Anatomically tailored k-Space sampling for bolus-chase three-dimensional MR digital subtraction angiography

Whole-body MR angiography using variable density sampling and dual-injection bolus-chase acquisition

Conventional bolus-chase acquisition generates peripheral runoff images using a single injection of the contrast material. Low spatial resolution, small slice coverage and venous contamination are major problems especially in the distal stations. A technique is presented herein in which whole-body magnetic resonance angiography is performed using a dual-contrast-injection four-station acquisition protocol. Bolus sharing was performed between two stations: the abdomen and calf stations share the first bolus injection, while the thorax and thigh stations share the second bolus injection. The combination of variable density sampling and elliptical centric acquisition order was applied to the abdomen and thorax stations. The scan time was extended to generate high spatial resolution arterial phase images with broad slice coverage for the calf and thigh stations. The feasibility of this technique was demonstrated using phantom and in vivo human volunteer studies.

Peripheral MR angiography

Peripheral arterial occlusive disease is a chronic and progressive disease with a reported incidence rate from 4.5% to 8.8% in men over 55 years of age. The diagnosis is usually made clinically, but for treatment planning and control, imaging of the peripheral arteries is required. Since its introduction in 1994, contrast-enhanced MR angiography has demonstrated a high diagnostic confidence and has replaced the invasive intra-arterial DSA, which is still the current gold standard for many different indications. For the peripheral arteries, clinical use of MR angiography was hampered for some years by the unsolved problem of the large imaging volume and the small diameter of the distal arteries. However, since the availability of ultra-fast high-gradient sequences and the possibility of moving-bed imaging, contrast-enhanced MR angiography, over the last few years, has shown its enormous potential and high accuracy in the diagnosis and follow-up of patients suffering from peripheral arterial occlusive disease. Exciting innovations in hardware and software allows very fast, very accurate, and very robust noninvasive imaging of the peripheral arteries, and both treatment planning as well as follow-up can be performed using contrast-enhanced MR angiography. The following review introduces the basic concepts of peripheral MR angiography--focusing on contrast enhanced imaging--and presents the different techniques as well as some potential limitations and how they could be solved. Finally, this article provides a look into the already-begun future of peripheral contrast-enhanced MR angiography with hybrid and combination techniques.

MR digital subtraction angiography in the diagnosis of meningiomas

OBJECTIVE

MR digital subtraction angiography (DSA) is a technique for demonstrating the vasculature combining a rapid two-dimensional T1-weighted sequence with a bolus injection of gadolinium. We attempted to determine its contribution to the diagnosis of intracranial meningiomas.

METHODS AND PATIENTS

MR DSA was performed in 18 patients with meningioma as well as in 28 patients with other tumors. The findings were analyzed regarding demonstration of tumor stain and tumor-related vessels.

RESULTS

All meningiomas except one were visualized as a homogeneous and intense stain. Feeding arteries were visualized in 2 patients, and draining or abnormal veins in three. In 21 of the 28 patients with other tumors, tumor stains of varying degrees were demonstrated.

CONCLUSION

MR DSA can serve as an adjunct to routine MR imaging, because it enables assessment of the hemodynamics of meningiomas and facilitates its differential diagnosis from other tumors.

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.

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.

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.

Cross-sectional pattern of collateral vessels in patients with superficial femoral artery occlusion

RATIONALE AND OBJECTIVES

The purpose of this study was to identify the cross-sectional location of collateral vessels in patients with peripheral vascular disease on three-dimensional magnetic resonance angiograms (3D MRAs) to suggest sites for intravascular or transcutaneous angiogenesis gene delivery in the lower extremity.

METHODS

The axial locations were measured and categorized by tissue compartments, as well as by radial coordinates with respect to the femur.

RESULTS

Collateral vessels in the thigh were identified in 24 of 93 consecutive patients who underwent peripheral 3D MRA. Ninety-one percent (99/109) of the observed collaterals were located near the adductor canal level of the thigh, with 78% (31/46) of these collaterals located in the fat in or surrounding the posterior muscle.

CONCLUSIONS

The majority of collateral vessels in the thigh are located in the fat or muscle within the posterior compartment near the femur at the level of the adductor canal.