Radko Krissak

Publications

• 2.95

  Impact points

  Aortoiliac CT Angiography for Planning Transcutaneous Aortic Valve Implantation: Aortic Root Anatomy and Frequency of Clinically Significant Incidental Findings.

  Paul Apfaltrer, Gerhard Schymik, Peter Reimer, Holger Schroefel, Tim Sueselbeck, Thomas Henzler, Radko Krissak, John W Nance, U Joseph Schoepf, Dirk Wollschlaeger, Stefan O Schoenberg, Christian Fink

  AJR. American journal of roentgenology. 04/2012; 198(4):939-45.

  The purpose of this article is to assess aortic root and iliofemoral vessel anatomy and the frequency of clinically significant incidental findings on aortoiliac CT angiography (CTA) performed for planning of transcutaneous aortic valve implantation. Aortoiliac CTA studies of 207 patients scheduled ... [more] The purpose of this article is to assess aortic root and iliofemoral vessel anatomy and the frequency of clinically significant incidental findings on aortoiliac CT angiography (CTA) performed for planning of transcutaneous aortic valve implantation. Aortoiliac CTA studies of 207 patients scheduled for transcutaneous aortic valve implantation were analyzed. Anatomic dimensions relevant to the interventional procedure, including diameter of the aortic annulus and sinus of Valsalva, distance between aortic annulus and coronary ostia, coronary leaflet length, left ventricular outflow tract diameter, and vessel diameter of iliac arteries, were analyzed. Clinically significant incidental findings were recorded. The mean (± SD) maximum and minimum diameters of the aortic annulus were 29 ± 3.9 mm and 23.5 ± 4.1 mm, respectively. The mean distances between aortic annulus and the ostium of the left and right coronary artery were 13.5 ± 3.2 mm and 14.8 ± 3.9 mm, respectively. The mean maximum and minimum diameters of the left ventricular outflow tract were 27 ± 4 mm and 1.9 ± 4 mm, respectively. The mean diameter of the sinus of Valsalva was 33.4 ± 5.1 mm. The mean diameters of the right and left external iliac artery were 8 ± 1 and 8 ± 2 mm, respectively. Almost half the patients (101/207) had clinically significant incidental findings, including noncalcified pulmonary nodules larger than 8 mm (n = 7), pulmonary embolism (n = 3), or aortic aneurysm (n = 12). Aortoiliac CTA provides relevant information on aortic root and iliofemoral vessel anatomy for preinterventional planning. CTA reveals clinically significant incidental findings in a high number of patients considered for transcutaneous aortic valve implantation, which may have a significant impact on patient selection.
• 3.54

  Impact points

  CT Angiography of the Aorta Is Superior to Transesophageal Echocardiography for Determining Stroke Subtypes in Patients with Cryptogenic Ischemic Stroke.

  A Chatzikonstantinou, R Krissak, S Flüchter, D Artemis, A Schaefer, S O Schoenberg, M G Hennerici, C Fink

  Cerebrovascular diseases (Basel, Switzerland). 02/2012; 33(4):322-328.

  Background: The etiology of ischemic strokes remains cryptogenic in about one third of patients, even after extensive workup in specialized centers. Atherosclerotic plaques in the aorta can cause thromboembolic events but are often overlooked. They can elude standard identification by transesophagea... [more] Background: The etiology of ischemic strokes remains cryptogenic in about one third of patients, even after extensive workup in specialized centers. Atherosclerotic plaques in the aorta can cause thromboembolic events but are often overlooked. They can elude standard identification by transesophageal echocardiography (TEE), which is invasive or at best uncomfortable for many patients. CT angiography (CTA) can be used as an alternative or in addition to TEE if this technique fails to visualize every part of the aorta and in particular the aortic arch. Methods: We prospectively studied 64 patients (47 men, age 60 ± 13 years) classified as having cryptogenic stroke after standard and full workup [including brain MRI and 24-hour electrocardiogram (ECG)] with ECG-triggered CTA of the aorta in search of plaques and compared the results with those of TEE. Investigators were blinded to the results of both techniques. Plaques were graded on CTA according to their presence (0 = not present; 1 = mild; 2 = severe) and degree of calcification (1a or 2a = noncalcified; 1b or 2b = calcified). Associations with risk factors and infarct localization were also assessed. Results: Only 21 of 64 patients (32.8%) had aortic plaques identified by TEE, compared to 43 of 64 (67.2%) with CTA (p < 0.05). The plaque localization was as follows (TEE vs. CTA): ascending aorta, 10 vs. 20 (p < 0.05); aortic arch, 10 vs. 40 (p < 0.05), and descending aorta, 20 vs. 34 (p < 0.05). Grade 1 plaques were most commonly found in the aortic arch (25; 39%), while grade 2 plaques were most often detected in the aortic arch (15; 23.4%) and the descending aorta (14; 21.9%). There was no significant correlation between plaque location, infarct territory or vascular risk profile, except for hypertension (p = 0.003), which was significantly associated with the presence of plaques. Conclusions: CTA identifies more plaques throughout the aortic arch and around the origins of the major cerebral arteries in particular compared to TEE. These may represent potential embolic sources of acute ischemic stroke. Better plaque detection may have an impact on the best available secondary prevention regimen in individual patients if proximal embolic sources are suspected.
• 2.65

  Impact points

  Dual-energy CT angiography of the lungs: comparison of test bolus and bolus tracking techniques for the determination of scan delay.

  Thomas Henzler, Mathias Meyer, Miriam Reichert, Radko Krissak, John W Nance, Stefan Haneder, Stefan O Schoenberg, Christian Fink

  European journal of radiology. 01/2012; 81(1):132-8.

  To prospectively compare test bolus and bolus tracking for the determination of scan delay of pulmonary dual-energy CT angiography in patients with suspected pulmonary embolism. 60 consecutive patients referred for CTA for exclusion of PE were randomized either into a test bolus group or into a bolu... [more] To prospectively compare test bolus and bolus tracking for the determination of scan delay of pulmonary dual-energy CT angiography in patients with suspected pulmonary embolism. 60 consecutive patients referred for CTA for exclusion of PE were randomized either into a test bolus group or into a bolus tracking group. All exams were performed on a 64-channel dual source CT scanner. A standard single-acquisition dual-energy CTA was performed after injection of 100ml Iomeprol 400 followed by a saline chaser of 4 ml/s. The scan delay was determined using either test bolus (n=30) or bolus tracking (n=30). Test bolus was performed using an additional 20 ml Iomeprol 400 injected with a rate of 4 ml/s during acquisition of a series of dynamic low-dose monitoring scans followed by injection of a saline bolus of 20 ml using the same flow rate. For DECT angiography of the lungs 100ml Iomeprol 400 was injected with an injection rate of 4 ml/s followed by a saline chaser of 20 ml using the same flow rate. Attenuation profiles of different vascular segments (pulmonary arteries, pulmonary parenchyma, aorta, all 4 heart chambers) were measured to evaluate the timing techniques. Overall image quality of dual-energy "perfusion" maps and virtual 120 kV CTA images was evaluated by two radiologists regarding the present of artifacts. In all patients an adequate and homogeneous contrast enhancement of more than 400 Hounsfield units (HU) was achieved in the different vascular districts. No statistically significant difference between test bolus and bolus tracking was found regarding vessel attenuation or overall image quality. A homogeneous opacification of the different vascular territories and the pulmonary parenchyma as well as a sufficient image quality can be achieved with either bolus tracking or test bolus techniques.

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• 2.65

  Impact points

  Attenuation-based characterization of coronary atherosclerotic plaque: comparison of dual source and dual energy CT with single-source CT and histopathology.

  Thomas Henzler, Stefan Porubsky, Hany Kayed, Nils Harder, U Radko Krissak, Mathias Meyer, Tim Sueselbeck, Alexander Marx, Henrik Michaely, U Joseph Schoepf, Stefan O Schoenberg, Christian Fink

  European journal of radiology. 10/2011; 80(1):54-9.

  To compare different CT acquisition techniques regarding for attenuation-based characterization of coronary atherosclerotic plaques using histopathology as the standard of reference. In a post mortem study 17 human hearts were studied with dual-source CT (DSCT) and dual energy CT (DECT) mode on a DS... [more] To compare different CT acquisition techniques regarding for attenuation-based characterization of coronary atherosclerotic plaques using histopathology as the standard of reference. In a post mortem study 17 human hearts were studied with dual-source CT (DSCT) and dual energy CT (DECT) mode on a DSCT as well as with 16-slice single-source CT (SSCT). At autopsy, atherosclerotic lesions were cut at 5 μm sections. Histopathologic classification of the plaques according to the American Heart Association (AHA) criteria was performed by two pathologists. Attenuation values of all plaques were measured in DSCT, DECT and SSCT studies, respectively and classified based on attenuation according to modified AHA criteria. 58 coronary plaques were identified at autopsy. Regardless of the CT technique only 52/58 plaques were found at CT (sensitivity=89.6%). There was no significant difference between the mean attenuation values of different plaque types between DSCT, DECT, and SSCT: type IV: 11HU/8HU/19HU; type Va: 44HU/45HU/52HU; type Vb: 1088HU/966HU/1079HU). The sensitivity for correct classification varied depending on the plaque type (type II=0%, type III=0%, type IV=43%, type Va=58%, Vb=97%). Independent of the used acquisition technique, SSCT, DSCT and DECT show similar results for attenuation-based characterization of atherosclerotic coronary plaques.
• 3.59

  Impact points

  Functional imaging of lung cancer using dual energy CT: how does iodine related attenuation correlate with standardized uptake value of 18FDG-PET-CT?

  G Schmid-Bindert, Thomas Henzler, T Q Chu, M Meyer, J W Nance, U J Schoepf, D J Dinter, P Apfaltrer, R Krissak, C Manegold, S O Schoenberg, C Fink

  European radiology. 08/2011; 22(1):93-103.

  To investigate the correlation between maximum standardized uptake value (SUV(max)) of (18)FDG PET-CT and iodine-related attenuation (IRA) of dual energy CT (DECT) of primary tumours and (18)FDG PET-CT positive thoracic lymph nodes (LN) in patients with lung cancer. 37 patients with lung cancer (27 ... [more] To investigate the correlation between maximum standardized uptake value (SUV(max)) of (18)FDG PET-CT and iodine-related attenuation (IRA) of dual energy CT (DECT) of primary tumours and (18)FDG PET-CT positive thoracic lymph nodes (LN) in patients with lung cancer. 37 patients with lung cancer (27 NSCLC, 10 SCLC, 86 (18)FDG PET-CT positive thoracic LN) who underwent both (18)FDG PET-CT and DECT were analyzed. The mean study interval between (18)FDG PET-CT and DECT was ≤21 days in 17 patients. The mean and maximum IRA of DECT as well as of virtual unenhanced and virtual 120 kV images of DECT was analyzed and correlated to the SUV(max) of (18)FDG PET-CT in all tumours and (18)FDG PET-CT positive thoracic lymph nodes. Further subgroup analysis was performed for histological subtypes in all groups. A moderate correlation was found between SUV(max) and maximum IRA in all tumours (n = 37;r = 0.507;p = 0.025) whereas only weak or no correlation were found between SUV(max) and all other DECT measurements. A strong correlation was found in patients with study intervals ≤21 days (n = 17; r = 0.768;p = 0.017). Analysis of histological subtypes of lung cancer showed a strong correlation between SUV(max) and maximum IRA in the analysis of all patients with NSCLC (r = 0.785;p = 0.001) and in patients with NSCLC and study intervals ≤21 days (r = 0.876;p = 0.024). Thoracic LN showed moderate correlation between SUV(max) and maximum IRA in patients with study intervals ≤21 days (r = 0.654; p = 0.010) whereas a weak correlation was found between SUV(max) and maximum IRA in patients with study intervals >21 days (r = 0.299; p = 0.035). DECT could serve as a valuable functional imaging test for patients with NSCLC as the IRA of DECT correlates with SUV(max) of (18)FDG PET-CT.
• 4.85

  Impact points

  Optimization of contrast material delivery for dual-energy computed tomography pulmonary angiography in patients with suspected pulmonary embolism.

  John W Nance, Thomas Henzler, Mathias Meyer, Paul Apfaltrer, Margarita Braunagel, Radko Krissak, Uwe J Schoepf, Stefan O Schoenberg, Christian Fink

  Investigative radiology. 05/2011; 47(1):78-84.

  To prospectively compare subjective and objective measures of image quality using 4 different contrast material injection protocols in dual-energy computed tomography pulmonary angiography (CTPA) studies of patients with suspected pulmonary embolism. A total of 100 consecutive patients referred for ... [more] To prospectively compare subjective and objective measures of image quality using 4 different contrast material injection protocols in dual-energy computed tomography pulmonary angiography (CTPA) studies of patients with suspected pulmonary embolism. A total of 100 consecutive patients referred for CTPA for the exclusion of pulmonary embolism were randomized into 1 of 4 contrast material injection protocols manipulating iodine concentration and iodine delivery rate (IDR, expressed as grams of iodine per second): Iomeprol 400 at 3 mL/s (IDR = 1.2 gI/s), iomeprol 400 at 4 mL/s (IDR = 1.6 gI/s), iomeprol 300 at 5.4 mL/s (IDR = 1.6 gI/s), or iomeprol 300 at 4 mL/s (IDR = 1.2 gI/s). Total iodine delivery was held constant. Dual-energy CTPA of the lungs were acquired and used to calculate virtual 120 kV CTPA images as well as iodine perfusion maps. Attenuation values in the thoracic vasculature and image quality of virtual 120 kV CTPAs were compared between groups. Iodine perfusion maps were also compared by identifying differences in the extent of beam-hardening artifacts and subjective image quality. Protocols with an IDR of 1.6 gI/s provided the best attenuation profiles. CTPA image quality was greatest in the high concentration, high IDR (1.6 gI/s) protocol (P < 0.05 for all group comparisons) with no differences between the other groups (all P ≥ 0.05). Extent of beam-hardening artifacts and perfusion map image quality was significantly better using the high concentration, high IDR protocol as compared with all groups (P < 0.05 for all comparisons) and significantly worse using the low concentration, low IDR protocol as compared with all groups (all P ≥ 0.05); no difference was found between the high concentration, low IDR protocol and the low concentration, high IDR protocol (P = 0.73 for comparison of beam-hardening artifacts; P = 0.50 for comparison of perfusion map image quality). High iodine concentration and high IDR contrast material delivery protocols provide the best image quality of both CTPA and perfusion map images of the lung through high attenuation in the pulmonary arteries and minimization of beam-hardening artifacts.
• 2.95

  Impact points

  Radiation dose at coronary CT angiography: second-generation dual-source CT versus single-source 64-MDCT and first-generation dual-source CT.

  Christian Fink, Radko Krissak, Thomas Henzler, Ursula Lechel, Gunnar Brix, Richard A P Takx, John W Nance, Joseph A Abro, Stefan O Schoenberg, U Joseph Schoepf

  AJR. American journal of roentgenology. 05/2011; 196(5):W550-7.

  The purpose of this study was to assess the radiation doses of different coronary CTA (CTA) protocols: second-generation dual-source 128-MDCT, first-generation dual-source 64-MDCT, and single-source 64-MDCT. Thermoluminescent dosimetry was used to determine scanner-specific dose coefficients for sta... [more] The purpose of this study was to assess the radiation doses of different coronary CTA (CTA) protocols: second-generation dual-source 128-MDCT, first-generation dual-source 64-MDCT, and single-source 64-MDCT. Thermoluminescent dosimetry was used to determine scanner-specific dose coefficients for standard coronary CTA of an anthropomorphic phantom. These coefficients were used to estimate the effective doses (EDs) of retrospectively gated, prospectively triggered, and prospectively triggered high pitch coronary CTA performed at 100 and 120 kV. The coronary CTA protocols used in imaging of 43 patients undergoing dual-source 128-MDCT were analyzed for ED, image quality, and signal-to-noise ratio. Regardless of coronary CTA protocol and CT system, imaging at 100 kV lowered the ED 40-50%. In retrospectively gated 120-kV coronary CTA, the ED ranged from 5.7 to 10.7 mSv and was approximately 50% lower with single-source 64-MDCT than with either DSCT protocol. In prospectively triggered 120-kV coronary CTA, the ED ranged from 3.8 to 4.0 mSv. The lowest ED of all protocols (1.3 mSv) was observed in prospectively triggered high-pitch 100-kV coronary CTA performed with dual-source 128-MDCT. Patient measurements showed similar dose reductions for prospective triggering and low voltage settings without an influence on signal-to-noise ratio or image quality. A combination of prospective triggering with low voltage settings is an effective measure for reducing the ED of coronary CTA to values of 2-4 mSv independent of scanner system. Further dose reduction to nearly 1 mSv can be achieved with high-pitch prospectively triggered coronary CTA.
• 2.65

  Impact points

  Venous thromboembolism: additional diagnostic value and radiation dose of pelvic CT venography in patients with suspected pulmonary embolism.

  Miriam Reichert, Thomas Henzler, Radko Krissak, Paul Apfaltrer, Kurt Huck, Karen Buesing, Tim Sueselbeck, Stefan O Schoenberg, Christian Fink

  European journal of radiology. 04/2011; 80(1):50-3.

  To assess the additional diagnostic value of indirect CT venography (CTV) of the pelvis and upper thighs performed after pulmonary CT angiography (CTA) for the diagnosis of venous thromboembolism (VTE). In a retrospective analysis, the radiology information system entries between January 2003 and De... [more] To assess the additional diagnostic value of indirect CT venography (CTV) of the pelvis and upper thighs performed after pulmonary CT angiography (CTA) for the diagnosis of venous thromboembolism (VTE). In a retrospective analysis, the radiology information system entries between January 2003 and December 2007 were searched for patients who received pulmonary CTA and additional CTV of the pelvis and upper thighs. Of those patients, the radiology reports were reviewed for the diagnosis of pulmonary embolism (PE) and deep venous thrombosis (DVT) in the pelvic veins and veins of the upper thighs. In cases with an isolated pelvic thrombosis at CTV (i.e. which only had a thrombosis in the pelvic veins but not in the veins of the upper thigh) ultrasound reports were reviewed for the presence of DVT of the legs. The estimated radiation dose was calculated for pulmonary CTA and for CTV of the pelvis. In the defined period 3670 patients were referred to our institution for exclusion of PE. Of those, 642 patients (353 men, 289 women; mean age, 65±15 years, age range 18-98 years) underwent combined pulmonary CTA and CTV. Among them, PE was found in 227 patients (35.4%). In patients without PE CTV was negative in all cases. In patients with PE, CTV demonstrated pelvic thrombosis in 24 patients (3.7%) and thrombosis of the upper thighs in 43 patients (6.6%). Of those patients 14 (2.1%) had DVT in the pelvis and upper thighs. In 10 patients (1.5%) CTV showed an isolated pelvic thrombosis. Of those patients ultrasound reports were available in 7 patients, which revealed DVT of the leg veins in 5 cases (1%). Thus, the estimated prevalence of isolated pelvic thrombosis detected only by pelvic CTV ranges between 1-5/642 patients (0.1-0.7%). Radiation dose ranges between 4.8 and 9.7 mSv for additional CTV of the pelvis. CTV of the pelvis performed after pulmonary CTA is of neglectable additional diagnostic value for the detection of VTE, because the additional radiation dose is high and isolated pelvic DVT is very rare. Venous imaging of the legs (preferably by radiation-free ultrasound) is sufficient for the diagnosis of underlying DVT in patients with suspected PE.
• 4.41

  Impact points

  Noise reduction and image quality improvement of low dose and ultra low dose brain perfusion CT by HYPR-LR processing.

  Radko Krissak, Charles A Mistretta, Thomas Henzler, Anastasios Chatzikonstantinou, Johann Scharf, Stefan O Schoenberg, Christian Fink

  PloS one. 01/2011; 6(2):e17098.

  To evaluate image quality and signal characteristics of brain perfusion CT (BPCT) obtained by low-dose (LD) and ultra-low-dose (ULD) protocols with and without post-processing by highly constrained back-projection (HYPR)-local reconstruction (LR) technique. Simultaneous BPCTs were acquired in 8 pati... [more] To evaluate image quality and signal characteristics of brain perfusion CT (BPCT) obtained by low-dose (LD) and ultra-low-dose (ULD) protocols with and without post-processing by highly constrained back-projection (HYPR)-local reconstruction (LR) technique. Simultaneous BPCTs were acquired in 8 patients on a dual-source-CT by applying LD (80 kV, 200 mAs, 14×1.2 mm) on tube A and ULD (80 kV, 30 mAs, 14×1.2 mm) on tube B. Image data from both tubes was reconstructed with identical parameters and post-processed using the HYPR-LR. Correlation coefficients between mean and maximum (MAX) attenuation values within corresponding ROIs, area under attenuation curve (AUC), and signal to noise ratio (SNR) of brain parenchyma were assessed. Subjective image quality was assessed on a 5-point scale by two blinded observers (1: excellent, 5: non-diagnostic). Radiation dose of ULD was more than six times lower compared to LD. SNR was improved by HYPR: ULD vs. ULD+HYPR: 1.9±0.3 vs. 8.4±1.7, LD vs. LD+HYPR: 5.0±0.7 vs. 13.4±2.4 (both p<0.0001). There was a good correlation between the original datasets and the HYPR-LR post-processed datasets: r = 0.848 for ULD and ULD+HYPR and r = 0.933 for LD and LD+HYPR (p<0.0001 for both). The mean values of the HYPR-LR post-processed ULD dataset correlated better with the standard LD dataset (r = 0.672) than unprocessed ULD (r = 0.542), but both correlations were significant (p<0.0001). There was no significant difference in AUC or MAX. Image quality was rated excellent (1.3) in LD+HYPR and non-diagnostic (5.0) in ULD. LD and ULD+HYPR images had moderate image quality (3.3 and 2.7). SNR and image quality of ULD-BPCT can be improved to a level similar to LD-BPCT when using HYPR-LR without distorting attenuation measurements. This can be used to substantially reduce radiation dose. Alternatively, LD images can be improved by HYPR-LR to higher diagnostic quality.

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• 2.65

  Impact points

  Triple-rule-out dual-source CT angiography of patients with acute chest pain: Dose reduction potential of 100kV scanning.

  Radko Krissak, Thomas Henzler, Anne Prechel, Miriam Reichert, Joachim Gruettner, Tim Sueselbeck, Stefan O Schoenberg, Christian Fink

  European journal of radiology. 12/2010;

  PURPOSE: To investigate the dose reduction potential of low kV triple-rule-out dual-source CT angiography (TRO-CTA) in non-obese (BMI≤25kg/m(2)) patients with acute chest pain. MATERIALS AND METHODS: Sixty consecutive patients were randomly assigned to two different retrospectively ECG-gated TRO-CTA... [more] PURPOSE: To investigate the dose reduction potential of low kV triple-rule-out dual-source CT angiography (TRO-CTA) in non-obese (BMI≤25kg/m(2)) patients with acute chest pain. MATERIALS AND METHODS: Sixty consecutive patients were randomly assigned to two different retrospectively ECG-gated TRO-CTA protocols in this prospective trial: Thirty patients were examined with a 120-kV standard protocol (320 reference mAs with automatic tube current modulation, automatically adapted pitch and ECG-pulsing) and served as the control group (group 1), an otherwise identical 100kV protocol was used in the other thirty patients (group 2) for a radiation dose reduction. Subjective image quality was assessed on a 5 point scale (1: excellent, 5: non-diagnostic) by two blinded observers. Quantitative image analysis assessed vascular attenuation, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in different vascular segments. The effective dose was calculated from the dose length product (DLP) using a conversion coefficient of 0.017mSvmGy(-1)cm(-1). RESULTS: There was no significant difference of age, BMI, heart rate, pitch or scan length between both patient groups. Subjective image quality was rated similar in both groups (group 1: 1.2±0.4, group 2: average score=1.3±0.5). Vessel attenuation was significantly higher in group 2 than in group 1 (ascending aorta: 456±83 HU vs. 370±78 HU, p<0.001; pulmonary artery: 468±118 HU vs. 411±91 HU, p=0.03; left coronary artery: 437±110 HU vs. 348±89 HU, p<0.001), however, there was no significant difference in SNR (13.2±7.6 vs. 14.5±7.5, p=0.49) or CNR (13.8±6.6 vs. 15.9±7.7, p=0.25). The effective radiation dose of the 100kV protocol was significantly lower (9.6±3.2mSv vs. 18.1±9.4mSv, p<0.0001). CONCLUSION: TRO-CTA with 100kV is feasible in non-obese patients and results in diagnostic image quality and significantly reduced radiation dose.

• CT imaging of acute pulmonary embolism.

  Thomas Henzler, J Michael Barraza, John W Nance, Philip Costello, Radko Krissak, Christian Fink, U Joseph Schoepf

  Journal of cardiovascular computed tomography. 10/2010; 5(1):3-11.

  CT pulmonary angiography (CTPA) has become the de facto clinical "gold standard" for the diagnosis of acute pulmonary embolism (PE) and has replaced catheter pulmonary angiography and ventilation-perfusion scintigraphy as the first-line imaging method. The factors underlying this algorithm... [more] CT pulmonary angiography (CTPA) has become the de facto clinical "gold standard" for the diagnosis of acute pulmonary embolism (PE) and has replaced catheter pulmonary angiography and ventilation-perfusion scintigraphy as the first-line imaging method. The factors underlying this algorithmic change are rooted in the high-sensitivity and specificity, cost-effectiveness, and 24-hour availability of CTPA. In addition, CTPA is superior to other imaging methods in its ability to diagnose and exclude, in a single examination, a variety of diseases that mimic the symptoms of PE. This article reviews the current role of CTPA in the diagnosis of acute PE as well as more recent developments, such as the use of CT parameters of right ventricular dysfunction for patient prognostication and the assessment of lung perfusion with CT.
• 4.85

  Impact points

  Dynamic contrast-enhanced CT studies: balancing patient exposure and image noise.

  Gunnar Brix, Ursula Lechel, Markus Petersheim, Radko Krissak, Christian Fink

  Investigative radiology. 09/2010; 46(1):64-70.

  To establish the essential basis for balancing the dose versus noise trade-off in dynamic contrast-enhanced (DCE) CT by means of a phantom study. Measurements were performed at a 64-section dual-source system, using the default protocols for DCE imaging (40 scans) of the trunk (current-time product ... [more] To establish the essential basis for balancing the dose versus noise trade-off in dynamic contrast-enhanced (DCE) CT by means of a phantom study. Measurements were performed at a 64-section dual-source system, using the default protocols for DCE imaging (40 scans) of the trunk (current-time product per scan, 100 mAs; voltage, 120 kVp; pixel size, 0.9 × 0.9 × 8 mm3; CTDIvol per examination, 264 mGy) and head (270 mAs, 80 kVp, 0.45 × 0.45 × 8 mm3, 429 mGy). For 3 representative sections of an anthropomorphic phantom (head, upper abdomen, pelvis) transaxial dose distributions were measured by thermoluminescent dosimeters. The image noise was determined for 5 values of the current-time product (but otherwise identical parameter settings) and 4 pixel resolutions at a water-filled trunk and head phantom. Highest exposures occurred at the periphery of the trunk and head with maximum skin entrance doses of about 300 mGy. Effective doses related to the 3 exposure scenarios were between 4 and 20 mSv, but were not at all predictive of local exposure levels. The image noise was inversely proportional to the square root of the current-time product and, with restrictions, to the pixel size. Noise levels determined for the standard settings were 13.8 HU (trunk) and 4.4 HU (head) and thus comparable with the contrast enhancement typically detected in tumors and ischemic brain tissues, respectively. The opposing requirements of risk and noise limitation in DCE-CT cannot be balanced without substantially reducing the spatial resolution. But even so, local radiation exposures are rather high for a diagnostic procedure. Indications to perform a DCE examination should thus be strictly limited to patients who really benefit from it.
• 4.85

  Impact points

  Enhanced visualization of lung vessels for diagnosis of pulmonary embolism using dual energy CT angiography.

  Radko Krissak, Thomas Henzler, Miriam Reichert, Bernhard Krauss, Stefan O Schoenberg, Christian Fink

  Investigative radiology. 06/2010; 45(6):341-6.

  To evaluate a software algorithm highlighting vascular iodine distribution in dual energy (DE) computed tomography angiography (CTA) for the diagnosis of pulmonary embolism (PE). Pulmonary DE-CTA of 16 patients with PE and 16 patients without PE were analyzed using a software algorithm highlighting ... [more] To evaluate a software algorithm highlighting vascular iodine distribution in dual energy (DE) computed tomography angiography (CTA) for the diagnosis of pulmonary embolism (PE). Pulmonary DE-CTA of 16 patients with PE and 16 patients without PE were analyzed using a software algorithm highlighting vascular iodine distribution. The algorithm color-codes lung vessels depending on their local iodine distribution on a 2-color scale. The diagnostic performance of the software for the detection of PE was assessed on patient and segmental basis by consensus reading of 2 blinded radiologists. The reading of the standard CTA data by an independent third radiologist and clinical follow-up served as the standard of reference for the diagnosis of PE. Of 576 analyzed segments CTA revealed 88 diseased lung segments with 1 or more emboli. The software correctly highlighted 62 segments as positive. Twenty-six segments with PE were not highlighted. Seventy-five segments were highlighted false positive. All 16 patients with PE were identified as positive, but 1 of these patients had no true positive finding on a segmental basis and was therefore classified as false negative. Twenty-three segments in 8 patients without PE were highlighted as positive. Sensitivity, specificity, positive predictive value, and negative predictive value of the software algorithm were 93.8%, 50%, 65.2%, 88.9% per patient and 70.5%, 84.6%, 45.3%, 94.1% per segment, respectively. Additional review of the DE-CTA with a dedicated software algorithm highlighting the vascular iodine distribution has a high negative predictive value important for exclusion of segmental PE.
• 2.09

  Impact points

  Volumetric analysis of pulmonary CTA for the assessment of right ventricular dysfunction in patients with acute pulmonary embolism.

  Thomas Henzler, Radko Krissak, Miriam Reichert, Tim Sueselbeck, Stefan O Schoenberg, Christian Fink

  Academic radiology. 03/2010; 17(3):309-15.

  To retrospectively determine the value of a volumetric ventricle analysis for the assessment of right ventricular dysfunction in patients with suspected pulmonary embolism (PE) by using image data from non-electrocardiographically (ECG)-gated multidetector computed tomography angiography (CTA). Hypo... [more] To retrospectively determine the value of a volumetric ventricle analysis for the assessment of right ventricular dysfunction in patients with suspected pulmonary embolism (PE) by using image data from non-electrocardiographically (ECG)-gated multidetector computed tomography angiography (CTA). Hypothesizing that the presence of PE and the embolus location correlated with right ventricular dysfunction, we retrospectively analyzed 100 non-ECG-gated pulmonary CTA datasets of patients with central, peripheral, and without PE. Right ventricle/left ventricle (RV/LV) diameter ratio measured in transverse sections (RV/LV(trans)), four-chamber view (RV/LV(4ch)), and RV/LV volume ratio (RV/LV(vol)) were assessed on CT images. The results were correlated with the embolus location, the 30-day mortality rate, and the necessity of intensive care treatment. All CT parameters showed statistically significant differences between all patients groups depended on embolus location. The receiver operating characteristic analysis RV/LV(vol) showed the strongest discriminatory power to differ between patients with central and without PE and between patients with central and peripheral PE (central PE vs. no PE: RV/LV(vol) = 0.932, RV/LV(trans) = 0.880, and RV/LV(4ch) = 0.811, central PE vs. peripheral PE: RV/LV(vol) = 0.950, RV/LV(trans) = 0.849, and RV/LV(4ch) = 0.881), indicating a correlation with embolus location predisposing for RVD. For the identification of high-risk patients with PE all three CT parameters showed statistically significant values (P < .0001), whereas in the receiver operating characteristic analysis, RV/LV(vol) had the strongest discriminatory power (RV/LV(vol) = 0.819, RV/LV(trans) = 0.799, and RV/LV(4ch) = 0.758). Ventricle volumetry of non-ECG-gated CTA allows the assessment of right ventricular dysfunction in patients with acute PE. Compared to unidimensional measurements, a volumetric analysis seems to be slightly superior to identify high-risk patients with adverse clinical outcome. However, the method is more time consuming and requires dedicated software tools compared to unidimensional parameters, which is disadvantageous in an emergency setting.
• 4.55

  Impact points

  Unexpected diagnosis of pseudoaneurysmal pulmonary artery sarcoma in a patient with acute chest pain.

  Thomas Henzler, Ishar-Singh Gill, Radko Krissak, Stefan O Schoenberg, Christian Fink

  Journal of thoracic oncology : official publication of the International Association for the Study of Lung Cancer. 11/2009; 4(11):1438-9.
• 2.77

  Impact points

  Half-fourier-acquisition single-shot turbo spin-echo (HASTE) MRI of the lung at 3 Tesla using parallel imaging with 32-receiver channel technology.

  Thomas Henzler, Olaf Dietrich, Radko Krissak, Tobias Wichmann, Titus Lanz, Maximilian F Reiser, Stefan O Schoenberg, Christian Fink

  Journal of magnetic resonance imaging : JMRI. 09/2009; 30(3):541-546.

  PURPOSE: To assess the feasibility of half-Fourier-acquisition single-shot turbo spin-echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32-channel torso array coil, and to determine the optimum acceleration factor for the delineation of intrapulmonary anatomy. MATE... [more] PURPOSE: To assess the feasibility of half-Fourier-acquisition single-shot turbo spin-echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32-channel torso array coil, and to determine the optimum acceleration factor for the delineation of intrapulmonary anatomy. MATERIALS AND METHODS: Nine volunteers were examined on a 32-channel 3T MRI system using a prototype 32-channel-torso-array-coil. HASTE-MRI of the lung was acquired at both, end-inspiratory and end-expiratory breathhold with parallel imaging (Generalized autocalibrating partially parallel acquisitions = GRAPPA) using acceleration factors ranging between R = 1 (TE = 42 ms) and R = 6 (TE = 16 ms). The image quality of intrapulmonary anatomy and subjectively perceived noise level was analyzed by two radiologists in consensus. In addition quantitative measurements of the signal-to-noise ratio (SNR) of HASTE with different acceleration factors were assessed in phantom measurements. RESULTS: Using an acceleration factor of R = 4 image blurring was substantially reduced compared with lower acceleration factors resulting in sharp delineation of intrapulmonary structures in expiratory scans. For inspiratory scans an acceleration factor of 2 provided the best image quality. Expiratory scans had a higher subjectively perceived SNR than inspiratory scans. CONCLUSION: Using optimized multi-element coil geometry HASTE-MRI of the lung is feasible at 3T with acceleration factors up to 4. Compared with nonaccelerated acquisitions, shorter echo times and reduced image blurring are achieved. Expiratory scanning may be favorable to compensate for susceptibility associated signal loss at 3T. J. Magn. Reson. Imaging 2009;30:541-546. (c) 2009 Wiley-Liss, Inc.

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• 2.03

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  [Compliance of the normal-sized aorta in adolescents with Marfan syndrome: comparison of MR measurements of aortic distensibility and pulse wave velocity]

  J G Eichhorn, R Krissak, H J Rüdiger, S Ley, R Arnold, J Boese, R Krug, M Gorenflo, M Khalil, H Ulmer, H U Kauczor, C Fink

  RöFo : Fortschritte auf dem Gebiete der Röntgenstrahlen und der Nuklearmedizin. 09/2007; 179(8):841-6.

  PURPOSE: To compare the aortic compliance of the normal-sized aorta of adolescents with Marfan syndrome and healthy controls using MR measurements of the aortic distensibility and pulse wave velocity. MATERIALS AND METHODS: Fourteen patients (median age: 15 years) and 11 healthy subjects (23 [12 - 3... [more] PURPOSE: To compare the aortic compliance of the normal-sized aorta of adolescents with Marfan syndrome and healthy controls using MR measurements of the aortic distensibility and pulse wave velocity. MATERIALS AND METHODS: Fourteen patients (median age: 15 years) and 11 healthy subjects (23 [12 - 32] years) were examined at 1.5 T. The MR protocol included 2D steady-state free precession (SSFP)-CINE MRI of the aortic distensibility and PC-MRI of the pulse wave velocity. All measurements were positioned perpendicular to the descending aorta at the level of the diaphragm for assessing the changes in the aortic cross-sectional areas and additionally above and below this plane for assessing the pulse wave velocity. In addition contrast-enhanced 3D-MR angiography was performed in adolescents with Marfan syndrome to exclude morphologic changes and to prove normal-sized aorta. RESULTS: Compared with control subjects, adolescents with Marfan syndrome had significantly decreased distensibility and significantly increased pulse wave velocity (chi (2)-test, p = 0.0002) using an age-related non-linear regression analysis. The related aortic compliance was significantly decreased (chi (2)-test, p = 0.0002). There was a good correlation between the two methods (r = 0.86). A low intraobserver variability was found for both methods (< or = 2 %). CONCLUSIONS: MRI allows detecting abnormal elastic aortic wall properties already in the normal-sized aorta of adolescents with Marfan syndrome. Monitoring of these properties could be relevant for evaluating disease onset and progression. MRI has the potential value of compliance measurements for the follow-up and to guide therapy indications.

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• 2.77

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  Time-resolved contrast-enhanced three-dimensional pulmonary MR-angiography: 1.0 M gadobutrol vs. 0.5 M gadopentetate dimeglumine.

  Christian Fink, Michael Bock, Fabian Kiessling, Matthias Philipp Lichy, Radko Krissak, Ivan Zuna, Astrid Schmähl, Stefan Delorme, Hans-Ulrich Kauczor

  Journal of magnetic resonance imaging : JMRI. 02/2004; 19(2):202-8.

  PURPOSE: To compare contrast characteristics and image quality of 1.0 M gadobutrol with 0.5 M Gd-DTPA for time-resolved three-dimensional pulmonary magnetic resonance angiography (MRA). MATERIALS AND METHODS: Thirty-one patients and five healthy volunteers were examined with a contrast-enhanced time... [more] PURPOSE: To compare contrast characteristics and image quality of 1.0 M gadobutrol with 0.5 M Gd-DTPA for time-resolved three-dimensional pulmonary magnetic resonance angiography (MRA). MATERIALS AND METHODS: Thirty-one patients and five healthy volunteers were examined with a contrast-enhanced time-resolved pulmonary MRA protocol (fast low-angle shot [FLASH] three-dimensional, TR/TE = 2.2/1.0 msec, flip angle: 25 degrees, scan time per three-dimensional data set = 5.6 seconds). Patients were randomized to receive either 0.1 mmol/kg body weight (bw) or 0.2 mmol/kg bw gadobutrol, or 0.2 mmol/kg bw Gd-DTPA. Volunteers were examined three times, twice with 0.2 mmol/kg bw gadobutrol using two different flip angles and once with 0.2 mmol/kg bw Gd-DTPA. All contrast injections were performed at a rate of 5 mL/second. Image analysis included signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements in lung arteries and veins, as well as a subjective analysis of image quality. RESULTS: In patients, significantly higher SNR and CNR were observed with Gd-DTPA compared to both doses of gadobutrol (SNR: 35-42 vs.17-25; CNR 33-39 vs. 16-23; P < or = 0.05). No relevant differences were observed between 0.1 mmol/kg bw and 0.2 mmol/kg bw gadobutrol. In volunteers, gadobutrol and Gd-DTPA achieved similar SNR and CNR. A significantly higher SNR and CNR was observed for gadobutrol-enhanced MRA with an increased flip angle of 40 degrees. Image quality was rated equal for both contrast agents. CONCLUSION: No relevant advantages of 1.0 M gadobutrol over 0.5 M Gd-DTPA were observed for time-resolved pulmonary MRA in this study. Potential explanations are T2/T2*-effects caused by the high intravascular concentration when using high injection rates.

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• CT imaging of acute pulmonary embolism

  T. Henzler, J. M. Barraza, J. W. Nance, P. Costello, R. Krissak, C. Fink, U. J. Schoepf

  J Cardiovasc Comput Tomogr. 5(1):3-11.

  CT pulmonary angiography (CTPA) has become the de facto clinical "gold standard" for the diagnosis of acute pulmonary embolism (PE) and has replaced catheter pulmonary angiography and ventilation-perfusion scintigraphy as the first-line imaging method. The factors underlying this algorithm... [more] CT pulmonary angiography (CTPA) has become the de facto clinical "gold standard" for the diagnosis of acute pulmonary embolism (PE) and has replaced catheter pulmonary angiography and ventilation-perfusion scintigraphy as the first-line imaging method. The factors underlying this algorithmic change are rooted in the high-sensitivity and specificity, cost-effectiveness, and 24-hour availability of CTPA. In addition, CTPA is superior to other imaging methods in its ability to diagnose and exclude, in a single examination, a variety of diseases that mimic the symptoms of PE. This article reviews the current role of CTPA in the diagnosis of acute PE as well as more recent developments, such as the use of CT parameters of right ventricular dysfunction for patient prognostication and the assessment of lung perfusion with CT.

• Radiation dose at coronary CT angiography: second-generation dual-source CT versus single-source 64-MDCT and first-generation dual-source CT

  C. Fink, R. Krissak, T. Henzler, U. Lechel, G. Brix, R. A. Takx, J. W. Nance, J. A. Abro, S. O. Schoenberg, U. J. Schoepf

  AJR Am J Roentgenol. 196(5):W550-7.

  OBJECTIVE: The purpose of this study was to assess the radiation doses of different coronary CTA (CTA) protocols: second-generation dual-source 128-MDCT, first-generation dual-source 64-MDCT, and single-source 64-MDCT. MATERIALS AND METHODS: Thermoluminescent dosimetry was used to determine scanner-... [more] OBJECTIVE: The purpose of this study was to assess the radiation doses of different coronary CTA (CTA) protocols: second-generation dual-source 128-MDCT, first-generation dual-source 64-MDCT, and single-source 64-MDCT. MATERIALS AND METHODS: Thermoluminescent dosimetry was used to determine scanner-specific dose coefficients for standard coronary CTA of an anthropomorphic phantom. These coefficients were used to estimate the effective doses (EDs) of retrospectively gated, prospectively triggered, and prospectively triggered high pitch coronary CTA performed at 100 and 120 kV. The coronary CTA protocols used in imaging of 43 patients undergoing dual-source 128-MDCT were analyzed for ED, image quality, and signal-to-noise ratio. RESULTS: Regardless of coronary CTA protocol and CT system, imaging at 100 kV lowered the ED 40-50%. In retrospectively gated 120-kV coronary CTA, the ED ranged from 5.7 to 10.7 mSv and was approximately 50% lower with single-source 64-MDCT than with either DSCT protocol. In prospectively triggered 120-kV coronary CTA, the ED ranged from 3.8 to 4.0 mSv. The lowest ED of all protocols (1.3 mSv) was observed in prospectively triggered high-pitch 100-kV coronary CTA performed with dual-source 128-MDCT. Patient measurements showed similar dose reductions for prospective triggering and low voltage settings without an influence on signal-to-noise ratio or image quality. CONCLUSION: A combination of prospective triggering with low voltage settings is an effective measure for reducing the ED of coronary CTA to values of 2-4 mSv independent of scanner system. Further dose reduction to nearly 1 mSv can be achieved with high-pitch prospectively triggered coronary CTA.