Determination of Calibration Factors and Uncertainties Associated with the Irradiation of MTS-N (LiF: Mg, Ti) Chips with Cesium-137 and X-ray Sources Under Low Doses for Personal Dosimetry in Diagnostic Radiology

Purpose: The purpose of this study was to compare calibration factors for deep dose equivalent Hp (10) and shallow dose equivalent Hp (0.07) between Cesium (Cs)-137 and X-ray sources when they are exposed to same dose and to determine uncertainties with MTS-N (LiF: Mg, Ti) chips when they are exposed to low dose ≤ 2mGy. Material and Methods: Thermoluminescent (TL) chips were annealed at 400oC for one hour and allowed to cool and were subjected to a temperature of 100oC for another two hours using a TLD Furnace Type LAB-01/400. They were then taken to a Secondary Standard Dosimetry Laboratory (SSDL) for irradiation using a Cs-137 source at known doses (0.2-2mGy). A RadPro Cube 400 manual TLD Reader was used to determine corresponding TL signal. The above process was replicated but with a calibrated X-ray unit as the source for calibration. Results: The calibration factors (CF) from the line graph of dose (mGy) against TL signal (count) for Cs-137 source with Hp (10) and Hp (0.07) were 3.72 x 10-6 and 5.97x10-6 mGy/count respectively. Those with X-ray source for Hp (10) and Hp (0.07) were 3.44x10-6 and 4.05x10-6 mGy/count respectively with an overall coefficient of determination (R2) = 0.99. The adjusted maximum percentage deviation between the actual and calculated dose for both sources was -2.74%. The percent (%) deviation of the mean with both sources for Hp (10) and Hp (0.07) was 3.9% and 19% respectively. Conclusion: Adjusted percent deviation from both sources were within the recommended dose limit of ±30% by the Radiological Protection Institute of Ireland (RPII) and within the International Commission on Radiological Protection (ICRP) limit respectively. Better accuracy was seen for Hp (10) with both sources compared to Hp (0.07). Calibration of the MTS-N chips using both sources was successful and can be used for personal dosimetry

Validation of a Locally Designed Computed Tomography Dose Phantom: A Comparison Study with a Standard Acrylic Phantom in South-South, Nigeria

Purpose: The aim of this study was to determine the mean volume computed tomography dose index (CTDIvol) for the standard head and body phantoms and locally designed head and body phantoms respectively. Similarly, this study determined and compared the displayed mean CTDIvol and Dose Length Product (DLP) for the above phantoms from the CT monitor. In addition, the percentage deviations of both phantoms were compared with the recommended limits from the International Atomic Energy Agency (IAEA) and the American College of Radiologists (ACR). Materials and Methods: Dose measurements were made using a standard polymethymethacrylate (PMMA) phantom for head and body as well as a locally designed phantom with four CT scanners using thermoluminescence dosimeters (TLDs). The locally designed phantoms were made using a PMMA sheet, which was bent to give the desired cylindrical shape and was made like the standard phantoms. The constructed phantom was filled with water and the TLD chips were inserted into the center and peripheries of the phantoms to obtain the absorbed doses. Results: The CTDIvol for the standard head and body phantom for center A was 66.97 and 21.85mGy and for B was 23.39 and 6.29mGy respectively. Similarly, the CTDIvol for the constructed head and body phantom for center A was 63.91 and 19.84mGy and for B was 24.67 and 6.30mGy respectively. The uncertainty between the standard and constructed head phantoms for centers A and B was 4.6 and 5.5% respectively, while that of the standard and constructed body phantoms for centers A and B was 9.2 and 0.0% respectively. The maximum percent deviation from the console CTDIvol and DLP values with the four phantoms for centers A and B was within ±20%. The mean correction factors for the head and body were 0.998 and 1.05 respectively. Conclusion: The uncertainties obtained in this study were within the IAEA and ACR recommended value of ±20%. The constructed phantom proved useful for CT dose measurements

Integrity test of lead apron and its effect on personnel and carer

The use of lead apron is known to protect radiation workers and carers (patient relatives) from the scatter radiation. The study intends to assess the integrity of lead apron by checking for defects and to estimate the mean dose rate to personnel and carers and also to compare the percentage mean absorbance of the apron with the related studies. Ten lead aprons were used involving three vendors. A fluoroscopy unit, floor mounted X-ray unit, survey meter, lead aprons and meter rule were used. Crack and tear were identified with some areas close to the critical organ site. Eighty percent of the aprons showed signs that they were defective. Correlation of the lead aprons mean age and the total number of defective lead aprons were not significant (p=0.866). The mean thickness of the aprons for the three brands affected the percentage absorbance (p<0.001). The mean dose rate was above 20 mSv recommended for radiation workers averaged over a single year. It is recommended that the defective apron close to the critical organ be replaced and those in areas distal from the critical organs be further evaluated using the rejection criteria test before they are replaced

Integrity test of lead apron and its effect on personnel and carers

The use of lead apron is known to protect radiation workers and carers (patient relatives) from the scatter radiation. The study intends to assess the integrity of lead apron by checking for defects and to estimate the mean dose rate to personnel and carers and also to compare the percentage mean absorbance of the apron with the related studies. Ten lead aprons were used involving three vendors. A fluoroscopy unit, floor mounted X-ray unit, survey meter, lead aprons and meter rule were used. Crack and tear were identified with some areas close to the critical organ site. Eighty percent of the aprons showed signs that they were defective. Correlation of the lead aprons mean age and the total number of defective lead aprons were not significant (p=0.866). The mean thickness of the aprons for the three brands affected the percentage absorbance (p<0.001). The mean dose rate was above 20 mSv recommended for radiation workers averaged over a single year. It is recommended that the defective apron close to the critical organ be replaced and those in areas distal from the critical organs be further evaluated using the rejection criteria test before they are replaced

Assessment of the impact of chest radiography on the breast of female patients in a medical facility in Asaba, Delta State: An evaluation of the lifetime cancer risk

Objectives: Posteroanterior (PA) Chest radiography is the most common medical investigation worldwide. This study is aimed at determining the mean and median entrance surface dose (ESD), 75th percentile ESD, dose to right (RT) and left (LT) breast, absorbed dose (DT) and organ dose from PA chest radiography for female patients between the ages of 20-79 years. It is also aimed at determining the effective dose (E) and estimating the lifetime cancer risk. Methods: This prospective study was carried out with 121 female subjects who came for routine PA chest radiography. Digital radiography (DR) unit was used for all patients. Thermoluminescent dosimeters (TLDs) was positioned at the centre of the collimated beam of each patient and transparent nylon was attached to the skin. The TLDs were also attached to both breasts with the patient facing the erect bucky to estimate the exit dose (ED). Results: The mean, median and 75th percentile ESD for the 6 age groups were 0.96 ±0.15 mGy, 0.95 (0.71-1.23) mGy and 1.07mGy respectively. The mean dose to the RT, LT breast and the DT were 0.35 ±0.12, 0.40 ±0.13 and 0.58 ±0.12 mGy respectively. The mean E for the age groups was 0.029 mSv, while the mean organ doses to the lungs, breast and thyroid were 0.290, 0.059 and 0.022 mGy respectively. The estimated lifetime cancer risk among the age groups ranged from 1.0-2.8 per million. Conclusion: The mean ESD and E were above recommended guidelines. ESD and DT were primarily affected by focus film distance (FFD) and field size for all age groups. An evaluation of the lifetime cancer risk from this study shows that the risk was twice as high as the United Kingdom (UK) Health Protection Agency (HPA) report. Though the risk was minimal, there may be need to review the current protocol to meet up with the reported values in the HPA published guidelines

Determination of Calibration Factors and Uncertainties Associated with the Irradiation of MTS-N (LiF: Mg, Ti) Chips with Cesium-137 and X-ray Sources Under Low Doses for Personal Dosimetry in Diagnostic Radiology

Purpose: The purpose of this study was to compare calibration factors for deep dose equivalent Hp (10) and shallow dose equivalent Hp (0.07) between Cesium (Cs)-137 and X-ray sources when they are exposed to same dose and to determine uncertainties with MTS-N (LiF: Mg, Ti) chips when they are exposed to low dose ≤ 2mGy. Material and Methods: Thermoluminescent (TL) chips were annealed at 400oC for one hour and allowed to cool and were subjected to a temperature of 100oC for another two hours using a TLD Furnace Type LAB-01/400. They were then taken to a Secondary Standard Dosimetry Laboratory (SSDL) for irradiation using a Cs-137 source at known doses (0.2-2mGy). A RadPro Cube 400 manual TLD Reader was used to determine corresponding TL signal. The above process was replicated but with a calibrated X-ray unit as the source for calibration. Results: The calibration factors (CF) from the line graph of dose (mGy) against TL signal (count) for Cs-137 source with Hp (10) and Hp (0.07) were 3.72 x 10-6 and 5.97x10-6 mGy/count respectively. Those with X-ray source for Hp (10) and Hp (0.07) were 3.44x10-6 and 4.05x10-6 mGy/count respectively with an overall coefficient of determination (R2) = 0.99. The adjusted maximum percentage deviation between the actual and calculated dose for both sources was -2.74%. The percent (%) deviation of the mean with both sources for Hp (10) and Hp (0.07) was 3.9% and 19% respectively. Conclusion: Adjusted percent deviation from both sources were within the recommended dose limit of ±30% by the Radiological Protection Institute of Ireland (RPII) and within the International Commission on Radiological Protection (ICRP) limit respectively. Better accuracy was seen for Hp (10) with both sources compared to Hp (0.07). Calibration of the MTS-N chips using both sources was successful and can be used for personal dosimetry

Evaluation of kilovoltage failure in conventional X-ray machines among selected X-ray Centers in Jos North Local government area of Plateau State, Nigeria

Background: The goal of quality assurance of x-ray machine is to obtain accurate and timely diagnosis and low dose to patients.Aims and Objectives: To determine peak kilovoltage (kVp) accuracy and reproducibility of 23 individual X-ray machine and compare their values with recommended standards.Materials and Methods: Measurements were taken in the 23 diagnostic centers (XRY1 – XRY23 ). Unfors Thinx RAD detector which served as the mimicked patient was placed at Source to Image Distance (SID) of 100 cm. At a constant tube current, several kVp values were used for both the accuracy and reproducibility test. Any results above ±5% were termed “Not Acceptable”. Data analysis value was done using GraphPad Prism version 5.0 statistics software.Results: A total of 16 X-ray machine passed the kVp accuracy test (69.57%) while 7 X-ray machine failed the test (30.43%). Also, 15 X-ray machine passed the kVp reproducibility test (65.22%), while 8 X-ray machine failed the test (34.78%).There was no correlation (P = 0.916) between kVp accuracy and reproducibility test also no significant difference (P = 0.5134). Very good statistical significant difference was seen between the machine age, kVp accuracy and reproducibility respectively (P&lt;0.05)Conclusion: This study has shown that more than one third of the total X-ray machines failed both kVp accuracy and reproducibility test. There are strong indications that machine age had significant effect on kVp accuracy and reproducibility.Keywords: Peak kilovoltage, Radiation dose, X-ray, Unfors Thinx RAD detector, Milliampere second

Radiological assessment of petroleum products in Aniocha South Local Government Area of Delta State, South-South Nigeria

Monitoring the background levels from petroleum products is essential because of the everyday use and the increasing number of fuel, diesel, kerosene, and gas stations in Delta State, Nigeria. The study aims to determine the background ionizing radiation (BIR) in milli-Roentgen per hour (mR/h), absorbed dose rate (ADR) (nGy/h), and annual effective dose rate (AED) (mSv/year) in selected fuel, diesel, kerosene, and cooking gas-dispensing stations in Aniocha South Local Government Area of Delta State. The study was carried out using a calibrated Geiger Muller detector (Radiation Alert Inspector) in count per minute mode for point measurements and a geographical positioning system for determining the longitude and latitude of each point where measurements were taken from. The mean outdoor BIR, ADR, and AED were 0.011 ± 0.002 mR/h, 91.6 ± 19.5 nGy/h, and 0.11 ± 0.02 mSv/year, respectively, with 84% of the BIR below the world average. The mean BIR was below the world average while the ADR and AED were above it. Kerosene stations had the highest BIR. The outdoor measurements from this study were comparable to similar articles with slight variation. The study shows that the attendant and customers were safe in the areas where this study was conducted

Determination of reference dose levels among selected X-ray centers in Lagos State, South-West Nigeria

Background: With increasing use of diagnostic X-ray machines across Lagos, South-West Nigeria, relevant international bodies have proposed the use of reference dose levels (RDLs) to help manage radiation dose to patients without compromising image quality. Objectives: The purpose of this study was to determine the entrance surface dose (ESD) at third quartile (75 th percentile) in Lagos metropolis for normal adult radiographic examinations and to compare them with national and international established reference dose guidelines. Materials and Methods: One dedicated X-ray unit in each diagnostic center was used for this study denoted as H1-H10. A noninvasive Unfors ThinX RAD kilovoltage (kVp) meter which served as the phantom (mimicked patient) was used for measurements. The ESDs were determined by placing the Unfors ThinX RAD kVp meter on the patient′s table bucky at a source to image distance (SID) of 100 cm and at the erect bucky at a SID of 180 cm. The peak tube kVp was varied at different milliampere seconds (mAs). Results : The mean ESD for adult postero-anterior (PA) chest, antero-posterior (AP) Abdomen and (AP) lumbar spine X-ray examination were 0.603, 2.57, and 2.57 mGy, respectively. While the ESD for the third quartile for adult (PA) chest, (AP) abdomen, and (AP) lumbar spine X-ray examination among the ten X-ray centers were 0.93, 2.74, and 2.47 mGy, respectively. Conclusion: Third quartile ESD which translate to RDL for adult (PA) chest examination for this study was higher compared to other national and international RDLs but adult (AP) abdomen and lumbar spine examinations were within accepted national and international range

Dosimetric effect of the gantry rotations of a novel trunk phantom using an area integration algorithm

Background: Treatment planning systems (TPSs) have proved to be a useful tool in predetermining how a treatment outcome will be in radiotherapy. The accuracy of any TPS to calculate dose to any arbitrary point within a material is largely dependent on the mathematical algorithm used. Aims: The purpose of this study was to design a local trunk phantom and use the phantom to check the percentage dose accuracy of the Area Integration Algorithm of a Precise PLAN 2.16 TPS if it is in agreement with results obtained from manufacturer's verification by varying the gantry angle and whether it is within ± 5% International Commission on Radiation Units and Measurements (ICRU) minimal limit. Materials and Methods: The study was executed with a locally designed phantom made of Plexiglas with six insert and an ionization chamber port. The phantom was simulated using a HiSpeed NX/i computed tomography scanner and Precise PLAN 2.16 TPS for application of beam setup parameters. The mimicked organs for the inserts were: 25%–75% Glycerol-Water for liver, pure carboxyl methyl cellulose was used for lungs, 30%–70% Glycerol-Water for muscle, 40%–60% Glycerol-Water was used for adipose, pure Sodium hypochlorite was used for bone and pure sodium laureth sulfate (Texapon) for kidney. Results: The maximum percentage (%) deviation with a large field for six inhomogeneous inserts and with bone only homogeneous inserts were 3.4% and 2.9%, respectively. The maximum % deviation with a small field for six inhomogeneous inserts was 3.2%. The % deviation between the solid water phantom and the locally designed phantom was 3.5%. Conclusion: The Area Integration Algorithm has shown an overall accuracy of 4% below 5% ICRU minimal limit. There was no statistically significant difference in field sizes and in inhomogeneity/homogeneity, respectively. Variation exists in % deviation for small field size with parallel opposed field between our verification and the manufacturers