Ajit Brindhaban | Kuwait University - Health Sciences Center (original) (raw)

Papers by Ajit Brindhaban

Research paper thumbnail of Enhancing Readability and Detection of Age-Related Macular Degeneration Using Optical Coherence Tomography Imaging: An AI Approach

Bioengineering, Mar 22, 2024

Research paper thumbnail of Comparison between conventional radiography and digital radiography for various kVp and mAs settings using a pelvic phantom

Radiography, May 1, 2004

Introduction A study was carried out to investigate the differences in the quality of images obta... more Introduction A study was carried out to investigate the differences in the quality of images obtained using film/screen radiography and computed radiography at various kVp and mAs settings within the range of values used for diagnostic imaging. Method Images of a pelvic phantom obtained at specific kVp/mAs combinations using Kodak film/screen combination were compared with images obtained using an AGFA computed radiography image plate. Images were assessed using a 5-point subjective scoring system and statistical significances were tested using un-paired t-test. Results and conclusion There were not any significant changes (P ! 0:05) in the quality of computed radiography images for kVp changes in the range ÿ15% to C30%. Lower limits for mAs at any specific kVp setting can be established for an individual computed radiography system to produce diagnostic quality images. These lower limits were 25% lower than the standard values used for film/screen systems.

Research paper thumbnail of The<i>Q</i>value for the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow /><mml:mrow><mml:mi mathvariant="italic">m</mml:mi></mml:mrow><mml:mrow /><mml:mrow /><mml:mprescri...

Physical review, May 1, 1994

The threshold energy of the Mg(p, n) Al reaction has been measured to be 5209.46+0.12 keV, using ... more The threshold energy of the Mg(p, n) Al reaction has been measured to be 5209.46+0.12 keV, using a 1 V standard as reference, and taking account of efFects due to 6nite beam energy spread, nonuniform proton energy loss in the target, and ionization of the magnesium atoms. The Q value derived for the Al beta decay then becomes 4232.17+0.12 keV, which is in clear disagreement with the most precise of the existing measurements. A further measurement is proposed.

Research paper thumbnail of Comparison between image quality in electronic zoom and geometric magnification in digital mammography

Journal of X-Ray Science and Technology, 2016

BACKGROUND: Magnification mammography is performed to enhance the visibility of small structures ... more BACKGROUND: Magnification mammography is performed to enhance the visibility of small structures at the expense of relatively high radiation dose as a complementary examination to standard mammography. The introduction of postprocessing capabilities and the widespread use of digital mammography has promoted some controversy in the last decade on whether similar visibility can be achieved using electronic zoom. The aim of this study is to compare the visibility of small structures in images obtained by the two techniques stated above for different exposure conditions. METHODS: Images of a Fluke Biomedical Model 18-220 Mammography Accreditation Phantom were obtained using standard techniques and geometric magnification, using a digital mammography unit, with different exposure factors. Three different target/filter combinations (Mo/Mo,Mo/Rh,Rh/Rh), variable kVp (26-32), and automatic exposure control were used. Images obtained using standard technique were electronically zoomed and compared to the corresponding magnification mammograms. Comparisons were based on the visibility of structures evaluated by five senior technologist with extensive experience in mammography. Statistical analysis was performed using non-parametric tests. RESULTS: Visibility of structures was not affected by the kV used for a given target/filter combination for both techniques (p > 0.065). Target/filter combination of Mo/Mo provided better visibility of micro-calcification and fibers (p < 0.026) in geometric magnification technique and Mo/Rh in the digital zoom technique. No significant differences were observed in the visibility of simulated breast masses. The overall image score was significantly higher (p < 0.001) for geometric magnification over the digital zoom for Mo/Mo & Rh/Rh combinations. CONCLUSION: Although sufficient image quality was maintained in electronically zoomed images, geometric magnification provided better overall visualization of structures in the phantom.

Research paper thumbnail of Accelerator beam energy calibration with the 27Al(p, n) and 27Al(p, γ) reactions

Nuclear Instruments and Methods in Physics Research, Mar 1, 1994

The energies of resonances in the Z~AI(p, y) reaction at 992 and 1317 keV and of the threshold of... more The energies of resonances in the Z~AI(p, y) reaction at 992 and 1317 keV and of the threshold of the Z7AI(p, n) reaction at 5804 keV have been measured accurately with respect to a 1 V standard. Both calibration energies and energies suitable for Q-value calculations are given. Corrections are made for the effects of the energy distribution of the proton beam, of nonuniform energy loss of the protons in the target and of ionisation of the target atoms.

Research paper thumbnail of SU-E-I-61: Application of the ALARA Principle in Digital Radiography Systems

Medical Physics, 2011

Purpose: To investigate the effect of using higher x‐ray tube voltage (kVp), than those recommend... more Purpose: To investigate the effect of using higher x‐ray tube voltage (kVp), than those recommended by manufacturers, on patient dose and image quality during digital radiography (DR) examination of the Lumber Spine. Methods: Reference images of an RSD (Radiology Support Devices, Long Beach, CA, USA) anthropomorphic lumber spine phantom were obtained using 3 different DR systems using exposure factors, kVp and tube‐current time product (mAs), recommended by the manufacturer of each system. Test images were obtained, on each system, using kVp values which were 15% and 30% higher than those recommended by the respective manufacturers, while reducing the mAs to 50% and 25% respectively of the reference exposure. The images were evaluated subjectively by 3 experienced Radiologist using the image quality criteria recommended by the Commission of the European Communities (CEC) for LS examination, on a 5‐point scale. For each image, the entrance surface exposure, including backscatter, to the phantom was measured using the Victoreen Model 8000 NERO TM mAx system and the entrance surface dose and effective dose were calculated. Any statistically significant differences between the average scores for the images were tested using Kruskal‐Wallis test at p=0.05. Results: The average score from the 3 Radiologists were above the clinically acceptable levels for all of the images. Within each system, the average scores for the images obtained with different exposure factors did not show any statistically significant differences. The entrance surface doses to the phantom and the calculated effective doses decreased by approximately 30% for a kVp increase of 15% and approximately by 50% for kVp increase of 30% in all 3 systems. Conclusions: Dose reduction up to 50% can be achieved without affecting the diagnostic quality of all images in the 3 systems by using kVp and mAs values other than those recommended by the DR system's manufacturer.

Research paper thumbnail of Radiation Dose to Patients in Coronary Interventional Procedures: A Survey

Radiation Protection Dosimetry, 2018

The objective of this study was to evaluate dose–area product (DAP) and peak skin dose (PSD) for ... more The objective of this study was to evaluate dose–area product (DAP) and peak skin dose (PSD) for coronary angiography (CA) and percutaneous coronary intervention (PCI). The DAP and PSD of 300 randomly selected patients who were referred to CA and/or PCI, over a period of 3 months were recorded and analyzed. The mean DAP of 32 Gy cm2 and mean PSD of 412 mGy for CA were lower than 118 Gy cm2 and 857 mGy, respectively, for PCI. The DAP range of 2–84 Gy cm2 for CA and 12–378 mGy for PCI were also established. The maximum value of PSD for PCI procedures reached above the 2 Gy threshold for erythema. However, these values are similar to those available in literature. Periodic surveys may be required to monitor and/or reduce radiation doses in coronary interventional procedures.

Research paper thumbnail of The effect of different exposure parameters on radiation dose in digital mammography and digital breast tomosynthesis: A phantom study

Radiography, 2019

INTRODUCTION There are concerns regarding the increase in radiation dose among women undergoing b... more INTRODUCTION There are concerns regarding the increase in radiation dose among women undergoing both digital mammography (DM) and digital breast tomosynthesis (DBT). The aim of this study was to evaluate the effect of different exposure parameters on entrance skin dose (ESD) and average glandular dose (AGD) for DM and DBT using a phantom. METHODS The ESD and AGD of 30 DM and DBT (cranio-caudal projection) examinations using a tissue equivalent phantom where acquired using a GE Senographe Essential DM unit. Commercial phantoms were used to simulate three different breast thicknesses and compositions. Tube potential, tube load, and target/filter combinations were also varied with ESD and AGD recorded directly from the DM unit. Comparisons were made using the non-parametric Kruskal Wallis, Mann-Whitney, and Wilcoxon signed rank tests. RESULTS The individual ESD values for 4 cm, 5 cm, and 6 cm thick phantoms for DM and DBT at Rh/Rh target/filter combination and 30-32 kV/56 mAs levels were 5.06 and 4.18 mGy; 5.82 and 5.08 mGy; and 7.26 and 11.4 mGy, respectively; while AGDs were 1.57 and 1.30 mGy, 1.33 and 1.39 mGy; and 1.29 and 3.60 mGy, respectively. The Kruskal-Wallis test showed a statistically significant difference in AGD for DM (P = .029) but not for DBT (P = 0.368). The Mann-Whitney and Wilcoxon signed rank tests showed no statistically significant difference for ESD or AGD between both DM and DBT techniques (P = .827 and .513). The percentage differences in ESD for phantom thicknesses of 4 cm, 5 cm, and 6 cm between DBT and DM ranged between -21% and 36%; while for AGD between -21% and 64.2%. CONCLUSIONS The ESD and AGD for single view projection in DM and DBT showed differences at 4 and 6 cm breast thicknesses and compositions but not at 5 cm thickness with 30-32 kV and a Rh/Rh target/filter combination. IMPLICATIONS FOR PRACTICE A fibro-fatty breast results in less radiation dose variations in terms of ESD and AGD between DM and DBT techniques.

Research paper thumbnail of Effect of X-ray beam energy and image reconstruction technique on computed tomography numbers of various tissue equivalent materials

Radiography, 2020

Introduction: Computed tomography (CT) numbers are used in radiological diagnosis, attenuation co... more Introduction: Computed tomography (CT) numbers are used in radiological diagnosis, attenuation correction and radiotherapy treatment planning. Modern CT scanners use iterative reconstruction methods instead of the traditional filtered back projection (FBP). Hence, the investigation of CT number accuracy with image reconstruction techniques and X-ray tube potential (kVp) used in CT is warranted. The aim of this study is to evaluate the effect of Sinogram Affirmed Iterative Reconstruction (SAFIRE) Technique and image acquisition at different tube potentials on CT numbers of different tissue equivalent materials. Methods: Images of the Computerised Imaging Reference System Model 062M Electron Density Phantom were acquired at different tube potentials and reconstructed using FBP and different strengths of SAFIRE. Average CT numbers, in circular regions of interest, and their standard deviations were used to investigate any dependence of CT numbers on tube potentials and/or image reconstruction technique using non-parametric statistical tests with p-values set at 0.05. Results: Statistically significant differences in CT numbers were not observed (p > 0.091) between the different image reconstruction techniques. CT number of bone equivalent materials increased significantly (p < 0.015), by up to 400 Hounsfield Units, when tube potential was decreased. Such extent of CT number change over the tube potentials range used in this study may influence diagnostic outcomes in lung nodule, contrast enhanced and calcium score studies. For all other tissue equivalent materials, the CT number did not change significantly for different tube potentials. Linear relationship was observed between CT numbers and electron densities. Conclusion: The study concludes that the CT numbers of all tissues did not change significantly with image reconstruction methods. However, the CT numbers of bone equivalent materials increased with decreasing tube potentials, which may result in misrepresentation of clinical information obtained. Implications for practice: When CT images are used to extract quantitative parameters such as calcium score, to characterise lung nodules and contrast enhanced structures, the kVp used for image acquisition should be carefully selected to avoid any misrepresentation of clinical information.

Research paper thumbnail of Iterative Reconstruction Techniques as a Dose Reduction Tool in Pediatric Computed Tomography Imaging: A Phantom Study

Research paper thumbnail of Comparison between Recorded and Measured Radiation Doses in Diagnostic Full-field Digital Mammography: A Phantom Study

Journal of Clinical Imaging Science, 2020

Objectives: There are concerns regarding the difference between directly recorded and measured en... more Objectives: There are concerns regarding the difference between directly recorded and measured entrance skin dose (ESD) and average glandular dose (AGD) in full-field digital mammography (FFDM). The objective of the study was to evaluate the effect of different exposure parameters on ESD and AGD recorded directly and measured from an FFDM unit using a phantom. Material and Methods: The ESD and AGD of 27 FFDM (craniocaudal [CC] projection) images of tissue-equivalent phantoms were acquired using a general electric (GE Senographe Essential) FFDM unit. The phantoms were used to simulate three different breast thicknesses and compositions. Tube potential, tube load, and target/ filter combinations also were recorded directly from the FFDM unit. Results: The mean differences between the directly recorded and measured ESD and AGD were 0.23 and 0.080, respectively. The 95% confidence intervals for ESD and AGD were 0.1–0.36 and 0.04–0.10, respectively. Results of paired t-test showed statis...

Research paper thumbnail of Comparison of radiation doses between diagnostic full‐field digital mammography (FFDM) and digital breast tomosynthesis (DBT): a clinical study

Journal of Medical Radiation Sciences, 2020

Introduction: There are increasing concerns about radiation exposure among women who undergo full... more Introduction: There are increasing concerns about radiation exposure among women who undergo full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT). The main aim of this study was to compare the entrance surface dose (ESD) and average glandular dose (AGD) from FFDM and DBT for different breast thicknesses. Methods: The ESD and AGD for FFDM in craniocaudal, mediolateral oblique and DBT in craniocaudal projection were recorded from a GE Senographe Essential FFDM unit. The accuracy of the ESD and AGD from the FFDM unit was verified during regular quality assurance programme. Patients were categorised according to their compressed breast thicknesses. X-ray tube potential and target filter combinations were varied with ESD and AGD recorded directly from the FFDM unit. The non-parametric Kruskal-Wallis, Mann-Whitney and Wilcoxon signed-rank tests were performed. Results: The median and interquartile range (IQR) age of the patients were 48 and 11 years, respectively. The highest median for ESD and median total AGD for different breast thicknesses were ranged from 3.3 to 9.1 mGy and 3.3 to 6.0 mGy, respectively, for two-view FFDM. However, it ranged from 3.1 to 8.9 mGy and 1.8 to 4.0 mGy, respectively, for single-view DBT. Both ESD and AGD were significantly lower for DBT (P < 0.001) compared with FFDM. There was a significant difference (P = 0.001) in the ESD and AGD values for different breast thicknesses in FFDM and DBT techniques. Conclusions: The AGD for a single-view DBT was lower than the two-view FFDM technique.

Research paper thumbnail of Investigation of Exposure Factors for Various Breast Composition and Thicknesses in Digital Screening Mammography Related to Breast Dose

Medical Principles and Practice, 2018

Objective: To investigate the effect of exposure factors used in digital screening mammography on... more Objective: To investigate the effect of exposure factors used in digital screening mammography on image quality of different breast compositions. Material and Methods: A digital mammography unit, with tungsten (W) as target, rhodium (Rh) and silver (Ag) as filters, and amorphous selenium detectors, was used to image Computerized Imaging Reference Systems (CIRS) Model 12A phantoms of thickness 4, 5, and 6 cm. Images of each phantom were obtained using target-filter combinations of W/Rh and W/Ag, at 28, 30, and 32 kVp. Images were evaluated by 5 senior technologists with experience in mammography. Image scores were assigned, for each type of feature present in the phantom. Statistical analysis was performed using nonparametric tests to compare sets of image scores at p = 0.05. Results: A small but statistically significant improvement was detected in the visibility of microcalcifications (8.8 ± 0.2; p = 0.031) for the W/Rh combination but this did not show any differences in the visib...

Research paper thumbnail of Extent of tube-current reduction using sinogram affirmed iterative reconstruction in pediatric computed tomography: phantom study

Pediatric Radiology, 2018

Background Iterative image reconstruction techniques can produce diagnostic-quality computed tomo... more Background Iterative image reconstruction techniques can produce diagnostic-quality computed tomography (CT) images with lower radiation dose. Objective To quantify the reduction in x-ray tube-current setting and optimize pediatric CT scans using different strengths of an iterative reconstruction technique. Materials and methods The head, chest and abdomen regions of an anthropomorphic phantom representing a 5-year-old patient were scanned using standard CT protocols. Images were reconstructed using filtered back projection and different strengths of a sinogram affirmed iterative reconstruction technique. Repeated measurements of contrast-to-noise ratios in the lungs, bone and soft-tissue regions of the phantom were carried out. Maximum increase in contrast-to-noise ratio with iterative reconstruction strength was identified and a tube-current reduction factor was calculated. Head scans were repeated with reduced tube current and compared to filtered back projection images. Results Iterative reconstruction strength of 3 for head and chest images and 4 for abdomen images were optimum, resulting in contrast-to-noise ratio increase of about 50%. A tube-current reduction factor of 1.2 for head images was calculated. Images of the head acquired using reduced tube-current showed similar contrast-to-noise ratio as images form filtered back projection with full tube current. Conclusion Optimum strength of iterative reconstruction technique has been identified for head, chest and abdomen images. Reductions in tube current of 20%, resulting in similar radiation dose reduction, have been established.

Research paper thumbnail of Image Quality and Radiation Dose for Fibrofatty Breast using Target/filter Combinations in Two Digital Mammography Systems

Journal of Clinical Imaging Science, 2020

Objectives: The aim of this study was to determine the optimum combinations of target and filter ... more Objectives: The aim of this study was to determine the optimum combinations of target and filter materials for various X-ray tube voltage settings, as well as their effects on image quality and radiation dose. This was done using different digital mammography (DM) imaging systems with a breast equivalent phantom. Material and Methods: Two DM units with a tungsten (W) target, silver (Ag), and rhodium (Rh) filters and dual molybdenum (Mo) and Rh targets/filters were used. A tissue-equivalent mammography phantom of 6 cm thickness equivalent to a fibrofatty breast was exposed 20 times to different target/filter material combinations (W/Rh, W/Ag, Rh/Rh, Mo/Rh, and Mo/Mo) and various kV settings (28–34 kV). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for each exposure. Results: The W/Ag combination resulted in the lowest entrance skin dose and mean glandular dose (MGD). The MGD for the W/Rh combination was 60% less than that of the W/Ag combination at...

Research paper thumbnail of Radiation dose in pelvic imaging.(PEER REVIEW)

Radiologic Technology, Sep 1, 2005

Research paper thumbnail of Effective dose to patients from single photon emission computed tomography and computed tomography during myocardial perfusion imaging

Journal of Nuclear Medicine Technology

Rationale: Radiation dose to patients from imaging modalities is measured or calculated to assess... more Rationale: Radiation dose to patients from imaging modalities is measured or calculated to assess the risk of the procedure and compare it to the benefits. Periodic review of image acquisition methods and radiation dose used are essential part of the optimization in medical imaging. The aim of this study was to estimate patient radiation dose from single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) using computed tomography (CT) images for attenuation correction. Method: SPECT and CT image acquisition parameters such as, administered activity (AA), CT dose index (CTDIvol) and dose-length product (DLP) of 415 patients who have undergone SPECT MPI using CT attenuation correction were reviewed. Effective dose (ED) for the SPECT part, CT part and the total ED for the procedure were calculated. AA, CTDIvol and ED values were compared between patient gender, body mass index, imaging scanner model and imaging centers. Statistical analyses were carried out using t-test and one-way analysis of variance at p < 0.05 level of significance. Results: The range of AA used for MPI was found to be 1206 to 1964 MBq per patient regardless of their gender. The resulting mean ED value of 8.8 mSv for males was significantly lower (p=0.002) than 10.4 mSv for females in SPECT. The range of CTDIvol was 1.12 to 3.97 mGy resulting in mean ED of 0.8 mSv for males, significantly lower (p<0.001) than 1.1 mSv for females in CT. The average combined ED for male and female patients were 9.6 and 11.5 mSv respectively. Positive correlation was found between AA and patient body mass index (r=0.48; p<0.001), indicating patient size related AA. However, CTDIvol was found to depend only on the scanner model regardless of body mass index. Conclusion: The ED from SPECT-CT MPI studies was found to be around 11 mSv with 10 mSv from the SPECT part of the study. The extra risk to the patients from CT imaging for attenuation corrections is small compared to the benefits incurred in accurate diagnosis.

Research paper thumbnail of The stability of dry and wet laser imaging systems.(Peer Review)

Radiologic Technology, 2005

Research paper thumbnail of Effect of mA Reduction on Image Quality Parameters and Patient Dose in Computed Tomography Imaging

Radiologic technology, 2016

To establish the extent of dose reduction that can be achieved using a computed tomography (CT) q... more To establish the extent of dose reduction that can be achieved using a computed tomography (CT) quality assurance phantom with various user-defined protocols at different milliamperage (mA) settings and kilovoltage peak (kVp) without affecting image quality. Images of a CT quality assurance phantom containing line-pair patterns and 3 tissue-equivalent inserts in water were acquired with different mA settings on 4 different CT scanners. The kVp was kept constant at 120 while the mA was changed in increments of 20, from 30 mA to 190 mA. Three images from each series acquired at different mA settings were selected: one each for the quantitative analysis of spatial resolution, contrast-to-noise ratio (CNR), and image noise using image analysis freeware. Statistical analysis was carried out with a statistical probability of P < .05 indicating significant difference. Results of the statistical analysis revealed significant differences in the CNR of all 3 types of tissue-equivalent inse...

Research paper thumbnail of Issues affecting the motivation of nuclear medicine technologists in Kuwait

Journal of allied health

The demand for nuclear medicine technologists (NMTs) in Kuwait has increased, especially with the... more The demand for nuclear medicine technologists (NMTs) in Kuwait has increased, especially with the introduction of multimodality imaging systems. In order to increase the number of NMTs in the workforce and retain the existing NMTs, there should be a better way to motivate them. To find out how satisfied NMTs are and the factors that motivate them. An interview was conducted with 40 randomly selected NMTs to explore deep-seated emotions and attitudes that were related to motivation. Questions about the recognition NMTs receive from the general public, whether they are acknowledged as significant contributors to health services, ways to improve the standing of NMTs in society, and the clarity of the job description were included. A questionnaire survey was then conducted with 100 randomly selected NMTs. The questions were designed to elicit wider perspective of the information obtained from the interviews. The results show a need for attention in the Ministry of Health to NMTs for recognition, motivation, and improvement. Giving the NMTs their own identity and opportunities to be part of decision-making in the health team would influence more students to join nuclear medicine departments and give more self-confidence to the existing NMTs.

Research paper thumbnail of Enhancing Readability and Detection of Age-Related Macular Degeneration Using Optical Coherence Tomography Imaging: An AI Approach

Bioengineering, Mar 22, 2024

Research paper thumbnail of Comparison between conventional radiography and digital radiography for various kVp and mAs settings using a pelvic phantom

Radiography, May 1, 2004

Introduction A study was carried out to investigate the differences in the quality of images obta... more Introduction A study was carried out to investigate the differences in the quality of images obtained using film/screen radiography and computed radiography at various kVp and mAs settings within the range of values used for diagnostic imaging. Method Images of a pelvic phantom obtained at specific kVp/mAs combinations using Kodak film/screen combination were compared with images obtained using an AGFA computed radiography image plate. Images were assessed using a 5-point subjective scoring system and statistical significances were tested using un-paired t-test. Results and conclusion There were not any significant changes (P ! 0:05) in the quality of computed radiography images for kVp changes in the range ÿ15% to C30%. Lower limits for mAs at any specific kVp setting can be established for an individual computed radiography system to produce diagnostic quality images. These lower limits were 25% lower than the standard values used for film/screen systems.

Research paper thumbnail of The<i>Q</i>value for the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow /><mml:mrow><mml:mi mathvariant="italic">m</mml:mi></mml:mrow><mml:mrow /><mml:mrow /><mml:mprescri...

Physical review, May 1, 1994

The threshold energy of the Mg(p, n) Al reaction has been measured to be 5209.46+0.12 keV, using ... more The threshold energy of the Mg(p, n) Al reaction has been measured to be 5209.46+0.12 keV, using a 1 V standard as reference, and taking account of efFects due to 6nite beam energy spread, nonuniform proton energy loss in the target, and ionization of the magnesium atoms. The Q value derived for the Al beta decay then becomes 4232.17+0.12 keV, which is in clear disagreement with the most precise of the existing measurements. A further measurement is proposed.

Research paper thumbnail of Comparison between image quality in electronic zoom and geometric magnification in digital mammography

Journal of X-Ray Science and Technology, 2016

BACKGROUND: Magnification mammography is performed to enhance the visibility of small structures ... more BACKGROUND: Magnification mammography is performed to enhance the visibility of small structures at the expense of relatively high radiation dose as a complementary examination to standard mammography. The introduction of postprocessing capabilities and the widespread use of digital mammography has promoted some controversy in the last decade on whether similar visibility can be achieved using electronic zoom. The aim of this study is to compare the visibility of small structures in images obtained by the two techniques stated above for different exposure conditions. METHODS: Images of a Fluke Biomedical Model 18-220 Mammography Accreditation Phantom were obtained using standard techniques and geometric magnification, using a digital mammography unit, with different exposure factors. Three different target/filter combinations (Mo/Mo,Mo/Rh,Rh/Rh), variable kVp (26-32), and automatic exposure control were used. Images obtained using standard technique were electronically zoomed and compared to the corresponding magnification mammograms. Comparisons were based on the visibility of structures evaluated by five senior technologist with extensive experience in mammography. Statistical analysis was performed using non-parametric tests. RESULTS: Visibility of structures was not affected by the kV used for a given target/filter combination for both techniques (p > 0.065). Target/filter combination of Mo/Mo provided better visibility of micro-calcification and fibers (p < 0.026) in geometric magnification technique and Mo/Rh in the digital zoom technique. No significant differences were observed in the visibility of simulated breast masses. The overall image score was significantly higher (p < 0.001) for geometric magnification over the digital zoom for Mo/Mo & Rh/Rh combinations. CONCLUSION: Although sufficient image quality was maintained in electronically zoomed images, geometric magnification provided better overall visualization of structures in the phantom.

Research paper thumbnail of Accelerator beam energy calibration with the 27Al(p, n) and 27Al(p, γ) reactions

Nuclear Instruments and Methods in Physics Research, Mar 1, 1994

The energies of resonances in the Z~AI(p, y) reaction at 992 and 1317 keV and of the threshold of... more The energies of resonances in the Z~AI(p, y) reaction at 992 and 1317 keV and of the threshold of the Z7AI(p, n) reaction at 5804 keV have been measured accurately with respect to a 1 V standard. Both calibration energies and energies suitable for Q-value calculations are given. Corrections are made for the effects of the energy distribution of the proton beam, of nonuniform energy loss of the protons in the target and of ionisation of the target atoms.

Research paper thumbnail of SU-E-I-61: Application of the ALARA Principle in Digital Radiography Systems

Medical Physics, 2011

Purpose: To investigate the effect of using higher x‐ray tube voltage (kVp), than those recommend... more Purpose: To investigate the effect of using higher x‐ray tube voltage (kVp), than those recommended by manufacturers, on patient dose and image quality during digital radiography (DR) examination of the Lumber Spine. Methods: Reference images of an RSD (Radiology Support Devices, Long Beach, CA, USA) anthropomorphic lumber spine phantom were obtained using 3 different DR systems using exposure factors, kVp and tube‐current time product (mAs), recommended by the manufacturer of each system. Test images were obtained, on each system, using kVp values which were 15% and 30% higher than those recommended by the respective manufacturers, while reducing the mAs to 50% and 25% respectively of the reference exposure. The images were evaluated subjectively by 3 experienced Radiologist using the image quality criteria recommended by the Commission of the European Communities (CEC) for LS examination, on a 5‐point scale. For each image, the entrance surface exposure, including backscatter, to the phantom was measured using the Victoreen Model 8000 NERO TM mAx system and the entrance surface dose and effective dose were calculated. Any statistically significant differences between the average scores for the images were tested using Kruskal‐Wallis test at p=0.05. Results: The average score from the 3 Radiologists were above the clinically acceptable levels for all of the images. Within each system, the average scores for the images obtained with different exposure factors did not show any statistically significant differences. The entrance surface doses to the phantom and the calculated effective doses decreased by approximately 30% for a kVp increase of 15% and approximately by 50% for kVp increase of 30% in all 3 systems. Conclusions: Dose reduction up to 50% can be achieved without affecting the diagnostic quality of all images in the 3 systems by using kVp and mAs values other than those recommended by the DR system's manufacturer.

Research paper thumbnail of Radiation Dose to Patients in Coronary Interventional Procedures: A Survey

Radiation Protection Dosimetry, 2018

The objective of this study was to evaluate dose–area product (DAP) and peak skin dose (PSD) for ... more The objective of this study was to evaluate dose–area product (DAP) and peak skin dose (PSD) for coronary angiography (CA) and percutaneous coronary intervention (PCI). The DAP and PSD of 300 randomly selected patients who were referred to CA and/or PCI, over a period of 3 months were recorded and analyzed. The mean DAP of 32 Gy cm2 and mean PSD of 412 mGy for CA were lower than 118 Gy cm2 and 857 mGy, respectively, for PCI. The DAP range of 2–84 Gy cm2 for CA and 12–378 mGy for PCI were also established. The maximum value of PSD for PCI procedures reached above the 2 Gy threshold for erythema. However, these values are similar to those available in literature. Periodic surveys may be required to monitor and/or reduce radiation doses in coronary interventional procedures.

Research paper thumbnail of The effect of different exposure parameters on radiation dose in digital mammography and digital breast tomosynthesis: A phantom study

Radiography, 2019

INTRODUCTION There are concerns regarding the increase in radiation dose among women undergoing b... more INTRODUCTION There are concerns regarding the increase in radiation dose among women undergoing both digital mammography (DM) and digital breast tomosynthesis (DBT). The aim of this study was to evaluate the effect of different exposure parameters on entrance skin dose (ESD) and average glandular dose (AGD) for DM and DBT using a phantom. METHODS The ESD and AGD of 30 DM and DBT (cranio-caudal projection) examinations using a tissue equivalent phantom where acquired using a GE Senographe Essential DM unit. Commercial phantoms were used to simulate three different breast thicknesses and compositions. Tube potential, tube load, and target/filter combinations were also varied with ESD and AGD recorded directly from the DM unit. Comparisons were made using the non-parametric Kruskal Wallis, Mann-Whitney, and Wilcoxon signed rank tests. RESULTS The individual ESD values for 4 cm, 5 cm, and 6 cm thick phantoms for DM and DBT at Rh/Rh target/filter combination and 30-32 kV/56 mAs levels were 5.06 and 4.18 mGy; 5.82 and 5.08 mGy; and 7.26 and 11.4 mGy, respectively; while AGDs were 1.57 and 1.30 mGy, 1.33 and 1.39 mGy; and 1.29 and 3.60 mGy, respectively. The Kruskal-Wallis test showed a statistically significant difference in AGD for DM (P = .029) but not for DBT (P = 0.368). The Mann-Whitney and Wilcoxon signed rank tests showed no statistically significant difference for ESD or AGD between both DM and DBT techniques (P = .827 and .513). The percentage differences in ESD for phantom thicknesses of 4 cm, 5 cm, and 6 cm between DBT and DM ranged between -21% and 36%; while for AGD between -21% and 64.2%. CONCLUSIONS The ESD and AGD for single view projection in DM and DBT showed differences at 4 and 6 cm breast thicknesses and compositions but not at 5 cm thickness with 30-32 kV and a Rh/Rh target/filter combination. IMPLICATIONS FOR PRACTICE A fibro-fatty breast results in less radiation dose variations in terms of ESD and AGD between DM and DBT techniques.

Research paper thumbnail of Effect of X-ray beam energy and image reconstruction technique on computed tomography numbers of various tissue equivalent materials

Radiography, 2020

Introduction: Computed tomography (CT) numbers are used in radiological diagnosis, attenuation co... more Introduction: Computed tomography (CT) numbers are used in radiological diagnosis, attenuation correction and radiotherapy treatment planning. Modern CT scanners use iterative reconstruction methods instead of the traditional filtered back projection (FBP). Hence, the investigation of CT number accuracy with image reconstruction techniques and X-ray tube potential (kVp) used in CT is warranted. The aim of this study is to evaluate the effect of Sinogram Affirmed Iterative Reconstruction (SAFIRE) Technique and image acquisition at different tube potentials on CT numbers of different tissue equivalent materials. Methods: Images of the Computerised Imaging Reference System Model 062M Electron Density Phantom were acquired at different tube potentials and reconstructed using FBP and different strengths of SAFIRE. Average CT numbers, in circular regions of interest, and their standard deviations were used to investigate any dependence of CT numbers on tube potentials and/or image reconstruction technique using non-parametric statistical tests with p-values set at 0.05. Results: Statistically significant differences in CT numbers were not observed (p > 0.091) between the different image reconstruction techniques. CT number of bone equivalent materials increased significantly (p < 0.015), by up to 400 Hounsfield Units, when tube potential was decreased. Such extent of CT number change over the tube potentials range used in this study may influence diagnostic outcomes in lung nodule, contrast enhanced and calcium score studies. For all other tissue equivalent materials, the CT number did not change significantly for different tube potentials. Linear relationship was observed between CT numbers and electron densities. Conclusion: The study concludes that the CT numbers of all tissues did not change significantly with image reconstruction methods. However, the CT numbers of bone equivalent materials increased with decreasing tube potentials, which may result in misrepresentation of clinical information obtained. Implications for practice: When CT images are used to extract quantitative parameters such as calcium score, to characterise lung nodules and contrast enhanced structures, the kVp used for image acquisition should be carefully selected to avoid any misrepresentation of clinical information.

Research paper thumbnail of Iterative Reconstruction Techniques as a Dose Reduction Tool in Pediatric Computed Tomography Imaging: A Phantom Study

Research paper thumbnail of Comparison between Recorded and Measured Radiation Doses in Diagnostic Full-field Digital Mammography: A Phantom Study

Journal of Clinical Imaging Science, 2020

Objectives: There are concerns regarding the difference between directly recorded and measured en... more Objectives: There are concerns regarding the difference between directly recorded and measured entrance skin dose (ESD) and average glandular dose (AGD) in full-field digital mammography (FFDM). The objective of the study was to evaluate the effect of different exposure parameters on ESD and AGD recorded directly and measured from an FFDM unit using a phantom. Material and Methods: The ESD and AGD of 27 FFDM (craniocaudal [CC] projection) images of tissue-equivalent phantoms were acquired using a general electric (GE Senographe Essential) FFDM unit. The phantoms were used to simulate three different breast thicknesses and compositions. Tube potential, tube load, and target/ filter combinations also were recorded directly from the FFDM unit. Results: The mean differences between the directly recorded and measured ESD and AGD were 0.23 and 0.080, respectively. The 95% confidence intervals for ESD and AGD were 0.1–0.36 and 0.04–0.10, respectively. Results of paired t-test showed statis...

Research paper thumbnail of Comparison of radiation doses between diagnostic full‐field digital mammography (FFDM) and digital breast tomosynthesis (DBT): a clinical study

Journal of Medical Radiation Sciences, 2020

Introduction: There are increasing concerns about radiation exposure among women who undergo full... more Introduction: There are increasing concerns about radiation exposure among women who undergo full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT). The main aim of this study was to compare the entrance surface dose (ESD) and average glandular dose (AGD) from FFDM and DBT for different breast thicknesses. Methods: The ESD and AGD for FFDM in craniocaudal, mediolateral oblique and DBT in craniocaudal projection were recorded from a GE Senographe Essential FFDM unit. The accuracy of the ESD and AGD from the FFDM unit was verified during regular quality assurance programme. Patients were categorised according to their compressed breast thicknesses. X-ray tube potential and target filter combinations were varied with ESD and AGD recorded directly from the FFDM unit. The non-parametric Kruskal-Wallis, Mann-Whitney and Wilcoxon signed-rank tests were performed. Results: The median and interquartile range (IQR) age of the patients were 48 and 11 years, respectively. The highest median for ESD and median total AGD for different breast thicknesses were ranged from 3.3 to 9.1 mGy and 3.3 to 6.0 mGy, respectively, for two-view FFDM. However, it ranged from 3.1 to 8.9 mGy and 1.8 to 4.0 mGy, respectively, for single-view DBT. Both ESD and AGD were significantly lower for DBT (P < 0.001) compared with FFDM. There was a significant difference (P = 0.001) in the ESD and AGD values for different breast thicknesses in FFDM and DBT techniques. Conclusions: The AGD for a single-view DBT was lower than the two-view FFDM technique.

Research paper thumbnail of Investigation of Exposure Factors for Various Breast Composition and Thicknesses in Digital Screening Mammography Related to Breast Dose

Medical Principles and Practice, 2018

Objective: To investigate the effect of exposure factors used in digital screening mammography on... more Objective: To investigate the effect of exposure factors used in digital screening mammography on image quality of different breast compositions. Material and Methods: A digital mammography unit, with tungsten (W) as target, rhodium (Rh) and silver (Ag) as filters, and amorphous selenium detectors, was used to image Computerized Imaging Reference Systems (CIRS) Model 12A phantoms of thickness 4, 5, and 6 cm. Images of each phantom were obtained using target-filter combinations of W/Rh and W/Ag, at 28, 30, and 32 kVp. Images were evaluated by 5 senior technologists with experience in mammography. Image scores were assigned, for each type of feature present in the phantom. Statistical analysis was performed using nonparametric tests to compare sets of image scores at p = 0.05. Results: A small but statistically significant improvement was detected in the visibility of microcalcifications (8.8 ± 0.2; p = 0.031) for the W/Rh combination but this did not show any differences in the visib...

Research paper thumbnail of Extent of tube-current reduction using sinogram affirmed iterative reconstruction in pediatric computed tomography: phantom study

Pediatric Radiology, 2018

Background Iterative image reconstruction techniques can produce diagnostic-quality computed tomo... more Background Iterative image reconstruction techniques can produce diagnostic-quality computed tomography (CT) images with lower radiation dose. Objective To quantify the reduction in x-ray tube-current setting and optimize pediatric CT scans using different strengths of an iterative reconstruction technique. Materials and methods The head, chest and abdomen regions of an anthropomorphic phantom representing a 5-year-old patient were scanned using standard CT protocols. Images were reconstructed using filtered back projection and different strengths of a sinogram affirmed iterative reconstruction technique. Repeated measurements of contrast-to-noise ratios in the lungs, bone and soft-tissue regions of the phantom were carried out. Maximum increase in contrast-to-noise ratio with iterative reconstruction strength was identified and a tube-current reduction factor was calculated. Head scans were repeated with reduced tube current and compared to filtered back projection images. Results Iterative reconstruction strength of 3 for head and chest images and 4 for abdomen images were optimum, resulting in contrast-to-noise ratio increase of about 50%. A tube-current reduction factor of 1.2 for head images was calculated. Images of the head acquired using reduced tube-current showed similar contrast-to-noise ratio as images form filtered back projection with full tube current. Conclusion Optimum strength of iterative reconstruction technique has been identified for head, chest and abdomen images. Reductions in tube current of 20%, resulting in similar radiation dose reduction, have been established.

Research paper thumbnail of Image Quality and Radiation Dose for Fibrofatty Breast using Target/filter Combinations in Two Digital Mammography Systems

Journal of Clinical Imaging Science, 2020

Objectives: The aim of this study was to determine the optimum combinations of target and filter ... more Objectives: The aim of this study was to determine the optimum combinations of target and filter materials for various X-ray tube voltage settings, as well as their effects on image quality and radiation dose. This was done using different digital mammography (DM) imaging systems with a breast equivalent phantom. Material and Methods: Two DM units with a tungsten (W) target, silver (Ag), and rhodium (Rh) filters and dual molybdenum (Mo) and Rh targets/filters were used. A tissue-equivalent mammography phantom of 6 cm thickness equivalent to a fibrofatty breast was exposed 20 times to different target/filter material combinations (W/Rh, W/Ag, Rh/Rh, Mo/Rh, and Mo/Mo) and various kV settings (28–34 kV). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for each exposure. Results: The W/Ag combination resulted in the lowest entrance skin dose and mean glandular dose (MGD). The MGD for the W/Rh combination was 60% less than that of the W/Ag combination at...

Research paper thumbnail of Radiation dose in pelvic imaging.(PEER REVIEW)

Radiologic Technology, Sep 1, 2005

Research paper thumbnail of Effective dose to patients from single photon emission computed tomography and computed tomography during myocardial perfusion imaging

Journal of Nuclear Medicine Technology

Rationale: Radiation dose to patients from imaging modalities is measured or calculated to assess... more Rationale: Radiation dose to patients from imaging modalities is measured or calculated to assess the risk of the procedure and compare it to the benefits. Periodic review of image acquisition methods and radiation dose used are essential part of the optimization in medical imaging. The aim of this study was to estimate patient radiation dose from single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) using computed tomography (CT) images for attenuation correction. Method: SPECT and CT image acquisition parameters such as, administered activity (AA), CT dose index (CTDIvol) and dose-length product (DLP) of 415 patients who have undergone SPECT MPI using CT attenuation correction were reviewed. Effective dose (ED) for the SPECT part, CT part and the total ED for the procedure were calculated. AA, CTDIvol and ED values were compared between patient gender, body mass index, imaging scanner model and imaging centers. Statistical analyses were carried out using t-test and one-way analysis of variance at p < 0.05 level of significance. Results: The range of AA used for MPI was found to be 1206 to 1964 MBq per patient regardless of their gender. The resulting mean ED value of 8.8 mSv for males was significantly lower (p=0.002) than 10.4 mSv for females in SPECT. The range of CTDIvol was 1.12 to 3.97 mGy resulting in mean ED of 0.8 mSv for males, significantly lower (p<0.001) than 1.1 mSv for females in CT. The average combined ED for male and female patients were 9.6 and 11.5 mSv respectively. Positive correlation was found between AA and patient body mass index (r=0.48; p<0.001), indicating patient size related AA. However, CTDIvol was found to depend only on the scanner model regardless of body mass index. Conclusion: The ED from SPECT-CT MPI studies was found to be around 11 mSv with 10 mSv from the SPECT part of the study. The extra risk to the patients from CT imaging for attenuation corrections is small compared to the benefits incurred in accurate diagnosis.

Research paper thumbnail of The stability of dry and wet laser imaging systems.(Peer Review)

Radiologic Technology, 2005

Research paper thumbnail of Effect of mA Reduction on Image Quality Parameters and Patient Dose in Computed Tomography Imaging

Radiologic technology, 2016

To establish the extent of dose reduction that can be achieved using a computed tomography (CT) q... more To establish the extent of dose reduction that can be achieved using a computed tomography (CT) quality assurance phantom with various user-defined protocols at different milliamperage (mA) settings and kilovoltage peak (kVp) without affecting image quality. Images of a CT quality assurance phantom containing line-pair patterns and 3 tissue-equivalent inserts in water were acquired with different mA settings on 4 different CT scanners. The kVp was kept constant at 120 while the mA was changed in increments of 20, from 30 mA to 190 mA. Three images from each series acquired at different mA settings were selected: one each for the quantitative analysis of spatial resolution, contrast-to-noise ratio (CNR), and image noise using image analysis freeware. Statistical analysis was carried out with a statistical probability of P < .05 indicating significant difference. Results of the statistical analysis revealed significant differences in the CNR of all 3 types of tissue-equivalent inse...

Research paper thumbnail of Issues affecting the motivation of nuclear medicine technologists in Kuwait

Journal of allied health

The demand for nuclear medicine technologists (NMTs) in Kuwait has increased, especially with the... more The demand for nuclear medicine technologists (NMTs) in Kuwait has increased, especially with the introduction of multimodality imaging systems. In order to increase the number of NMTs in the workforce and retain the existing NMTs, there should be a better way to motivate them. To find out how satisfied NMTs are and the factors that motivate them. An interview was conducted with 40 randomly selected NMTs to explore deep-seated emotions and attitudes that were related to motivation. Questions about the recognition NMTs receive from the general public, whether they are acknowledged as significant contributors to health services, ways to improve the standing of NMTs in society, and the clarity of the job description were included. A questionnaire survey was then conducted with 100 randomly selected NMTs. The questions were designed to elicit wider perspective of the information obtained from the interviews. The results show a need for attention in the Ministry of Health to NMTs for recognition, motivation, and improvement. Giving the NMTs their own identity and opportunities to be part of decision-making in the health team would influence more students to join nuclear medicine departments and give more self-confidence to the existing NMTs.