Organ doses to adult patients for chest CT
- Department of Radiology and Radiological Science, Medical University of South Carolina, 96 Jonathan Lucas Street, MSC 323, Charleston, South Carolina 29425-3230 (United States)
Purpose: The goal of this study was to estimate organ doses for chest CT examinations using volume computed tomography dose index (CTDI{sub vol}) data as well as accounting for patient weight. Methods: A CT dosimetry spreadsheet (ImPACT CT patient dosimetry calculator) was used to compute organ doses for a 70 kg patient undergoing chest CT examinations, as well as volume computed tomography dose index (CTDI{sub vol}) in a body CT dosimetry phantom at the same CT technique factors. Ratios of organ dose to CTDI{sub vol} (f{sub organ}) were generated as a function of anatomical location in the chest for the breasts, lungs, stomach, red bone marrow, liver, thyroid, liver, and thymus. Values of f{sub organ} were obtained for x-ray tube voltages ranging from 80 to 140 kV for 1, 4, 16, and 64 slice CT scanners from two vendors. For constant CT techniques, we computed ratios of dose in water phantoms of differing diameter. By modeling patients of different weights as equivalent water cylinders of different diameters, we generated factors that permit the estimation of the organ doses in patients weighing between 50 and 100 kg who undergo chest CT examinations relative to the corresponding organ doses received by a 70 kg adult. Results: For a 32 cm long CT scan encompassing the complete lungs, values of f{sub organ} ranged from 1.7 (thymus) to 0.3 (stomach). Organs that are directly in the x-ray beam, and are completely irradiated, generally had f{sub organ} values well above 1 (i.e., breast, lung, heart, and thymus). Organs that are not completely irradiated in a total chest CT scan generally had f{sub organ} values that are less than 1 (e.g., red bone marrow, liver, and stomach). Increasing the x-ray tube voltage from 80 to 140 kV resulted in modest increases in f{sub organ} for the heart (9%) and thymus (8%), but resulted in larger increases for the breast (19%) and red bone marrow (21%). Adult patient chests have been modeled by water cylinders with diameters between {approx}20 cm for a 50 kg patient and {approx}28 cm for a 100 kg patient. At constant x-ray techniques, a 50 kg patient is expected to have doses that are {approx}18% higher than those in a 70 kg adult, whereas a 100 kg patient will have doses that are {approx}18% lower. Conclusions: We describe a practical method to use CTDI data provided by commercial CT scanners to obtain patient and examination specific estimates of organ dose for chest CT examinations.
- OSTI ID:
- 22096635
- Journal Information:
- Medical Physics, Vol. 37, Issue 2; Other Information: (c) 2010 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
Similar Records
The feasibility of a regional CTDI{sub vol} to estimate organ dose from tube current modulated CT exams
Comparison of patient specific dose metrics between chest radiography, tomosynthesis, and CT for adult patients of wide ranging body habitus