Evaluation of image quality, organ doses, effective dose, and cancer risk from pediatric brain CT scans.

PURPOSE: The present study was conducted to assess organ doses, effective dose, and image quality, and to estimate the risk of exposure-induced cancer death (REID) in pediatric brain computed tomography examinations. METHODS: This investigation was performed on 179 pediatric patients (99 men and 80 women) under 12 years old who underwent non-contrast brain CT scans. Patients were classified into four age groups of ≤ 1, 2-5, 6-9, and 10-12 years old. Organ doses and effective doses were calculated using the ImpactDose program. Cancer risk models presented in the BEIR VII report were used to estimate REID values. Image quality assessment in this study was performed by measuring image quality parameters such as noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). RESULTS: The highest organ dose in all age groups belonged to the brain. The mean REID values were 12.34 per 100,000 males and 16.77 per 100,000 females. REID values decreased with the increasing age of patients in both genders and were higher for female children than male children. The mean SNR of gray matter, SNR of white matter, and CNR were 11.04, 10.5, and 2.31, respectively. CONCLUSIONS: According to the results of this study, brain CT scans in children are associated with an increased potential risk of cancer. Therefore, minimizing unnecessary radiation exposure in pediatric patients and using alternative imaging modalities are of particular importance. Moreover, optimizing the radiation parameters while maintaining the diagnostic image quality in children should be considered.

Assessment of radiation treatment chain for cervical cancer with combined external and brachy radiation therapy.

UNLABELLED: Performing radiotherapy of cervical cancer by combined external radiotherapy and brachytherapy includes several stages. Inaccuracy of each stage may cause insufficient dose delivery and produce complications in neighboring radiosensitive organs. In this study a technique was developed in order to assure the quality of treatment delivery. METHOD: A solid pelvic phantom was designed and fabricated for simulation of the entire radiotherapy procedure of the cervical cancer. Treatment planning for external radiotherapy was accomplished using computed tomography images and for intracavitary brachytherapy using orthogonal radiographs. Dose measurements were performed with an intracavitary ionization chamber. External radiotherapy was done using linear accelerator. The Nucletron Selectron low dose rate (LDR) machine was used for brachytherapy. For both modalities, the software calculated dose values were compared to the values measured in the pelvic phantom. RESULTS: The calculated data obtained from the treatment planning system was consistent with the measured data. The comparison between measurements and calculations showed a maximum variation of ±2 % for external radiation therapy and ±3.6 % for brachytherapy. CONCLUSION: The phantom and the procedure developed in this study successfully provided a tool for comprehensive evaluation of each step in the chain of radiation therapy under the same conditions found in actual treatment. This method can be used to verify the accuracy and reproducibility of this treatment in any department and also during commissioning of the treatment planning systems.

Reduction of radiation risks in patients undergoing some X-ray examinations by using optimal projections: A Monte Carlo program-based mathematical calculation.

The objectives of this paper were calculation and comparison of the effective doses, the risks of exposure-induced cancer, and dose reduction in the gonads for male and female patients in different projections of some X-ray examinations. Radiographies of lumbar spine [in the eight projections of anteroposterior (AP), posteroanterior (PA), right lateral (RLAT), left lateral (LLAT), right anterior-posterior oblique (RAO), left anterior-posterior oblique (LAO), right posterior-anterior oblique (RPO), and left posterior-anterior oblique (LPO)], abdomen (in the two projections of AP and PA), and pelvis (in the two projections of AP and PA) were investigated. A solid-state dosimeter was used for the measuring of the entrance skin exposure. A Monte Carlo program was used for calculation of effective doses, the risks of radiation-induced cancer, and doses to the gonads related to the different projections. Results of this study showed that PA projection of abdomen, lumbar spine, and pelvis radiographies caused 50%-57% lower effective doses than AP projection and 50%-60% reduction in radiation risks. Also use of LAO projection of lumbar spine X-ray examination caused 53% lower effective dose than RPO projection and 56% and 63% reduction in radiation risk for male and female, respectively, and RAO projection caused 28% lower effective dose than LPO projection and 52% and 39% reduction in radiation risk for males and females, respectively. About dose reduction in the gonads, using of the PA position rather than AP in the radiographies of the abdomen, lumbar spine, and pelvis can result in reduction of the ovaries doses in women, 38%, 31%, and 25%, respectively and reduction of the testicles doses in males, 76%, 86%, and 94%, respectively. Also for oblique projections of lumbar spine X-ray examination, with employment of LAO rather than RPO and also RAO rather than LPO, demonstrated 22% and 13% reductions to the ovaries doses and 66% and 54% reductions in the testicles doses, respectively.

The optimization of an energy-dispersive X-ray diffraction system for potential clinical application.

In the past decade, energy-dispersive X-ray diffraction (EDXRD) has been used to identify the nature of tissues. However, these systems have limited clinical use because of problems such as the long measurement times. In this study, the relation between various setup parameters and some performance specifications such as sensitivity, spatial resolution and momentum transfer resolution were assessed using both geometrical calculations and modeling. Accuracy of the derived relations was also confirmed by means of experimental measurements. As an example, the optimum parameters were determined for obtaining diffraction patterns of breast tissue for an efficient acquisition time. Accordingly, the results of this study could introduce a useful tool for EDXRD optimization in clinical application.