Evaluation of organ doses in CT examinations with an infant anthropomorphic phantom

DEVELOPMENT OF A JAPANESE INFANT HEAD-CHEST PHANTOM AND INVESTIGATION OF THE CURRENT STATUS OF INFANT HEAD CT EXAMINATIONS IN JAPAN

The aim of this study was to develop a head-chest phantom that could mimic the physique of a Japanese 0.5-year-old child and to investigate the current status of exposure dose in infant head computed tomography examinations in Japan. The phantom was produced by machine processing, and radiophotoluminescence glass dosemeters were installed in the phantom for dose measurement. Organ doses were measured for seven different head scan protocols routinely used in three hospitals. In this study, the average dose of the brain and lens within the scan region was equivalent to that measured using infant phantoms in previous studies. In contrast, the doses of both salivary glands and thyroid glands adjacent to the scan region were 1.4-1.8 times higher than those in previous studies. Expansion of the scan area accompanied by a transition of the scan mode from non-helical to helical may have resulted in the differences in organ doses.

Radiation doses with various body weights of phantoms in brain 128-slice MDCT examination

The effective dose (HE) and organ or tissue equivalent dose (HT) for use in brain computed tomography (CT) examinations with various body weights were evaluated. Thermoluminescent dosimeters (TLD-100H) were inserted into Rando and five anthropomorphic phantoms. These phantoms were made of polymethylmethacrylate (PMMA), according to the specifications of ICRU 48, with masses from 10 to 90 kg. Brain CT examinations were conducted, scanning the maxillae from the external auditory meatus to the parietal bone using a 128-slice multi-detector CT (MDCT) scanner. To reduce errors, three independent trials were conducted. Calculated HE,TLD, based on the weighting factor recommended by ICRP 103, was 1.72 ± 0.28 mSv, which slightly exceeds the HE,DLP of 1.70 mSv, that was calculated from the dose-length product (DLP) of the Rando phantom. This experiment yielded HE,TLD values of ICRP 103 from the highest 1.85 ± 0.28 (90 kg) to the lowest 1.47 ± 0.22 (10 kg) mSv. HE,TLD (mSv) = 5.45×10-3 W(kg) + 1.361, with an R2 of 0.87667. Using the DLP protocol, HE,DLP was estimated from CTDIvol that was recorded directly from the console display of the CT unit and multiplied by the conversion coefficient (k) recommended by the ICRP 103. Finally, the experimental results obtained herein are compared with those in the literature. Physicians should choose and adjust protocols to prevent the exposure of patients to unnecessary radiation, satisfying the as low as reasonably achievable (ALARA) principle. These findings will be valuable to patients, physicians, radiologists and the public.

A survey of pediatric CT doses in the Shanghai metropolitan area

The purpose of this study was to evaluate computed tomography (CT) doses in child examinees at different ages throughout the Shanghai metropolitan area. The head and body CT dose indices (CTDIs) of 50 CT scanners were tested by phantom measurements using standard imaging protocols. The values of CTDI_w, CTDI_vol and dose length product (DLP) were calculated and saved in a table along with the parameters of routine head and chest scans for different age groups of children and adults. The effective doses were estimated from the K-factors by age and DLP. The CTDI_vol, DLP and effective dose for multi-detector row CT (MDCT) in children during routine head scans were larger than those for single-detector row CT (SDCT) and dual-detector row CT (DDCT). The CTDI_vol, DLP and effective dose for MDCT and DDCT in children during routine chest scans were lower than those for SDCT. Radiation risks are higher for children in CT examinations compared to adults.

PEDIATRIC HEAD CT EXPOSURE DOSES IN TUNISIA: A PILOT STUDY TOWARDS THE ESTABLISHMENT OF NATIONAL DIAGNOSTIC REFERENCE LEVELS

The purpose of this study was to assess and analyze the radiation doses during head pediatric CT from different CT units within six Tunisian hospitals representing different geographic regions in order to optimize the dose given and minimize the radiology risk to this category of patients and towards the derivation of national diagnostic reference levels. Patient data and exposure parameters were collected for four age groups (<1, 1-5, 5-10 and 10-15 y). Clinical protocols and exposure settings were analyzed. Doses were collected in terms of CTDIvol and DLP values. Effective and Organ doses to specific radiosensitive organs were estimated using the Monte Carlo simulation software 'Impact CTDosimetry'. Results showed large variations in CT protocols and doses between different radiology departments. CTDIvol and DLP values demonstrated a broad range between the CT units and between the axial and helical scan techniques in the same unit. CTDI vol values were estimated to be 24.9, 31.7, 45.5 and 47.8 mGy for <1, 1-5, 5-10 and 10-15 y age groups, respectively. In term of DLP, median values were ~346, 528, 824, 897 mGy cm for the same age groups, respectively. Effective dose ranged from 1.4 to 5 mSv. Dose values were comparable with those reported in the literature. The study shows an evident need for continuous training of staff in radiation protection concepts, especially within the regional hospitals, emphasizes the importance of the production and the update of recommendations and good practice guidelines using interdisciplinary working groups and opens the way for the establishment of national DRLs.

EOS Micro-dose Protocol: First Full-spine Radiation Dose Measurements in Anthropomorphic Phantoms and Comparisons with EOS Standard-dose and Conventional Digital Radiology

STUDY DESIGN

A comparative study of radiation dose measured in anthropomorphic phantoms.

OBJECTIVES

The aim of this study was to first report the first organ dose and effective dose measurements in anthropomorphic phantoms using the new EOS imaging micro-dose protocol in full-spine examinations, and to compare these measurements of radiation dose to measurements in the EOS standard-dose protocol and conventional digital radiology (CR).

SUMMARY OF BACKGROUND DATA

Few studies evaluating organ dose and effective dose for the EOS low-dose scanner exist, and mainly for the standard-dose protocol. To the best of our knowledge, no studies of effective dose based on anthropomorphic phantom measurements exist for the new micro-dose protocol.

METHODS

Two anthropomorphic phantoms, representing a 5-year-old (pediatric) and a 15-year-old (adolescent). The phantoms were exposed to EOS micro-dose and standard-dose protocols during full-spine imaging. Additionally, CR in scoliosis settings was performed. For all modalities, organ doses were measured and effective doses were calculated using thermoluminescent dosimeters.

RESULTS

We found a 17-fold reduction (94%) of effective dose in micro-dose protocol compared with our CR system in the adolescent phantom. Micro-dose versus standard-dose protocol, showed a 6-fold reduction (83%), and for standard-dose versus our CR system a 2.8-fold reduction (64%) reduction of effective dose was observed.For the pediatric phantom, a 5-fold reduction (81%) of effective dose in micro-dose protocol compared to our CR system was observed. Micro-dose versus standard-dose protocol, showed a seven-fold (86%) reduction. However, we observed an increase in absorbed dose of 38% when comparing the EOS standard-dose protocol with our CR system.

CONCLUSION

The EOS imaging micro-dose option exposes patients to lower radiation doses than any currently available modality for full-spine examination. Expected reduction of dose was established for the adolescent phantom when comparing CR and standard-dose protocol. However, no reduction of effective dose with EOS standard-dose protocol compared to our reference CR system was observed in the pediatric phantom.

LEVEL OF EVIDENCE

N/A.

Estimation of Organ and Effective Doses for Neonate and Infant Diagnostic Cardiac Catheterizations

OBJECTIVE

Radiation exposure to neonates and infants during cardiac catheterizations is an important issue. Smaller patient size and higher heart rate in these patients result in a greater need for magnification modes and higher frame rates, all of which contribute to a significant increase in radiation doses. The aims of our study were to evaluate organ and effective doses for neonates and infants during diagnostic cardiac catheterizations on the basis of in-phantom dosimetry and conversion factors from dose-area product (DAP) to the effective dose.

MATERIALS AND METHODS

Organ doses for 0- and 1-year-old children during diagnostic cardiac catheterizations were measured by radiophotoluminescence glass dosimeters implanted in neonate and infant anthropomorphic phantoms. The effective doses were evaluated according to recommendations of the International Commission on Radiologic Protection (ICRP) publication 103.

RESULTS

The mean effective doses evaluated according to ICRP 103 were 7.7 mSv (range, 0.1-18.4 mSv) for a neonate and 7.3 mSv (range, 1.9-18.6 mSv) for an infant. Conversion factors from DAP to the effective dose were 2.2 and 4.0 in posteroanterior and lateral cine angiography, respectively, for a neonate and 1.4 and 2.7 in posteroanterior and lateral cine angiography, respectively, for an infant.

CONCLUSION

The dose data and conversion factors evaluated in this study could be useful for the estimation of radiation exposure in neonates and infants during diagnostic cardiac catheterization.

Evaluation of organ doses in adult and paediatric CT examinations based on Monte Carlo simulations and in-phantom dosimetry

The aim of this study was to validate the computed tomography dose index (CTDI) and organ doses evaluated by Monte Carlo simulations through comparisons with doses evaluated by in-phantom dosimetry. Organ doses were measured with radio-photoluminescence glass dosemeter (RGD) set at various organ positions within adult and 1-y-old anthropomorphic phantoms. For the dose simulations, the X-ray spectrum and bow-tie filter shape of a CT scanner were estimated and 3D voxelised data of the CTDI and anthropomorphic phantoms from the acquired CT images were derived. Organ dose simulations and measurements were performed with chest and abdomen-pelvis CT examination scan parameters. Relative differences between the simulated and measured doses were within 5 % for the volume CTDI and 13 % for organ doses for organs within the scan range in adult and paediatric CT examinations. The simulation results were considered to be in good agreement with the measured doses.

Development of age-specific Japanese head phantoms for dose evaluation in paediatric head CT examinations

In this study, the authors developed age-specific physical head phantoms simulating the physique of Japanese children for dose evaluation in paediatric head computed tomography (CT) examinations. Anatomical structures at 99 places in 0-, 0.5-, 1- and 3-y-old Japanese patients were measured using DICOM viewer software from CT images, and the head phantom of each age was designed. For trial manufacture, a 3-y-old head phantom consisting of acrylic resin and gypsum was produced by machine processing. Radiation doses for the head phantom were measured with radiophotoluminescence glass dosemeters and Si-pin photodiode dosemeters. To investigate whether the phantom shape was suitable for dose evaluation, organ doses in the same scan protocol were compared between the 3-y-old head and commercially available anthropomorphic phantoms having approximately the same head size. The doses of organs in both phantoms were equivalent. The authors' designed paediatric head phantom will be useful for dose evaluation in paediatric head CT examinations.

Comparison of radiation doses between newborns and 6-y-old children undergoing head, chest and abdominal CT examinations: a phantom study

Radiation doses in paediatric computed tomography (CT) were investigated for various types of recent CT scanners with newborn and 6-y-old phantoms in which silicon-photodiode dosemeters were implanted at various organ positions. In the head, chest and abdominal CT for the newborn phantom, doses for organs within the scan region were 21-40, 3-8 and 3-12 mGy, respectively. The corresponding doses for the child phantom were 20-37, 2-11 and 4-17 mGy, respectively. In the head, chest and abdominal CT, the effective doses were respectively 2.1-3.3, 2.0-6.0 and 2.2-10.0 mSv for the newborn, and 1.0-2.0, 1.2-6.6 and 2.9-11.8 mSv for the child. Radiation doses for the newborn were at the same levels as those for the child, excepting effective doses in head CT for the newborn, which were 1.8 times higher than those for the child.

Prenatal diagnosis of fetal skeletal dysplasia with 3D CT

BACKGROUND

Clinical use of 3D CT for fetal skeletal malformations is controversial.

OBJECTIVE

The purpose of this study was to evaluate the efficacy of fetal 3D CT using three protocols with different radiation doses and through comparing findings between fetal CT and conventional postnatal radiographic skeletal survey.

MATERIALS AND METHODS

Seventeen fetuses underwent CT for suspected skeletal dysplasia. A relay of three CT protocols with stepwise dose-reduction were used over the study period. The concordance between the CT diagnosis and the final diagnosis was assessed. Ninety-three radiological findings identifiable on radiographs were compared with CT.

RESULTS

Fetal CT provided the correct diagnosis in all 17 fetuses, the detectability rate of cardinal findings was 93.5 %. In 59 % of the fetuses an US-based diagnosis was changed prenatally due to CT findings. The estimated fetal radiation dose in the final protocol was 3.4 mSv (50 %) of the initial protocol, and this dose reduction did not result in degraded image quality.

CONCLUSION

The capability of fetal CT to delineate the skeleton was almost the same as that of postnatal skeletal survey. The perinatal management was altered due to these more specific CT findings, which aided in counseling and in the management of the pregnancy.