Substantial Dose Reduction in Modern Multi-Slice Spiral Computed Tomography (MSCT)-Guided Craniofacial and Skull Base Surgery
ABSTRACT Reduction of the radiation exposure involved in image-guided craniofacial and skull base surgery is an important goal. The purpose was to evaluate the influence of low-dose protocols in modern multi-slice spiral computed tomography (MSCT) on target registration errors (TREs).
An anthropomorphic skull phantom with target markers at the craniofacial bone and the anterior skull base was scanned in Sensation Open (40-slice), LightSpeed VCT (64-slice) and Definition Flash (128-slice). Identical baseline protocols (BP) at 120 kV/100 mAs were compared to the following low-dose protocols (LD) in care dose/dose modulation: (LD-I) 100 kV/35ref. mAs, (LD-II) 80 kV/40 - 41ref. mAs, and (LD-III) 80 kV/15 - 17ref. mAs. CTDIvol and DLP were obtained. TREs using an optical navigation system were calculated for all scanners and protocols. Results were statistically analyzed in SPSS and compared for significant differences (p ≤ 0.05).
CTDIvol for the Sensation Open/LightSpeed VCT/Definition Flash showed: (BP) 22.24 /32.48 /14.32 mGy; (LD-I) 4.61 /3.52 /1.62 mGy; (LD-II) 3.15 /2.01 /0.87 mGy; and (LD-III) na/0.76 /0.76 mGy. Differences between the BfS (Bundesamt für Strahlenschutz) reference CTDIvol of 9 mGy and the lowest CTDIvol were approximately 3-fold for Sensation Open, and 12-fold for the LightSpeed VCT and Definition Flash. A total of 33 registrations and 297 TRE measurements were performed. In all MSCT scanners, the TREs did not significantly differ between the low-dose and the baseline protocols.
Low-dose protocols in modern MSCT provided substantial dose reductions without significant influence on TRE and should be strongly considered in image-guided surgery.
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ABSTRACT: Abstract Background: Minimally invasive ostesynthesis of scaphoid fractures may reduce the risk of fracture non-union and shorten the duration of illness. The aim of this study was to analyze the technical feasibility and targeting accuracy of computed tomography (CT) - guided stereotactic Kirschner (K)-wire positioning in the scaphoid. Methods: Nineteen Formalin preserved cadaveric upper extremities (10 right, 9 left) were fixed in 90 degree dorsal extension for percutaneous access from palmar. An ideal central position of the K-wire was planned on the computer adapted from intraoperative CT data. A 3D navigation system and stereotactic targeting device were used for K-wire placement. Target positioning errors were evaluated by fusion of the control CT with the K-wire in place with the planning CT. Results: The procedure allowed for an easy and rigid wrist fixation. K-wire placement showed mean ± SD lateral targeting errors of 0.9 ± 0.5 mm at the scaphoid bone entry and 1.2 ± 0.7 mm at the K-wire tip. The mean angular error was 1.3° ± 1.1° . Total duration of the intervention ranged between 19 and 23 min. Conclusion: CT-guided stereotactic K-wire placement in scaphoid bones is highly accurate. The technique may guide minimally invasive screw-osteosynthesis of scaphoid fractures.Minimally invasive therapy & allied technologies: MITAT: official journal of the Society for Minimally Invasive Therapy 10/2012; 22(3). DOI:10.3109/13645706.2012.724688 · 1.18 Impact Factor
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ABSTRACT: Purpose: The necessity of refresher courses is controversial and is frequently questioned. The present study examines whether the courses have a lasting effect and whether improvements are indicated.Materials and Methods: With the help of a questionnaire (9 questions) to be answered before the course, a self-assessment was performed and questions about the knowledge and structure of radiation protection were asked. 1361 participants were surveyed (55 % physicians, 31 % doctor's assistants, 13 % technicians, 1 % medical physicists) in the period of 2005 - 2013 (3) and 39 courses were evaluated. The assessment entailed the comparison of 3 subgroups: 2005 - 2007, 2008 - 2010, 2011 - 2013.Results: The self-assessment is about 3.0 (1 - very good, 5 - very poor) with fluctuations regarding time course and occupation. For all questions, there was an increase in correct answers from the period 2005 - 2007 to the period 2008 - 2010 (+ 15 %), while the rate fell again for the period 2011 - 2013 (3) (- 8 %). The questions were answered significantly better for organization-related topics than knowledge-based topics. Overall 53 % of the answers were correct.Conclusion: This study shows an increase in knowledge since starting refresher courses. However, recently the effect has decreased again. In order to maintain the knowledge, the yearly instruction must be held on time, which according to participants' statements actually occurs in only 60 % of cases.Key Points:Citation Format:RöFo - Fortschritte auf dem Gebiet der R 07/2013; 185(11). DOI:10.1055/s-0033-1335677 · 1.96 Impact Factor
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ABSTRACT: Purpose: The aim of this study was to evaluate the potential of iterative reconstruction (IR) in chest computed tomography (CT) to reduce radiation exposure. The qualitative and quantitative image quality of standard reconstructions with filtered back projection (FBP) and half dose (HD) chest CT data reconstructed with FBP and IR was assessed. Materials and Methods: 52 consecutive patients underwent contrast-enhanced chest CT on a dual-source CT system at 120 kV and automatic exposure control. The tube current was equally split on both tube detector systems. For the HD datasets, only data from one tube detector system was utilized. Thus, FD and HD data was available for each patient with a single scan. Three datasets were reconstructed from the raw data: standard full dose (FD) images applying FBP which served as a reference, HD images applying FBP and IR. Objective image quality analysis was performed by measuring the image noise in tissue and air. The subjective image quality was evaluated by 2 radiologists according to European guidelines. Additional assessment of artifacts, lesion conspicuity and edge sharpness was performed. Results: Image noise did not differ significantly between HD-IR and FD-FBP (p = 0.254) but increased substantially in HD-FBP (p < 0.001). No statistically significant differences were found for the reproduction of anatomical and pathological structures between HD-IR and FD-FBP, except subsegmental bronchi and bronchioli. The image quality of HD-FBP was rated inferior because of increased noise. Conclusion: A 50 % dose reduction in contrast-enhanced chest CT is feasible without a loss of diagnostic confidence if IR is used for image data reconstruction. Iterative reconstruction is another powerful tool to reduce radiation exposure and can be combined with other dose-saving techniques.RöFo - Fortschritte auf dem Gebiet der R 01/2014; 186(6). DOI:10.1055/s-0033-1356254 · 1.96 Impact Factor