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Biomedical subjects

Joern O Balzer

Publications and source records attributed to Joern O Balzer.

7 recordsLinked to original sources
PubMed2005

Peripheral artery stent visualization and in-stent stenosis analysis in 16-row computed tomography: an in-vitro evaluation.

The accuracy of 16-row multidetector CT in the visualization of different peripheral artery stents and in the appraisal of in-stent stenosis was assessed. Nine different stent types (nitinol and stainless steel) with three diameters (6, 8 and 10 mm) were used; altogether 27 stents were analyzed in a barrel-shaped vascular model. Low-grade (<40%) and high-grade (>60%) in-stent stenoses were simulated by polyurethane sticks (70 HU) of differing diameters (2-6 mm). Imaging was performed with 16x0.75-mm detector collimation, 130 mAs, 120 kV, 12-mm table feed/rotation, 1.0-mm slice thickness and 0.5-mm increment. The stent diameter, strut thickness, in-stent attenuation values, degree and degree of in-stent stenosis were evaluated. Nitinol stents showed significantly (P<10-6) less stent lumen narrowing, artificial strut thickening and overestimation of the degree of in-stent stenoses than stainless steel stents. In-stent attenuation values and artificial strut thickening were significantly (P<10-6) lower in 10- and 8-mm stents than in 6-mm stents. Stent lumen narrowing was significantly less in 10-mm stents than in 8-mm (P<10-4) or 6-mm (P<10-6) stents. In-stent stenoses were significantly overestimated, irrespective of the stent diameter. In 6-mm stents overestimation was significantly higher than in 8-mm (P<0.01) or 10-mm stents (P<10-6). Under in-vitro conditions 16-row MDCT allowed an accurate identification of in-stent stenosis, but significantly overestimated the effective degree of the stenosis.

Constriction, Pathologic↗
PubMed2005

Evaluation of the stereotactic 8G vacuum-assisted breast biopsy in the histologic evaluation of suspicious mammography findings (BI-RADS IV).

PURPOSE: The purpose of this study was to evaluate the potential of the new 8G stereotactic vacuum-assisted breast biopsy (ST-driver, Mammotome; Ethicon Endosurgery) in the histologic evaluation of BI-RADS IV microcalcifications. MATERIALS AND METHODS: Fifty-eight patients with 61 mammographic BI-RADS IV microcalcifications underwent stereotactic vacuum-assisted breast biopsy (SVAB). The new 8G system was mounted on the ST driver, which was formerly used only with the hand-held version under sonographic guidance. The evaluation criteria for each biopsy were minimally invasive and operative histologies, the time needed for biopsy, the amount of bleeding, number of rotations and specimen, the degree of resection, and the complications. RESULTS: Fifty-eight of 61 biopsies were technically successful because > or = 50% were resected (29 x 100%, 8 x 90%, 5 x 80%, 6 x 70%, 3 x 50%, 3 x 0%). In 7 cases with representative biopsies of segmental suspicious microcalcifications, the degree of resection could not be exactly measured. All but 2 biopsies were performed without clinically relevant complications and after gaining enough specimens (Ø 12.6 specimen, 1.85 rotations). Those 2 patients showed evidence of severe bleeding into the breast tissue and operative revision had to be performed (3.5%). The size of intramammary hematoma was measurable in 27 biopsies and showed a range from 0.5 to 5 cm (Ø 2.7 cm). The average external bleeding was still low with 16 mL (5-80 mL). In 3 of 61 lesions, it was not possible to gain representative tissue as a result of displacement of the lesion after introducing or shooting the needle. The average time needed for all biopsies was 28.2 minutes for all but 5 very complicated biopsies, which took 16.1 minutes. The histologic findings with further operative workup were: 10 ductal carcinomas in situ (DCIS), 4 atypical ductal hyperplasias, 1 atypical lobular hyperplasias (ALH), 3 lobular carcinomas in situ (LCIS), and 6 invasive ductal carcinomas. In 7 of 12 of the initial DCIS histologies, the operative histology was also DCIS, whereas in 4 of 12, no residual malignant tumor was found. In 1 of 12 patients with an initial DCIS histology, operative histology revealed invasive ductal cancer (8.3%). The cases with lobular lesions (ALH, LCIS) did not show any evidence for residual tissue in the operative workup. Most frequent benign histologies were mastopathy (13), ductal hyperplasia (9), fibroadenoma (8), and sclerosing adenosis (5). The control examinations (maximum 1 year) did not show any signs for a false-negative biopsy. CONCLUSION: The 11-G SVAB has proven to be a perfect adjunct to the existing breast biopsy methods. The new 8G SVAB speeds up the method when used for the same size of lesions and enables the user to representatively biopsy lesions up to 3 cm in diameter. The method is still minimally invasive; however, the amount of hematomas as well as clinically relevant complications is increased.

Biopsy, Needle↗
PubMed2003

Multidetector-row cardiac CT: diagnostic value of calcium scoring and CT coronary angiography in patients with symptomatic, but atypical, chest pain.

The aim of this study was to investigate the accuracy of multidetector-row cardiac CT (MDCT), calcium scoring (Ca-Sc), and MDCT coronary angiography (MD CTA) in the assessment of coronary atherosclerosis. Thirty-eight patients underwent invasive coronary angiography (CA) and MDCT (collimation 4x1 mm, pitch 1.5 mm, TI 500 ms, 120 kV, 300 mAs, and retrospective ECG-gating). Calcium scoring was calculated for the total coronary artery territory and for RCA, LCA, and LCX separately. The MD CTA served to assess the degree and the localization of stenoses. All findings were compared to invasive coronary angiography. Approximately 68.4% (390 of 570) of all coronary segments could be visualized by MDCT. Correlation coefficient for MD CTA and CA amounted to r=0.58, showing distinct differences for the individual segments. Proximal segments generally showed better correlation (range 0.81-0.77) than medial segments (range 0.91-0.20), distal segments (range 0.55-0.04), or side branches (range 0.76-0.00). Patients with hemodynamically relevant (>75%) stenoses were detected by MD CTA with 72.2% sensitivity (13 of 18) and 100% specificity (20 of 20). For Ca-Sc sensitivity ranged between 94.7% (17 of 18) and 66.7% (12 of 18), specificity between 20% (4 of 20) and 80% (16 of 20) respectively, depending on the prevailing cutoff value. Combination of both methods led to 83.3% sensitivity (15 of 18) and 100% specificity (20 of 20), reaching no level of significance as compared with Ca-Sc (p=0.73) or MD CTA (p=0.23) alone. Calcium scoring as a single method showed highest sensitivity in the detection of coronary atherosclerosis but at the expense of low specificity. In patients with no or moderate calcifications, combination with MD CTA helped to distinctly increase specificity and NPV.

Adult↗
PubMed2003

Multidetector-row CT: cardiosurgery indications.

This article critically evaluates the role of multidetector-row CT before and after cardiosurgical procedures. In addition, technical aspects, such as scan protocols, optimal image reconstruction intervals, image reformation techniques, and data evaluation, are presented and briefly discussed.

Aortic Valve↗
PubMed2002

Heart-rate-adapted image reconstruction in multidetector-row cardiac CT: influence of physiological and technical prerequisite on image quality.

The purpose of this study was to develop strategies for optimal image reconstruction in multidetector-row cardiac CT and to discuss the results in the context of individual heart rate, cardiac physiology, and technical prerequisite. Sixty-four patients underwent multidetector-row cardiac CT. Depending on the heart rate either a single-segmental reconstruction (SSR) or an adaptive two-segmental reconstruction (ASR) was applied. Image reconstruction was done either antegrade (a) or retrograde (r) in relation to the R-peak. Reconstruction of all data sets was performed at multiple time points within the t-wave/p-wave interval, differing from each other by 50 ms. In addition, each reconstruction was assigned to one of six reconstruction intervals (A-F), each corresponding to a specific event in the cardiac cycle. While no significant time points were found for absolute values, the following interval/reconstruction technique combinations provided significant better image quality: F/r at HR <60 bpm for all coronary segments ( p</=0.004) and at HR 60-65 bpm for segments 5-10 ( p</=0.001); B/a at HR 60-65 bpm for segments 1-4 and 11-15 ( p<0.001) and at HR >65 bpm for all segments ( p</=0.002). The results show that in order to achieve optimal image quality, image reconstruction has to be adjusted to each patient's ECG curve and heart rate individually. The moment of reconstruction should be determined as absolute rather than as relative distance from the previous R-peak.

Algorithms↗