Optimizing CT Image Quality Online Training - Part 1 - CT Dose - OUS

Optimizing CT Image Quality CT Dose     Walter Huda, PhD Professor of Radiology Medical University of South Carolina     CT Dose Index [CTDI] CTDI & X-ray Techniques CTDI & Patient Dose Acrylic Cylindrical Phantom adsg Hole locations in center and periphery... ... for placement of pencil-shaped ionization chamber. CTDIvol DLP (Dose Length Product) CTDI volume measured in mGy (CTDIvol) Depends on: X-ray tube voltage (kV)   X-ray tube current (mA) X-ray tube rotation time (s) CT Pitch (P) Phantom Size (S or L) CTDIvol 15 mGy Independent of Scan Length DLP = CTDIvol x Scan Length (units are expressed in mGy-cm) CTDIvol - Radiation Intensity   DLP - Total Radiation Used Source? — — 400 mAs 60 mGy @ 120 kV 21 mGy @ 80 kV CTDIvol is a Universal Metric Regardless of: Voltage (kV) X-ray filter Model type Vendor Phantom Size mAs (axial) Effective mAs (helical) Voltage (kV) 16 cm (S) 32 cm (L) Measurements taken with a large phantom will be half the value of those taken with a small phantom. CTDIvol (S) 60 mGy CTDIvol (L) 11 mGy CTDIvol (L) 11 mGy   ↵ CTDIvol (S) 60 mGy CTDIvol (S) 22 mGy   ↵ CTDIvol (S) 60 mGy CTDIvol is directly proportional to: Tube current (mA) Tube rotation time (s) mAs CTDIvol is: directly proportional to tube current (mA) directly proportional to tube rotation time (s) inversely proportional to pitch directly proportional to the effective mAs           - Effective mAs = mAs / Pitch CTDIvol ∞ kV 2.6 80 kV  ► 140 kV CTDI Increases >400% CTDIvol is the radiation incident on the Patient NOT the patient dose CTDIvol = 20 mGy Organ Dose Total CTDIvol (i.e., Incident Radiation) Patient Size Factor Scan Length Factor Embryo Dose Estimates in Body CT Huda et al. American Journal Roentgenology 194 (2010) 874-880 Abdomen/Pelvic Scan (Pregnant) CTDIvol is 20 mGy Normal-sized patient Absorbed Dose to Fetus = 28 mGy + Chest Scan no significant change to fetal dose but DLP is increased Organ Doses are obtained from CTDIvol Total Dose (Effective Dose) is related to Dose Length Product (DLP) Effective Dose (mSv) North American Natural Background Radiation ~ 3 mSv/Year Cosmic - 12% Terrestial - 12% Internal - 16% Radon - 60% Effective Dose (E) = Dose Length Product (DLP)  X  k factor (k) CT effective dose per dose length product W. Huda, D. Magill Medical Physics - Volume 38, March 2011, pp 1261-1265 Adult Head CT Exam CTDIvol: 60 mGy DLP: 1000 mGy-cm x   k [0.002 mSv/mGy-cm] ____________________ 2 mSv - Effective Dose One Year-old Head CT Exam CTDIvol: 30mGy DLP: 360 mGy-cm x   k [0.005 mSv/mGy-cm] ____________________ 1.8 mSv - Effective Dose Adult Chest CTDIvol: 7.5 mGy DLP: 150 mGy-cm x   k [0.02 mSv/mGy-cm] x   k [0.02 mSv/mGy-cm] ____________________ 0.02 mSv - Effective Dose Adult Body Size Correction Fixed CTDIvol and DLP CT Dose Index (CTDI) CTDIvol is “Radiation Intensity” DLP is the total amount of radiation used to perform a CT scan (NOT patient dose). CTDI & X-ray Techniques CTDIvol directly proportional to mAs (axial), effective mAs (helical) and kV 2.6 CTDI & Patient Dose Total CTDIvol → Organ Dose Total DLP → Effective Dose Please note that the learning material is for training purposes only! For the proper use of the software or hardware, please always use the Operator Manual or Instructions for Use (hereinafter collectively “Operator Manual”) issued by Siemens Healthineers. This material is to be used as training material only and shall by no means substitute the Operator Manual. Any material used in this training will not be updated on a regular basis and does not necessarily reflect the latest version of the software and hardware available at the time of the training. The Operator Manual shall be used as your main reference, in particular for relevant safety information like warnings and cautions. Note: Some functions shown in this material are optional and might not be part of your system. The information in this material contains general technical descriptions of specifications and options as well as standard and optional features that do not always have to be present in individual cases. Certain products, product related claims or functionalities described in the material (hereinafter collectively “Functionality”) may not (yet) be commercially available in your country. Due to regulatory requirements, the future availability of said Functionalities in any specific country is not guaranteed. Please contact your local Siemens Healthineers sales representative for the most current information. The reproduction, transmission or distribution of this training or its contents is not permitted without express written authority. Offenders will be liable for damages. All names and data of patients, parameters and configuration dependent designations are fictional and examples only. All rights, including rights created by patent grant or registration of a utility model or design, are reserved. Copyright © Siemens Healthcare GmbH, 2018 Please proceed to the Assessment.