Embryo dose estimates in body CT.
AJR Am J Roentgenol
; 194(4): 874-80, 2010 Apr.
Article
em En
| MEDLINE
| ID: mdl-20308485
ABSTRACT
OBJECTIVE:
The purpose of this article is to develop a method for estimating embryo doses in CT. MATERIALS ANDMETHODS:
Absorbed doses to the uterus (embryo) of a 70-kg woman were estimated using the ImPACT CT Patient Dosimetry Calculator. For a particular CT scan length, relative uterus doses and normalized plateau uterus doses were determined for a range of commercial CT scanners. Patient size characteristics were obtained from cross-sectional axial images of 100 consecutive patients (healthy women undergoing unenhanced pelvic CT examinations). For each patient, the diameter of a water cylinder with the same mass as the patient's pelvis was computed. Relative dose values were generated for cylinder diameters ranging from 16 to 36 cm at x-ray tube voltages between 80 and 140 kV.RESULTS:
Values of relative uterus dose increased monotonically with increasing scan length, independently of scanner model, and reached a plateau for scan lengths greater than approximately 50 cm. The average normalized plateau uterus dose for all scanners was approximately 1.4 and showed interscanner differences of less than 10% for modern scanners operated at 120 kV. Normalized plateau doses show little dependence on the x-ray tube voltage used to perform the CT examination. Our results show that the uterus dose estimate in an abdominal or pelvis CT examination performed on a 70-kg patient is about 40% higher than the reported value of the volume CT dose index (CTDI(vol)). The pelvis of a 70-kg patient may be modeled as a water cylinder with a diameter of 28 cm and has an average anteroposterior dimension of 22 cm. For constant CT technique factors, embryo dose estimates for a 45-kg patient would be approximately 18% higher than those for a 70-kg patient, whereas the corresponding dose estimates in a 120-kg patient would be approximately 37% lower.CONCLUSION:
Embryo doses can be estimated using relative uterus doses, normalized plateau uterus doses, and CTDI(vol) data with correction factors for patient size.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Doses de Radiação
/
Útero
/
Imagem Corporal Total
/
Feto
Tipo de estudo:
Health_economic_evaluation
/
Prognostic_studies
Limite:
Female
/
Humans
/
Pregnancy
Idioma:
En
Revista:
AJR Am J Roentgenol
Ano de publicação:
2010
Tipo de documento:
Article
País de afiliação:
Estados Unidos