Estimation of organ and effective doses from newborn radiography of the chest and abdomen

Radiation dose evaluation to organs in neonatal patients by field size during potable X-ray examination in incubators: A Monte Carlo simulation study

BACKGROUND

Neonatal patients located in incubators are exposed to as many as 159 radiographs until discharge. To reduce the dose exposed to the patient, factors that may cause unnecessary exposure to the patient were judged. When conducting portable X-rays of neonatal patients located in an incubator, it is not easy to determine the exact field size because collimation light is exposed on the acrylic plate, an incubator canopy, and the resulting shadow is reflected on the patient's body.

OBJECTIVE

This study aims to measure the organ dose exposed to the patient according to the field size when a portable radiograph is given to a neonatal patient in a neonatal intensive care unit (NICU) incubator.

METHODS

To identify the absorbed organ dose depending on the radiation field size during portable X-ray examination of neonatal patient, a Monte Carlo N-Particle (MCNP) simulation, a SpeckCalc program, and a neonatal phantom from the ICRP 89 are applied for the calculation. According to the minimal field size (MinFS) standards of the European Commission (EC), the smaller field size is intended to measure tightly from the top of the lung apices to the bottom of the genitals; a larger field size is also calculated by adding 6 cm in width and length.

RESULTS

Compared to the hospital C condition from the previous study, the larger and smaller field sizes are decreased by an average of 45% and 67%, respectively. Study results also show a 42% reduction in smaller field size compared to the larger field size.

CONCLUSION

When taking chest and abdomen radiographic images of neonatal patients in incubators, appropriate field sizes are required to prevent inappropriate dose absorption for non-thoracic organs.

Radiation dose reduction for chest radiography of infants in intensive care units using a high peak kilovoltage-technique

BACKGROUND

Chest radiography is an important tool in the care of infants in intensive care units. Image optimization must be monitored to minimize radiation exposure in this susceptible population.

OBJECTIVE

To examine the use of a high tube peak kilovoltage technique to achieve radiation dose reduction while maintaining adequate image quality.

MATERIALS AND METHODS

A retrospective study was conducted. Radiation doses of chest radiographs performed in the pediatric intensive care units in our institution were calculated. The radiographs were divided into two groups based on the value of the peak kilovoltage used: above and below 60 kilovolts (kV). Image quality was blindly assessed by two fellowship-trained pediatric radiologists. Air kerma, effective dose and quality score for the high versus the low peak kilovoltage group were compared and analyzed.

RESULTS

The study included 376 radiographs. One hundred and seven radiographs were performed using peak kilovoltage values equal to or above 60 kV and 269 radiographs were performed using values under 60 kV. The average air kerma for the lower peak kilovoltage group was 56.6 microgray (µGy) (30.7-81.9) vs. 22.9 µGy (11.8-34.4) for the higher peak kilovoltage group (P<0.0001). The mean difference in effective dose between the groups was 11.68 (P<0.0001). The mean difference for the quality score was 0.06 (±0.03, P=0.10), not statistically significant.

CONCLUSION

A high peak kilovoltage technique may enable a statistically significant radiation dose reduction without compromising the diagnostic value of the image.

Evaluation of radiation dose to organs of neonatal patients during portable X-ray examination in incubators: A Monte Carlo simulation study

BACKGROUND

Infants admitted to neonate intensive care units (NICUs) are placed in incubators to maintain body temperature and condition, which undergo normal radiographs and are exposed to radiation. Furthermore, different incubator structures in different hospitals exhibit varying object to image receptor distance (OID), source to image receptor distance (SID), presence of canopy, which results in variations in X-ray radiation conditions and doses absorbed by the neonatal patients.

OBJECTIVE

To measure organ dose exposed to neonatal patient in different incubator settings.

METHODS

A portable X-ray was performed on a neonatal patient placed in an incubator to identify disease progress, the injection path of the drug, and various factors. To minimize direct contact between neonatal patients and image receptor, radiologic technologists place the image receptor on a tray underneath the incubator and place the portable X-ray tube on top of the acrylic canopy of the incubators. SID and OID settings and value of organ dose exposed to the patient varied based on the incubator structure, and the organ absorbed dose was determined using Monte Carlo N-Particle (MCNP) simulation, PC-based Monte Carlo program (PCXMC) 2.0 simulation, and neonate phantoms.

RESULTS

Evaluations of organ dose of neonatal patients in three hospitals with different incubator settings reveal that the average organ dose differs by 36% depending on change in OID and SID settings and reduces by 10% with an acrylic canopy. Therefore, owing to the presence of an acrylic canopy on the top of the incubator and the longer SID with the corresponding shorter OID, a lower dose was absorbed by organs of neonatal patient.

CONCLUSION

Our results provide proof that proper incubator standard decreases organ dose to neonatal patient during continuously diagnostic X-ray procedure.

A COMPARATIVE STUDY OF ORGAN DOSES ASSESSMENT FOR PATIENTS UNDERGOING CONVENTIONAL X-RAY EXAMINATIONS: PHANTOM EXPERIMENTS VS. CALCULATIONS

A series of phantom experiments were performed with the aim of estimating organ doses for patients undergoing conventional X-ray chest and pelvis examinations. The experiments were performed using physical phantoms corresponding to an adult and a 5-year-old child. Mean organ doses and entrance surface dose were measured using TL-dosemeters. The measured organ doses were compared with the data obtained by calculations using available software tools (EDEREX and PCXMC 2.0) based on the computational MIRD-5 stylized models. The differences between calculated and measured doses for organs located fully or partly in the primary radiation beam did not exceed ±33% with the probability of 95% for the tube voltage 60-140 kV both for an adult and a 5-year-old child phantom. This study suggests that EDEREX and PCXMC 2.0 can be used to estimate organ and effective dose for adult as well as pediatric patients undergoing conventional X-ray examinations.

Excess Radiation to Newborns Hospitalized in the Intensive Care Unit

Newborns in intensive care units are generally subjected to a great number of X-rays procedures and to the risk of radiation-induced damage. This study evaluated a possible excess radiation by excess of radiographs, excess of dose per radiograph or under-collimation of the X-ray beam. The mean of X-rays per newborn was 12 (1-65) during a mean hospitalization of 29 d (1-226 d). The mean frequency was 0.8 X-ray exposures per newborn. About 13% of X-rays were performed without a well-defined clinical motivation. The mean entrance surface dose of 72 μGy was higher than in most of comparative studies. Under-collimation caused non-thoracic structures to appear frequently on chest radiographs. This study indicates a possible reduction in X-rays exposures by applying the justification principle for each X-ray procedure, recommends a multiprofessional work in the attempt to dose optimization, and shows need of correctly use of collimation system to avoid irradiation of non-thoracic structures.

Image quality and dose differences caused by vendor-specific image processing of neonatal radiographs

BACKGROUND

Image processing plays an important role in optimizing image quality and radiation dose in projection radiography. Unfortunately commercial algorithms are black boxes that are often left at or near vendor default settings rather than being optimized.

OBJECTIVE

We hypothesize that different commercial image-processing systems, when left at or near default settings, create significant differences in image quality. We further hypothesize that image-quality differences can be exploited to produce images of equivalent quality but lower radiation dose.

MATERIALS AND METHODS

We used a portable radiography system to acquire images on a neonatal chest phantom and recorded the entrance surface air kerma (ESAK). We applied two image-processing systems (Optima XR220amx, by GE Healthcare, Waukesha, WI; and MUSICA(2) by Agfa HealthCare, Mortsel, Belgium) to the images. Seven observers (attending pediatric radiologists and radiology residents) independently assessed image quality using two methods: rating and matching. Image-quality ratings were independently assessed by each observer on a 10-point scale. Matching consisted of each observer matching GE-processed images and Agfa-processed images with equivalent image quality. A total of 210 rating tasks and 42 matching tasks were performed and effective dose was estimated.

RESULTS

Median Agfa-processed image-quality ratings were higher than GE-processed ratings. Non-diagnostic ratings were seen over a wider range of doses for GE-processed images than for Agfa-processed images. During matching tasks, observers matched image quality between GE-processed images and Agfa-processed images acquired at a lower effective dose (11 ± 9 μSv; P < 0.0001).

CONCLUSION

Image-processing methods significantly impact perceived image quality. These image-quality differences can be exploited to alter protocols and produce images of equivalent image quality but lower doses. Those purchasing projection radiography systems or third-party image-processing software should be aware that image processing can significantly impact image quality when settings are left near default values.

Radiation doses for pregnant women in the late pregnancy undergoing fetal-computed tomography: a comparison of dosimetry and Monte Carlo simulations

The purposes of this study were (1) to compare the radiation doses for 320- and 80-row fetal-computed tomography (CT), estimated using thermoluminescent dosimeters (TLDs) and the ImPACT Calculator (hereinafter referred to as the "CT dosimetry software"), for a woman in her late pregnancy and her fetus and (2) to estimate the overlapped fetal radiation dose from a 320-row CT examination using two different estimation methods of the CT dosimetry software. The direct TLD data in the present study were obtained from a previous study. The exposure parameters used for TLD measurements were entered into the CT dosimetry software, and the appropriate radiation dose for the pregnant woman and her fetus was estimated. When the whole organs (e.g., the colon, small intestine, and ovaries) and the fetus were included in the scan range, the difference in the estimated doses between the TLD measurement and the CT dosimetry software measurement was <1 mGy (<23 %) in both CT units. In addition, when the whole organs were within the scan range, the CT dosimetry software was used for evaluating the fetal radiation dose and organ-specific doses for the woman in the late pregnancy. The conventional method using the CT dosimetry software cannot take into account the overlap between volumetric sections. Therefore, the conventional method using a 320-row CT unit in a wide-volume mode might result in the underestimation of radiation doses for the fetus and the colon, small intestine, and ovaries.