Development and testing of a cross-sectional area measurement tool for evaluating vein size.

This paper describes a software system for measuring cross-sectional area in reconstructed elliptical tubular structures. A measurement tool was developed using the freely available, cross-platform, open-source three-dimensional (3-D) Slicer environment. The software is easy to operate and allows the user to make multiple measurements on the fly. Results can be displayed to the screen, output to the system printer, and written to a user-specified data file for later analysis in commercial spreadsheet software. Measuring a known cross-sectional area tested the software. Phantoms of known physical dimensions were imaged using both CT and MR. The measured cross-sectional areas reported by the software were compared to each other, and the cross-sectional areas calculated from the known physical dimensions of the phantoms. The measurement errors were negligible. The results of this study indicate that the cross-sectional area measurement tool described provides reliable measurements and is an inexpensive and versatile alternative to high-end 3-D modeling software.

Incidence of adrenal masses in patients referred for renal artery stenosis screening MR.

RATIONALE AND OBJECTIVES: Prior work has shown the efficacy of magnetic resonance (MR) in renal artery stenosis evaluation. The increasing role of renal artery stenosis in the differential diagnostic evaluation of hypertension raises the question of whether MR should be used as a screening modality. This project evaluated the additional potential benefits of MR by determining the incidence of adrenal masses in this selected population. METHODS: A 2-year retrospective study analysis of patients who failed to respond to antihypertensive medical management and were referred for renal MR for hypertension amassed 77 subjects ranging in age from 18 to 88 years. A masked analysis for adrenal masses was performed on this data set. Magnetic resonance techniques included T2-weighted turbo spin-echo (repetition time [TR] 2000-4000 ms, echo time [TE] 80-100 ms, turbo factor 2-16), T1-weighted spin-echo (TR 200-500 ms, TE 10-30 ms), gradient-echo time-of-flight (TR 26 ms, TE 6.9 ms, 40 degrees flip angle, 2 excitations), and dynamic gadopentetate dimeglumine-enhanced MR angiography (three-dimensional gradient recalled echo, TR 10 ms, TE 3 ms, 40 degrees flip angle, 1 excitation). RESULTS: Thirty-three patients had renal artery disease, 44 had normal renal arteries, and 7 had adrenal masses. Forty-three percent of patients who underwent renal MR had disease of the renal arteries detected, and 9% of patients referred for MR had adrenal masses that would have been missed with scintigraphy and/or angiography, of which 57% were responsible for hypertension. CONCLUSIONS: The ability to evaluate renal artery and adrenal anatomy globally can be useful, as exemplified in the current series, and the adrenals should be examined carefully in any renal MR in a hypertensive patient.

Carotid MR angiography: phase II study of safety and efficacy for MS-325.

PURPOSE: To evaluate the safety and efficacy of MS-325 in patients suspected of having carotid arterial disease. MATERIALS AND METHODS: Fifty carotid arteries in 26 patients were imaged with three-dimensional spoiled gradient-recalled-echo magnetic resonance (MR) angiography at 5 and 50 minutes after injection of MS-325. MS-325 was administered intravenously as a single dose of 0.01, 0.03, or 0.05 mmol per kilogram of body weight as determined with a dose randomization scheme for four, nine, and 13 patients, respectively. Safety, including clinical laboratory changes and electrocardiographic monitoring, was assessed until approximately 3 days after injection. Conventional contrast agent-enhanced angiography was used as the standard of reference. Independent readers blinded to the dose interpreted the MR angiographic and conventional images. Images were assessed for location and extent of carotid arterial stenosis. RESULTS: There were no severe or serious adverse events. For the determination of clinically significant stenosis (>70%) on the 5-minute images, sensitivity, specificity, and accuracy (P =.07, three-way comparison) were 100%, 100%, and 100%; 63%, 100%, and 88%; and 40%, 75%, and 55% at 0.01, 0.03, and 0.05 mmol/kg, respectively. Sensitivity and specificity for images at 50 minutes after MS-325 administration showed the same trends as the 5-minute images. CONCLUSION: Overall accuracy for MS-325-enhanced carotid MR angiography performed during steady-state conditions of circulating contrast agent approximately 5 minutes after injection was high (88%-100%) at 0.03 and 0.01 mmol/kg. MS-325 was well tolerated at all evaluated doses.

Prediction rule for characterization of hepatic lesions revealed on MR imaging: estimation of malignancy.

OBJECTIVE: Our aims were to establish factors that are most predictive of hepatic lesion malignancy and to formulate a prediction rule. MATERIALS AND METHODS: A cross-sectional study of 227 abdominal MR imaging examinations revealed 85 lesions in 67 patients (29 men, 38 women; age range, 29-78 years; mean age, 51.4 years) who were being examined for primary malignancy (n = 42) or unknown lesion characterization (n = 25). All were referred for MR imaging after CT or sonography. Patient demographics (age, sex, history of malignancy), lesion size and morphology, quantitative T2 calculation, and pattern of enhancement on gadopentetate dimeglumine administration were evaluated for predictive ability. RESULTS: Thirty-two liver lesions were malignant (eight colon cancer, five breast cancer, four cervical cancer, three renal cancer, three lung cancer, and nine miscellaneous cancers), 53 were benign (37 hemangiomas, 15 cysts, and one focal nodular hyperplasia). Calculated T2 relaxation times (mean +/- standard deviation [SD]) were as follows: malignant tumors (91.72 +/- 21.9 msec), hemangiomas (136.1 +/- 26.3 msec), cysts (284.1 +/- 38.2 msec) (p < 0.001). Logistic regression analysis indicated that lesion size and sex and age of patient were not significant independent predictors (p > 0.05). However, the combination of a history of malignancy, T2 value, and gadopentetate dimeglumine-enhancement pattern allowed generation of a prediction rule with an area under the receiver operating characteristic curve of 0.95. The patient's weight, lesion morphology, and cell type of the primary malignancy did not provide additional predictive information (p > 0.2). CONCLUSION: We recommend using the combination of T2 quantification and patient history of malignancy before deciding to administer gadopentetate dimeglumine for optimal lesion characterization, especially for equivocal lesions with T2 values between 90 and 130 msec. These factors allowed the construction of a prediction rule for lesion characterization.

Contrast-enhanced moving-table MR angiography: prospective comparison to catheter arteriography for treatment planning in peripheral arterial occlusive disease.

PURPOSE: Prospective comparison of contrast-enhanced moving-table magnetic resonance (MR) angiography to catheter arteriography in endovascular and surgical treatment planning in patients with peripheral arterial occlusive disease. MATERIALS AND METHODS: Thirteen patients scheduled for catheter arteriography for lower extremity arterial occlusive disease underwent contrast-enhanced moving-table MR angiography immediately prior to arteriography. A treatment plan was determined by the vascular surgeon, based on MR angiography, who was blinded to the catheter arteriogram. The treatment plan determined by the MR angiogram was compared to the final treatment plan, which was based on the catheter arteriogram and intraluminal pressure measurements. RESULTS: Treatment plans based on MR angiography and catheter arteriography were identical in 10 of 13 patients (71%). For identifying lesions resulting in intervention, MR angiography had sensitivity of 100% and a positive predictive value of 92%. MR angiography had a treatment specific predictive value of 88% for each lesion identified, and 95% for lesions identified in patients evaluated for claudication. If treatment plans were based on MR angiography only, 46% of patients would have avoided catheter arteriography. CONCLUSION: Contrast-enhanced moving-table MR angiography may be an effective alternative to catheter arteriography in endovascular and surgical treatment planning in selected patients with peripheral arterial occlusive disease, but larger studies are necessary to confirm this.

Turbo STIR magnetic resonance imaging as a whole-body screening tool for metastases in patients with breast carcinoma: preliminary clinical experience.

This study was undertaken to assess the utility of whole-body turbo short tau inversion recovery (STIR) magnetic resonance imaging (MRI) to detect metastases to liver, brain, and bone as a single examination in women with breast cancer. Seventeen patients with biopsy-proven breast cancer and suspected metastatic disease attending over a 12-month period referred for both conventional imaging and whole-body MRI were included in the study. Three patients were found to be free of metastases at both conventional and MR imaging. Appendicular or axial skeletal metastases were identified in 11 of 17 patients, with correlation between findings at whole-body MRI and scintigraphy in 15 of the 17 patients. Five patients had evidence of hepatic metastases on whole-body MRI, of which metastases were identified in only three patients at CT despite contrast enhancement. Four patients had brain abnormalities (metastases in three patients, meningioma in one patient) detected on both whole-body and dedicated brain MRI. Preliminary clinical experience suggests that turbo STIR whole-body MRI may represent a convenient and cost-effective method of total body screening for metastases in patients with breast carcinoma.

Signal characteristics of focal liver lesions on double echo T2-weighted conventional spin echo MRI: observer performance versus quantitative measurements of T2 relaxation times.

PURPOSE: The purpose of this work was to evaluate the ability of expert readers to differentiate benign from malignant liver lesions based on visual assessment of lesion signal intensity on double echo T2-weighted conventional spin echo (CSE) MR images and to compare reader performance with quantitative measurements of T2 relaxation times. METHOD: Sixty-seven MR examinations demonstrating 85 liver lesions (37 hemangiomas, 32 malignancies, 15 cysts, and 1 focal nodular hyperplasia) on double echo T2-weighted CSE sequences (TR 3,600 ms/TE 50, 160 ms) were qualitatively reviewed by three independent readers. T2 relaxation times were calculated for each lesion. Receiver operating characteristic (ROC) analyses of expert readers were compared with calculated T2 relaxation times. RESULTS: T2 values performed significantly better than subjective reader analysis for liver lesion characterization (area under ROC = 0.93 vs. 0.81, 0.78, and 0.75; p < 0.0001). With use of a T2 threshold of 125 ms, the sensitivity of T2 values for malignant lesions was 100%, specificity 71%, and accuracy 84%. By comparison, the sensitivity of the three readers for malignant lesions was 76-83%, with a specificity of 61-72% and an overall accuracy of 71-80%. CONCLUSION: Despite expert reader analyses, subjective evaluations of liver lesion signal characteristics are prone to inaccuracy and lack certainty and consistency when intermediate TEs (50/160 ms) are used. Quantitative measurements of T2 relaxation times should be performed to accurately and confidently differentiate benign from malignant liver lesions. Use of a higher T2 threshold than previously recommended is required to avoid misclassification of malignancies.

Contrast agent-enhanced, free-breathing, three-dimensional coronary magnetic resonance angiography.

For free-breathing, high-resolution, three-dimensional coronary magnetic resonance angiography (MRA), the use of intravascular contrast agents may be helpful for contrast enhancement between coronary blood and myocardium. In six patients, 0.1 mmol/kg of the intravascular contrast agent MS-325/AngioMARK was given intravenously followed by double-oblique, free-breathing, three-dimensional inversion-recovery coronary MRA with real-time navigator gating and motion correction. Contrast-enhanced, three-dimensional coronary MRA images were compared with images obtained with a T2 prepulse (T2Prep) without exogenous contrast. The contrast-enhanced images demonstrated a 69% improvement in the contrast-to-noise ratio (6.6 +/- 1.1 vs. 11.1 +/- 2.5; P < 0.01) compared with the T2Prep approach. By using the intravascular agent, extensive portions (> 80 mm) of the native left and right coronary system could be displayed consistently with sub-millimeter in-plane resolution. The intravascular contrast agent, MS-325/AngioMARK, leads to a considerable enhancement of the blood/muscle contrast for coronary MRA compared with T2Prep techniques. The clinical value of the agent remains to be defined in a larger patient series. J. Magn. Reson. Imaging 1999;10:790-799.

Whole-body MR imaging. Practical issues, clinical applications, and future directions.

Whole-body MR imaging is in evolution, and although accepting and recognizing limitations, it is likely that both technique and incurred acquisition times will shorten over the next decade. Although the development of dedicated whole-body MR scanners appears to offer the greatest promise for the future, the development of moving table tops, optimized pulse sequences, and advances in gradient technology now facilitate practical whole-body MR imaging using existing clinical systems.

Advances in abdominal, aortic, and peripheral contrast-enhanced MR angiography.

This article reviews the basic principles of contrast-enhanced MR angiography, including methods used for sequence optimization and bolus timing, and describes clinical applications of contrast-enhanced MR angiography in the aortic, abdominal, and peripheral arteries. Novel MR angiography imaging techniques also are described, including moving table-top MR angiography, MR fluoroscopy, and time-resolved MR angiography.

Voxel sensitivity function description of flow-induced signal loss in MR imaging: implications for black-blood MR angiography with turbo spin-echo sequences.

The conditions in which the image intensity of vessels transporting laminar flow is attenuated in black-blood MR angiography (BB-MRA) with turbo spin-echo (TSE) and conventional spin-echo (CSE) pulse sequences are investigated experimentally with a flow phantom, studied theoretically by means of a Bloch equation-voxel sensitivity function (VSF) formalism, and computer modeled. The experiments studied the effects of: a) flow velocity, b) imaging axes orientation relative to the flow direction, and c) phase encoding order of the TSE train. The formulated Bloch equation-VSF theory describes flow effects in two-dimensional (2D)- and 3D-Fourier transform magnetic resonance imaging. In this theoretical framework, the main attenuation mechanism instrumental to BB-MRA, i.e., transverse magnetization dephasing caused by flow in the presence of the imaging gradients, is described in terms of flow-induced distortions of the individual voxel sensitivity functions. The computer simulations predict that the intraluminal homogeneity and extent of flow-induced image intensity attenuation increase as a function of decreasing vessel diameter, in support of the superior image quality achieved with TSE-based BB-MRA in the brain.

Black-blood MR angiography with GRASE: measurement of flow-induced signal attenuation.

We investigated the feasibility of performing black-blood MR angiography (MRA) with the gradient and spin-echo (GRASE) pulse sequence. Phantom experiments and human testing were conducted, and the results were compared with those of turbo spin-echo (TSE). We demonstrated that both techniques are able to produce signal suppression of flowing fluid to background level. With fewer radiofrequency (RF)-refocusing pulses, GRASE pulse sequences could serve as an alternative black-blood technique of reduced RF power exposure and shorter scan time. These relative advantages of GRASE may become useful when high-resolution images are taken.

Steady-state and dynamic MR angiography with MS-325: initial experience in humans.

PURPOSE: To evaluate the imaging performance and patient tolerance of a blood-pool contrast agent (MS-325) for magnetic resonance (MR) angiography. MATERIALS AND METHODS: Imaging of peripheral and carotid vessels was performed in seven healthy volunteers in a phase I clinical trial of the gadolinium chelate MS-325. Each volunteer received an intravenous injection of 0.05 mmol/kg MS-325 over 30 seconds. Dynamic (arterial phase) and steady-state (arterial-venous phase) three-dimensional gradient-echo MR angiograms were acquired during, immediately after, and approximately 50 minutes after injection. Images were ranked (1 [poor] to 5 [excellent]) for overall image quality, and signal-to-noise ratio (S/N) and contrast-to-noise ratio (C/N) were measured by using standard techniques. RESULTS: All volunteers tolerated the procedure well. The MS-325-enhanced studies demonstrated intense vascular signal. Mean peripheral arterial C/N was 12.9 +/- 4.8 (standard deviation), 78.8 +/- 29.4, 46.1 +/- 10.9, and 41.9 +/- 14.1 for the two-dimensional (2D) time-of-flight (TOF) and the contrast material-enhanced dynamic, early steady-state, and late steady-state images, respectively. Image quality of steady-state postcontrast images was statistically significantly (P < .02) higher than that of 2D TOF images. Image quality of early and late postcontrast images was similar, but a small (10%) decrease in C/N was noted from early to late images. CONCLUSION: MS-325 provides excellent vascular and selective arterial enhancement during dynamic MR angiography. The long blood residence time also allows acquisition of steady-state images of the arteries and veins with excellent spatial resolution.