Evaluation of the Dose Index using Cone-Beam Computed Tomography for Pediatric Patients

A. Lisovskaya; A. Loginova; K. Galich; V. Belyaev; A. Nechesnyuk

doi:doi:10.12737/article_5c0e7486915d55.10064971

UDC 61 CSCSTI 76.03 CSCSTI 76.33 Russian Classification of Professions by Education 14.04.02 Russian Classification of Professions by Education 31.06.2001 Russian Classification of Professions by Education 31.08.08 Russian Classification of Professions by Education 32.08.12 Russian Library and Bibliographic Classification 51 Russian Library and Bibliographic Classification 534 Russian Trade and Bibliographic Classification 5708 Russian Trade and Bibliographic Classification 5712 Russian Trade and Bibliographic Classification 5734 Russian Trade and Bibliographic Classification 6212

Evaluation of the Dose Index using Cone-Beam Computed Tomography for Pediatric Patients

Published в Medical Radiology and radiation safety · Volume 63, Issue 6, 2018 · Pages 65–70 · Rubrics: Radiation physics, technology and dosimetry

DOI 10.12737/article_5c0e7486915d55.10064971

Received: 17.11.2018 Accepted: 10.12.2018 Published: 10.12.2018 Language of publication: RUS

Authors

A. Lisovskaya ¹ · A. Loginova ² · K. Galich ³ · V. Belyaev ⁴ · A. Nechesnyuk ⁵

1 Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (Medical Physicist)
, National Research Nuclear University MEPhI
Russian Federation

2 Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (Senior Medical Physicist)
Russian Federation

3 National Research Nuclear University MEPhI
Russian Federation

4 National Research Nuclear University MEPhI (Professor)
Russian Federation

5 Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (Head of Department)
Russian Federation

ABSTRACT

Purpose: Cone-beam computed tomography (CBCT) is an indispensable procedure for accurate patient positioning during radiation therapy (RT) in many clinical cases. However, the patients get an additional dose using CBCT. This dose is neither therapeutic nor diagnostic. It is very difficult to obtain the reliable information about the dose distribution within the patient using the CBCT. Despite this, there is a need to control the additional dose for the pediatric patients and reduce it. There are different approaches of imaging dose evaluation. Most accurate methods are based on the Monte-Carlo calculation and thermoluminescent dosimeters-based measurements. However, the implementation of these methods is complex and cumbersome, that makes impossible their application in routine clinical practice. The evaluation of dose indexes is an accessible and convenient alternative. The purpose of this study is evaluation of the cone beam computed tomography dose indexes for different imaging protocols and object sizes. Material and methods: The technique based on absolute and relative dose measurements for CBCT was used in this study. Absolute dose measurements were performed at the periphery and center of the FREEPOINT (CIRS) phantom using the Farmer type chamber FC65-P for each CBCT protocols. FREEPOINT (20 cm height, 30 cm width, 30 cm length) was used for imitation big chest and pelvis. Inner insert (16 cm diameter) of the phantom was used for imitation head, small chest and pelvis. The dose profiles were measured using I’mRT MatriXX (IBA) and analyzed by OmniPro-I’mRT software, dose indexes DLP (dose–length product) were calculated. Results: The dose indexes were identified for five protocols corresponding three scanning areas (Head and Neck, Chest and Pelvis). The dose indexes were 51.82 and 90.25 mGy×cm using Head and Neck S20 and Head and Neck M20 protocols respectively. The lowest dose index was obtained 13.28 mGy×cm for Fast Head and Neck S20. It was established that the scanning object size strongly affects on the dose index values and, as result, on the absorbed dose within the patient. The dose indexes were 305.42 and 187.53 mGy×cm using scanning protocol Chest M20 for small and big phantoms respectively. The similar results were obtained for scanning protocol Pelvis M15. The highest dose index was obtained 846.93 mGy×cm for the small phantom, while the dose index was 563.79 mGy×cm for the big phantom. The necessity of several clinical protocols to scan different areas was shown. Using of the Pelvis M15 protocol for head scanning may increase the additional point dose 96 times in comparison with Fast Head and Neck S20 protocol. Conclusion: The dose indexes were evaluated taking into account the size of the scanning object for different imaging protocols. Routine use of CBCT in clinical practice requires a sensible choice of the scanning protocol based on the results of the dose index estimation.

KEYWORDS

IGRT CTCB dose index scanning protocols visualization dose

Information References

Authors:

1. Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (Medical Physicist)

National Research Nuclear University MEPhI

Russian Federation

2. Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (Senior Medical Physicist)

Russian Federation

3. National Research Nuclear University MEPhI

Russian Federation

4. National Research Nuclear University MEPhI (Professor)

Russian Federation

5. Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (Head of Department)

Russian Federation

Type:

Article

Pages:

from 65 to 70

Status:

Published

Subject area:

UDC 61
CSCSTI 76.03
CSCSTI 76.33
Russian Classification of Professions by Education 14.04.02
Russian Classification of Professions by Education 31.06.2001
Russian Classification of Professions by Education 31.08.08
Russian Classification of Professions by Education 32.08.12
Russian Library and Bibliographic Classification 51
Russian Library and Bibliographic Classification 534
Russian Trade and Bibliographic Classification 5708
Russian Trade and Bibliographic Classification 5712
Russian Trade and Bibliographic Classification 5734
Russian Trade and Bibliographic Classification 6212

Language:

Russian, English

Keywords:

IGRT, CTCB, dose index, scanning protocols, visualization dose

References

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