age (r = 0.31; P =.003), male sex (r = 0.3; P =.005), myocardial infarction (r = 0.26; P =.016), and type 2 diabetes mellitus (r = -0.22; P =.041). Predicted travel time to CFA was 10.6 seconds, plus 0.143 seconds times patient age, plus 4.8 seconds if aneurysm was present, plus 3.8 seconds if male sex, plus 2.8 seconds if history of myocardial infarction. CONCLUSION: Contrast material injected intravenously traveled rapidly down the peripheral arteries at approximately 6 seconds per station, but a long arterial phase time window allowed bolus-chase peripheral MR angiography to function with slower table stepping. Patient-to-patient variations in contrast material kinetics may be anticipated on the basis of age, sex, and clinical parameters.

Adult↗
PubMed2002

Morphologic and functional magnetic resonance imaging of renal artery stenosis: a multireader tricenter study.

The effect of combined morphologic and functional magnetic resonance (MR) imaging on the interobserver and intermodality variability for the grading of renal artery stenosis is assessed. In a randomized, blinded tricenter analysis, seven readers evaluated 43 renal arteries on x-ray digital subtraction angiography (DSA), 3D-Gadolinium MR angiography (3D-Gd-MRA), cine phase-contrast flow measurement (PC-flow), and a combined analysis of the last two. Interobserver variability was assessed for the grading of renal artery stenosis as well as regional vessel visibility. Intermodality variability for stenosis grading was analyzed in cases in which the readers agreed on the degree of stenosis in DSA. DSA had a substantial interobserver variability for the grading of stenosis (mean kappa kappa 0.64). 3D-Gd-MRA revealed a slightly improved interobserver variability but incorrectly graded 6 of 34 stenoses on a two-point scale (<50%, > or =50%). The combined approach of 3D-Gd-MRA and PC-flow revealed the best (P = 0.0003) interobserver variability (median kappa = 0.75) and almost perfect intermodality agreement with DSA (97% of cases). These findings were confirmed in a prospective analysis of 97 renal arteries. The vessel visibility of the renal artery ostium was significantly better in 3D-Gd-MRA than in DSA, whereas the visibility of the hilar and intrarenal vessels was significantly worse (P = 0.0001). A combined morphologic and functional MR examination significantly reduces interobserver variability and offers reliable and reproducible grading of renal artery stenosis based on stenosis morphology and hemodynamic changes. It can be considered a safe and noninvasive alternative for diagnostic DSA in cases that do not require assessment of intrarenal vessels.

Aged↗