Computed tomography dose index free-in-air and single scan dose profile analysis of multi-slice scanners

The increasing use of computed tomography (CT) in clinical practice marks the needs to understand the dose descriptor and dose profile. The purpose of the current study is to determine the computed tomography dose index free-in-air (CTDIair) and to evaluate the single scan dose profile (SSDP) in two types of multi-slice CT (MSCT) scanners. The MSCT scanners involved were 128-slice CT scanner Siemens SOMATOM Definition AS+ at Hospital Sultanah Aminah (HSA), Johor Bahru and 16-slice CT scanner Siemens SOMATOM Emotion 16 at Hospital Permai, Johor Bahru. Two types of dosimeters were used for the measurements which were thermoluminescence dosimeter (TLD-100) and optically stimulated luminescence dosimeter (nanoDot OSLD). For each CT scanner, all protocols were set based on the routine CT abdominal examinations for adult male. The scan time, slice thickness and nominal beam width were held on constant while the tube current and tube potential were modified. In total, there were seven protocols for 128-slice CT scanner and six protocols for 16-slice scanner. For both CT scanners, when the tube current or the tube potential was increased, the CTDIair was increased as well. For 128-slice CT scanner using TLD-100, when the tube current was constant at 100 mAs, the CTDIair ranged from 3.560 mGy (80 kV) to 13.585 mGy (140 kV). When the tube potential was constant at 120 kV, the CTDIair ranged from 8.825 mGy (100 mAs) to 21.528 mGy (250 mAs). From OSL dosimeter, when the tube current was constant at 100 mAs, the CTDIair ranged from 2.391 mGy (80 kV) to 7.751 mGy (140 kV). When the tube potential was constant at 120 kV, the CTDIair ranged from 6.084 mGy (100 mAs) to 14.604 mGy (250 mAs). For 16-slice CT scanner using TLD-100, when the tube current was constant at 100 mAs, the CTDIair ranged from 1.924 mGy (80 kV) to 4.624 mGy (130 kV). When the tube potential was constant at 110 kV, the CTDIair ranged from 2.456 mGy (50 mAs) to 6.493 mGy (200 mAs). From OSL dosimeter, when the tube current was constant at 100 mAs, the CTDIair ranged from 0.747 mGy (80 kV) to 1.649 mGy (130 kV). When the tube potential was constant at 110 kV, the CTDIair ranged from 1.058 mGy (50 mAs) to 3.833 mGy (200 mAs). For both MSCT scanners, the SSDP plotted using OriginPro 9.0 software showed that peaks in which the tube current was varied were higher and sharper than the SSDP peaks when the tube potential was changed. The full width at half maximum (FWHM) obtained from the SSDP presented the nominal beam width set for the MSCT scanner. For 128-slice CT scanner, the FWHM of OSLD was more reliable as it coincided with the nominal beam width which was 38.4 mm while for 16-slice CT scanner, the FWHM of TLD-100 was more reliable as it coincided with the nominal beam width which was 10.0 mm. The results showed good agreement between FWHM and nominal beam width. In conclusion, the X-ray tube output generated from the MSCT scanners was in line with the CT protocol setup

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

Response of optically stimulated luminescence dosimeters subjected to x-rays in diagnostic energy range

The use of optically stimulated luminescence (OSL) for dosimetry applications has recently increased considerably due to availability of commercial OSL dosimeters (nanoDots) for clinical use. The OSL dosimeter has a great potential to be used in clinical dosimetry because of its prevailing advantages in both handling and application. However, utilising nanoDot OSLDs for dose measurement in diagnostic radiology can only be guaranteed when the performance and characteristics of the dosimeters are apposite. In the present work, we examined the response of commercially available nanoDot OSLD (Al2O3:C) subjected to X-rays in general radiography. The nanoDots response with respect to reproducibility, dose linearity and signal depletion were analysed using microStar reader (Landauer, Inc., Glenwood, IL). Irradiations were performed free-in-air using 70, 80 and 120 kV tube voltages and tube currents ranging from 10 – 100 mAs. The results showed that the nanoDots exhibit good linearity and reproducibility when subjected to diagnostic X-rays, with coefficient of variations (CV) ranging between 2.3% to 3.5% representing a good reproducibility. The results also indicated average of 1% signal reduction per readout. Hence, the nanoDots showed a promising potential for dose measurement in general X-ray procedure

Magnetic flux leakage system for wire rope inspection using bluetooth communication

A wireless data communication Magnetic Flux Leakage (MFL) system for steel wire rope cable inspection has been designed and constructed to facilitate the remote data transferring. The system incorporates permanent magnets and Hall Effect sensor arrays, with its signal processing circuit and data acquisition system. Strong permanent magnetic discs of about 1T are used to magnetize the cable. Hall Effect sensors are arranged in parallel to detect the leakage flux from different angles. The system is battery operated, which is three units of AA batteries function as a power source. Another three units of AA batteries can also be fitted in as the backup power supply. The wireless data communication system has been constructed using Bluetooth module. The signals are digitized using an Emant380 Bluetooth data acquisition module consist of six channels of differential multiplexed analog-to-digital converter, and the data can be stored in computer or Smartphone’s memory. Python programming language is used to collect and interpret the data in a graphical form. This system use Tkinter graphical user interface toolkit for the computer while HTML is a platform for full screen user interface display on Smartphone. The screen displays the location and the flaws signal. System was tested and evaluated on various simulated wire rope defects of different depth and width, ranging from 2 mm to 6 mm depth and 1 mm width and also 2 mm to 6 mm width and 2 mm to 3 mm depth. This system has a relatively high sensitivity for the detection of magnetic flux leakage through defects with a depth of 2 mm and 1 mm wide

Assessment of knowledge and awareness among radiology personnel regarding current computed tomography technology and radiation dose

In this paper, we evaluate the level of knowledge and awareness among 120 radiology personnel working in 7 public hospitals in Johor, Malaysia, concerning Computed Tomography (CT) technology and radiation doses based on a set of questionnaires. Subjects were divided into two groups (Medical profession (Med, n=32) and Allied health profession (AH, n=88). The questionnaires are addressed: (1) demographic data (2) relative radiation dose and (3) knowledge of current CT technology. One-third of respondents from both groups were able to estimate relative radiation dose for routine CT examinations. 68% of the allied health profession personnel knew of the Malaysia regulations entitled 'Basic Safety Standard (BSS) 2010', although notably 80% of them had previously attended a radiation protection course. No significant difference (p < 0.05) in mean scores of CT technology knowledge detected between the two groups, with the medical professions producing a mean score of (26.7 ± 2.7) and the allied health professions a mean score of (25.2 ± 4.3). This study points to considerable variation among the respondents concerning their understanding of knowledge and awareness of risks of radiation and CT optimization techniques

Radiation dose to physicians' eye lens during interventional radiology

The demand of interventional radiology has increased, leading to significant risk of radiation where eye lens dose assessment becomes a major concern. In this study, we investigate physicians' eye lens doses during interventional procedures. Measurement were made using TLD-100 (LiF: Mg, Ti) dosimeters and was recorded in equivalent dose at a depth of 0.07 mm, Hp(0.07). Annual Hp(0.07) and annual effective dose were estimated using workload estimation for a year and Von Boetticher algorithm. Our results showed the mean Hp(0.07) dose of 0.33 mSv and 0.20 mSv for left and right eye lens respectively. The highest estimated annual eye lens dose was 29.33 mSv per year, recorded on left eye lens during fistulogram procedure. Five physicians had exceeded 20 mSv dose limit as recommended by international commission of radiological protection (ICRP). It is suggested that frequent training and education on occupational radiation exposure are necessary to increase knowledge and awareness of the physicians' thus reducing dose during the interventional procedure