AYŞEGÜL YURT, Rukiye ÇAKIR HALİLOĞLU, İsmail ÖZSOYKAL, Gi̇zem ŞİŞMAN, EMEL ADA

Baş-Boyun BT Anjiyografi’de Otomatik Tüp Akımı Modülasyon Sisteminin Hasta Dozu ve Görüntü Kalitesi Üzerine Etkisi

Giriş: Bilgisayarlı tomografi (BT) cihazları teknolojik gelişmeleri ile birlikte hastalıkların tanısında her geçen gün dahafazla kullanılmakta ve bunun sonucu olarak hasta dozlarında büyük bir artışa neden olmaktadır. Klinik olarak BTçekimleri çok yararlı olmasına rağmen, radyasyon dozu ve bunun meydana getirebileceği olası kanser riski geleceğinen büyük problemi olarak değerlendirilmektedir. Bu nedenle BT taramalarında, görüntü kalitesinden ödün vermedengörüntüleme parametrelerini kontrol ederek hasta dozlarının düşürülmesi temel ilke olmalıdır.Amaç: Bu çalışmanın amacı, baş-boyun BT anjiyografi çekimlerinde otomatik tüp akım modülasyon (OTAM)sisteminin kullanılmasının hasta dozlarının azaltılması ve görüntü kalitesi üzerindeki etkilerini araştırmaktır.Yöntemler: Serebrovasküler hastalık nedeniyle izlenen 23 hasta bu çalışmaya dahil edilmiştir. Sabit tüp akımı (mAs)kullanılarak yapılmış rutin baş boyun BT anjiyografi taramasının takibi için gelen hastaya tüm görüntülemeparametreleri sabit kalmak kaydıyla sadece otomatik tüp akımı modülasyonu tekniği kullanılarak tetkikgerçekleştirildi. Her iki yöntemle elde edilen veriler, hem hastaya verilen doz hem de görüntü kalitesi açısındandeğerlendirildi ve karşılaştırıldı.Bulgular: Akım modülasyonu sistemi kullanıldığında etkin doz değerinde %35’lik bir azalma gözlendi. Objektifdeğerlendirme için baş-boyun kısmında belirlenen 3 farklı anatomik bölgede sinyal-gürültü oranı (SNR) değerleri içinbeyin sapında %49, omuz bölgesinde %25, serebellumda ise %42 lik bir azalma olduğu bulundu. Subjektifdeğerlendirmede ise akım modülasyon sistemi kullanılarak elde edilen görüntüler 2 radyolog tarafından incelendi ve0-4 arasındaki puanlama sonucunda bu görüntülerin ortalama puanı 2,2 olarak bulundu. Sonuç: Baş-boyun anjiyo BT incelmelerinde otomatik akım modülasyonu ile radyasyon dozlarında belirgin azalmaelde edilmiş, SNR nin azalmasına rağmen klinik açıdan tanısal kayıp olmadığı görülmüştür. Hasta dozlarınınazaltılması ve tanısal açıdan dezavantaj oluşturmaması için uygun kriterlerde kullanılacak OTAM tekniğininnöroanjiyo çekimlerinde rutin uygulamaya girmesi kesinlikle önerilmektedir.

The Effect of Automatic Tube Current Modulation System on Patient Dose and Image Quality in Head-Neck CT Angiography

Objective: Use of Computed Tomography (CT) in the diagnosis of diseases is increasing parallel to the technological advances in scanner designs, however, leading to a large increase in patient doses. Although the CT scans offer clinically useful information, the radiation dose and the potential risk of cancer is considered as the biggest problem for the future. For this reason, reducing the patient dose without leading to any degradation in the image quality must be the primary concern in CT scans. Objectives: In this study, we aimed to investigate the effects of the use of automatic tube current modulation (ATCM) technique on patient dose and image quality in head-neck CT angiography scans. Method: 23 patients have been included in the study who are being followed for their cerebrovascular diseases. Following the routine head and neck CT angiography protocol performed using constant tube current (mAs), next scan for the patients were carried out by using automatic tube current modulation technique, with all other exposure parameters held constant. Results obtained from two scanning methods were compared based on both dosimetric parameters and image quality. Results: With the use of automatic tube current modulation technique, 35% reduction was observed in the effective dose. For objective evaluation, signal-to-noise ratio (SNR) values of 3 different anatomical regions of the head and neck were reduced by 49% in the brain stem, 25% in the shoulder region, and 42% in the cerebellum, respectively. In the subjective evaluation, images have been rated by 2 radiologists according to a grading scale between 0-4 and an average grade of 2.2 was obtained for the images acquired using automatic tube current modulation technique. Conclusion: There was a significant decrease in radiation doses with the use of automatic tube current modulation in head and neck CT angiography. Despite decreases in SNR values, there was no handicap observed for achieving diagnostic purpose. According to these results, the routine use of automatic tube current modulation technique in CT neuroangiography exams is highly recommended.

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1. AAPM Report 96. The Measurement, Reporting and management of radiation dose in CT. USA. 2008; 1-34.
2. Frush D, Denham CR, Goske MJ, et al. Radiation protection and dose monitoring in medical ımaging: a journey from awareness, through accountability, ability and action but where will we arrive? J Patient Saf. 2012; 8: 1-11.
3. Dougeni E, Faulkner K, Panayiotakis G. A review of patient dose and optimisation methods in adult and paediatric CT scanning. Eur J Radiol. 2012; 81: 665-83.
4. Wiest PW, Locken JA, Heintz PH, et al. CT scanning: a major source of radiation exposure. Semin Ultrasound CT MR. 2002; 23: 402–10.
5. Feng ST, Law MWM, Huang B, et al. Radiation dose and cancer risk from pediatric CT examinations on 64-slice CT: a phantom study. Eur J Radiol. 2010; 76: 19-23.
6. Rogers LF. Radiation Exposure in CT: Why So High? AJR. 2001; 277.
7. Parker MS, Kelleher NM, Hoots JA, et al. Absorbed radiation dose of the female breast during diagnostic multidetector chest CT and dose reduction with a tungsten-antimony composite breast shield: preliminary results. Clin Radiol. 2008; 63: 278–88.
8. Spampinato S, Gueli AM, Milone P, et al. Dosimetric changes with computed tomography automatic tubecurrent modulation techniques. Radiol Phys Technol. 2018; 11: 184–91.
9. Greffier J, Larbi A, Macri F, et al. Effect of patient size, anatomical location and modulation strength on dose delivered and image-quality on CT examination. Radiat Prot Dosimetry. 2017; 177: 373–81.
10. Namasivayam S, Kalra MK, Pottala KM, et al. Optimization of Z-axis automatic exposure control for multidetector row CT evaluation of neck and comparison with fixed tube current technique for image quality and radiation dose. Am J Neuroradiol. 2006; 27: 2221–5.
11. Lee CH, Goo JM, Ye HJ, et al. Radiation dose modulation techniques in the multidetector CT era: from basics to practice. Radiographics. 2008; 28: 1451- 9.
12. Yurt A. Bilgisayarlı Tomografide Radyasyon Dozu ve Doz Azaltıcı Yöntemler. Turkiye Klinikleri J Radiol. 2014; 7: 33–9.
13. Lee CH, Goo JM, Lee HJ, et al. Radiation dose modulation techniques in the multidetector CT era : from basics to practice. RadioGraphics. 2008; 1451–59.
14. Zhao YX, Zuo ZW, Hong-Na Suo MM, et al. CT pulmonary angiography using automatic tube current modulation combination with different noise index with iterative reconstruction algorithm in different body mass index: image quality and radiation dose. Acad Radiol. 2016; 23: 1513–20.
15. Fu W, Tian X, Sturgeon GM, et al. CT breast dose reduction with the use of breast positioning and organbased tube current modulation. Med Phys. 2017; 44: 665–78.
16. Kim S, Yoshizumi TT, Frush DP, et al. Dosimetric characterisation of bismuth shields in CT: measurements and Monte Carlo simulations. Radiat Prot Dosimetry. 2009; 133: 105–10.
17. Sookpeng S, Martin CJ, Gentle DJ, et al. Relationships between patient size, dose and image noise under automatic tube current modulation systems. J Radiol Prot. 2014; 34: 103–23.
18. Chen JH, Jin EH, He W, et al. Combining automatic tube current modulation with adaptive statistical iterative reconstruction for low-dose chest CT screening. PLoS One. 2014; 9: e92414.
19. Shrimpton PC, Hillier MC, Meeson S, et al. Doses from computed tomography (CT) examinations in the UK – 2011 Review. Public Health England. 2014; 1–87.
20. Lee EJ, Lee SK, Agid R, et al. Comparison of image quality and radiation dose between fixed tube current and combined automatic tube current modulation in craniocervical CT angiography. Am J Neuroradiol. 2009; 30: 1754–9.
21. Dehairs M, Bosmans H, Desmet W, et al. Evaluation of automatic dose rate control for flat panel imaging using a spatial frequency domain figure of merit. Phys Med Biol. 2017; 62: 6610-30.
22. Wang J, Duan X, Christner J, et al. Bismuth shielding, organ-based tube current modulation, and global reduction of tube current for dose reduction to the eye at head CT . Radiology. 2012; 262: 191–8.
23. Mulkens TH, Bellinck P, Baeyaert M, et al. Use of an automatic exposure control mechanism for dose optimization in multi-detector row CT examinations: clinical evaluation. Radiology. 2005; 237: 213–23.
24. Curtis JR . Computed Tomography Shielding Methods: A Literatüre Review. Radiol Technol. 2010; 81: 428–36.
25. Brenner DJ and Elliston CD. Estimation radiation risks potentially associated with full-body CT screening. Radiology. 2004; 232: 735–8.
26. Kanal KM, Butler PF, Sengupta D, et al. U.S. Diagnostic Reference Levels and Achievable Doses for 10 Adult CT Examinations. Vol. 284, Radiology. 2017. p. 120–33.