Diagnostic radiology dosimetry: Status and trends

Lumbar discectomy and fusion: Organs’ dose and effective dose estimation using Monte Carlo simulation

In this study, the effect of patient- and procedure-related parameters on organs' dose (OD), peak skin dose (PSD) and effective dose (ED) during lumbar discectomy and fusion (LDF) was assessed. Intra-operative parameters obtained from 102 LDFs were inserted into VirtualDose-IR software implementing sex-specific and BMI-adjustable anthropomorphic phantoms for dosimetric calculations. Fluoroscopy time (FT), kerma-area product (KAP), cumulative and incident air-kerma (K_air) were also recorded from the dosimetric report of the mobile C-arm. An increase in KAP, K_air, PSD and ED was found for male or higher BMI patients, multi-level or fusion or L5/S1 procedures. However, a significant difference was found only for PSD and incident K_air between normal and obese patients and for FT between discectomy and discectomy and fusion procedures. The spleen, kidneys and colon received the highest doses. The BMI have a significant impact only for kidneys, pancreas, and spleen doses when comparing obese to overweight and for urinary bladder when comparing overweight to normal patients. Multi-level and fusion procedures resulted in significantly higher doses for lungs, heart, stomach, adrenals, gallbladder and kidneys, while pancreas and spleen doses significantly increased only for multi-level procedures. Additionally, a significant increase was found only for urinary bladder, adrenals, kidneys, and spleen ODs when comparing L5/S1 and L3/L4 levels. The mean ODs were lower compared to the literature. These data may aid neurosurgeons in optimising exposure techniques during LDF to keep patients' dose as low as is practicably possible.

Evaluation occupationally radiation exposure during diagnostic imaging examinations

Occupational radiation exposure can occur due to various human activities, including the use of radiation in medicine. Occupationally exposed personnel surpassing 7.4 millions, and respresent the biggest single group of employees who are exposed to artificial radiation sources at work. This study compares the occupational radiation dose levels for 145 workers in four different hospitals located in the Aseer region in Saudi Arabia. The occupational exposure was quantified using thermoluminescence dosimeters (TLD-100). The levels of annual occupational exposures in targeted hospitals were calculated and compared with the levels of the international atomic energy agency (IAEA) Safety Standards. An average yearly cumulative dose for the two consecutive years. The average, highest and lowest resulted occupational doses under examination in this work is 1.42, 3.9 mSv and 0.72 for workers in various diagnostic radiology procedures. The resulted annual effective dose were within the IAEA approved yearly dose limit for occupational exposure of workers over 18, which is 20 mSv. Staff should be monitored on a regular basis, according to current practice, because their annual exposure may surpass 15% of the annual effective doses.

Optically stimulated Al2O3:C luminescence dosimeters for teletherapy: Hp(10) performance evaluation

The performance of optically stimulated luminescence dosimeters (OSLDs, Al₂O₃:C) was evaluated in terms of the operational quantity of H_P(10) in Co-60 external beam teletherapy unit. The reproducibility, signal depletion, and dose linearity of each dosimeter was investigated. For ten repeated readouts, each dosimeter exposed to 50mSv was found to be reproducible below 1.9 ± 3% from the mean value, indicating good reader stability. Meanwhile, an average signal reduction of 0.5% per readout was found. The dose response revealed a good linearity within the dose range of 5-50mSv having nearly perfect regression line with R² equals 0.9992. The accuracy of the measured doses were evaluated in terms of operational quantity H_P(10), wherein the trumpet curve method was used respecting the 1990 International Commission on Radiological Protection (ICRP) standard. The accuracy of the overall measurements from all dosimeters was discerned to be within the trumpet curve and devoid of outlier. It is established that the achieved OSL Al₂O₃:C dosimeters are greatly reliable for equivalent dose assessment.

Afterglow based detection and dosimetry of beta particle irradiated ZrO2

In this work, we report on the afterglow (AG) response characterization of commercially available ZrO₂. Pellet shaped samples previously annealed in air at 1000°C during 24h were exposed to beta particle irradiation in the dose range from 0.5 up to 128Gy and their AG decay curves recorded during 600s after irradiation exposure. The characteristic glow curves of beta particle irradiated ZrO₂ show two maxima located around 80°C and 150°C. The first one rapidly vanishes at room temperature, giving rise to AG. The integrated AG signal increases as dose increases from 0.5 to 128Gy, with a linear dependence from 0.5 up to ca. 32Gy. Excellent reproducibility of the AG response was observed in 10 irradiation - AG readout cycles, showing that the studied ZrO₂ samples are reusable. The results here presented show that ZrO₂ is a promising material for use as a radiation dosimeter based on the AG phenomenon.

Measurements of air kerma index in computed tomography: A comparison among methodologies

As CT exams impart high doses to patients in comparison to other radiologist techniques, reliable dosimetry is required. In this work, dosimetry in CT beams was carried out in terms of air kerma index in air or in a phantom measured by a pencil ionization chamber, thermoluminescent (TL) detectors and radiochromic film. Calibration results showed the low energy dependence of all three dosimetric systems for the 100-120kV range, the very high uncertainty of the TL dosimeters in comparison to the other systems and high nonlinearity response in terms of air kerma of the radiochromic film. Measurements with the three systems in a 120kV CT protocol showed an acceptable agreement among the weighted air kerma index values, but TL dosimeters presented the highest uncertainties in the values.