Peripheral arteries in diabetic patients: standard bolus-chase and time-resolved MR angiography

Peripheral bolus-chase MR angiography: analysis of risk factors for nondiagnostic image quality of the calf vessels--a combined retrospective and prospective study

OBJECTIVE

The objective of our study was to evaluate the influence of endogenous and exogenous risk factors on the rate of nondiagnostic examinations of the calves in peripheral bolus-chase MR angiography (MRA).

SUBJECTS AND METHODS

Peripheral bolus-chase MRA runoff studies in 177 patients with peripheral arterial occlusive disease (PAOD) were retrospectively assessed with regard to the rate of nondiagnostic image quality due to substantial venous overlay in the calf arteries requiring repeated MRA examinations. Logistic regression was used to analyze the rate of nondiagnostic MRA examinations as a function of several endogenous and exogenous risk factors and of the stage of PAOD. To probe the retrospective data, 22 consecutive patients were prospectively included and underwent a standard peripheral MRA examination if the probability of a nondiagnostic examination was less than 50% based on the results of logistic regression; otherwise, a hybrid MRA examination was ordered.

RESULTS

Nondiagnostic image quality of the calf arteries was found in 53 patients (30%). The incidence increased with each stage of PAOD up to 39% for stage IV. For each increase in the stage of PAOD, the probability of nondiagnostic image quality increased by a factor of 1.5561 (p = 0.0024). With an increasing number of risk factors, a significantly (p = 0.0074) higher rate of nondiagnostic images was found.

CONCLUSION

Based on the retrospective statistical analysis of PAOD stages and risk factors, selected patients can be triaged to undergo a specific hybrid MRA technique and thus circumvent the occurrence of nondiagnostic images and the need for repeated MRA examinations.

Current concepts in imaging diabetic pedal osteomyelitis

Diabetic pedal osteomyelitis is primarily a manifestation of vascular insufficiency with resultant tissue ischemia, neuropathy, and infection. Nearly all cases of pedal osteomyelitis arise from a contiguous ulcer and soft tissue infection. MR imaging is the modality of choice to assess for the presence of osteomyelitis and associated soft tissue complications, to guide patient management, and to aid in limited limb resection.

Time-resolved dynamic contrast-enhanced MR urography for the evaluation of ureteral peristalsis: initial experience

PURPOSE

To determine the feasibility of time-resolved dynamic contrast-enhanced magnetic resonance urography (MRU) for the evaluation of ureteral peristalsis using a data-sharing 3D gradient echo sequence with spiral k-space filling.

MATERIALS AND METHODS

Eight patients (M=3, F=5, mean 48.1 years) were referred for MRU for the evaluation for renal mass (n=3), hematuria (n=2), urinary tract tuberculosis (n=1), postoperative bladder cancer (n=1), and postoperative ureteric reimplantation (n=1). Dynamic MRU was performed for 120 seconds at 1.5T after intravenous furosemide and gadolinium administration using an oblique sagittal, time-resolved T1 3D gradient echo sequence with 1 second effective temporal resolution. Study quality was assessed based on artifacts and extent of ureteric visualization. Frequency of peristalsis from the renal pelvis to urinary bladder was evaluated for each subject.

RESULTS

A total of 16 ureters were examined. Image quality was good in four ureters, satisfactory in 11 ureters, and poor in one ureter. Mean peristaltic frequency was 3.5 waves per minute (range, 2.5-6.5 waves/minute) in normal ureters (n=11). Five ureters were considered abnormal (one urinary tract tuberculosis and four postsurgical ureters), and all had decreased or no peristalsis (0-1.5 waves per minute).

CONCLUSION

MRU using a time-resolved, data-sharing 3D contrast-enhanced technique is able to demonstrate ureteral peristalsis and permits quantification of ureteral peristaltic frequency.

[MR angiography of peripheral arterial disease of the distal legs: is time resolved MRA (TRICKS) necessary?]

PURPOSE

To demonstrate the added diagnostic value of time-resolved imaging of contrast kinetics (TRICKS) in the evaluation of lower limb arteries compared to standard 3 level MRA with stepping table method.

PATIENTS AND METHODS

Forty patients (30% diabetics) with lower extremity peripheral arterial disease (87.5% with chronic ischemia) underwent standard contrast MRA including TRICKS of the distal arteries. Five arterial segments were defined per leg, and 395 arterial segments were compared (one patient with amputation). Two reviewers evaluated the quality of arterial imaging, presence of venous return and degree of stenosis per segment. The degree of interobserver agreement for arterial stenosis measurement was calculated.

RESULTS

More arterial segments could be analyzed on the TRICKS sequence (good or excellent analysis in 63.03%-66.32% of arterial segments compared to 41.51%-47.08% on routine MRA). There was less venous contamination on TRICKS images (25.57% to 27.60% gain). The degree of interobserver agreement was superior with TRICKS compared to standard MRA (kappa 0.85 vs 0.69).

CONCLUSION

The TRICKS sequence can be added to standard MRA for pre-therapeutic evaluation of distal arteries in patients with peripheral arterial disease, especially with chronic ischemic with rest pain and/or trophic changes.

Peripheral MR angiography with blood pool contrast agent: prospective intraindividual comparative study of high-spatial-resolution steady-state MR angiography versus standard-resolution first-pass MR angiography and DSA

PURPOSE

To prospectively compare the accuracy of high-spatial-resolution steady-state magnetic resonance (MR) angiography with standard-resolution first-pass MR angiography in the lower extremities, with digital subtraction angiography (DSA) as the reference standard.

MATERIALS AND METHODS

Institutional ethics committee approval and written informed consent were obtained. Twenty-seven patients (16 men, 11 women; mean age, 64.4 years +/- 14.8 [standard deviation]; range, 26-87 years) suspected of having or known to have peripheral arterial disease underwent first-pass and steady-state MR angiography and DSA. First-pass and steady-state MR angiography were performed in the same patient in the same session and with the same dose of blood pool contrast agent. The most severe stenosis grade of each evaluated segment was measured; sensitivity, specificity, and positive and negative predictive values were calculated at first-pass and steady-state MR angiography, with DSA as the reference standard. The kappa coefficient was used to measure the agreement between first-pass MR angiography, steady-state MR angiography, and DSA.

RESULTS

A total of 334 arterial segments were available for intraindividual comparison of first-pass MR angiography, steady-state MR angiography, and DSA in 27 patients. In 20 (74%) of 27 patients, the stenosis grade of at least one of the evaluated vessels differed at steady-state MR angiography from that at first-pass MR angiography. In total, stenosis grade was judged as higher at first-pass MR angiography than at DSA (overestimation) in 28 of 334 segments and as lower (underestimation) in 15 of 334 segments. The stenosis grade as judged at steady-state MR angiography matched with that at DSA in 334 of 334 vessel segments.

CONCLUSION

High-spatial-resolution steady-state MR angiography allowed for better agreement with DSA regarding stenosis grade in patients with arterial disease compared with standard-resolution arterial-phase first-pass MR angiography.

Magnetic resonance angiographic demonstration of carotid-cavernous fistula using elliptical centric time resolved imaging of contrast kinetics (EC-TRICKS)

Magnetic resonance angiographic evaluation of the intracranial vasculature has been predominantly carried out using conventional angiographic techniques such as time of flight and phase contrast sequences. These techniques have good spatial resolution but lack temporal resolution. Newer faster angiographic techniques have been developed to circumvent this limitation. Elliptical centric time-resolved imaging of contrast kinetics (EC-TRICKS) is one such technique which has combined the use of elliptical centric ordering of the k-space with multiphase 3D digital subtraction MR angiogram (MRA) to achieve excellent temporal resolution of the arterial and venous circulations. Its applications have been mainly in the peripheral vasculature. We report the use of this technique in a case of a high-flow, direct carotid-cavernous fistula to demonstrate its potential in intracranial MR angiography.