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Rolf W Huegli

Publications and source records attributed to Rolf W Huegli.

6 recordsLinked to original sources
PubMed2006

Intraarterial MR angiography and DSA in patients with peripheral arterial occlusive disease: prospective comparison.

PURPOSE: To prospectively evaluate the accuracy of intraarterial magnetic resonance (MR) angiography in the depiction of significant stenoses and occlusions, with intraarterial digital subtraction angiography (DSA) serving as the reference standard. MATERIALS AND METHODS: Approval of the local ethics committee and informed consent were obtained. Twenty patients (11 men; nine women; age range, 48-86 years; mean age, 69.5 years+/-11.2 [standard deviation]) with symptomatic peripheral arterial occlusive disease (PAOD) were prospectively enrolled. After percutaneous transluminal angioplasty (PTA), intraarterial MR angiography was performed in the thigh and the calf with a 1.5-T MR imager in two consecutive runs. Intraarterial MR angiography was performed with a low-dose injection protocol (ie, two 20-mL injections of a 50-mmol gadolinium-based contrast agent). Moderate stenoses (luminal narrowing 50%) or vessel occlusions; 95% confidence intervals (CIs) were calculated for sensitivity and specificity. RESULTS: Intraarterial DSA revealed 78 moderate stenoses, 57 significant stenoses, and 28 occlusions. Sensitivity, specificity, and accuracy of intraarterial MR angiography in the characterization of significant stenoses or occlusions were 92% (95% CI: 72%, 99%), 94% (95% CI: 82%, 98%), and 93%, respectively, in femoropopliteal arteries and 93% (95% CI: 83%, 98%), 71% (95% CI: 51%, 86%), and 86%, respectively, in infrapopliteal arteries. The main artifact observed with intraarterial MR angiography was venous contamination (12%). CONCLUSION: Intraarterial MR angiography is an accurate method used to depict significant stenoses and occlusions in lower extremity arteries with a low-dose injection protocol.

Aged↗
PubMed2006

Fluoroscopic contrast-enhanced MR angiography with a magnetization-prepared steady-state free precession technique in peripheral arterial occlusive disease.

OBJECTIVE: The objective of our study was to evaluate the feasibility of intraarterial (IA) near-real-time contrast-enhanced MR angiography (CE-MRA) with a frame rate of 1.3 frames per second in seven patients with lower extremity peripheral arterial occlusive disease (PAOD). For optimized background suppression, a modified 2D steady-state free precession (SSFP) technique with magnetization preparation and mask subtraction was developed. The femoropopliteal and infrapopliteal arteries were covered in two separate steps. Acceptable contrast-to-noise ratios were obtained, and road maps were reconstructed from the same data set. CONCLUSION: Mastering IA near-real-time CE-MRA, including road map reconstruction, with an SSFP technique in the lower extremity of patients with PAOD is an important building block toward successfully performing endovascular catheter MR-guided interventions.

Aged↗
PubMed2005

MR imaging of post-traumatic articular cartilage injuries confined to the femoral trochlea. Arthroscopic correlation and clinical significance.

OBJECTIVE: To assess and describe post-traumatic articular cartilage injuries isolated to the trochlear groove and provide insight into potential mechanism of injury. MATERIALS AND METHODS: We retrospectively evaluated MR imaging findings of all knee MRIs performed at our institution over the last 2 years (2450). Thirty patients met the criteria of a cartilage injury confined to the trochlear groove. In 15 cases, which were included in our study, arthroscopic correlation was available. Each plane was evaluated and graded for the presence and appearance of articular cartilage defects using a standard arthroscopic grading scheme adapted to MR imaging. Any additional pathological derangement was documented and information about the mechanism of injury was retrieved by chart review. RESULTS: In all cases the cartilaginous injury was well demonstrated on MRI. In 13 patients additional pathological findings could be observed. The most frequently associated injury was a meniscal tear in nine patients. In eight cases, the arthroscopic grading of the trochlear injury matched exactly with the MRI findings. In the remaining seven cases, the discrepancy between MRI and arthroscopy was never higher than one grade. In 13 out of 15 of patients trauma mechanism could be evaluated. Twelve patients suffered an indirect twisting injury and one suffered a direct trauma to their knee. CONCLUSION: The findings of this study demonstrate that MR imaging allows reliable grading of isolated injury to the trochlear groove cartilage and assists in directing surgical diagnosis and treatment. These injuries may be the only hyaline cartilage injury in the knee and meniscal tears are a frequently associated finding. Therefore, it is important to search specifically for cartilage injuries of the trochlear groove in patients with anterior knee pain, even if other coexistent pathology could potentially explain the patient's symptoms.

Adolescent↗
PubMed2004

Use of the modified three-point Dixon technique in obtaining T1-weighted contrast-enhanced fat-saturated images on an open magnet.

The purpose of this study was to investigate the modified three-point Dixon technique as a method for obtaining fat-saturated T1-weighted sequences before and after intravenous gadolinium administration using an open MR imaging scanner. A preliminary experiment using an oil/gadolinium phantom was performed on a 0.35-T open magnet and an advanced 1.5-T unit. Fat saturation was achieved at 1.5 T using a frequency selective presaturation technique and a modified three-point Dixon technique on the low-field scanner. The modified three-point Dixon sequence was then evaluated in ten patients undergoing MRI examinations of the spine with gadolinium enhancement to determine image characteristics and diagnostic potential. The phantom study demonstrated a homogenous suppression of signal from oil and a good distinction between fat and a gadolinium chelate on the 0.35-T unit comparable to that on the 1.5-T scanner. By applying the modified three-point Dixon technique on the open-magnet, the distinction between fat and gadolinium dimeglumine was rated as very good in 139 and good in 17 axial slices in a total of 156 images. No image was rated as difficult or not possible. Motion artifacts that hampered the reading were detected in the lower cervical spine due to respiratory movement in four (3% of all) images. The modified three-point Dixon technique provides the combination of gadolinium enhancement with fat saturation on an open magnet. Early clinical applications appear promising.

Adipose Tissue↗
PubMed2004

Modality-based navigation.

Modality-based navigation (MBN) means the interactive tracking of instruments in a co-ordinate system defined by an imaging modality, eg, CT, MR, or a fluoroscope. During the registration process, a transformation matrix between the two co-ordinate systems of the digitizer and imaging modality is calculated. Navigation can start immediately after collection of the images without an intraprocedural registration process. Since the imaging modality belongs to the OR or the intervention suite, image update can be performed at any time. Following a step-by-step procedure with navigation and image update in a reasonable sequence, the risk for a virtual-real mismatch is minimized. For CT-MBN, we obtained a freehand absolute positioning accuracy of 1.9+/-1.1 mm in vitro. The in vivo freehand absolute positioning accuracy in pelvic fracture fixation was determined to be 3.1 mm (unpublished data). From our point of view, modality-based navigation is an efficient and safe alternative tool for computer aided interventions.

Fluoroscopy↗