Treatment Planning Considerations for Robotic Guided Cardiac Radiosurgery for Atrial Fibrillation.

PURPOSE: Robotic guided stereotactic radiosurgery has recently been investigated for the treatment of atrial fibrillation (AF). Before moving into human treatments, multiple implications for treatment planning given a potential target tracking approach have to be considered. MATERIALS & METHODS: Theoretical AF radiosurgery treatment plans for twenty-four patients were generated for baseline comparison. Eighteen patients were investigated under ideal tracking conditions, twelve patients under regional dose rate (RDR = applied dose over a certain time window) optimized conditions (beam delivery sequence sorting according to regional beam targeting), four patients under ultrasound tracking conditions (beam block of the ultrasound probe) and four patients with temporary single fiducial tracking conditions (differential surrogate-to-target respiratory and cardiac motion). RESULTS: With currently known guidelines on dose limitations of critical structures, treatment planning for AF radiosurgery with 25 Gy under ideal tracking conditions with a 3 mm safety margin may only be feasible in less than 40% of the patients due to the unfavorable esophagus and bronchial tree location relative to the left atrial antrum (target area). Beam delivery sequence sorting showed a large increase in RDR coverage (% of voxels having a larger dose rate for a given time window) of 10.8-92.4% (median, 38.0%) for a 40-50 min time window, which may be significant for non-malignant targets. For ultrasound tracking, blocking beams through the ultrasound probe was found to have no visible impact on plan quality given previous optimal ultrasound window estimation for the planning CT. For fiducial tracking in the right atrial septum, the differential motion may reduce target coverage by up to -24.9% which could be reduced to a median of -0.8% (maximum, -12.0%) by using 4D dose optimization. The cardiac motion was also found to have an impact on the dose distribution, at the anterior left atrial wall; however, the results need to be verified. CONCLUSION: Robotic AF radiosurgery with 25 Gy may be feasible in a subgroup of patients under ideal tracking conditions. Ultrasound tracking was found to have the lowest impact on treatment planning and given its real-time imaging capability should be considered for AF robotic radiosurgery. Nevertheless, advanced treatment planning using RDR or 4D respiratory and cardiac dose optimization may be still advised despite using ideal tracking methods.

Systematic Comparison of Reduced Tube Current Protocols for High-pitch and Standard-pitch Pulmonary CT Angiography in a Large Single-center Population.

RATIONALE AND OBJECTIVES: Benefits of iterative reconstruction (IR) algorithms combined with dose-reduction techniques have been shown at computed tomography pulmonary angiography (CTPA) in several medium to small patient collectives. In this study, we performed a systematic comparison of image quality to combinations of reduced tube current (RC) and IR for both standard-pitch (SP) single-source and high-pitch (HP) dual-source CTPA in a large, single-center population. MATERIALS AND METHODS: Three hundred eighty-two consecutive patients (October 2010 through December 2012) received clinically indicated CTPA with one of four consecutively changed protocols: (1) HPSC: 180 mAs, weighted filtered back projection, pitch = 3; (2) HPRC: 90 mAs, IR, pitch = 3; (3) SPSC: 180 mAs, weighted filtered back projection, pitch = 1.2; and (4) HPRC: 90 mAs, IR, pitch = 1.2. Tube potential was 100 kV. Vascular attenuation and standardized signal-to-noise ratio (sSNR) were measured in the pulmonary trunk (sSNRPT) and on segmental artery level (sSNRS1, sSNRS10). Dose-length-product was recorded per series. Two independent investigators rated image quality. Kolmogorov-Smirnov test, Kruskal-Wallis test, and kappa statistics were used for statistical analysis. Median values are presented per group. RESULTS: Image quality was consistent between all groups (observer 1: P = 0.118; observer 2: P = 0.122). Inter-reader consistency was very good (κ = 0.866, P < 0.001). Dose-length-product was significantly reduced in HP and RC groups (P < 0.001 for each; SPSC: 139.5 mGycm; HPRC: 92 mGycm; SPSC: 211 mGycm; HPRC: 137 mGycm). sSNR was comparable (sSNRPT overall: P = 0.052; sSNRS1 overall: P = 0.161; and sSNRS10 overall: P = 0.259). CONCLUSIONS: Substantial dose reduction can be within a routine clinical setting without quantifiable loss of image quality either by HP pulmonary angiography or by a combination of IR and RC in either HP or SP acquisition.

One-Year Patency of Valvulotomized Vein Grafts Is Similar to That of Arterial Grafts.

BACKGROUND: Inferior vein graft patency after coronary artery bypass grafting (CABG) is attributed to various factors. Venous valves may limit flow, cause thrombus formation, and diminish diastolic backflow. The aim of our study was to compare clinical outcome and midterm patency rate of valvulotomized vein grafts and arterial grafts in patients undergoing CABG. METHODS: Between 2007 and 2010, valvulotomized saphenous vein segments were used to graft the right coronary artery (RCA) in 147 patients undergoing CABG with mean 2.8 ± 1 arterial and 1.5 ± 0.6 venous anastomoses. Outcome, reintervention, and reoperation were assessed after 4 ± 1.6 years. Intraoperative bypass flow rate was measured before and after valvulotomy of venous bypass grafts in 12 patients. Patency of the grafts was assessed by means of multislice computed tomography (MSCT) in 45 patients. RESULTS: A total of 102 patients underwent isolated CABG and 45 had combined procedures. In-hospital mortality was 2%. At 4 years' clinical follow-up, 95% of the patients were asymptomatic. Five patients underwent recoronary angiography because of angina pectoris. The MSCT and reangiography patency rate of all valvulotomized saphenous vein grafts was 97.1 versus 95.8% of arterial grafts 18 ± 6 months postoperatively. Intraoperative measurements showed a significant increase (+20.2 mL/min; p = 0.01) of flow in the venous bypass grafts to the RCA after valvulotomy. There were no reoperations at the latest follow-up. CONCLUSION: Patients with valvulotomized venous grafts had good clinical outcome. The one-year patency rate of those grafts is comparable to that of arterial grafts. However, long-term results and angiography studies will be needed to strengthen these findings.

Multidisciplinary sliding-gantry CT: from concept to reality.

Sliding-gantry computed tomography offers an interesting variety of treatment options for emergency radiology and clinical routine. The Frankfurt 2-room installation provides an interdisciplinary, multifunctional, and cost-effective concept. It is based on a magnetically sealed rail system for the permanent movement of the gantry between 2 adjacent rooms with fixed-mounted tables. In case of emergency or intensive care patients, routine scanning can be performed in room 1 until computed tomography diagnosis is required in room 2 and can then be continued in room 1 again. Moreover, this concept allows the simultaneous handling of 2 emergency patients.

Bolus timing in high-pitch CT angiography of the aorta.

OBJECTIVE: To investigate the bolus geometry in high-pitch CT angiography (CTA) of the aorta without ECG synchronisation in comparison to single-source CT. METHODS: Overall 160 consecutive patients underwent CTA either in conventional single-source mode with a pitch of 1.2 (group 1), or in dual-source mode with a pitch of 3.0 (groups 2, 3 and 4) using different contrast media timings with bolus triggering at 140 HU (5s, group 1; 10s, group 2; 12s, group 3; 14s, group 4). Contrast material, saline flush, flow rate and kV/mAs settings were kept equal for optimum comparability. Aortic attenuation was measured along the z-axis of the patient at different anatomic landmarks and subjective image quality was compared. RESULTS: The most homogeneous enhancement of the aorta was reached with a delay of 10s after reaching the trigger threshold. The imaging length was not significantly different, but the examination time was significantly (p<0.001) shorter in the high-pitch group (7.7s vs. 1.7s for group 1 vs. 2, 3 and 4). CONCLUSION: In high-pitch CT angiography using a start delay of 10s after a trigger threshold of 140 HU in the descending aorta is reached, a homogenous contrast along the z-axis is accomplished.

Extensive dissecting aneurysm of the ascending aorta.

We present the case of a 69-year-old female surviving an extensive dissecting thoracic aortic aneurysm. Due to the initial presentation with angina and epigastric pain the first working diagnosis was acute coronary syndrome. However, on transthoracic and transesophageal echocardiography (TEE), the dissecting aneurysm (type Stanford A) could be detected. Our article stresses the importance of imaging for the rapid and accurate diagnosis of thoracic aortic aneurysms with dissection. In our case, TEE detected the intimal flap separating true and false lumen, and the consecutive hemodynamically relevant aortic valve regurgitation, in addition to the aneurysm extent. The patient underwent surgical repair with aortic arch replacement and recovered without sequelae. .

Automatic bone removal technique in whole-body dual-energy CT angiography: performance and image quality.

OBJECTIVE: The purpose of this study was to evaluate the efficiency of automatic bone removal in dual-energy CT angiography (CTA) of the trunk. SUBJECTS AND METHODS: Nineteen patients underwent dual-energy CTA of the trunk (tube A, 140 kV; tube B, 100 kV). In addition to the dual-energy dataset, an image equivalent to that of a standard 120-kV single-energy examination was generated with both tubes. Automated bone segmentation was performed on both datasets, and the results were analyzed. The time required for and subjective image quality of the maximum intensity projections (MIPs) generated were evaluated. RESULTS: Errors in bone segmentation were found for 1.5% of bones on dual-energy images and 12.4% of bones on single-energy images (p < 0.01). The most important differences were found in the rib cage, sternum, and pelvis. The times required for postprocessing of MIPs were similar for the dual-energy (113.5 seconds) and single-energy (106.8 seconds) techniques. The subjective image quality of the arteries was considered better for dual-energy CTA (4.5 points) than for single-energy CTA (4.1 points) owing to false cutoff of vessels during the bone removal process on the single-energy images (p = 0.026). CONCLUSION: For CTA of the trunk, the dual-energy postprocessing capabilities for 3D visualization are superior to the threshold-based bone removal of single-energy CT. Dual-energy CTA can generate boneless MIP images of substantial quality.

Quantitative analysis of motion artifacts in high-pitch dual-source computed tomography of the thorax.

PURPOSE: The purpose of this study was to objectively analyze motion artifacts on thoracic computed tomography (CT) with dual-source high-pitch and single-source techniques when using a no-breath-hold technique to examine patients who have difficulty complying with breath-holding instructions. MATERIALS AND METHODS: A total of 120 patients who received CT of the thorax with a free-breathing technique in single-source (16 slices and 128 slices; pitch = 1.2) and dual-source (pitch = 3.0) manners were evaluated retrospectively. In each of the 3 study groups, movements of the diaphragm and pulsations of the aortic root and main pulmonary artery were analyzed for their number and severity (blurred distance). RESULTS: No motion artifacts of the diaphragm were identified using a pitch of 3.0 (compared with n = 14 for single-source CT using 128 slices and n = 24 using 16-slice CT). In single-source examinations, the severity of artifacts was similar between 128-slice CT and 16-slice CT: blurring distance of the lung parenchyma due to diaphragm movements was 14 versus 16 mm, and double contours of the aorta were measured as 8 and 9 mm, respectively. CONCLUSIONS: A high-pitch, dual-source mode is potentially advantageous for evaluating the lung parenchyma and vascular structures in patients who have difficulty complying with breath-holding instructions. Increasing from 16 to 128 slices can significantly reduce the number and severity of motion artifacts.

Ultra-low dose dual-source high-pitch computed tomography of the paranasal sinus: diagnostic sensitivity and radiation dose.

BACKGROUND: Today's gold standard for diagnostic imaging of inflammatory diseases of the paranasal sinus is computed tomography (CT). PURPOSE: To evaluate diagnostic sensitivity and radiation dose of an ultra-low dose dual-source CT technique. MATERIAL AND METHODS: Paranasal sinuses of 14 cadaveric heads were independently evaluated by two readers using a modern dual-source CT with lowest reasonable dosage in high-pitch mode (100 kV, 10 mAs, collimation 0.6 mm, pitch value 3.0). Additionally the head part of an anthropomorphic Alderson-Rando phantom was equipped with thermoluminiscent detectors to measure radiation exposure to the eye lenses and thyroid gland. RESULTS: Diagnostic accuracy regarding sinusoidal fluid, nasal septum deviation, and mucosal swelling was 100%. Mastoid fluid was detected in 76% and 92%, respectively. In the phantom study, average measured eye lens dosage was 0.64 mGy; radiation exposure of the thyroid gland was 0.085 mGy. CONCLUSION: Regarding evaluation of inflammatory diseases of the paranasal sinus this study indicates sufficient accuracy of the proposed CT protocol at a very low dosage level.