Radiation doses, cancer risks and optimization process of routine computed tomography (ct) examinations in Johor

The concerns towards radiation–induced cancer from Computed Tomography (CT) examinations have led to the encouragement of CT dose monitoring and further optimization of the scanning parameters. Therefore, in this study, radiation dose from CT scan and its related risks to the patients from current CT practice were analysed. In the first stage, this thesis started the discussion on the level of current knowledge among radiology personnel towards CT radiation risk and its optimization. There is no significant difference of the current knowledge of CT optimization between the two professions of interest herein, the medical and the allied health groups. A CT dose survey was conducted in 8 CT facilities for a 6-month period, encompassing data for 1024 patients with various CT examinations that included regions of the abdomen, brain and thorax. CT-EXPO (Version 2.3.1, Germany) software was used to validate the dose information such as CT Dose Index (CTDI) and dose-length product (DLP). The proposed Diagnostic Reference Levels (DRLs) were indicated by rounding off the third quartiles (Q3s) of whole dose distributions for weighted CTDI (CTDIw) (in mGy), volume CTDI (CTDIvol) (in mGy) and DLP (in mGy.cm) and their values were; 16, 17, and 650 respectively for CT abdomen; 70, 70, and 1030 respectively for CT Brain and 15, 16, and 670 respectively for CT thorax. In the second stage, the cancer risks of the CT examinations were estimated and the calculation was based on International Commission on Radiation Protection (ICRP) Publication 103 Report and Biological Effects of Ionizing Radiation (BEIR) VII Report. Based on BEIR VII recommendation, the study discovered that the lifetime attributable risks (LARs) of 100,000 populations who underwent abdominal CT examinations for stomach cancer were 2.3 for male and 1.0 for female; while for colon cancer the LARs were 2.3 for male and 0.7 for female. The effectiveness of optimization of CT parameters and application of shielding in routine CT procedures were evaluated. Of 7 protocols (P1 – P7), the k factors were constant for all protocols and decreased by ~8% compared to the universal k factor. It is of interest that k factors from CT-EXPO were found to vary between 0.010 for protocol P5 and 0.015 for protocol P3 due to inconsistency in tube potential and pitch factor. The application of breast shielding to routine CT thorax protocols reduced by 14% the breast’s equivalent dose. Hence, this study supports the importance of initiating protection and optimization processes of routine CT examinations in order to offer safer imaging practices

Radiation doses, cancer risks and optimization process of routine computed tomography (CT) exminations in Johor

ABSTRACT The concerns towards radiation–induced cancer from Computed Tomography (CT) examinations have led to the encouragement of CT dose monitoring and further optimization of the scanning parameters. Therefore, in this study, radiation dose from CT scan and its related risks to the patients from current CT practice were analysed. In the first stage, this thesis started the discussion on the level of current knowledge among radiology personnel towards CT radiation risk and its optimization. There is no significant difference of the current knowledge of CT optimization between the two professions of interest herein, the medical and the allied health groups. A CT dose survey was conducted in 8 CT facilities for a 6-month period, encompassing data for 1024 patients with various CT examinations that included regions of the abdomen, brain and thorax. CT-EXPO (Version 2.3.1, Germany) software was used to validate the dose information such as CT Dose Index (CTDI) and dose-length product (DLP). The proposed Diagnostic Reference Levels (DRLs) were indicated by rounding off the third quartiles (Q3s) of whole dose distributions for weighted CTDI (CTDIw) (in mGy), volume CTDI (CTDIvol) (in mGy) and DLP (in mGy.cm) and their values were; 16, 17, and 650 respectively for CT abdomen; 70, 70, and 1030 respectively for CT Brain and 15, 16, and 670 respectively for CT thorax. In the second stage, the cancer risks of the CT examinations were estimated and the calculation was based on International Commission on Radiation Protection (ICRP) Publication 103 Report and Biological Effects of Ionizing Radiation (BEIR) VII Report. Based on BEIR VII recommendation, the study discovered that the lifetime attributable risks (LARs) of 100,000 populations who underwent abdominal CT examinations for stomach cancer were 2.3 for male and 1.0 for female; while for colon cancer the LARs were 2.3 for male and 0.7 for female. The effectiveness of optimization of CT parameters and application of shielding in routine CT procedures were evaluated. Of 7 protocols (P1 – P7), the k factors were constant for all protocols and decreased by ~8% compared to the universal k factor. It is of interest that k factors from CT-EXPO were found to vary between 0.010 for protocol P5 and 0.015 for protocol P3 due to inconsistency in tube potential and pitch factor. The application of breast shielding to routine CT thorax protocols reduced by 14% the breast’s equivalent dose. Hence, this study supports the importance of initiating protection and optimization processes of routine CT examinations in order to offer safer imaging practices

Direct and indirect entrance surface dose measurement in X-ray diagnostics using nanoDot OSL dosimeters

This study investigated the suitability of nanoDot optically stimulated luminescence (OSL) dosimeters for entrance surface dose (ESD) measurements in common X-ray diagnostics. OSL dosimetry system supplied by Landauer Inc, (Glenwood, IL, USA) consisting of nanoDot OSL dosimeters and microStar reader were used. ESDs were measured with nanoDots placed on whole-body anthropomorphic phantom (for direct measurements) and in free air without backscatter material (for indirect measurements) in accordance with the IAEA Technical Report Series No. 457. Measurements were carried out in five X-ray projections including AP abdomen, AP chest, PA chest, AP thoracic spine and AP skull. The mean ESD for each projection was evaluated from multiple measurements with three different field sizes. Mean ESDs (direct measurements) for AP abdomen, AP chest, PA chest, AP thoracic spine and AP skull were 4.3 mGy, 0.7 mGy, 0.3 mGy, 6.8 mGy and 2.8 mGy respectively. While in the case of indirect measurements, the corresponding mean ESD values were 4.8 mGy, 0.7 mGy, 0.2 mGy, 7.2 mGy and 3.7 mGy respectively. The results were found to be within IAEA and European Commission (EC) diagnostic reference levels (DRLs) range. The percentage difference of the ESDs measured by direct and indirect methods in all projections were between 0 to 40%. It was affirmed that nanoDot OSL dosimeter is a good candidate for ESD measurement in common radiographic examinations, while taking into account the effect of energy dependence

Image quality of coronary CT angiography (CCTA) using 640-slice scanner: qualitative and quantitative assessments of coronary arteries visibility

The purpose of this study was to evaluate the image quality and diagnostic accuracy of coronary computed tomography angiography (CCTA) using 640-slice scanner. Advancement of multidetector computed tomography (MDCT) technology with higher spatial, temporal resolution, and increasing detector array have improved the image quality and diagnostic accuracy of CCTA. A total of 25 patients (12 men and 13 women) underwent CCTA was chosen and data was acquired by 640-slice scanner. All 16 segments of coronary arteries were evaluated by two reviewers using a 4-likert scale for qualitative assessment. In quantitative assessment, the evaluation of 4 main coronary arteries were analysed in terms of signal intensity (SI), image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). All 25 patients with a mean age of 52.88 ± 14.75 years old and body mass index (BMI) of 24.24 ± 3.28 kg/m2 were analysed. In qualitative assessment, from the total of 400 segments, 379 segments (95 %) have diagnostic value while 21 segments do not have diagnostic value, which means 5 % artefact was detected. In quantitative assessment, there was no statistical differences in gender, race, and BMI (p>0.05). Overall evaluation showed that higher SI at the left main artery (LM) at 393.7 ± 47.19. Image noise was higher at right coronary artery (RCA) at 39.01 ± 13.97. SNR and CNR showed higher at left anterior descending (LAD) with 12.73 ± 5.17 and LM 9.14 ± 4.2, respectively. In conclusion, this study indicates that 640-slice MDCT has higher diagnostic value in CCTA examination with 95 % vessel visibility with 5 % artefact detection

Comparison of dose calculation algorithms model: convolution, superposition, and fast superposition in 3-D Conformal Radiotherapy (3D-CRT) treatment plan

The important task of radiotherapy is to make sure that the radiation dose to the target tumour is accurate as prescribed and the dose to the organ at risk is minimized. Therefore, the aim of this study is to compare and evaluate the efficiency of the dose calculation algorithms: namely convolution, superposition, and fast superposition which installed in Treatment Planning System (TPS) (CMS XiO, USA). In this study, we modified protocols described in IAEATecdoc-1583, where four typical treatment techniques such as single field, multiple field, wedge field, and multi-leaf collimated (MLC) field were analysed from the system. The measurement data for calculated dose and measured dose were taken from thorax CIRS anthropomorphic phantom. The assessment of algorithms was done by comparing the point dose calculated with the measured dose. The study shows that the superposition algorithm produced relative error less than ±3% which passed 100% of all reference points, whilst the convolution algorithm and fast superposition presented relative error more than ±3% which passed 82% and 91% of reference points, respectively. In conclusion, the evaluation of radiotherapy treatment plan shall take into account the type of dose calculation algorithm model in order to optimize radiotherapy treatment and ensure the radiation safety to the patient

Radiation dose comparison in CT thorax, CT abdomen and CT thorax-abdomen-pelvis (TAP) using 640-and 160-slice computed tomography (CT) scanners

This study was carried out to compare the effective dose, size specific dose estimation (SSDE) and scan length between genders and between CT scanner with different slice number. A total of 245 set data of radiation dose and scan length for CT scanning procedure involving thorax, abdomen and pelvis regions were obtained retrospectively for comparisons. 111 patients (60 males and 51 females) were scanned using 160-slices CT scanner while 134 patients (71 males and 63 females) were scanned using 640-slices CT scanner. Generally, there were no significant differences in the radiation dose and scan length among genders. However, differences for SSDE in CT thorax and CT thorax-abdomen-pelvis (TAP) protocols exist whereby in CT thorax protocol, 640-slices CT scanner had a significantly higher value of SSDE (9.06±2.67 mGy) than that in 160-slices CT scanner (7.82±1.33 mGy). Similarly to the CT TAP protocol, whereby 640-slices CT scanner had a significantly lower value in SSDE (9.17±1.59 mGy) than that in 160-slices CT scanner (10.76±3.72 mGy). In conclusion, there was no significant difference in the radiation dose and scan length between genders but significant difference was only observed in SSDE due to the presence of body size variation among the study population especially in different CT scanners

Adaptive iterative dose reduction (AIDR) 3D in low dose CT abdomen-pelvis: effects on image quality and radiation exposure

The widespread use of computed tomography (CT) has increased the medical radiation exposure and cancer risk. We aimed to evaluate the impact of AIDR 3D in CT abdomen-pelvic examinations based on image quality and radiation dose in low dose (LD) setting compared to standard dose (STD) with filtered back projection (FBP) reconstruction. We retrospectively reviewed the images of 40 patients who underwent CT abdomen-pelvic using a 80 slice CT scanner. Group 1 patients (n=20, mean age 41 ± 17 years) were performed at LD with AIDR 3D reconstruction and Group 2 patients (n=20, mean age 52 ± 21 years) were scanned with STD using FBP reconstruction. Objective image noise was assessed by region of interest (ROI) measurements in the liver and aorta as standard deviation (SD) of the attenuation value (Hounsfield Unit, HU) while subjective image quality was evaluated by two radiologists. Statistical analysis was used to compare the scan length, CT dose index volume (CTDIvol) and image quality of both patient groups. Although both groups have similar mean scan length, the CTDIvol significantly decreased by 38% in LD CT compared to STD CT (p<0.05). Objective and subjective image quality were statistically improved with AIDR 3D (p<0.05). In conclusion, AIDR 3D enables significant dose reduction of 38% with superior image quality in LD CT abdomen-pelvis

Entrance surface dose measurement and lifetime attribute risk analysis from postero-anterior chest x-ray imaging via direct and indirect measurement

This study aimed to estimate the entrance surface dose (ESD) of routine chest X-ray (CXR) examination and to compare the direct and indirect measurement. The work also extended to relate with the patients body thickness and the lifetime attributable risk of the examinations. A total of 101 CXR examinations in posteroanterior (PA) projections are selected as subjects and recorded the data, such as scanning acquisition parameter and patient habitus. The mean ESD value obtained from the TLD-100 and the software calculation was 0.31 mGy and 0.17 mGy, respectively. The percentage deviation obtained ranged from 25.5% to 61.3%. In comparison with the national diagnostic reference level, 0.90 mGy (MOH), the mean values of ESD obtained from this study were lower. Furthermore, it was observed that the mean absorbed dose of the adrenals, kidneys, lungs, oesophagus, and heart walls were lower as compared to the ESD value. The examinations were only associated with very low risk of cancer incidence and mortality. The results of this study also suggested a need for standardizations of the personnel training to perform X-ray examinations according to ALARA principles

The effectiveness of bismuth breast shielding with protocol optimization in CT scans of the thorax

Background: Numerous techniques had been proposed to reduce radiation exposure in computed tomography (CT) including the use of radiation shielding. Objective: This study aims to evaluate efficacy of using a bismuth breast shield and optimized scanning parameter to reduce breast absorbed doses from CT thorax examination. Methods: Five protocols comprising the standard CT thorax clinical protocol (CP1) and four modified protocols (CP2 to CP5) were applied in anthropomorphic phantom scans. The phantom was configured as a female by placing a breast component on the chest. The breast component was divided into four quadrants, where 2 thermoluminescence dosimeters (TLD-100) were inserted into each quadrant to measure the absorbed dose. The bismuth shield was placed over the breast component during CP4 and CP5 scans. Results: The pattern of absorbed doses in each breast and quadrant were approximately the same for all protocols, where the 4th quadrant > 3rd quadrant > 2nd quadrant > 1st quadrant. The mean absorbed dose value in CP3 was reduced to almost 34% of CP1's mean absorbed dose. It was reduced even lower to 15% of CP1's mean absorbed dose when the breast shield was used in CP5. Conclusion: This study showed that CT radiation exposure on the breast could be reduced by using a bismuth shield and low tube potential protocol without compromising the image quality

Evaluation of healthcare science student learning styles based VARK analysis technique

This study aimed to evaluate the learning styles among healthcare students and to study the relationship with their academic achievement. This cross-sectional study was conducted among 137 healthcare students from six different courses. Data was collected using a self-administered questionnaire and developed based on the original visual, aural/auditory, read/write, and kinesthetic (VARK) assessment. The questionnaire was divided into two sections: the demographic status and the learning style perspective. A total of 119 respondents (86.8%) has chosen unimodal as their learning styles, while the rest of the 18 respondents (13.2%) choose multimodal as their preferred learning method. Among the unimodal learning styles, visual (32%) and reading (26%) were most preferred among respondents. The auditory and kinesthetic methods of learning were less and accounted for 10% to 20%. Notably, in multimodal learning styles preferences, 4% of students prefer a combination learning style of visual and kinesthetic methods. There was no significant relationship between learning styles and academic achievement using Pearson’s Chi-square test (p>0.05). Hence, both were independent of one another. Hence, some of the dominant learning styles needed to be considered based on their future profession