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YY/T 1821-2022 English PDF

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YY/T 1821-2022: Methods for calculating size specific dose estimates for computed tomography
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Basic data

Standard ID YY/T 1821-2022 (YY/T1821-2022)
Description (Translated English) Methods for calculating size specific dose estimates for computed tomography
Sector / Industry Medical Device & Pharmaceutical Industry Standard (Recommended)
Classification of Chinese Standard C43
Word Count Estimation 17,170
Issuing agency(ies) State Drug Administration

YY/T 1821-2022: Methods for calculating size specific dose estimates for computed tomography

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Methods for calculating size specific dose estimates for computed tomography ICS 11.040.50 CCSC43 People's Republic of China Pharmaceutical Industry Standard X-ray computed tomography equipment body size specific Dose Estimate Calculation Method tomography (IEC 62985.2019,MOD) Published on 2022-05-18 2023-12-01 Implementation Released by the State Drug Administration directory Preface III Introduction IV 1 Scope 1 2 Normative references 1 3 Terms and Definitions 1 4 Verification of DW(z) Calculation Method 3 4.1 Overview 3 4.2 Features of the water phantom 3 4.3 Features of phantom phantoms 3 4.4 Generation of DW, REF(z) of water phantom 3 4.5 Verification of DW and REF of water phantom 4 4.6 DW and IMP generation of water phantom 4 4.7 Verification of DW,IMP(z) against DW,REF(z) on the water phantom 4 4.8 Generation of DW, REF(z) mimicking phantom 4 4.9 Generation of DW and IMP imitating phantom 4 4.10 Validation of DW,IMP(z) against DW,REF(z) on a manikin 5 5 Requirements and Limitations 5 5.1 Calculation of SSDE and DW for CT Scanner, RDIMS 5 5.2 Pre-scan display of SSDE on CT scanning device 5 5.3 Post-scan update of SSDE and DW on CT scanners5 5.4 Display of pre-scan and post-scan SSDE and DW values on the CT scanner 5 5.5 Recording of pre-scan and post-scan SSDE and DW values on the CT scanning device 5 5.6 Calculation and display limitations of SSDE 6 5.7 Requirements for indicating restrictions in accompanying documents6 5.8 Update SSDE conversion factor f 6 Appendix A (normative) SSDE conversion factor 7 A.1 Clarification on Use of Effective Diameter and DW7 A.2 Equation 7 for determining the SSDE conversion factor Appendix B (normative) for accompanying documents using general restrictive language on SSDE methodology9 Appendix C (Informative) Estimation of Uncertainty Margins in Special Clinical Scenarios10 C.1 Overview 10 C.2 Scanning Anatomy Including Neck 10 C.3 Exceeding the range of scanning projection flat film 10 C.4 Unilateral or bilateral extremity scan10 C.5 The patient is not placed in the center of the source/detector rotation direction 10 C.6 The patient's anatomy is outside the scanning field of view 11 C.7 Scanning Projection Patches or Scan Volumes Containing External Targets 11 Reference 12

foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for Standardization Work Part 1.Structure and Drafting Rules of Standardization Documents" drafted. This document uses the redrafted method to modify the use of IEC 62985.2019 "Size-specific doses for X-ray computed tomography equipment Estimated Value Calculation Method.” The technical differences between this document and IEC 62985.2019 and their reasons are as follows. --- Regarding normative reference documents, this document has made adjustments with technical differences to adapt to the technical conditions of our country and the circumstances of the adjustment. The situation is reflected in Chapter 2 "Normative References", and the specific adjustments are as follows. ● Replacing IEC 60601-1 with GB 9706.1 modified to adopt international standards; ● Replacing IEC 60601-1-3 with GB 9706.103 which has been modified to adopt international standards; ● Replacing IEC 60601-2-44 with GB 9706.244 which has been modified to adopt the international standard. The following editorial changes have been made to this document. --- Added numbers to formulas; --- Scope has been sequentially adjusted and editorially revised. Please note that some content of this document may be patented. The issuing agency of this document assumes no responsibility for identifying patents. This document is proposed by the State Drug Administration. This document is approved by the National Medical Electrical Equipment Standardization Technical Committee Medical X-ray Equipment and Appliances Sub-Technical Committee (SAC/TC10/ SC1) focal point. This document was drafted by. Kuanteng (Beijing) Medical Equipment Co., Ltd., Shanghai Siemens Medical Equipment Co., Ltd., Philips Medical (Suzhou) State) Co., Ltd. Shenyang Branch, Liaoning Provincial Medical Device Inspection and Testing Institute. The main drafters of this document. Xing Zhanfeng, Tian Yi, Liang Jian, Xianghuicai, Cai Xiaolu, Huang Kelei, Meng Zhaoyang.

Introduction

The size-specific dose estimate (SSDE) is based on the attenuation of X-rays by the scanned organ (using the water equivalent diameter) and the CT scan. The radiation output of the scanning device (using CTDIVOL) was used to estimate an estimate of the mean absorbed dose over the scanned volume. The purpose of SSDE is to provide a dose estimate for patients of all body sizes. SSDE in mGy for small children Patients are especially important because the corresponding radiation level used (CTDIVOL is also given in mGy) is not sufficient to indicate its absorption dose. SSDE is calculated using the SSDE conversion factor (f) at longitudinal position z and CTDIVOL, CTDIVOL(z) at longitudinal position z to, where f is a function of the water-equivalent diameter DW(z) at longitudinal position z and the size of the CTDI phantom used to report CTDIVOL. f are given in Appendix A. This document provides a method (in Chapter 4) for manufacturers to verify their method of calculating DW(z), which is used to determine f and calculated Count SSDE. This method calculates the water-equivalent diameter DW,REF(z) at the reference longitudinal position z and compares it with the known phantom dimensions and The achieved water-equivalent diameter at longitudinal position z, DW,IMP(z) is compared. The phantom type and allowable error are also specified. Note 1.The definition of SSDE used in this document differs from AAPM Report 204 [1], which estimates the flatness at the center of the scan volume. mean dose, whereas in this paper SSDE estimates the mean dose over the entire scan volume. Note 2.CTDIVOL is a dose index that allows quantification of the radiation output of a CT scanning device according to one of two PMMA test objects. These two tests The diameters of the test subjects were 16 cm and 32 cm, respectively. SSDE works by transforming a dose index based on one of these motifs into a specific body type of patient An estimate of the absorbed radiation dose is calculated. The magnitude of the difference in SSDE and CTDIVOL varies with patient size and the value used to measure CTDIVOL The differences in CTDI phantom size increased with increasing size. For infants, the calculated SSDE value may reach the corresponding CTDIVOL dose index value 3 times. Conversely, CTDIVOL values for large patients may overestimate the SSDE value, which represents the patient's actual absorbed radiation dose. for In oversized adult patients, the CTDIVOL dose index may overestimate SSDE by up to 40% [1]. Potential applications of SSDE include the following. a) used in the quality assurance process to assess patient absorbed dose; b) Establish diagnostic reference levels for patients of different body types; c) display the estimated patient absorbed dose to the operator before starting the CT scan; d) provide an estimate of absorbed dose to DICOMRDSR; e) Investigate dose-indicating values and dose-warning values that take patient size into consideration; f) Provide an estimate of patient absorbed dose for a unified dose record. X-ray computed tomography equipment body size specific Dose Estimate Calculation Method

1 Scope

This document specifies the size-specific dose estimates for calculating, displaying or recording size-specific dose estimates, size-specific dose estimates at longitudinal position z Standardized methods and requirements for calculated values, water equivalent diameters, and water equivalent diameters at longitudinal position z The CT scan data of two cylindrical water phantoms and one or more simulated human phantoms specified by the piece determine the reference water at the longitudinal position z, etc. The method for effective diameter, for the method implemented by the manufacturer to calculate the water equivalent diameter at the longitudinal position z, by using the method specified in this document The measurement object and method are tested and confirmed by comparison with the reference water equivalent diameter at the longitudinal position z. This document applies to CT scanning devices capable of displaying and reporting CTDIvol in accordance with the requirements of GB 9706.244, as well as radiation dose indicators Data monitoring software (RDIMS) was used for its calculation, display and recording of size-specific dose estimates (SSDE) and their associated parameters. NOTE. This normalization is important to ensure comparability between reported SSDE values.

2 Normative references

The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, dated citations documents, only the version corresponding to that date applies to this document; for undated references, the latest edition (including all amendments) applies to this document. GB 9706.1 Medical Electrical Equipment Part 1.General Requirements for Basic Safety and Basic Performance (GB 9706.1-2020, IEC 60601-1.2012, MOD) GB 9706.103 Medical Electrical Equipment Part 1-3.General Requirements for Basic Safety and Essential Performance Collateral Standard. Diagnosis X Radiation protection of radiation equipment (GB 9706.103-2020, IEC 60601-1-3.2013, MOD) GB 9706.244 Medical Electrical Equipment Part 2-44.Basic Safety and Basic Performance of X-ray Computed Tomography Equipment Special requirements (GB 9706.244-2020, IEC 60601-2-44.2016, MOD) finedterms)

3 Terms and Definitions

The terms and definitions defined in GB 9706.1, GB 9706.103, GB 9706.244, IEC /T R60788 and the following apply to this document. 3.1 CTDIVOL(z) A quantified value of the radiation output at a certain z-position for the selected CT operating condition. 3.2 reconstruction length reconstructionlength The distance between the center position of the first reconstructed image and the center position of the last reconstructed image, where the first and last images The center of the reconstructed image is as far away as possible given the CT operating conditions of the protocol unit and the width of the reconstructed image, essentially is the maximum extent of the reconstructed image over that scan range for a given reconstructed slice thickness.

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