Alfred Stadler

Multidetector CT angiography in the assessment of peripheral arterial occlusive disease: accuracy in detecting the severity, number, and length of stenoses

The purpose was to evaluate the accuracy of multidetector CT angiography (MD-CTA) in the morphologic assessment of peripheral arterial occlusive disease (PAOD) compared to digital subtraction angiography (DSA). Fifty consecutive patients referred for DSA of the peripheral arteries due to PAOD were prospectively included in this study and underwent 16-row MD-CTA prior to DSA. Maximum intensity projections and multipath curved planar reformations were created with a semi-automated toolbox. Twenty-one vascular segments were defined in each leg and compared to DSA findings with regard to gradation, length, and number of lesions. Mean sensitivity and specificity in the detection of significant stenoses (over 70%) were 100% and 99.5% in the iliac arteries, 97.4% and 99.0% in the femoro-popliteal arteries, and 98.3% and 99.8% in the infrapopliteal arteries, respectively. High kappa values for exact stenoses gradation (0.74–1), lesion length (0.74–1), and number of lesions (0.71–1) were reached by MD-CTA, indicating high agreement with DSA. Non-invasive MD-CTA is an accurate tool for the assessment of all treatment-relevant morphologic information of PAOD (gradation, length, and number of stenoses) compared to DSA.

Artifacts in body MR imaging: their appearance and how to eliminate them

A wide variety of artifacts can be seen in clinical MR imaging. This review describes the most important and most prevalent of them, including magnetic susceptibility artifacts and motion artifacts, aliasing, chemical-shift, zipper, zebra, central point, and truncation artifacts. Although the elimination of some artifacts may require a service engineer, the radiologist and MR technologist have the responsibility to recognize MR imaging problems. This review shows the typical MR appearance of the described artifacts, explains their physical basis, and shows the way to solve them in daily practice.

Endovascular Management of Lost or Misplaced Intravascular Objects: Experiences of 12 Years

This paper reports our experience with endovascular techniques for the retrieval of lost or misplaced intravascular objects. Over 12 years, 78 patients were referred for interventional retrieval of intravascular foreign objects. In this retrospective study, radiological procedure records and patients’ medical records were reviewed to determine the exact removal procedure in every case, to report success rates, and to identify significant procedure-related complications. Written, informed consent was obtained from all patients prior to the intervention; this retrospective analysis was performed according to the guidelines of the Institutional Review Board. Thirty-six of seventy-eight foreign objects (46%) were located in the venous system, 27 of 78 (35%) in the right heart, and 15 of 78 (19%) in the pulmonary arteries. For foreign object removal, in 71 of 78 (91%) cases a snare loop was used, in 6 of 78 (8%) cases a sidewinder catheter combined with a snare loop was used, and in 1 case (1%) a sidewinder catheter alone was used for foreign object removal. In 68 of 78 (87%) cases, primary success was achieved. In 3 of 78 cases (4%), foreign objects were successfully mobilized to the femoral vessels and surgically removed. In 7 of 78 cases (9%), complete removal of the foreign object was not possible. In 5 of 78 cases (6%), minor complications occurred during the removal procedure. In conclusion, endovascular retrieval of lost or misplaced intravascular objects is highly effective, with relatively few minor complications. On the basis of our findings, these techniques should be considered as the therapy of choice.

Analysis of the utility of diffusion-weighted MRI and apparent diffusion coefficient values in distinguishing central nervous system toxoplasmosis from lymphoma

IntroductionToxoplasmosis and lymphoma are common lesions of the central nervous system in patients with AIDS. It is often difficult to distinguish between these lesions both clinically and radiographically. Previous research has demonstrated restricted diffusion within cerebral lymphomas and bacterial abscesses. However, little work has been done to evaluate the diffusion characteristics of toxoplasmosis lesions. This study was designed to explore further the utility of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps and values in making the distinction between toxoplasmosis and lymphoma.MethodsThe magnetic resonance imaging (MRI) studies of 36 patients, including 22 with toxoplasmosis (all of whom had AIDS) and 14 with lymphoma (8 of whom had AIDS), at two institutions were reviewed retrospectively. The characteristics of the lesions on DWI were evaluated, and the ADC ratios of the lesions were calculated and compared.ResultsThere was significant overlap of the ADC ratios of toxoplasma and lymphoma, most notably in the intermediate (1.0–1.6) range. There was variability in ADC ratios even among different lesions in the same patient. In only a minority of the lymphoma patients were the ADC ratios low enough to suggest the correct diagnosis.ConclusionOur study showed that toxoplasmosis exhibits a wide spectrum of diffusion characteristics with ADC ratios which have significant overlap with those of lymphoma. Therefore, in the majority of patients, ADC ratios are not definitive in making the distinction between toxoplasmosis and lymphoma.

T1 mapping of the entire lung parenchyma: influence of the respiratory phase in healthy individuals

To determine the effect of respiratory phase on the T1 values of the entire lung.

T1 mapping of the entire lung parenchyma: Influence of respiratory phase and correlation to lung function test results in patients with diffuse lung disease.

The T1 values of lung parenchyma of 25 patients with fibrosis and emphysema were measured in the entire lung, and the effect of inspiration and expiration was investigated. T1 map acquisition was based on a snapshot‐fast low‐angle shot (FLASH) sequence. Lung function and blood gas tests were measured. The study documents reverse respiratory phase dependence of T1 measurements of the entire lung parenchyma in patients with emphysema and fibrosis. Furthermore, expiratory measurements showed higher and reverse differences between patient groups compared to inspiratory measurements. For the emphysema group, the average T1 value in inspiration was 1033 ± 74 ms. The average of the mean T1 values in expiration was 982 ± 56 ms. For the patients with fibrosis, the average T1 value in inspiration was 996 ± 103 ms. Compared to that, the average T1 value in expiration was 1282 ± 170 ms. Linear regression of T1 vs. lung function parameters showed the highest regression coefficients for total lung capacity (TLC) and residual volume (RV) in expiration, the values were inversely proportionally dependent on the pooled expiratory T1 values. These findings underline the strong but nonuniform influence of the inspirational status during T1 measurements of the lung. T1 maps in both emphysema and fibrosis should preferably be acquired at expiration if reliable data are to be obtained. Magn Reson Med 59:96–101, 2008.

CT fluoroscopy-guided vs. multislice CT biopsy mode-guided lung biopsies: Accuracy, complications and radiation dose

BACKGROUND The aim of this retrospective study was to compare the diagnostic accuracy, the frequency of complications, the duration of the interventions and the radiation doses of CT fluoroscopy (CTF) guided biopsies of lung lesions with those of multislice CT (MS-CT) biopsy mode-guided biopsies. METHODS Data and images from 124 consecutive patients undergoing CTF-guided lung biopsy (group A) and 132 MS-CT-biopsy mode-guided lung biopsy (group B) were reviewed. CTF-guided biopsies were performed on a Siemens Emotion 6 CT scanner with intermittent or continuous CT-fluoroscopy, MS-CT biopsy mode-guided biopsies were performed on a Siemens Emotion 16 CT scanner. All biopsies were performed with a coaxial needle technique. RESULTS The two groups (A vs. B) did not differ significantly regarding sensitivity (95.5% vs. 95.9%), specificity (96.7% vs. 95.5%), negative predictive value (87.9% vs. 84%) or positive predictive value (98.8% vs. 98.9%). Pneumothorax was observed in 30.0% and 32.5% of the patients, respectively. Chest tube placement was necessary in 4% (group A) and 13% (group B) of the patients. The duration of the intervention was significantly longer in group A (median 37 min vs. 32 min, p=0.04). The mean CT dose index (CTDI) was 422 in group A and 36.3 in group B (p<0.001). CONCLUSION Compared to CTF-guided biopsies, chest biopsies using the MS-CT biopsy mode show dramatically lower CTDI levels. Although the diagnostic yield of the procedures do not differ significantly, biopsies using the MS-CT-biopsy mode have a three-fold higher rate of chest tube placement.

3D versus 2D ultrasound: accuracy of volume measurement in human cadaver kidneys.

Partik B, Stadler A, Schamp S, et al. 3D versus 2D ultrasound. Accuracy of volume measurement in human cadaver kidneys. Invest Radiol 2002;37:489–495. Rationale and Objectives.Comparison of the accuracy of 3D and 2D ultrasound in assessing the volume of human cadaver kidneys. Materials and Methods.Before autopsy the volume of 22 kidneys was assessed from a 3D data set after manually tracing organ contours (3D volumetry) and by applying a 3D ellipsoid formula both on a 3D data set and 2D images. Measurements by water-displacement served as the gold standard. Results.3D volumetry showed a mean absolute deviation of 31 mL (18.5%) compared with the mean gold standard measurement (168 mL), yielding a concordance correlation (Lin’s &rgr;c) of 0.71. Calculation based on the ellipsoid formula revealed a mean absolute deviation of 37 mL (22.0%) when applied on the 3D data set (&rgr;c = 0.65) and of 42 mL (25.0%) when applied on 2D images (&rgr;c = 0.61), respectively. Conclusions.3D volumetry showed a satisfactory concordance correlation and is superior to volume calculation based on the ellipsoid formula either applied to a 3D data set or to conventional 2D images in assessing the volume of human cadaver kidneys.

Intraoperative and interventional MRI: Recommendations for a safe environment

In this paper we report on current experience and review magnetic resonance safety protocols and literature in order to define practices surrounding MRI‐guided interventional and surgical procedures. Direct experience, the American College of Radiology White paper on MR Safety, and various other sources are summarized. Additional recommendations for interventional and surgical MRI‐guided procedures cover suite location/layout, accessibility, safety policy, personnel training, and MRI compatibility issues. Further information is freely available for sites to establish practices to minimize risk and ensure safety. Interventional and intraoperative MRI is emerging from its infancy, with twelve years since the advent of the field and well over 10,000 cases collectively performed. Thus, users of interventional and intraoperative MRI should adapt guidelines utilizing universal standards and terminology and establish a site‐specific policy. With policy enforcement and proper training, the interventional and intraoperative MR imaging suite can be a safe and effective environment.

Characterization of hepatocellular tumors: value of mangafodipir-enhanced magnetic resonance imaging.

Purpose: To assess the value of mangafodipir trisodium-enhanced MR imaging for characterization of hepatocellular lesions. Materials and Methods: Magnetic resonance images of 41 patients with 48 histopathologically proven hepatocellular lesions (20 cases of focal nodular hyperplasia [FNH], 4 adenomas, 15 hepatocellular carcinomas [HCCs], 7 regenerative nodules, and 2 others) were retrospectively studied. Magnetic resonance imaging was performed on a 1.5-T unit (Vision, Siemens, Erlangen, Germany; ACS-NT, Philips, Best, The Netherlands) using T2-weighted, fat-saturation, turbo spin echo imaging and T1-weighted gradient echo imaging before and 20 minutes after infusion of 5 μmol/kg mangafodipir (Amersham Health, Oslo, Norway). Qualitative analysis by 4 blinded independent readers included assessment of unenhanced images and, in a second step, assessment of unenhanced and contrast-enhanced images together. Lesions were classified as benign or malignant using a 5-point scale, and readers made a specific diagnosis. Results: For characterization of hepatocellular lesions, mangafodipir-enhanced imaging was significantly superior to unenhanced imaging (P < 0.05). On receiver operating characteristic analysis, the area under the curve was 0.768 (95% confidence interval: 0.633-0.903) for unenhanced images and 0.866 (95% confidence interval: 0.767-0.966) for evaluation of unenhanced and contrast-enhanced images together (P < 0.05). Analysis of enhancement patterns aided in characterization and classification of tumors. Conclusion: Administration of mangafodipir improves the differentiation between adenoma or HCC and “nonsurgical” lesions (FNH or regenerative nodules). The accuracy for arriving at a specific diagnosis is higher when unenhanced and mangafodipir-enhanced images are considered together than for unenhanced MR images alone.