Occupational orthopedic problems and its relation to personal radiation protection in interventional radiology.

PURPOSE: Several studies report occupational orthopedic problems among interventional cardiologists. These health problems are usually multifactorial. However, the personal protective equipment used should play a major role. An online survey was conducted to determine the frequency of such health problems among interventional radiologists and to correlate them with the use of personal radiation protective clothing. MATERIAL AND METHODS: An anonymous online survey that comprised of 17 questions was sent via e-mail to 1427 members of the German Society for Interventional Radiology (DeGIR) in Germany, Austria and Switzerland. The questions were focused on interventional workload, the use of personal radiation protection apparel and orthopedic problems. Given the different scale levels, the associations between the variables were analyzed using different statistical methods. A significance level of p < 0.05 was chosen. RESULTS: There were 221 survey responders (15.5% response rate). About half of responders (47.7%) suffered from more than five episodes of orthopedic problems during their interventional career. Lumbar spine was involved in 81.7% of these cases, cervical spine in 32.8%, shoulder in 28.5% and knee in 24.7%. Because of orthopedic problems, 16.1% of the responders had to reduce and 2.7% had to stop their interventional practice. The number of affected body regions correlates with the fit of the radiation protection means (p < 0.05, r = 0.135) and the reduction of activity as an interventional radiologist (p < 0.05, r = -0.148). CONCLUSION: Overall, the survey reveals widespread orthopedic problems at several body regions among interventional radiologists, associated with the fit of radiation protection systems, among other factors. A connection between the orthopaedic complaints and the radiation protection system used could not be established.

Joint replacement increases radiation exposure to the staff in angiography: A phantom study.

INTRODUCTION: The present study investigates the influence of joint prostheses on the amount of scattered radiation in a simulated angiography set-up. MATERIALS AND METHODS: A clinical angiography system (Artis Zee, Siemens Healthineers, Germany) with a water phantom as a scattering object was used. The scattered radiation of the water phantom was repeatedly measured without prosthesis, with a knee prosthesis and a hip prosthesis made from titanium, aluminum, vanadium, ceramics and polyethylene. For radiation measurement an ionization chamber (ambient dose equivalent rate from 0.1 µSv/h - 100 Sv/h, UMo, Berthold Technologies, Germany) was used. It was positioned on the right side of the phantom simulating an interventional procedure via the right femoral artery. The ionization chamber was positioned at 5 different heights (30, 100, 130, 150 and 165 cm), simulating different body parts of the interventionist. In addition, the amount of scattered radiation in relation to the tube angulation was investigated. RESULTS: Averaged over all angulations at a height of 165 cm, the radiation dose was 2.7 times higher (1935 µSv/h, p < 0.01) when a hip prosthesis was present in comparison to no prosthesis (713 µSv/h). The radiation dose was 3.9 times higher with the integration of a knee prosthesis (2778 µSv/h, p < 0.01) compared to that without prosthesis. The average radiation dose over all angulations and all heights was 1491 µSv/h without prosthesis, 4538 µSv/h with a hip prothesis and 5023 µSv/h with a knee prosthesis respectively. CONCLUSION: This experimental study shows a significant increase in the radiation dose when a joint prosthesis is present in the examination field. Special attention and sufficient radiation protection is therefore necessary for investigations with implanted prostheses.

Digital Variance Angiography in Lower-Limb Angiography with Metal Implants.

PURPOSE: The presence of metal implants may reduce angiographic image quality due to automated beam adjustments. Digital variance angiography (DVA) is reported to be superior to digital subtraction angiography (DSA) with increased contrast-to-noise ratio (CNR) and better image quality. The aim of the study was to evaluate whether DVA could counterbalance the image quality impairment of lower-limb angiographies with metal implants. MATERIALS AND METHODS: From November 2019 to January 2020, 85 raw lower-limb iodine contrast angiograms of 12 patients with metal implants were processed retrospectively with DVA analyses. For objective comparison, CNR of DSA and DVA images was calculated and the ratio CNRDVA/CNRDSA was determined. Visual image quality was evaluated in a paired comparison and by a five-grade Likert scale by three experienced radiologists. RESULTS: The CNR was calculated and compared in 1252 regions of interest in 37 image pairs containing metal implants. The median ratio of CNRDVA/CNRDSA was 1.84 with an interquartile range of 1.35-2.32. Paired comparison resulted in 84.5% in favour of DVA with an interrater agreement of 83.2% (Fleiss κ 0.454, p < 0.001). The overall image quality scores for DSA and DVA were 3.64 ± 0.08 and 4.43 ± 0.06, respectively (p < 0.001, Wilcoxon signed-rank test) with consistently higher individual ratings for DVA. CONCLUSION: Our small-sample pilot study shows that DVA provides significantly improved image quality in lower-limb angiography with metal implants, compared to DSA imaging. The improved CNR suggest that this approach could reduce radiation exposure for lower-limb angiography with metal implants. LEVEL OF EVIDENCE: Level 4, case studies.

Scatter radiation reduction with a radiation-absorbing pad in interventional radiology examinations.

PURPOSE: Radiation-absorbing pads are an additional possibility to reduce scattered radiation at its source. The goal of this study is to investigate the efficacy of a new reusable radiation-absorbing pad at its origin in an experimental setup. MATERIAL AND METHODS: All measurements were carried out using a clinical angiography system with a standardized fluoroscopy protocol, different C-arm angulations and an anthropomorphic torso phantom as a scattering body. An ionization chamber was used to measure the radiation exposure at five different heights of a simulated operator during a simulated transfemoral angiography intervention. Measurements were carried out with and without radiation-absorbing pads with lead equivalents of 0.25 and 0.5 mm placed onto the scattering body. For all measurements a mobile acrylic shield and an under-table lead curtain was used. RESULTS: At all operator heights from 100 to 165 cm a significant radiation dose reduction of up to 80.6 % (p < 0.01) using the radiation-absorbing pad was measured, when compared to no radiation-absorbing pad. At the height of 165 cm the radiation-absorbing pad with a lead equivalence of 0.5 mm showed a significant radiation dose reduction (51.4 %, p < 0.01) in comparison to a lead equivalence of 0.25 mm. CONCLUSION: The addition of a radiation-absorbing pad to the standard protection means results in a significant dose reduction for the operator, particularly for upper body parts.

Comparison of different resuscitation methods with regard to injury patterns in cardiac arrest survivors based on computer tomography.

PURPOSE: To ensure that patients survive cardiac arrest, cardiopulmonary resuscitation (CPR) is needed. However, the procedure itself can lead to severe injuries. This study aims to examine both possibilities of resuscitation - mechanical or manual - with regard to their risk of injury. To this end, we compare the injuries patterns in both groups of patients after successful resuscitation based on computer tomography (CT). METHODS: This single-centre retrospective study included 32 patients (female: 21.87 %, male: 78.12 %, Mean age: 60.22 ± 13.93 years) with cardiac arrest followed by successful mechanical CPR, who underwent an early whole-body CT. A control group of 32 patients (female: 21.87 %, male: 78.12 %, mean age: 60.75 ± 13.34 years) that had been resuscitated successfully with manual CPR was matched according to gender and age for a better statistical comparison. Patients with cardiac arrest due to trauma were excluded from the study population. RESULTS: Mechanically resuscitated patients showed significantly more CPR-related injuries than those who were resuscitated manually (100 % vs. 84.37 %; p = 0.02). In particular, dislocated rib fractures (40.47 vs. 23.80 mean rank, p < 0.01), sternal fractures (74.19 % vs. 25 %; p < 0,01), bleeding complications (29.03 % vs. 3.12 %; p = 0.01), pneumothorax (38.71 % vs. 9.37 %; p = 0.01), mediastinal haematomas (58.01 % vs. 25 %, p = 0.01) and liver lacerations (29.03 % vs. 0 %, p = 0.04) were observed significantly more in patients after mechanical CPR compared to those with manual resuscitation. CONCLUSIONS: The guideline-based use of mechanical CPR results in a significant increase of internal and musculoskeletal injuries compared to manual CPR.

Protective Efficacy of Different Ocular Radiation Protection Devices: A Phantom Study.

PURPOSE: The aim of this study was to investigate the efficacy of different designs and types of ocular radiation protection devices depending on simulated varied body heights in a phantom-simulated thoracic intervention. MATERIALS AND METHODS: A clinical angiography system with a standardized fluoroscopy protocol with an anthropomorphic chest phantom as a scattering object and optically stimulated luminescence dosimeters for measuring radiation dose were used. The dosimeters were placed at the position of eyes of an anthropomorphic head phantom simulating the examiner. The head phantom was placed on a height-adjustable stand simulating the height of the examiner from 160 to 200 cm with 10 cm increments. The dose values were then measured with no radiation protection, a weightless-like radiation protection garment, radiation protection glasses and visors. RESULTS: The average dose reduction using radiation protection devices varied between 57.7 and 83.4% (p < 0.05) in comparison with no radiation protection. Some radiation protection glasses and visors showed a significant dose reduction for the eye lenses when the height of the examiner increased. The right eye was partially less protected, especially if the distances between the simulated examiner's head and the scatter object were small. CONCLUSION: All the investigated protection devices showed a significant reduction in radiation exposure to the simulated examiner. For some devices, the radiation dose increased with decreasing distance to the scattering object, especially for the right eye lens.

Early whole-body CT for treatment guidance in patients with return of spontaneous circulation after cardiac arrest.

PURPOSE: Non-traumatic cardiac arrest (CA) and return of spontaneous circulation (ROSC) after cardiopulmonary resuscitation (CPR) are often associated with multiple pathologies. Expecting a high prevalence of important findings, a whole-body CT (WBCT) could be of relevance for therapy. The aim of this study is to investigate the feasibility and diagnostic yield of an early WBCT in this setting. METHODS: This single-center retrospective study included 100 consecutive patients (27 female; 73 male; mean age 68.5± 12.57 years) with non-traumatic, in- and out-of-hospital CA and ROSC following CPR, who underwent a contrast-enhanced WBCT within 6 h after ROSC over 12 months. CT findings were determined corresponding to anatomical region. RESULTS: Early WBCT was successfully carried out in 100% of the patients with CA and ROSC after CPR. Acute pathologies were found not only in the chest but also in the head (15%) and the abdomen (6%). Early global brain edema (n = 12), acute stroke (n = 3), pulmonary embolism (n = 10), pneumothorax (26%), acute abdominal pathologies (n = 6), iatrogenic bleeding (4%), and CPR-related injuries (93%) were detected by CT right from the beginning of the post-cardiac arrest care. CONCLUSIONS: An early WBCT is feasible and provides added diagnostic value for patients with ROSC after non-traumatic CA.

Preoperative Imaging Overestimates the Tumor Size in Pancreatic Neuroendocrine Neoplasms Associated with Multiple Endocrine Neoplasia Type 1.

BACKGROUND: Radiological tumor size of non-functioning pancreatic neuroendocrine neoplasms (Nf-pNENs) associated with multiple endocrine neoplasia type 1 (MEN1) is a crucial parameter to indicate surgery. The aim of this study was to compare radiological size (RS) and pathologic size (PS) of MEN1 associated with pNENs. METHODS: Prospectively collected data of MEN1 patients who underwent pancreatic resections for pNENs were retrospectively analyzed. RS was defined as the largest tumor diameter measured on endoscopic ultrasound (EUS), magnetic resonance imaging (MRI) or computed tomography (CT). PS was defined as the largest tumor diameter on pathological analysis. Student's t test and linear regression analysis were used to compare the median RS and PS. p < 0.05 was considered significant. RESULTS: Forty-four patients with a median age of 37 (range 10-68) years underwent primary pancreatic resections for pNENs. Overall, the median RS (20 mm, range 3-100 mm) was significantly larger than the PS (13 mm, range 4-110 mm) (p = 0.001). In patients with pNENs < 20 mm (n = 27), the size difference (median RS 15 mm vs PS 12 mm) was also significant (p = 0.003). However, the only modality that significantly overestimated the PS was EUS (median RS 14 mm vs 11 mm; p = 0.0002). RS overestimated the PS in 21 patients (21 of 27 patients, 78%). Five of 11 patients (12%) with a Nf-pNEN and a RS > 20 mm had in reality a PS < 20 mm. MRI was the imaging technique that best correlated with PS in the total cohort (r = 0.8; p < 0.0001), whereas EUS was the best correlating imaging tool in pNENs < 20 mm (r = 0.5; p = 0.0001). CONCLUSION: Preoperative imaging, especially EUS, frequently overestimates the size of MEN1-pNENs, especially those with a PS < 20 mm. This should be considered when indicating surgery in MEN1 patients with small Nf-pNENs.

White Paper: Radiological Curriculum for Undergraduate Medical Education in Germany.

Purpose: Radiology represents a highly relevant part of undergraduate medical education from preclinical studies to subinternship training. It is therefore important to establish a content base for teaching radiology in German Medical Faculties. Materials and Methods: The German Society of Radiology (DRG) developed a model curriculum for radiological teaching at German medical universities, which is presented in this article. There is also a European model curriculum for undergraduate teaching (U-level curriculum of the European Society of Radiology). In a modular concept, the students shall learn important radiological core principles in the realms of knowledge, skills and competences as well as core scientific competences in the imaging sciences. Results: The curriculum is divided into two modules. Module 1 includes principles of radiation biology, radiation protection and imaging technology, imaging anatomy as well as the risks and side effects of radiological methods, procedures and contrast media. This module is modality-oriented. Module 2 comprises radiological diagnostic decision-making and imaging-based interventional techniques for various disease entities. This module is organ system-oriented. Conclusion: The curriculum is meant as a living document to be amended and revised at regular intervals. The curriculum can be used as a basis for individual curricular development at German Medical Faculties. It can be integrated into traditional or reformed medical teaching curricula. Key Points: • Radiology is an integral and important part of medical education.• The German Society of Radiology (DRG) developed a model curriculum for teaching radiology at German Medical Faculties to help students develop the ability to make medical decisions based on scientific knowledge and act accordingly.• This curriculum can be used for individual curricular development at medical departments. It is divided into two modules with several chapters. Citation Format: • Ertl-Wagner B, Barkhausen J, Mahnken AH et al. White Paper: Radiological Curriculum for Undergraduate Medical Education in Germany. Fortschr Röntgenstr 2016; 188: 1017 - 1023.

Diffusion weighted MRI of osteoid osteomas: Higher ADC values after radiofrequency ablation.

PURPOSE: Feasibility of diffusion weighted MRI (DWI) pre- and post-radiofrequency ablation (RFA) in patients with osteoid osteoma (OO). MATERIAL AND METHODS: Ten patients (1 female, 24±9years) received RFA of OO (mean size 8.7±3.2mm). Two OO recurred, in one of these a second RFA was performed. A 1.5T DWI (b=50, 400, and 800s/mm(2)) and a fat saturated DCE MRI were obtained the day before and after RFA. In DWI, the mean apparent diffusion coefficient (ADC) was recorded. With DCE MRI, signal-to-noise ratio, contrast-to-noise ratio, absolute signal intensity (SI), relative SI, and SI ratio were documented. All parameters were compared pre- and post-RFA using paired Wilcoxon rank test. RESULTS: ADC values were significantly higher post-ablation, 1.6±0.5µm(2)/ms versus 1.3±0.6µm(2)/ms (p<0.05). Perfusion was significantly reduced after ablation [SNR, CNR, SI, %SI, and SI OO/SI muscle]; post-RFA: 55±13, 27±20, 757±534, 102±16, and 1.6±0.2; pre-RFA: 88±37, 65±22, 1038±755, 226±51, and 2.0±0.5 (p<0.05). DISCUSSION: DWI is feasible in OO. ADC values increased and contrast enhancement decreased after RFA of OO. This may be explained by RFA-induced necrosis and devascularization.

Effect of sherbet timing on distension and evaluation of the esophagus with multidetector-row computed tomography.

PURPOSE: The goal of this study was to analyze the effect of oral sherbet application on esophageal distension and esophageal evaluation with thoracic multidetector-row computed tomography (MDCT) regarding sherbet timing. MATERIALS AND METHODS: A total 120 patients (65 men, 55 women) with a mean age of 59.7 years who were given 4g sherbet powder to be swallowed 60, 30 or 10seconds before thoracic MDCT were included. Inner esophageal diameter was measured in three planes at three anatomic levels. Area of esophageal lumen and assessable length of the esophagus were calculated and statistically analyzed using repeated-measures-ANOVA and post-hoc-t-tests. Results were compared groupwise and intra-individually with previous examinations without sherbet. RESULTS: Intra-individual comparison and subgroup-analysis showed that esophageal distension was significantly better when sherbet was used (mean inner area: 1.98±0.66cm(2) vs. 0.49±0.14cm(2)) (P<0.001). After preparation, in average 80.2% of the esophageal length were assessable compared to 39.2% without sherbet (P<0.001). Timing of sherbet administration within one minute before scan-start revealed no significant differences (P=0.9), yet a shorter delay to scan-start led to the best results. CONCLUSION: Oral sherbet administration within one minute before scan-start improves esophageal distension and evaluation using thoracic MDCT. This method of esophageal preparation is simple, can easily be applied in clinical routine and may improve the diagnosis of esophageal pathologies.

[Transarterial ablative therapy of hepatocellular carcinoma]. / Transarterielle ablative Therapien des hepatozellulären Karzinoms.

CLINICAL/METHODICAL ISSUE: Due to late diagnosis and a lack of organs only about 30 % of patients suffering from hepatocellular carcinoma (HCC) undergo curative treatment. STANDARD RADIOLOGICAL METHODS: Transarterial chemoembolization (TACE) is a routine procedure in intermediate stage HCC. In addition transarterial embolization (TAE) and transarterial radioembolization (TARE) are available for these patients. PERFORMANCE: For inoperable patients with HCC, TACE is superior to best supportive care in terms of survival. Combined with percutaneous ablation TACE achieves results similar to resection. ACHIEVEMENTS: Current developments, such as drug-eluting beads, TARE and multimodal treatment are well suited to further improve outcome in patients with intermediate stage HCC. PRACTICAL RECOMMENDATIONS: Transarterial therapies in HCC should be applied in accordance with the Barcelona Clinic Liver Cancer (BCLC) criteria. Due to a better safety profile and potentially improved disease-free survival the use of drug-eluting beads should be liberally considered.

Vascular closure devices after endovascular procedures in swine: a reliable method?

PURPOSE: To investigate the safety and feasibility of the use of a vascular closure device (VCD) after endovascular procedures in swine. MATERIAL AND METHODS: In a study on endovascular therapy, VCD (StarClose, Abbott Vascular, Il, USA) was used in 20 female swines to achieve immediate hemostasis after percutaneous right femoral artery (FA) access. 10 animals were sacrificed immediately after the study and 10 animals were sacrificed 28 days after the initial study. To ensure complete hemostasis and patency of the femoral artery, a CT-angiography of the puncture site was performed on day 1 (acute and chronic group) and day 28 (chronic group). After the sacrifice, the femoral artery was explanted and examined macroscopically for signs of VCD dysfunction. RESULTS: Technical success rate was 100% with immediate hemostasis being achieved in all animals. No animals showed evidence of hematoma. During explantation, only small traces of coagulated blood were found in the acute group, while there were no signs of hematoma in the chronic group. CT-angiography immediately after VCD application as well as before sacrifice (chronic group) showed patency of the FA in all cases. CONCLUSION: The use of VCD to achieve hemostasis after endovascular studies in swine is feasible and safe.

[Invasive procedure for clarification of pulmonary nodules]. / Invasive Verfahren zur Abklärung pulmonaler Rundherde.

CLINICAL/METHODICAL ISSUE: The management of solitary lung nodules poses a common clinical problem and biopsy is oftten required. Several guidelines provide slightly different recommendations and there are no uniform recommendations regarding the ideal technique of puncture guidance (e.g. percutaneous versus bronchoscopic or thoracoscopic). STANDARD RADIOLOGICAL METHODS: Fine needle aspiration biopsy (FNA) and core biopsy are well established techniques. Both can be performed under CT and to some extent ultrasound guidance. PERFORMANCE: Diagnostic accuracies of FNA and core biopsy for malignant lesions are around 95 %. Core biopsy is superior to FNA for establishing a specific diagnosis with a diagnostic yield of 81-88 % versus 17-21 %. ACHIEVEMENTS: In clinical routine practice core biopsy is the superior tool when compared to FNA. PRACTICAL RECOMMENDATIONS: Central lesions in close proximity to bronchi may be biopsied with endobronchial ultrasound (EBUS)-guided bronchoscopy. In all other lesions percutaneous, ideally CT-guided biopsy should be the method of first choice.

Efficacy of magnetic thermoablation using SPIO in the treatment of osteoid osteoma in a bovine model compared to radiofrequency and microwave ablation.

PURPOSE: To evaluate heating efficacy of superparamagnetic iron oxide nanoparticles (SPIO) for electromagnetic ablation (EMA) of osteoid osteoma (OO) using an ex vivo model compared to radiofrequency ablation (RFA) and microwave ablation (MWA). METHODS: A model for OO using sliced bovine tibia and sliced muscle tissue was developed. A bone cavity filled with either a mixture of SPIO and agarose or pure agarose (control group) was established. EMA was performed using an experimental system, RFA and MWA using clinically approved systems, and the ablation protocols recommended by the vendor. For temperature measurements, fiberoptic temperature probes were inserted inside the cavity, on the outside of the periosteum, and at a 5 mm distance to the periosteum. RESULTS: Maximum temperatures with or without SPIO in the nidus were as follows: EMA: 79.9 ± 2.5/22.3 ± 0.7 °C; RFA: 95.1 ± 1.8/98.6 ± 0.9 °C; MWA: 85.1 ± 10.8/83.4 ± 9.62 °C. In RFA with or without SPIO significantly higher temperatures were achieved in the nidus compared to all other groups (p < 0.05). In MWA significantly higher temperatures were observed in the 5 mm distance to the periosteum compared to EMA and RFA with or without SPIO (p < 0.05). In MWA temperature decrease between nidus and the 5 mm distance to the periosteum was significantly lower than in RFA with or without SPIO (p < 0.0001). In MWA without SPIO temperature decrease was significantly lower than in the EMA group (p < 0.05). CONCLUSION: In the experimental setting, ablation of OO is safe and effective using EMA. It is less invasive than RFA and MWA, and it theoretically allows repeated treatments without repeated punctures. In comparison, the highest temperatures in the nidus are reached using RFA.

[Vena cava filter. Which indications remain in the era of differentiated anticoagulation?]. / Vena-cava-Filter. Welche Indikationen bleiben in Zeiten differenzierter Antikoagulation?

CLINICAL/METHODICAL ISSUE: Venous thromboembolism (VTE) is the third most common disease of the cardiovascular system. It is associated with a 30-day lethality in the range of 6  % in deep vein thrombosis and 12  % in pulmonary embolism (PE). There are various guidelines with sometimes controversial recommendations regarding the use of inferior vena cava (IVC) filters. STANDARD RADIOLOGICAL METHODS: Implantation of IVC filters is a standard therapy in selected patients with an estimated 259,000 filters implanted in 2012. METHODICAL INNOVATIONS: Optionally retrievable filters are increasingly being used in clinical routine practice. Future developments will include biodegradable and drug-eluting filters. PERFORMANCE: When compared to anticoagulation as the reference therapy of VTE, IVC filters will significantly reduce the frequency of symptomatic PE; however, there is no advantage in overall survival for either therapy. ACHIEVEMENTS: Despite different guidelines in clinical routine practice the use of IVC filters appears to depend on the individual clinical experience and assessment of the interventionalist. PRACTICAL RECOMMENDATIONS: Nowadays retrievable filters should be used although there are relevant differences between the various devices. As a matter of principle all IVC filters should be removed as soon as adequate anticoagulation can be established.

Carbon dioxide-contrasted computed tomography angiography: high pitch protocols and adapted injection parameters improve imaging quality.

PURPOSE: To systematically investigate the impact of image acquisition and contrast injection parameters for CO2-enhanced CT angiography (CTA) of the aorto-iliac and peripheral arteries in a pig model using commercially available equipment. The aim was to establish an imaging protocol that is ready for use in human subjects. MATERIALS AND METHODS: Three domestic swine underwent CO2-CTA with varying injection parameters: pitch (1.0, 3.0), injection pressure (0.7 bar, 1.0 bar, 1.3 bar) and scan delay (2 s, 4 s, 6 s). Objective (vessel diameter) and subjective (image quality) parameters and applied radiation doses were systematically evaluated. To ensure clinical applicability of the setting, only approved catheters/injectors and standard injection parameters were evaluated. RESULTS: The image quality scores were superior and the vessel diameter was larger with high pitch in comparison to standard pitch (diameters: 4.7 ± 2.0 mm vs. 3.6 ± 2.1 mm, p = 0.0040, scores: 2.6 ± 1.1 vs. 2.0 ± 1.1, p = 0.0038). High injection pressure (1.3 bar) improved the image quality as assessed by subjective and objective ratings (diameters: 3.6 ± 2.0 mm, 4.0 ± 2.1 mm and 4.6 ± 2.1 mm, for 0.7, 1.0 and 1.3 bar, p-values ≤ 0.0052, scores: 1.9 ± 1.1, 2.3 ± 1.1 and 2.7 ± 1.2, p-values ≤ 0.0017), the same was observed for a shorter injection delay (diameters: 3.5 ± 2.0 mm, 4.2 ± 2.1 mm and 4.8 ± 2.1 mm, for 6 s, 4 s, and 2 s, p ≤ 0.0022, scores: 1.9 ± 1.1, 2.3 ± 1.1 and 2.7 ± 1.1, p-values ≤ 0.0013). The dose length products were 239 ± 47 mGycm (high pitch) and 565 ± 63 mGycm (standard pitch, p-values < 0.0001). CONCLUSION: A higher pitch, shorter delay and higher injection pressure improve image quality in CO2-enhanced CTA. Since commercially available, clinically approved equipment was used. The protocol is now ready for use in human subjects.

Reconstructions with identical filling (RIF) of the heart: a physiological approach to image reconstruction in coronary CT angiography.

OBJECTIVES: To compare image quality in coronary artery computed tomography angiography (cCTA) using reconstructions with automated phase detection and Reconstructions computed with Identical Filling of the heart (RIF). METHODS: Seventy-four patients underwent ECG-gated dual source CT (DSCT) between November 2009 and July 2010 for suspected coronary heart disease (n = 35), planning of transcatheter aortic valve replacement (n = 34) or evaluation of ventricular function (n = 5). Image data sets by the RIF formula and automated phase detection were computed and evaluated with the AHA 15-segment model and a 5-grade Likert scale (1: poor, 5: excellent quality). Subgroups regarding rhythm (sinus rhythm = SR; arrhythmia = ARR) and potential premedication were evaluated by a per-segment, per-vessel and per-patient analysis. RESULTS: RIF significantly improved image quality in 10 of 15 coronary segments (P < 0.05). More diagnostic segments were provided by RIF regarding the entire cohort (n = 693 vs. 590, P < 0.001) and all of the subgroups (e.g. ARR: n = 143 vs. 72, P < 0.001). In arrhythmic patients (n = 19), more diagnostic vessels (e.g. LAD: n = 10 vs. 3; P < 0.014) and complete data sets (n = 7 vs. 1; P < 0.001) were produced. CONCLUSIONS: RIF reconstruction is superior to automatic diastolic non-edited reconstructions, especially in arrhythmic patients. RIF theory provides a physiological approach for determining the optimal image reconstruction point in ECG-gated CT angiography. KEY POINTS: Conventional CT coronary angiography suffers from numerous artefacts in patients with irregular rhythms. Coronary computed tomography angiograms (cCTA) were reconstructed with identical cardiac filling (RIF). RIF reconstructions provide improved image quality compared to non-edited standard reconstructions. RIF theory links physiology with cardiac CT.

Silicon carbide-enhanced microwave ablation in an ex-vivo bovine liver model - effects on heat distribution and ablation volume.

PURPOSE: Evaluation of the maximum temperatures and ablation volumes in microwave ablation (MWA) after injection of different concentrations of silicon carbide (SiC) particles in an ex-vivo bovine liver model. MATERIALS AND METHODS: 15 ml of different concentrations of SiC particles (20 vol% SiC; 50 vol% SiC) mixed with 2 % gelatin were injected into an ex-vivo bovine liver. As a reference group, 2 % gelatin without SiC was injected. MWA was performed using a clinical MWA system with different generator settings (10 - 45 W/10 minutes). The temperature was measured at a distance of 5 mm and 10 mm from the applicator. Afterwards the liver tissue was sliced along the short and long axis, the ablation zones were measured on the x, y and z-axis and the ablation volume was calculated. All experiments were performed 5 times (total: 40 experiments). RESULTS: The average maximum temperatures measured at a generator setting of 45 W at a distance of 5 mm from the applicator were 103.4 ± 4.6 °C (20 vol% SiC), 103.3 ± 6.5 °C (50 vol% SiC) and 96.0 ± 4.2 °C in the control group (0 vol% SiC). At 45 W, injection of 20 vol% SIC caused a significantly higher maximum temperature than that achieved in the control group (p = 0.016). No significant temperature increase compared to the control group could be measured using 50 vol% SiC. The mean ablation volumes at 45 W and 20 vol% SiC and 50 vol% SiC were significantly larger (172.7 ± 31.5 ml and 171.0 ± 34.7 ml, respectively) than those achieved in the control group (111.2 ± 23.8 ml) (p = 0.027 and p = 0.045). CONCLUSION: In an ex-vivo bovine liver model, the SiC particles demonstrated an enhancing effect of MWA with respect to maximum temperatures and ablation volume. Therefore, SiC is a promising candidate for enhancing MWA in vivo.