Biomedical subjects

Georg Mühlenbruch

Publications and source records attributed to Georg Mühlenbruch.

25 records · Page 2Linked to original sources

PubMed2005

Influence of a small field-of-view size on the detection of coronary artery calcifications with MSCT: in vitro and in vivo study.

The purpose of this study is to asses the impact of small field-of-view (FOV) sizes on the detection of coronary artery calcifications using multislice-spiral computed tomography (MSCT). First, a static chest phantom containing calcium inserts was scanned 10 times using a standardized scan protocol. Secondly, 50 patients (28 male, 63.6+/-10.6 years) underwent cardiac MSCT using the same protocol. Images were reconstructed with three different FOV sizes (180x180, 220x220, 380x380 mm(2)). Coronary calcium scoring and risk stratification were performed for each image series. In the phantom study, the Agatston score calculated with a FOV size of 180x180 mm(2) was 657.80+/-20.05. At a FOV of 220x220 mm(2) and 380x380 mm(2), the corresponding values were 657.04+/-21.36 and 655.04+/-20.74, respectively. The corresponding values in the patient study were 541.65+/-869.87, 541.91+/-872.57 and 536.61+/-867.81. No statistically significant differences in the calcium score were found comparing different FOV sizes. Significantly more lesions (p=0.00149) were detected in the patient study. Comparing the different FOV sizes of 180x180 mm(2) and 220x220 mm(2) (380x380 mm(2)), four (six) patients had to be assigned to different risk groups. The use of small FOV sizes resulted in an improved detection of coronary calcifications influencing the risk stratification for further cardiac events in MSCT coronary calcium scoring.

Adult↗

PubMed2005

Optimized image reconstruction for detection of deep venous thrombosis at multidetector-row CT venography.

The aims of this study were to optimize image quality for indirect CT venography (sequential versus spiral), and to evaluate different image reconstruction parameters for patients with suspected deep venous thrombosis (DVT). Fifty-one patients (26/25 with/without DVT) were prospectively evaluated for pulmonary embolism (PE) with standard multidetector-row computed tomography (MDCT) protocols. Retrospective image reconstruction was done with different slice thicknesses and reconstruction increments in sequential and spiral modes. All reconstructions were read for depiction of DVT and to evaluate best reconstruction parameters in comparison with the thinnest reconstruction ("gold standard"). Image noise and venous enhancement were measured as objective criteria for image quality. Subjective image quality was rated on a four-point scale. Effective dose was estimated for all reconstructions. In sequential 10/50 reconstruction DVT was completely detected in 13/26 cases, partially in 10/26 cases and was not detected at all in 3/26 cases, and 15/26, 9/26 and 2/26 cases for the 10/20 reconstruction, respectively. DVT was completely detected in all spiral reconstructions. Image noise ranged between 14.8-29.1 HU. Median image quality was 2. Estimated effective dose ranged between 2.3 mSv and 11.8 mSv. Gaps in sequential protocols may lead to false negative results. Therefore, spiral scanning protocols for complete depiction of DVT are mandatory.

Adult↗

PubMed2005

Coronary calcium scoring using 16-row multislice computed tomography: nonenhanced versus contrast-enhanced studies in vitro and in vivo.

OBJECTIVES: We sought to assess the agreement of coronary artery calcium score in nonenhanced and contrast-enhanced multislice-spiral computed tomography. MATERIALS AND METHODS: Vessel phantoms and 36 patients underwent nonenhanced and contrast-enhanced cardiac multislice-spiral computed tomography (Sensation 16; Siemens, Germany). Reconstruction-parameters: slice thickness 3 mm, increment 2 mm, kernels B35f and B30f. The Agatston score, calcium mass, and number of lesions were calculated. Images were scored using detection thresholds of 130 Hounsfield units (HU) and 350 HU. Based on the Agatston score, risk stratification was performed. RESULTS: In the phantom and patient study, altering the threshold from 130 to 350 HU led to a significant decrease in the mean Agatston score (phantom: 54.6%, patients: 66.7%) and calcium mass (33.0%, 47.0%) (B35f). Contrast-enhanced studies (threshold: 350 HU) showed an increase of the mean Agatston score (71.0%, 20.7%) and calcium mass (81.0%, 16.0%) when compared with nonenhanced scans (threshold: 350 HU). A total of 57% of all patients were assigned to different risk groups. CONCLUSIONS: Contrast material may simulate calcification; therefore, calculation of the coronary calcium score from contrast-enhanced images is not reliable.

Calcinosis↗

PubMed2005

Effect of varying slice thickness on coronary calcium scoring with multislice computed tomography in vitro and in vivo.

OBJECTIVES: To compare coronary calcium scoring results (calcium volume, calcium mass, Agatston score, and number of lesions) of different slice thicknesses using a 16-slice CT (MSCT) scanner. MATERIALS AND METHODS: A nonmoving anthropomorphic thorax phantom with calcium cylinders of different sizes and densities was scanned 30 times with repositioning applying a standardized retrospectively ECG-gated MSCT (SOMATOM Sensation 16; Siemens, Forchheim, Germany) scan protocol: collimation 12 x 0.75 mm, tube voltage 120 kV, effective tube current time-product 133 mAs(eff). Fifty patients (29 male; age 57.2 +/- 8.4 years) underwent a nonenhanced scan applying the same scan protocol. Two image sets (effective slice thicknesses 3 mm and 1 mm) were reconstructed at 60% of the RR interval. Image noise was measured in both studies. Calcium volume, calcium mass and Agatston score were calculated using a commercially available software tool. RESULTS: Due to increased image noise in thinner slices, calcium scoring in all scans was performed applying a scoring threshold of 350 HU. In the phantom study, 1-mm slices showed significantly higher scoring results in respect to calcium volume (+8.2%), calcium mass (+12.5%), and Agatston score (+5.3%) (all P < 0.0001). In the patient study, 27 patients had coronary calcifications in 3-mm slices, and 31 patients had coronary calcifications in 1-mm slices. Thinner slices showed significantly higher scoring results in respect to volume (+47.1%), mass (+47.2%), and Agatston score (+29.7%) (all P < 0.0001). CONCLUSIONS: When comparing 3-mm and 1-mm slices in coronary calcium scoring in MSCT, thinner slices lead to significantly increased scoring results.

Aged↗

PubMed2005

Imaging of the cardiac venous system: comparison of MDCT and conventional angiography.

OBJECTIVE: Diagnostic and therapeutic strategies in electrophysiology and interventional cardiology include the coronary venous system. The purpose of this study was to compare MDCT angiography with conventional coronary sinus angiography in terms of detailed anatomic display of the coronary veins. CONCLUSION: MDCT angiography is a reliable alternative to conventional coronary sinus angiography for detailed anatomic display of the coronary veins.

Coronary Angiography↗

PubMed2005

Radiation dose reduction to the male gonads during MDCT: the effectiveness of a lead shield.

OBJECTIVE: Our study was designed to quantify the effect of a standard gonad shield on the testicular radiation exposure due to scatter during routine abdominopelvic MDCT. SUBJECTS AND METHODS: Routine abdominopelvic MDCT was performed in 34 patients with gonadal lead shielding and 32 patients without this shielding; the testes were not exposed to the direct beam during the examination. We estimated the testicular dose administered with thermoluminescent dosimetry, taking into account each patient's body weight and body mass index (BMI). RESULTS: With a 1-mm lead shield, the mean testicular dose was reduced from 2.40 to 0.32 mSv, a reduction of 87%. The difference was found to be statistically significant (p < 0.0001). No correlation between testicular dose and body weight or BMI was found. CONCLUSION: Shielding the male gonads reduces the testicular radiation dose during abdominopelvic MDCT significantly and can be recommended for routine use.

Adult↗

PubMed2005

Individually adapted examination protocols for reduction of radiation exposure for 16-MDCT chest examinations.

OBJECTIVE: The purpose of our study was to develop a simple protocol for reduction of radiation exposure without loss of diagnostic information in chest 16-MDCT. MATERIALS AND METHODS: Two hundred and four patients underwent MDCT of the thorax (Somatom Sensation 16, Siemens). Group 1 was scanned using a standard protocol with 100 mAs(effective) (mAs(eff)). Group 2 was scanned using a dose modulation template (CareDose). Group 3 was scanned with mAs(eff) = body weight (kg). Group 4 was scanned with a combination of weight-adapted mAs(eff) and dose modulation. All other parameters were kept constant. Signal-to-noise ratio was assessed as an objective measurement for image quality, and subjective image quality was rated by three experienced radiologists on a 4-point scale. Effective dose was calculated using dedicated software. RESULTS: The mean noise measurement values were 8.31 H for the 100 mAs(eff) protocol for the regression between weight and signal-to-noise (p < 0.0001), 9.08 H for group 2 (p < 0.0001), 9.0 H for group 3 (p = 0.5051), and 9.98 H for group 4 (p = 0.0152). The median image quality was 1 (1 = highest quality) in all subgroups. The mean effective dose was 6.83 mSv, 5.92 mSv, 4.73 mSv, and 3.97 mSv, respectively. The least correlation between weight and image noise was achieved for the individually weight-adapted protocol and in the weight-adapted with CareDose combination. CONCLUSION: By tube current time product adaptation (kg = mAs(eff)) combined with an online tube current modulation template, a well-balanced examination without significant loss of information was achieved for this specific scanner. Thus, individually adapted protocols for chest 16-MDCT can be recommended.

Algorithms↗