Which of the following would increase both the quantity and quality of the primary beam?

J Biomed Phys Eng. 2017 Jun; 7[2]: 101–106.

Published online 2017 Jun 1.

Abstract

Introduction:

Collimating the primary beam to the area of diagnostic interest [ADI] has been strongly recommended as an effective method to reduce patient’s radiation dose and to improve image quality during radiology practice. Lack or inadequate collimation results in excessive radiation dose to patients and deterioration image quality.

Objective:

To assess the quality of beam collimation during lumbar spine radiography at two general hospitals in Ahvaz, Iran.

Materials and Methods:

We retrospectively reviewed 830 digital antero-posterior [AP] lumbar spine radiographs in term of beam collimation. For each radiograph, the distance between current and optimal collimation was calculated [in cm]. The area of ADI and total field size for each radiograph were also calculated [in cm2].

Results:

The total mean ADI and irradiated region outside ADI for each radiograph were estimated 360 and 454 cm2, respectively. The total irradiated region outside ADI was 1.26 times more than ADI. In contrast to cranial regions outside ADI, caudal regions were more commonly included inside the primary beam [12% vs. 24.4%; P-value 0.005].

Table 1

Total mean field size, ADI, irradiated region outside ADI and percentage distance outside ADI of each side

Discussion

This study evaluated the quality of beam collimation during lumbar spine radiography. Transition from analogue to digital radiography has increased concerns in terms of neglecting proper collimation. Two primary concerns are the digital image receptors are more sensitive to the low levels of radiation produced due to the large collimation, which causes a reduction in image contrast [14], and also electronic masking or cropping of digital images to the ADI may be a reason to become complacent of radiographers toward proper collimation [9,14]. These concerns have led to several published studies [9,10,15]. Zetterberg and Espeland [2011] conducted a study to examine the quality of beam collimation in 86 analogues and 86 digital lumbar spine radiographs, and reported that the mean total field size was 46% larger in digital than in analogue images. They highlighted these larger irradiated areas as causing unnecessary high radiation doses to patients [9]. Debess et al. [2015] evaluated collimation in 186 chest radiographs and reported that 76% to 90% of the evaluated radiographs had large collimations [10]. A survey of 450 radiographers by the American Society of Radiologic Technologists [ASRT] revealed that half of the respondents used electronic cropping after the exposure [15].

The results of this study reveal that all radiographs evaluated more and less had large collimations, as the total irradiated field size outside ADI was 1.26 times more than ADI. Previous studies that evaluated the lumbar spine radiographs [9] and chest radiographs [10] found also larger collimation than acceptable. The results of this study also are in contrast to Rahimi et al. [16] in which the collimation of primary beam to the ADI during general radiography was reported 46.4%.

A Monte Carlo study by Chaparian et al. [2014] revealed that the mean radiation absorbed doses to the colon, breast, ovaries and testicles from only AP projection of the lumbar spine radiography were 0.902, 0.014, 0.613 and 0.429 mSv, respectively [17]. Following this, the mean risk of radiation-induced fatal cancer for males and females has also been estimated 18.55 and 17.50 per million, respectively [17]. These values certainly simulated the assumption of good collimation and proper alignment of x-ray field with appropriate anatomical landmarks; therefore, it can substantially increase if these organs are included in the primary beam due to large collimation. Although excessive radiation dose produced by large collimation may not be significant, due to frequency of examinations [LS radiography has been identified as the third mostly frequent radiographic procedure performed [18]] and the use of various views [six views for individual person in the same area], the cumulative radiation dose could be significant. As reported by Vader et al. [2004], a number of 273,000 lumbar spine radiographies are performed annually in Switzerland which is responsible for 1130 Sv collective radiation dose to the population [18].

The results of this study emphasize the fact that patients receive avoidable excessive radiation dose due to large collimation. Based on our results, at least in 62/5% of radiographs evaluated, ovaries were included in the primary beam while they were not of interest. As known from literature [19-21], a significant dose reduction can be achieved by using gonadal shield, of 830 radiographs under investigation; we found that only one radiograph had an evidence of gonad shielding. However, discussion on gonad protection is not the focus of this study.

One of the common reasons to apply larger collimation by radiographers is the fear of cutting the ADI and the attitude that it is better to be larger than cutting of the ADI and/or repetition of the examination. An appropriate solution is learning to use anatomical landmarks for collimation guide. Adequate collimation during spine radiography is required to understand these surface anatomical landmarks associated with various vertebral segments that can be easily palpated. The most reliable landmarks for collimation guide are shown in Table 2. It is note that it should serve as the only point of departure for radiographers toward orientation since considerable individual variation will be encountered in daily practice. This study only evaluated the status of collimation during lumbar spine radiography. Other directions of future studies can evaluate the length status of the field of scan during computerized tomography [CT] examinations. It is significant since the doses from CT are 100-500 times more than conventional radiography [22].

Table 2

Superficial anatomical landmarks associated with spines for collimation guide

Conclusion

Our results demonstrated that patients in hospitals investigated received excessive radiation doses due to large collimation. Improper radiation collimation causes unnecessarily high radiation doses to patients which should be reversed. Radiographers should make considerable effort to limit the primary beam to the ADI to reduce patient’s exposure and to increase image quality, simultaneously. The provision of written collimation guidelines in radiography rooms and its practical training are also recommended.

Acknowledgement

The Ethical Committee of Ahvaz Jundishapur University of Medical Sciences approved the study [Grant No. 93s.90].

Conflict of Interest:The authors have no conflicts of interest to declare.

References

1. Gyekye PK, Simon A, Geoffrey ER, Johnson Y, Stephen I, Engmann CK, et al. Radiation dose estimation of patients undergoing lumbar spine radiography. J Med Phys. 2013;38:185–8. doi: 10.4103/0971-6203.121196. [ PMC Free Article] [PMC free article] [PubMed] [CrossRef] [Google Scholar]

2. Gholamhosseinian-Najjar H, Bahreyni-Toosi M-T, Zare M-H, Sadeghi H-R, Sadoughi H-R. Quality Control Status of Radiology Centers of Hospitals Associated with Mashhad University of Medical Sciences. Iranian Journal of Medical Physics. 2014;11:182–7. [Google Scholar]

4. Clancy CL, O’Reilly G, Brennan PC, McEntee MF. The effect of patient shield position on gonad dose during lumbar spine radiography. Radiography. 2010;16:131–5. doi: 10.1016/j.radi.2009.10.004. [CrossRef] [Google Scholar]

5. Protection R. ICRP publication 103. Ann. ICRP. 2007;37:2. [Google Scholar]

6. Dowd SB, Tilson ER. Practical radiation protection and applied radiobiology: WB Saunders; 1999. [Google Scholar]

7. Bailey E, Anderson V. Syllabus on Radiography Radiation Protection. Sacramento, State of California: 1995. pp. 46–50. [Google Scholar]

8. Engel-Hills P. Radiation protection in medical imaging. Radiography. 2006;12:153–60. doi: 10.1016/j.radi.2005.04.008. [CrossRef] [Google Scholar]

9. Zetterberg LG, Espeland A. Lumbar spine radiography--poor collimation practices after implementation of digital technology. Br J Radiol. 2011;84:566–9. doi: 10.1259/bjr/74571469. [ PMC Free Article] [PMC free article] [PubMed] [CrossRef] [Google Scholar]

10. Debess J, Johnsen K, Thomsen H. Digital chest radiography: collimation and dose reduction. Breast. :14.0–9.2. [Google Scholar]

11. Long BW, Rollins JH, Smith BJ. Merrill’s Atlas of Radiographic Positioning and Procedures: Elsevier Health Sciences; 2015. [Google Scholar]

12. Carver E, Carver B. Medical imaging: techniques, reflection and evaluation: Elsevier Health Sciences; 2012. [Google Scholar]

13. Adams JE, Lenchik L, Roux C, Genant HK. Radiological Assessment of Vertebral Fracture. International Osteoporosis Foundation Vertebral Fracture Initiative Resource Document Part II; 2010. [Google Scholar]

14. Herrmann TL, Fauber TL, Gill J, Hoffman C, Orth DK, Peterson PA, et al. Best practices in digital radiography. Radiol Technol. 2012;84:83–9. [PubMed] [Google Scholar]

15. Morrison G, John SD, Goske MJ, Charkot E, Herrmann T, Smith SN, et al. Pediatric digital radiography education for radiologic technologists: current state. Pediatr Radiol. 2011;41:602–10. doi: 10.1007/s00247-010-1904-3. [PubMed] [CrossRef] [Google Scholar]

16. Rahimi S, Salar S, Asadi A. Evaluation of Technical, Protective and Technological operation of Radiologists in Hospitals of Mazandaran Medical Science Universities. J Mazandaran Univ Med Sci. 2007;17:131–40. [Google Scholar]

17. Chaparian A, Kanani A, Baghbanian M. Reduction of radiation risks in patients undergoing some X-ray examinations by using optimal projections: A Monte Carlo program-based mathematical calculation. J Med Phys. 2014;39:32–9. doi: 10.4103/0971-6203.125500. [ PMC Free Article] [PMC free article] [PubMed] [CrossRef] [Google Scholar]

18. Vader JP, Terraz O, Perret L, Aroua A, Valley JF, Burnand B. Use of and irradiation from plain lumbar spine radiography in Switzerland. Swiss Med Wkly. 2004;134:419–22. [PubMed] [Google Scholar]

19. Karami V, Zabihzadeh M, Gholami M. Gonad Shielding for Patients Undergoing Conventional Radiological Examinations: Is There Cause for Concern? . Jentashapir Journal of Health Research. 2016 [In Press] doi: 10.17795/jjhr-31170. [CrossRef] [Google Scholar]

20. Doolan A, Brennan PC, Rainford LA, Healy J. Gonad protection for the antero-posterior projection of the pelvis in diagnostic radiography in Dublin hospitals. Radiography. 2004;10:15–21. doi: 10.1016/j.radi.2003.12.002. [CrossRef] [Google Scholar]

21. Gul A, Zafar M, Maffulli N. Gonadal shields in pelvic radiographs in pediatric patients. Bull Hosp Jt Dis. 2005;63:13–4. [PubMed] [Google Scholar]

22. Miglioretti DL, Johnson E, Williams A, Greenlee RT, Weinmann S, Solberg LI, et al. The use of computed tomography in pediatrics and the associated radiation exposure and estimated cancer risks. JAMA Pediatr. 2013;167:13–4. doi: 10.1001/jamapediatrics.2013.311. [ PMC Free Article] [PMC free article] [PubMed] [CrossRef] [Google Scholar]

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