Doses Metrics and Patient Age in Ct

Abstract

The aim of this study was to investigate how effective dose and size-specific dose estimate (SSDE) change with patient age (size) for routine head and abdominal/pelvic CT examinations. Heads and abdomens of patients were modelled as a mass-equivalent cylinder of water corresponding to the patient 'effective diameter'. Head CT scans were performed at CTDIvol(S) of 40 mGy, and abdominal CT scans were performed at CTDIvol(L) of 10 mGy. Values of SSDE were obtained using conversion factors in AAPM Task Group Report 204. Age-specific scan lengths for head and abdominal CT scans obtained from the authors' clinical practice were used to estimate the dose-length product for each CT examination. Effective doses were calculated from previously published age- and sex-specific E/DLP conversion factors, based on ICRP 103 organ-weighting factors. For head CT examinations, the scan length increased from 15 cm in a newborn to 20 cm in adults, and for an abdominal/pelvic CT, the scan length increased from 20 cm in a newborn to 45 cm in adults. For head CT scans, SSDE ranged from 37.2 mGy in adults to 48.8 mGy in a newborn, an increase of 31 %. The corresponding head CT effective doses range from 1.4 mSv in adults to 5.2 mSv in a newborn, an increase of 270 %. For abdomen CT scans, SSDE ranged from 13.7 mGy in adults to 23.0 mGy in a newborn, an increase of 68 %. The corresponding abdominal CT effective doses ranged from 6.3 mSv in adults to 15.4 mSv in a newborn, an increase of 140 %. SSDE increases much less than effective dose in paediatric patients compared with adults because it does not account for scan length or scattered radiation. Size- and age-specific effective doses better quantify the total radiation received by patients in CT by explicitly accounting for all organ doses, as well as their relative radio sensitivity.

A Novel Liposomal Nanoparticle for the Imaging of Amyloid Plaque by Magnetic Resonance Imaging

“…However, their spatial resolution is limited by that of the PET modality, and is on the order of 5–10mm, limiting any anatomy-specific information available in the image. PET imaging also requires the use of radio-isotopes, and carries the risk of significant radiation: an amyloid PET scan is estimated to expose the patient to about 7mSv [1] of radiation dose, roughly equivalent to several CT scans (a typical head CT in an adult is about 2mSv [2]). Global distribution of the PET agents also remains a challenge due to their short half-life.…”

Size‐Specific Dose Estimates of Radiation Based on Body Weight and Body Mass Index for Chest and Abdomen‐Pelvic CTs

“…Because age is an easily obtainable factor, the correlation between age and d w was also assessed to determine whether age can be used as a d w surrogate to estimate SSDEs. Unfortunately, unlike [28], no significant correlation was observed between d w and age for chest and abdomen-pelvis CT, which is attributed to the lack of growth of d w with the increasing ages of adult patients. However, similar to previous results reported by Menke [20,25], we also found that both body weight and BMI strongly correlated with d w in chest and abdomen-pelvis, despite different populations in Asian-Pacific and European-American regions.…”

Consideration of the usefulness of a size-specific dose estimate in pediatric CT examination

“…In addition, the number of obese patients at our hospital is very small, and the effective dose calculated using SSDE was higher than that determined via the conventional method using CTDI vol alone in all cases (DLP). Given these results, when estimating the organ dose and effective dose for pediatric patients and the standard and thin body type patients, the SSDE-corrected value is less likely to underestimate the exposure dose than the conventional method using CTDI vol and DLP, making SSDE a very effective method [ 20 , 21 ].…”