Comparison of radiation doses of various approaches of MR arthrograms with fluoroscopic guided contrast injection

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1 Comparison of radiation doses of various approaches of MR arthrograms with fluoroscopic guided contrast injection Poster No.: C-1294 Congress: ECR 2014 Type: Scientific Exhibit Authors: H. M. Cheng, C. W. Tam, M. H. B. Lai, J. S. F. Shum; Hong Kong/ HK Keywords: Radioprotection / Radiation dose, Musculoskeletal joint, Fluoroscopy, MR, Arthrography DOI: /ecr2014/C-1294 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 14

2 Aims and objectives Ever since the introduction of magnetic resonance in obtaining spatial information by the Nobel Laureate Paul Lauterbur in 1973, its application in medical imaging had been expanding rapidly and extensively for the past 40 years. With the advantage of absence of ionizing radiation, magnetic resonance has now become one of the most important imaging modality for visualization of soft tissue structures, particularly in the assessment of the musculoskeletal system. Magnetic resonance arthrography is an imaging technique that utilizes fluoroscopic guided injection of gadolinium contrast into a joint, thereby improving the delineation and details of intra-articular structures, and hence the corresponded pathologies for guiding of treatment. However, along with injection of contrast during fluoroscopy screening, ionizing radiation is inevitably introduced to the patients simultaneously. In order to minimize the risk of ionizing radiation for each diagnostic procedure for both the patients and radiologists, it is important to ensure the radiation doses are not only within international reference levels, but also kept as low as reasonably achievable (ALARA). In this retrospective study, we reviewed the radiation doses of various regional arthrograms at our center, and compared with the international reference range. In particular, for various injection approaches of shoulder arthrography, namely, rotator interval, low anterior and posterior approaches, we compared the differences in the associated radiation doses. Images for this section: Page 2 of 14

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4 Fig. 1: A) Fluoroscopic image of a left shoulder after fluoroscopic guided intra-articular contrast injection with needle in situ. B) Plain MRI T1 weighted with fat saturation coronal image of the same patient showing presence of intra-articular contrast material. Fig. 2: A) Fluoroscopic image of a right hip after fluoroscopic guided intra-articular contrast injection with needle in situ, insertion site at lateral aspect of femoral head and neck junction. Plain MRI images in T1 weighted with fat saturation axial (B), T1 weighted oblique coronal (C) and T2 weighted with fat saturation oblique coronal (D) of the same patient showing presence of intra-articular contrast material. Page 4 of 14

5 Fig. 3: A) Fluoroscopic image of a right wrist after fluoroscopic guided intra-articular contrast injection with needle in situ. Plain MRI coronal B) T1 weighted with fat saturation and D) T2 weighted with fat saturation of the same patient showing presence of intraarticular contrast material. Page 5 of 14

6 Methods and materials 29 cases of MR arthrography were performed at our center during the period from January 2013 to June 2013 and were retrospectively analyzed. The cases were referred by the Orthopedics department at our hospital for suspected soft tissue injury of shoulder, hip and wrist joints. A total of 18 shoulder arthrograms, 4 hip arthrograms and 7 wrist arthrograms were performed respectively. The arthrograms were performed by musculoskeletal radiologists at our center. For each arthrogram, diluted gadolinium contrast medium was injected by a radiologist into the affected joint under fluoroscopic guidance. The fluoroscopic procedures were performed with Siemens Artis zee/zeego VC14 and images were stored in a single digital imaging archive system. For each examination, the technical parameters and dose reports were automatically generated by the fluoroscopic system and were routinely recorded. Plain MRI images were then obtained by a 1.5T MRI scanner (Siemens Magnetom Avanto). At our center, approaches of wrist and hip intra-articular contrast injection are standardized. However, three different approaches of intra-articular contrast injection were adopted for shoulder arthrograms, namely, rotator interval, low anterior and posterior approaches. Choice of various approaches depends on variation in the clinical scenario and respective radiologist preferences. Figure 4 demonstrates the various approaches in shoulder arthrogram. Dose area product (DAP) is the total energy absorbed by the patient, which is approximated from the absorbed dose generated by the fluoroscopic system. Taking into account the various organ differential radiosensitivities, a tissue-weighting factor has to be included. As recommended by the National Council of Radiation Protection -1-2 (NCRP), the conversion coefficient for arthroscopy is 0.1mSvGy cm, and we obtained the effective dose of arthroscopy by multiplying the absorbed dose (DAP) with the conversion coefficient. Statistical analysis was performed using SPSS Version 19 (SPSS Inc, Chicago, USA). Normal distribution was tested using Shapiro-Wilk test. Mean examination time, radiation dose, dose-area product, effective dose were analyzed. As data was distributed with non-gaussian pattern, Kallis-Wall test was used for comparison of examination, Page 6 of 14

7 radiation dose, dose-area-product and effective dose for various approaches for shoulder arthrograms. Images for this section: Fig. 4: Fluoroscopic images demonstrating various approaches of shoulder arthrogram with needle in-situ: A) Rotator interval approach B) anterior low approach and C) posterior approach. Page 7 of 14

8 Results Figures 5-8 show the demographic and examinatiom data of the 29 patients in our study (Male = 16, female = 13). The mean age was 40 years, with the age range of years. The mean screening times for hip, shoulder and wrist arthrograms were 0.60min, 0.72min and 1.05min respectively. The DAPs values of hip, shoulder and wrist arthrograms were 1.76 mgycm, 0.87 mgycm, and 0.33 mgycm respectively. Despite the longest screening times for wrist arthrograms, the absorbed doses and hence the effective doses were the lowest. This is related to the thinnest tissue thickness of the wrist, and thus the volume of tissue penetrated by the radiation beam. The calculated mean effective dose values of the three corresponding regions were 0.17mSv, 0.09mSv, and 0.03mSv. [Figure 9] For shoulder arthrograms, the DAPs values for rotator interval (R.I.), low anterior and posterior approaches were 0.37 mgycm, 1.49 mgycm and 0.71 mgycm respectively, with mean screening times of 0.54min, 1.06min and 0.56min. The corresponding calculated effective doses were 0.04mSv, 0.18mSv and 0.08mSv. According to our analysis, a significantly lower radiation dose was achieved with rotator interval approach comparing with low anterior and posterior approaches. (R.I. Vs low anterior: p=0.006; R.I. Vs posterior: p=0.042). [Figure 10] With reference to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2008, which offers a large scale assessment of the magnitude of medical radiation exposure around the globe during the period , the average effective dose of arthrogram is 0.17mSv. The overall mean effective dose of arthrograms analyzed from the 29 included case of our study is 0.09mSv. In comparison, our center offers a well below radiation dose level than the international reference level. Images for this section: Page 8 of 14

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14 Conclusion In conclusion, the radiation doses of arthrograms performed at our center are well compared with the international reference level. In regard to shoulder arthrography, rotator interval approach of intra-articular contrast injection offers the lowest radiation dose. Personal information References 1. Sources and Effects of Ionizing Radiation. United Nations Scientific Committee on the Effects of Atomic Radiation 2008 Report : Volume MR Arthrography update 209. Advanced MRI From Head to Toe. 3. Joshua Yellin, MD, Jeffrey J. Peterson, MD. MR Arthrography. Applied Radiology; September L. Struelens, F. Vanhavere, K. Bacher, H. Thierens. DAP to effective dose conversion in cardiology and vascular/interventional radiology. FANC/SCK/UGent. 5. D. Hart, PhD, M C Hillier, and B F Wall, BSc. National reference doses for common radiographic, fluoroscopic and dental X-ray examinations in the UK. The British Journal of Radiology, 82 (2009), P.A. Campos, M.V. Redondo, J.D. Berna -Serna, M. Reus y F. Mart# nez. Optimizacio n de las dosis de radiacio n en la artrograf# a de hombro. Radiolog# a. 2009;51(3): Page 14 of 14