Effect of contrast dilution on contrast-enhanced MR angiography of the aorta and renal arteries

The aim of this study was to investigate the effect of gadolinium chelate dilution on vascular enhancement in contrast-enhanced two-dimensional (2D) MR subtraction angiography of aorta and renal arteries. Twenty patients were prospectively included. 2D subtraction MR angiography consisted of successive multisection breathhold GRE acquisitions of 16 s (2D FLASH, TR/TE 72/4, flip angle 60 degrees) obtained in the coronal plane before and after intravenous bolus administration of 0.1 mmol/kg BW gadolinium chelate. Patients underwent both diluted and undiluted gadolinium chelate administration in a random order. The data were studied both qualitatively and quantitatively on source and maximum intensity projection images. The length of renal arteries opacified was found not to differ significantly according to contrast dilution. The contrast enhancement percentage was not significantly modified according to the dilution used, but the time to peak enhancement was observed to be longer with the diluted contrast. Qualitatively, the best MR images were those obtained when undiluted contrast was injected first (chi2, P = 0.01). At a dosage of gadolinium chelate 0.1 mmol/kg BW, undiluted contrast 2D MR subtraction angiography seems to be more appropriate for studying diseases of the aorta and renal arteries than a similar diluted dose.     

Time-of-flight MR angiography of kidney transplants

The aim of the study was to apply time-of-flight MR angiography to renal transplant arteries with comparison of two- and three-dimensional (2D and 3D) sequences and to correlate the findings with colour flow sonography (CFS) and digital subtraction angiography (DSA). A total of 102 MR studies were performed in 101 patients: 87 with the 2D-FLASH sequence (18 repeated after Gd-DOTA administration), 49 with the 3D-FISP (both in 34). All patients were also studied with CFS and 15 with intra-arterial DSA. The 3D sequence produced good-quality MR angiograms in 94% of cases (82% in 2D). Gd-DOTA infusion improved the quality of the 2D angiograms in 7 of 18 cases. Only these patients were included in the remainder of the evaluation (90 patients with 103 arteries). CFS showed 72 normal and 10 abnormal arteries. In this group, the 2D sequence led to 7 (12%) false positives of stenosis and the 3D sequence yielded 1 (3%). Correlation between MR angiography and DSA was obtained for 21 arteries (15 patients) with suspicion of arterial complications. The 2D-FLASH (n = 13) and the 3D-FISP (n = 12) MR sequences allowed the correct diagnosis of all main artery complications (14 stenoses and 4 thromboses) without any false negatives and without discordance when both sequences were performed (n = 4). In the 3 other cases with a normal main artery, 2 segmental thromboses were correctly identified by both sequences and 1 stenosis of a segmental branch was correctly identified by the 2D sequence only but misdiagnosed as a thrombosis with the 3D sequence. Grading of the severity of stenoses was inaccurate with both sequences. It is concluded that the 3D time-of-flight MR sequence provides better MR angiograms than the 2D, with fewer false positives for stenosis. No false-negative arterial complications were noted. Correspondence to: N. Grenier     

Prospective evaluation of peripheral arterial occlusive disease by 2D MR subtraction angiography

The purpose of this study was to assess the diagnostic value of two-dimensional (2D) MR subtraction angiography of lower extremities in patients with symptomatic peripheral arterial occlusive disease with conventional angiography as the standard of reference. Twenty patients were prospectively included. 2D subtraction MR angiography (MRA) consisted of multisection gradient-recalled echo (GRE) acquisitions with the shortest TE available on our machine (4 msec), obtained in the coronal plane before and after intravenous bolus administration of gadolinium chelate. MR images were reconstructed after subtraction with a maximum-pixel-intensity-projection (MIP) algorithm. MRA was performed in all cases 1–4 days before diagnostic angiography. In a prospective blinded analysis, the number and location of significant (ie, >50%) stenoses and occlusions were evaluated for each vascular segment. Sensitivity and specificity were used to evaluate MRA data. Significant stenoses (38 of 46, 83%) and occlusions (66 of 67, 99%) seen at conventional angiography were identified with MRA. The sensitivity and specificity of MRA for determination of stenoses >50% or occlusions was 100% and 97%, respectively. The location and extent of stenoses and/or occlusions on MRA and angiograms were well correlated (kappa values, r = .73, P < .05). Contrast 2D MR subtraction angiography, by providing comparable information to that of conventional angiography, is well suited to evaluate the presence and severity of atherosclerotic lesions of the lower limbs.     

Comprehensive MR angiography of the lower limbs: a hybrid dual-bolus approach including the pedal arteries

The purpose of this study was to include the pedal vasculature into the coverage of peripheral multistation magnetic resonance angiography (3DceMRA). A total of 216 patients suffering from peripheral vascular disease were examined with a modified hybrid dual-bolus technique. The cruropedal arteries were acquired first with two sagittal slabs and time-resolved 3D sequences. Then the aortofemoral vessels were visualized using the bolus-chase technique and a second contrast injection. Interventional procedures were performed in 104 patients, and in 69 of those, the cruropedal vessels were also examined with digital subtraction angiography (iaDSA). Using 3DceMRA, the cruropedal arteries were displayed with both excellent and good quality in 95% (205/216 cases), and without any venous overlay in 94% (203/216 cases). The aortofemoral vessels were not jeopardized by the first contrast injection. With iaDSA as the standard of reference, observed sensitivity of 3DceMRA was found in ranges from 80% (29%, 99%) to 100% (86%, 100%) for assessing significant stenoses, and observed specificity ranged between 93% [80%, 98%] and 100% (82%, 100%). In conclusion, hybrid dual-bolus 3DceMRA significantly reduces the limitations of standard single-bolus 3DceMRA in anatomic coverage and temporal resolution of the cruropedal arteries, thus providing high-quality images of the entire peripheral vasculature.     

Gadolinium-enhanced, vessel-tracking, two-dimensional coronary MR angiography: single-dose arterial-phase vs. delayed-phase imaging

The purposes of our study were to investigate the benefits of using a single dose of an extracellular contrast agent for coronary magnetic resonance angiography (CMRA) and to determine the relative benefits of arterial-phase vs. delayed-phase image acquisition. The right coronary artery was imaged in 10 healthy adults using a breath-hold, two-dimensional fast gradient echo pulse sequence designed for vessel tracking (multiphase, multislice image acquisition). Pre- and postcontrast CMRA was performed. Postcontrast imaging consisted of arterial- and delayed-phase CMRA following a 15 mL bolus (single dose) of contrast media and of delayed-phase imaging following a cumulative 45 mL contrast dose (triple dose). Contrast-enhanced CMRA provided a significantly higher (P < 0.001) signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) than noncontrast CMRA. CNR was highest for single-dose arterial-phase CMRA (13.1 +/- 4.5) and triple-dose delayed-phase CMRA (13.0 +/- 4.8), followed by single-dose delayed-phase CMRA (8.4 +/- 3.5) and noncontrast CMRA (4.2 +/- 1.8). Single-dose arterial-phase CMRA provided the best visualization of the distal right coronary artery and was preferred for blinded physician assessments. We concluded that utilization of a single dose of extracellular contrast media improves CMRA, especially if timed for arterial-phase imaging. J. Magn. Reson. Imaging 2001;13:682-689.     

Blood flow modeling in carotid arteries with computational fluid dynamics and MR imaging

RATIONALE AND OBJECTIVES: The authors' goal was to develop a noninvasive method for detailed assessment of blood flow patterns from direct in vivo measurements of vessel anatomy and flow rates. MATERIALS AND METHODS: The authors developed a method to construct realistic patient-specific finite element models of blood flow in carotid arteries. Anatomic models are reconstructed from contrast material-enhanced magnetic resonance (MR) angiographic images with a tubular deformable model along each arterial branch. A surface-merging algorithm is used to create a watertight model of the carotid bifurcation for subsequent finite element grid generation, and a fully implicit scheme is used to solve the incompressible Navier-Stokes equations on unstructured grids. Physiologic boundary conditions are derived from cine phase-contrast MR flow velocity measurements at two locations below and above the bifurcation. Vessel wall compliance is incorporated by means of fluid-solid interaction algorithms. RESULTS: The method was tested on imaging data from a healthy subject and a patient with mild stenosis. Finite element grids were successfully generated, and pulsatile blood flow calculations were performed. Computed and measured velocity profiles show good agreement. Flow patterns and wall shear stress distributions were visualized. CONCLUSIONS: Patient-specific computational fluid dynamics modeling based on MR images can be performed robustly and efficiently. Preliminary validation studies in a physical flow-through model suggest that the model is accurate. This method can be used to characterize blood flow patterns in healthy and diseased arteries and may eventually help physicians to supplement imaging-based diagnosis and predict and evaluate the outcome of interventional procedures.     

MR imaging-guided percutaneous angioplasty and stent placement in a swine model comparison of open- and closed-bore scanners

RATIONALE AND OBJECTIVES: The purpose of this study is to compare the feasibility and precision of renal artery angioplasty and stent placement using two different MR scanners. MATERIALS AND METHODS: MR imaging-guided angioplasty and stent placements were performed on seven pigs using 0.2 and 1.5 T scanners (Magnetom Open and Magnetom Sonata, Siemens Medical Solutions, Erlangen, Germany). For guidance of catheters, guide wires and stents susceptibility artifact-based tracking was used. The end point of each intervention was to position a stent in the renal artery with its proximal end at the level of the aortic wall. Procedure time and stent position were evaluated. RESULTS: Catheterization, angioplasty, and stent placement were feasible using MRI guidance at both 0.2 and 1,5 Tesla. At 1.5 T all catheter manipulations and interventions were performed in less than 30 minutes. At 0.2 T the interventions took up to 90 minutes. No significant difference in the stent deviation was noted between the two scanners. CONCLUSION: The use of a high-performance 1.5 T scanner helped to reduce the procedure time to half of that of a low-field system. Since no difference in stent placement precision was noted, a dedicated MR-stent might be mandatory for more precise stent placement.     

MR angiography of the carotid arteries: parameters affecting image quality

RATIONALE AND OBJECTIVES: This study was performed to evaluate the relationship between dose levels of contrast medium and image quality in magnetic resonance (MR) angiography of the carotid arteries with fluoroscopically monitored, manually triggered, elliptically ordered image acquisitions. MATERIALS AND METHODS: Twenty-five patients with clinical indications for angiography of the carotid arteries were examined with MR at 1.5 T by using a fluoroscopically monitored, manually triggered, elliptically ordered pulse sequence with the administration of one of three different volumes of gadolinium-based contrast medium. The signal intensities of the vessel lumen and the surrounding tissues were measured in single partitions at the origin of the common carotid artery, the carotid bifurcation, and the intracranial internal carotid arteries. The contrast-to-noise ratio in these regions of interest also was measured. Maximum intensity projection image quality was appraised for blurring, artifacts, venous enhancement, background suppression, and contrast medium distribution. RESULTS: No artifacts or venous enhancement was observed. The position of the fluoroscopic section affected the distribution of contrast medium along the vessel, as evidenced by the difference between the contrast-to-noise ratio at the origin of the common carotid artery and the ratio at the carotid bifurcation and the intracranial internal carotid arteries (P < .01). The contrast medium dose administered was strongly correlated with image quality (r = 0.90). CONCLUSION: Contrast medium dose is related to image quality in MR angiography of the carotid arteries performed with elliptical ordering, fluoroscopic monitoring, and manual triggering.     

Renal MR angiography: A comprehensive approach

Renal artery MR angiography has now emerged as a safe, accurate approach to renal arteriography. A comprehensive examination, including both three-dimensional (3D) dynamic gadolinium-enhanced and 3D phase contrast MRA techniques, allows evaluation of both the aorta-renal and splanchnic arterial anatomy as well as the hemodynamic significance of any stenoses identified. The 3D gadolinium-enhanced MRA technique produces a contrast arteriogram but without risks of iodinated contrast or ionizing radiation. The 3D phase contrast technique is a flow-based technique, which may show dephasing in the presence of hemodynamically significant stenoses. A comprehensive examination should also include T1- and T2-weighted imaging for the assessment of potential neoplastic masses and the ubiquitous renal cysts. Through trial and error over the course of over a thousand examinations, this comprehensive approach to the MR evaluation of renal vascular pathology has emerged.     

US, CT, and MR evaluation of accessory renal arteries and proximal renal arterial branches

RATIONALE AND OBJECTIVES: The purpose of this study was to compare color Doppler ultrasound (US), computed tomographic (CT) angiography, and magnetic resonance (MR) angiography for the evaluation of accessory renal arteries and proximal branches of the main renal artery. MATERIALS AND METHODS: Fifty-six subjects who had undergone conventional arteriography of the renal arteries participated in a prospective comparison of Doppler US (45 patients), CT angiography (52 patients), and nonenhanced MR angiography (28 patients). Conventional arteriography depicted 28 accessory renal arteries and 21 proximal branches of the main renal artery within 2 cm of the aorta. RESULTS: US depicted five of 24 accessory renal arteries seen at arteriography but no proximal arterial branches. CT angiography depicted 24 of 26 accessory renal arteries and 13 of 17 proximal arterial branches, as well as 15 additional accessory renal arteries not seen at conventional arteriography. MR demonstrated 11 of 15 accessory arteries, as well as four additional accessory arteries not seen at conventional arteriography. MR did not depict any of nine proximal arterial branches seen at conventional arteriography. CONCLUSION: When compared with US or nonenhanced MR angiography, CT is the preferred method for evaluation of accessory renal arteries and proximal branches of the renal artery.     

Two-dimensional time-of-flight magnetic resonance angiography of renal arteries without maximum intensity projection: A prospective comparison with angiography in 21 patients screened for renovascular hypertension

Purpose We compared magnetic resonance angiography (MRA) with conventional angiography to establish its value as a screening test in the workup for renal hypertension.Methods Twenty one patients underwent MRA and angiography within a three day interval. Fifteen patients were suspected of having renovascular hypertension on the basis of clinical findings; the remaining six had multivessel atherosclerosis with renal insufficiency. MRA was performed on a 1 Tesla magnet in three planes: axial, coronal and perpendicular to the axis of each renal artery, by means of several contiguous or overlapping individual slice acquisitions. The two examinations were read by the same two independent observers, before and after an interval of 3 months.Results Conventional angiography showed 48 renal arteries. All main and three of six accessory renal arteries were correctly identified by MRA, as well as 11 of 14 significant stenoses or thromboses. Overreading of stenoses by MRA was observed in 4 cases. There were two false negatives for the two readers. The sensitivity and specificity of MRA for the detection of stenoses of the main renal arteries were found to be 70 and 78% respectively, for the first reading and 85 and 86% for the second reading.Conclusion MRA is considered a useful noninvasive method to determine the need for conventional angiography in patients in whom renal artery stenosis is suspected.Presented at CIRSE '92, Barcelona, Spain, 31 August 1992     

Value of image subtraction in 3D gadolinium-enhanced MR angiography of the renal arteries

The objective of this study was to evaluate quantitatively and qualitatively the effect of image subtraction on the image quality of three-dimensional (3D) gadolinium-enhanced MR angiograms of the renal arteries. Breath-hold 3D gadolinium MR angiography (MRA) as well as conventional contrast angiography of the renal arteries was performed on 20 patients with suspected renovascular hypertension. MR angiograms were acquired before and during dynamic infusion of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). Contrast-enhanced images were compared with images that had undergone voxel-by-voxel signal intensity subtraction of contrast-enhanced data from precontrast data. One false positive finding for significant renal artery stenosis was recorded with MRA using conventional angiography as the gold standard. Image subtraction did not alter the diagnosis at MRA in any case. The mean contrast-to-noise ratio (CNR) was significantly higher (P < .05) on the subtraction MR angiograms compared to the nonsubtracted MR angiograms. There was no significant difference in the signal-to-noise ratio (SNR). Qualitative analysis revealed a significant improvement in image quality after image subtraction with respect to visualization of the distal renal arteries. In conclusion, image subtraction improves the quality of renal MRA in terms of both CNR and visualization of the distal renal arteries.     

Poststenotic signal attenuation on 3 D phase-contrast MR angiography: a useful finding in haemodynamically significant carotid artery stenosis

We performed blinded visual evaluation of MR angiography (MRA) films in 44 patients with unilateral carotid artery stenosis to determine whether a flow gap and poststenotic signal attenuation on 3 D-PC MRA were useful signs of severe carotid artery stenosis. Although nine patients with a flow gap alone had various degrees of stenosis ranging from 22.2 to 77.3 % without any decrease in regional cerebral blood flow (rCBF), 13 patients with both a flow gap and poststenotic signal attenuation had severe stenoses of 80 % or more, with a definite decrease in baseline rCBF. The presence of both a flow gap and poststenotic signal attenuation on 3 D-PC MRA appeared to be a reliable marker of severe carotid artery stenosis with a decrease in rCBF. Received: 30 April 1999/Accepted: 11 August 2000     

Contrast-enhanced MR angiography of the run-off vasculature: intraindividual comparison of gadobenate dimeglumine with gadopentetate dimeglumine

PURPOSE: To compare intraindividually gadobenate dimeglumine (Gd-BOPTA) with gadopentetate dimeglumine (Gd-DTPA) for multi-station MR Angiography of the run-off vessels. MATERIALS AND METHODS: Twenty-one randomized healthy volunteers received either Gd-BOPTA or Gd-DTPA as a first injection and then the other agent as a second injection after a minimum interval of 6 days. Each agent was administered at a dose of 0.1 mmol/kg bodyweight followed by a 25-mL saline flush at a single constant flow rate of 0.8 mL/second. Images were acquired sequentially at the level of the pelvis, thigh, and calf using a fast three-dimensional (3D) gradient echo sequence. Source, subtracted source, maximum intensity projection (MIP), and subtracted MIP image sets from each examination were evaluated quantitatively and qualitatively on a segmental basis involving nine vascular segments. RESULTS: Significantly (P < 0.05) higher signal-to-noise and contrast-to-noise ratios were noted for Gd-BOPTA compared to Gd-DTPA, with the more pronounced differences evident in the more distal vessels. Qualitative assessmentrevealed no differences in the abdominal vasculature, a preference for Gd-BOPTA in the pelvic vasculature, and markedly better performance for Gd-BOPTA in the femoral and tibial vasculature. Summation of individual diagnostic quality scores for each segment revealed a significantly (P = 0.0001) better performance for Gd-BOPTA compared to Gd-DTPA. CONCLUSION: Greater vascular enhancement of the run-off vasculature is obtained after Gd-BOPTA, particularly in the smaller more distal vessels. Enhancement differences are not merely dose dependent, but may be due to different vascular enhancement characteristics of the agents.     

Contrast-enhanced,ultrafast 3d pulmonary MR angiography in a single breath-hold: Initial assessment of imaging performance

An ultrafast three-dimensional (3D) sequence was developed, enabling the acquisition of 44 contiguous 2.0-to 2.2-mm thin sections, during intravenous application of paramagnetic contrast, in a single breath-hold. To estimate the potential clinical usefulness, images were assessed qualitatively and quantitatively with regard to visibility of main, lobar, segmental, and subsegmental pulmonary arteries. Five volunteers were examined using a 192 × 192 matrix with an imaging time of 23 seconds and five other volunteers with a 160 × 160 matrix (18 seconds). Each volunteer was imaged in apnea and during shallow respiration. The breath-held 23-second scans revealed excellent image quality and near complete visualization of central and segmental, as well as 81% of subsegmental, pulmonary arteries. Imaging time can be shortened to 18 seconds with only marginal loss in visualization performance (P < .05). Respiratory motion was found to cause significant worsening of image quality and vessel detectability. To maintain relevance in a clinical setting, imaging time can be minimized at the cost of a reduction in spatial resolution.     

Gadolinium-enhanced T1-weighted renal and abdominal MR imaging: quantitative discrepancy between clinical and in vitro findings

RATIONALE AND OBJECTIVES: This study was conducted to compare the magnetic resonance (MR) contrast medium enhancement of abdominal organs in vivo with the signal intensity (SI) values of known in vitro gadolinium solutions. MATERIALS AND METHODS: A phantom was imaged with the MR contrast medium gadodiamide (Omniscan; Nycomed, Princeton, NJ) of solutions at full-strength (0.5 mmol/mL), one-third, 1/10, and 1/100 concentrations. A fat-suppressed fast spoiled gradient-echo pulse sequence with flip angles ranging from 10 degrees to 170 degrees (at 20 degrees increments) was performed with a 1.5-T magnet. In 12 subjects, the SIs of abdominal organs were determined with identical imaging parameters, before and after administration of gadodiamide injection at 0.1 mmol/kg. RESULTS: As anticipated, the plot of SI in relation to gadodiamide concentration is nonlinear, with a decrease in SI due to T2 effects at concentrations above 0.05 mmol/mL. The kidney showed the highest SI after gadodiamide enhancement (125.2 +/- 11.6 [standard error] at 2.5 minutes), followed by the liver (76.5 +/- 11.5 at 1 minute) and spleen (57.26 +/- 9.35 at 30 seconds). The SI of the renal medulla (114.2 +/- 9.8 at 4.5 minutes) was approximately one-third that in phantom observations. CONCLUSION: The authors observed a marked discrepancy between empirical contrast medium performance in abdominal organs and SI values for comparable gadodiamide concentrations in vitro. One possible reason is the intracellular compartmentalization of water molecules in vivo. These results suggest a need for a better understanding of MR contrast medium performance in vivo.     

Use of a three-station phased array coil to improve peripheral contrast-enhanced magnetic resonance angiography

PURPOSE: To explore the imaging capabilities of a new commercially available, three-station, 129-cm long, 12-element phased array coil for contrast-enhanced magnetic resonance angiography (CE-MRA) in patients with symptomatic peripheral arterial occlusive disease. MATERIALS AND METHODS: Nineteen patients, referred for peripheral CE-MRA, were evaluated using the new three-station coil. For each station four coil elements (two anterior and two posterior to the patient) were used. The expected improvements in signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were used to improve spatial resolution and increase anatomic coverage for the distal two stations compared to our previous protocol. Images obtained in the 19 patients imaged with the new coil were compared to those of the last 19 patients scanned without the use of the new coil. Differences in image quality before vs. after the availability of the new coil were compared in terms of SNR and CNR, subjective interpretability score (SIS), degree of venous enhancement, and anatomic coverage. Images were interpreted by two experienced observers, blinded for imaging technique and each other's results. RESULTS: Use of the coil enabled acquisition of high resolution peripheral vasculature images in all cases and allowed for substantially smaller voxel sizes (thighs: 5.3 vs. 8.4 mm(3) [-37%]; legs: 1.8 vs. 8.0 mm3 [-78%]) and much shorter acquisition durations in the aortoiliac and thigh stations (aortoiliac: 16 vs. 27 seconds [-41%]; thighs: 11 vs. 23 seconds [-52%]). Acquisition duration in the leg station was prolonged (68 vs. 29 seconds [+134%]). SNR and CNR were significantly higher only in the aortoiliac station using the three-station coil (both: P < 0.001). There were no significant differences in SIS for the aortoiliac and thigh stations (aortoiliac station: observer 1: P = 0.16, observer 2: P = 0.19; thigh station: both observers: P = 0.27). Images acquired with the new coil had significantly higher SIS for the leg station (both observers: P = 0.004). There were no significant differences in venous enhancement between the two protocols for any of the stations (all P > 0.11). In 12/12 (100%) requested cases the entire pedal arch was depicted using the new coil, whereas this was not possible with the old protocol. CONCLUSION: The new three-station dedicated peripheral vascular coil allows for much higher resolution imaging in the thigh and leg stations with greater anatomic coverage and substantially improves peripheral MRA quality of the lower leg vasculature.     

Proximal coronary artery stenosis: Three-dimensional MRI with fat saturation and navigator echo

The purpose of this study was to compare the diagnostic value of MR angiography (MRA) with conventional contrast angiography in coronary artery disease. Thirty-five patients underwent MRA and coronary angiography within 4 hours. Of these, three patients were investigated twice: once before and once after balloon angioplasty. The pulse sequence was a cardiac-triggered, single-slab, three-dimensional gradient-echo sequence, employing a spin-echo navigator echo measurement to track the variation of the diaphragm during the scan. The following segments of the coronary arteries were included in this prospective study: left main coronary artery, proximal and middle left anterior descending, proximal and middle left circumflex, proximal and middle right coronary artery, and intermediate branch, if present. In total, 176 segments were classified as normal or having a stenosis of less than 50% and as having a stenosis of more than 50%. Five patients were excluded because of lack of cooperation. Over all, 45 of 54 stenoses were detected and interpretable by MRA. Sensitivity, specificity, and positive and negative predictive values of MRA for detecting significant stenoses were 83%, 94%, 87%, and 93%, respectively. MRA identified significant stenoses within the major coronary arteries with a high degree of accuracy. Sensitivity and specificity are higher compared with exercise tests or scintigraphy or top of the precise localization.     

Cortical,medullary, and pelvocaliceal MR renography with and without diuretic modification

RATIONALE AND OBJECTIVES: This study was conducted to define and characterize magnetic resonance (MR) contrast medium enhancement of the renal cortex, medulla, and pelvocaliceal system in normal and hydronephrotic kidneys with and without furosemide administration. MATERIALS AND METHODS: In 30 subjects known or suspected to have unilateral hydronephrosis and normal serum creatinine levels, multiple timed sets of coronal fast spoiled gradient-echo images were acquired before and after contrast medium administration. MR renograms were derived from changes in the signal intensity (SI) of the cortex, medulla, and pelvocaliceal system. Ten subjects received 40 mg of intravenous furosemide approximately 10 minutes before contrast medium administration. RESULTS: The following values were significantly different between subjects who were given furosemide and those who were not: the peak cortical, medullary, and pelvocaliceal system SIs measured in the normal kidneys during the 4 1/2 minutes following contrast medium administration (163.2 +/- 17.7 [mean arbitrary units plus or minus standard error] vs 120.5 +/- 10.2 [P = .033], 155.5 +/- 18.8 vs 111.5 +/- 9.4 [P = .025], and 332.5 +/- 27.2 vs 229.3 +/- 31.9 [P = .026], respectively); the crossover time between the SI curves of the pelvocaliceal system and the medulla in the normal kidney (2.45 minutes +/- 0.2 vs 3.27 minutes +/- 0.25 [P = .02]); and the peak SIs of the cortex, medulla, and pelvocaliceal system in the unilateral obstructive hydronephrotic kidneys throughout the first 4 1/2 minutes after contrast medium administration (174.6 +/- 16.4 vs 90.6 +/- 13.7 [P = .003], 117.6 +/- 14.1 vs 86.7 +/- 11.8 [P = .015], and 337.2 +/- 41.4 vs 143.1 +/- 74.4 [P = .034], respectively). CONCLUSION: MR renography can be used to depict three separate components of renal enhancement: cortical, medullary, and pelvocaliceal. Furosemide-induced diuresis increases renal parenchymal and pelvocaliceal SI and urinary flow rates.