Diagnostic X-ray Research Articles

Evaluation of the scattered radiations of lead and lead-free aprons in diagnostic radiology by MCNPX.

Over the past few years, because of high attenuation and lightweight, non-toxic, lead-free aprons (LFAs) have been replaced by lead aprons (LAs). Lots of studies declared that this fact was based on the interactions of diagnostic X-ray with material such as the photoelectric effect (PE) and Compton scattering. These studies have demonstrated that in these types of aprons, due to the presence of different K-edge absorption, PE has a wide absorption in various metals with divers K-edges. The measurement geometry in most of these studies was narrow beam geometry, i.e. a collimated source and a collimated detector with a large source-detector distance. The present study intended to evaluate the attenuation of radiology scattered radiations in LAs and LFAs in both narrow and broad beam geometries, which is a more realistic situation, in order to check whether or not the higher attenuation is valid. In this study, a lead apron contains (Pb + EPV) and two non-lead compounds of (W + Sn + EPVC) with different weight percent (Wt%) were evaluated in the energy range of diagnostic radiology (100 kVp). The MCNPX code was applied to simulate broad - and narrow-beam measurement geometries. The evaluations have been performed in three situations: 1st) the same density thickness of LA and LFAs 2nd) same line thickness of LA and LFAs 3rd) considering the thickness of LFAs which has the same attenuation with LAs i.e. lead equivalent thickness for LFAs in the narrow beam. Finally, the x-ray transmission ratio (I/I_0) of LAs and LFAs was compared in 100 kVp for three mentioned conditions. Our results indicated that LFAs had more radiation attenuation rather than LA in the 1st and 2nd conditions with both geometries. However, LFAs had lower attenuation in comparison to LAs in the 3rd condition with broad beam geometry. More importantly, the transmission ratio (I/I_0) of LFAs in the broad beam condition was more significant than LA. The scattered radiations produced by LFAs are more than LAs because of the production of characteristic radiations resulted from K-edge absorption in composited aprons. Consequently, the LFAs should be evaluated in both narrow and broad beam situation using the lead equivalent thickness of LFAs to make sure that the non-lead aprons do not increase the radiation dose of the user.

Estimation of the shielding ability of a tungsten functional paper for diagnostic x-rays and gamma rays.

Tungsten functional paper (TFP) is a novel paper‐based radiation‐shielding material. We measured the shielding ability of TFP against x‐rays and gamma rays. The TFP was supplied in 0.3‐mm‐thick sheets that contained 80% tungsten powder and 20% cellulose (C6H10O5) by mass. In dose measurements for x‐rays (60, 80, 100, and 120 kVp), we measured doses after through 1, 2, 3, 5, 10, and 12 TFP sheets, as well as 0.3 and 0.5 mm of lead. In lead equivalence measurements, we measured doses after through 2 and 10 TFP sheets for x‐rays (100 and 150 kVp), and 0, 7, 10, 20, and 30 TFP sheets for gamma rays from cesium‐137 source (662 keV). And then, the lead equivalent thicknesses of TFP were determined by comparison with doses after through standard lead plates (purity >99.9%). Additionally, we evaluated uniformity of the transmitted dose by TFP with a computed radiography image plate for 50 kVp x‐rays. A single TFP sheet was found to have a shielding ability of 65%, 53%, 48%, and 46% for x‐rays (60, 80, 100, and 120 kVp), respectively. The lead equivalent thicknesses of two TFP sheets were 0.10 ± 0.02, 0.09 ± 0.02 mmPb, and of ten TFP sheets were 0.48 ± 0.02 and 0.51 ± 0.02 mmPb for 100 and 150 kVp x‐rays, respectively. The lead equivalent thicknesses of 7, 10, 20, and 30 sheets of TFP for gamma rays from cesium‐137 source were estimated as 0.28, 0.43, 0.91, and 1.50 mmPb with an error of ± 0.01 mm. One TFP sheet had nonuniformity, however, seven TFP sheets provided complete shielding for 50 kVp x‐rays. TFP has adequate radiation shielding ability for x‐rays and gamma rays within the energy range used in diagnostic imaging field.

Research on the effect of iodinate contrast agent on the DNA radiation damage at CT

Objective: To evaluate the effect of iodinate contrast agent (ICA) on the formation of DNA double-stand breaks (DSBs) in human peripheral blood lymphocytes during computed tomography (CT) examinations. Methods: Peripheral venous blood (16 ml/person) of 36 volunteers were collected during the period of February to May 2016. Each blood sample was divided into 8 tubes and 4 groups on average, which were marked as groups of A, B, C, D randomly. 25 μl ICA was respectively added into one tube of each group and the groups of B, C, D accepted the same CT scan for once, twice and three times. The lymphocytes in these blood samples were separated by using density-gradient centrifugation, fixed and immunostained with γH2AX antibody. The average number of phosphorylated histone H2AX (γH2AX) foci per lymphocyte was counted under a fluorescence microscopy. Results: The numbers of γH2AX foci were increased approximately 82.9% ((0.064±0.025) vs (0.035±0.010) foci/cell) if ICA was simply added into the blood. With the increase of CT radiation, the foci numbers of the groups of B, C, D would increase and the samples containing ICA could have a more amount of foci numbers than those without ICA (B: (1.217±0.158) vs (0.774±0.258); C: (2.128±0.185) vs (1.569±0.201); D: (3.812±0.490) vs (2.938±0.480) foci/cell). The more radiation it had, the more significant the difference of foci numbers would be ((0.489±0.323), (0.549±0.278), (0.692±0.462) foci/cell). Conclusion: The ICA itself can lead to an increase of the DSBs level and the application of ICA can amplify the DNA damage as assessed with γH2AX foci formation during diagnostic X-ray procedures.

Evaluation of the Quality Control Program for Diagnostic Radiography and Fluoroscopy Devices in Syria during 2005-2013

Introduction: Extensive use of diagnostic radiology is the largest contributor to total population radiation doses. Thus, appropriate equipment and safe practice are necessary for good-quality images with optimal doses. This study aimed to perform quality control (QC) audit for radiography and fluoroscopy devices owned by private sector in Syria (2005-2013) to verify compliance of performance of X-ray machines with the regulatory requirements stipulated by the national regulatory body. Materials and Methods: In this study, QC audit included 487 X-ray diagnostic machines, (363 radiography and 124 fluoroscopy devices), installed in 306 medical diagnostic radiology centers in 14 provinces in Syria. We employed an X-ray beam analyzer device (NERO model 8000, Victoreen, USA), which was tested and calibrated at the National Secondary Standard Dosimetry Laboratory traceable to the IAEA Network of Secondary Standard Dosimetry Laboratories. Standard QC tool kits were used to evaluate tube and generator of the X-ray machines, which constituted potential (kVp), timer accuracy, radiation output consistency, tube filtration, small and large focal spot sizes, X-ray beam collimation and alignment, as well as high- and low-resolution and entrance surface dose in fluoroscopy. Results: According to our results, most of the assessed operating parameters were in compliance with the standards stipulated by the National Regulatory Authority. In cases of noncompliance for the assessed parameters, maximum value (28.77%) pertained to accuracy of kVp calibration for radiography units, while the lowest value (2.42%) belonged to entrance surface dose in fluoroscopy systems. Conclusion: Effective QC program in diagnostic radiology leads to obtaining information regarding quality of radiology devices used for medical diagnosis and minimizing the doses received by patients and medical personnel. The findings of this QC program, as the main part of QA program, illustrated that most of the considered diagnostic X-ray devices had acceptable performance and few of them need to be recalibrated for some parameters.

Automated and observer based light field indicator edge evaluation in diagnostic X-ray equipment

Abstract Introduction To analyze edge detection and optical contrast calculation of light field-indicators used in X-ray via automated- and observer-based methods, and comparison with current standard approaches, which do not give exact definition for light field edge determination. Methods Automated light sensor array was used to measure the penumbra zone of the edge in the standard X-ray equipment, while trained and naive human observers were asked to mark the light field edge according to their own determination. Different interpretations of the contrast were then calculated and compared. Results In contrast to automated measurements of edge definition and detection, measurements by human observers showed large inter-observer variation independent of their training with X-ray equipment. Different contrast calculations considering the different edge definitions gave very different contrast values. Conclusion As the main conclusion, we propose a more exact edge definition of the X-ray light field, corresponding well to the average human observer’s edge determination. The new edge definition method with automated systems would reduce human variability in edge determination. Such errors could potentially affect the approval of X-ray equipment, and also increase the radiation dose. The automated measurement based on human observers’ edge definition and the corresponding contrast calculation may lead to a more precise light field calibration, which enables reduced irradiation doses on radiology patients.

Shielding Evaluation of Diagnostic X-Ray Rooms in Khartoum State

The purpose of this study is to evaluate the shielding of some conventional x-ray rooms in Khartoum state. This study is based on the shielding calculations stated in the NCRP report number 49. This is the first time in Sudan to evaluate the shielding of diagnostic x-ray rooms based on this report.The total number of conventional x- ray rooms included in this study is 9 and the main parameters recorded during the evaluation are the KVp, mAs, and distance from the x-ray source to the measuring points. The dose rate at some selected points both inside and outside each x-ray room have been recorded using two dosimeters.The result of the evaluation revealed that 75% of the tested controlled area and 71.4% of the uncontrolled areas passed the test and do comply with the recommended limiting doses. However, only one room was found to be well shielded for both controlled and uncontrolled areas. The maximum allowed dose rate in controlled and uncontrolled areas was taken equal to 5 mSv/year & 1 mSv/year respectively and as recommended by the International Atomic Energy Agency (IAEA). Calculations of the required shielding have been made for those areas which have not passed the tests and for lead and concrete.

Properties of a non-toxic, self-healing X-ray radiation shielding bandage developed using smart gel

For the first time, we report a novel process for developing novel, non-toxic, self-healing as well as X-ray radiation shielding, smart material in the form of a bandage, which is capable of performing a dual function. Firstly, it is capable of shielding X-ray radiation and secondly possesses a self-healing matrix which on exposure to X-ray radiation repairs itself. The structural and compositional designing ensures dynamicity of the gel-like polymeric networks as well as effective interdiffusion and interaction of dangling chains on the damaged surface of developed smart shielding material. The nanohydro gel matrix of the developed smart gel has been further used for the impregnation of cotton flannel fabric to form novel, non-toxic, self-healing as well as an X-ray radiation shielding bandage. The developed smart shielding bandage was evaluated for its diagnostic X-ray attenuation as well as self-healing characteristics and found to possess highly effective properties. The developed shielding smart bandage possesses excellent X-ray attenuation properties for the energies of X-ray photons, i.e., 60, 80 and 100 kVp and therefore can be successfully used as radiation shielding material. It is found that the exposure of 100 kVp X-ray radiation for a duration of 40 ms leads to the complete self-healing of the matrix of the developed smart shielding bandage. Also, the developed smart shielding bandages were characterized by using various complementary techniques like TGA, DSC, FESEM and AFM for studying the chemical compatibility of complementary cellulosic species of cotton flannel fiber with hydro gel matrix. The developed smart shielding bandage is highly functional and can be widely oriented as it can be easily used and put on (1) body parts (2) windows (3) doors (4) the lining of instrumental parts, etc. and thus has a broad application spectrum ranging from diagnostic X-ray and CT scanner rooms to other strategic radiation shielding installations.

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.

Development and Design Mix of Radiation Shielding Concrete for Gamma-ray Shielding

For the first time in the world the development and design mix of radiation shielding concrete using innovative red mud based synthetic shielding aggregates has been reported. The developed shielding aggregates are made up of red mud and are basically ceramic materials consisting of shielding phases namely barium silicate (sanbornite), barium iron titanium silicate (bafertisite), barium aluminum silicate, Iron titanium oxide (pseudorutile), barium titanate, barium iron titanium oxide, barium aluminium oxide and magnetite, which are multi elemental, multi phases, multi layered crystal structures and therefore are excellent shielding materials. The design mix calculations for the development of radiation shielding concrete using developed synthetic shielding aggregates were carried out by adopting IS 10262-2009 for grade designation of M-30 concrete. The reference hematite ore concrete and developed concrete, slabs of size 30 cm × 30 cm × 7.2 cm were casted and sucessfully tested both for radiation shielding attenuation properties for gamma rays of factor using 137Cs (of photon energy 662 keV) and 241Am (of photon energy 60 keV) as well as X-rays of 300 kVp and found to posses highly effective shielding properties. For high energy radiation source i.e. 137Cs, the developed novel design mix concrete achieved attenuation factor of 5.8 as compared to 5.1 attenuation factor for hematite ore concrete. Further, the developed optimized design mix concrete have been tested for durability and the corrosion resistant test using standard 3.5% NaCl solution for optimized design mix were also carried out. The developed design mix of radiation shielding concrete using innovative red mud based synthetic shielding aggregates posses broad application spectrum ranging from construction of nuclear power plants, diagnostic X-ray, CT scanner rooms and storing radioactive waste.

Enhanced radiation damage caused by iodinated contrast agents during CT examination

ObjectiveTo access the effect of iodinate contrast agent (ICA) on DNA double-stand breaks (DSBs) in human peripheral blood lymphocytes during computed tomography (CT) examinations. Materials and methodsThis present study was approved by the institutional ethics committee; written informed patient consent was obtained from 70 patients. A total of 48 patients underwent computed tomography urography (CTU), in which only one time CT scanning was examined after injecting ICA, and 22 patients received unenhanced whole abdominal CT, among them 10 patients were selected to get ICA injection immediately after irradiation. Blood samples were taken from all patients prior to and immediately after CT scan, as well as 8min after the injection of ICA. The lymphocytes in these blood samples were separated by using density-gradient centrifugation, fixed and immunostained with γH2AX antibody. The average number of phosphorylated histone H2AX (γH2AX) foci per lymphocyte was counted under a fluorescence microscopy. Differences in the number of γH2AX-foci were statistically analyzed using independent sample t test and one way ANOVA. ResultThe three patient groups had no significant differences in the baseline foci numbers(P>0.05). The γH2AX-focus levels increased in both groups after CT scan. Patients who underwent CTU examinations had a greater DSBs level (mean±standard error of mean, 0.945±0.184 foci per cell) than those who received unenhanced whole abdominal CT scan (mean±standard error of mean, 0.700±0.112 foci per cell), increasing by about 37.9%; The ICA injected before CT scan itself had an effect on the DSBs, which increased DSBs level by approximately 90.3% (0.059±0.018vs 0.031±0.025, P<0.05), but no significant difference was found if added after irradiation, increasing DSBs level only by 3.2% approximately (0.711±0.091vs 0.689±0.108, P=0.499). ConclusionThe iodinated contrast agent itself can lead to an increase in the level of DSBs as assessed with γH2AX foci formation, and the application of ICA can amplify DNA damage induced by diagnostic x-ray procedures such as whole abdominal CT.

Luminescence imaging of biological subjects during X-ray irradiations lower energy than Cerenkov-light threshold

It is commonly thought that UV or visible-light luminescence imaging of biological subjects during X-ray irradiation at the energy below 120 keV is impossible because the secondary electrons produced in this energy range do not emit Cerenkov light. Contrary to this consensus, we found UV or visible-light luminescence imaging of the subjects were possible with X-ray irradiations of this energy range. We placed one of the biological subjects in a black box; visible-light luminescence images were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray irradiation at energy below 120 keV. We also conducted the imaging of air without subjects during irradiation of the same X-ray. The biological subjects emitted visible-light luminescence, and the imaging was possible with the irradiation of the X-ray below 120 keV. The luminescence images were observed in only the X-ray irradiated areas. Also air luminescence images could be obtained and the intensity of the luminescence measured from the images was proportionally increased with the exposure dose. UV or visible-light luminescence imaging of biological subjects was possible during X-ray irradiations lower energy than the Cerenkov-light threshold. The phenomenon was different from general X-ray fluorescence because wavelength of the luminescence is UV or visible-light. The luminescence imaging method is promising for estimating the irradiated area with X-ray, which could be used for interventional radiology (IVR). Also air luminescence imaging would be applied to the exposure dose distribution measurements for X-ray of diagnostic X-ray systems.

Dosimetric evaluation of Rhizophora spp. binderless particleboard phantom for diagnostic X-ray energy

This research aims to evaluate the suitability of using binderless particleboard made from Rhizophora spp. mangrove wood as a dosimetric phantom for X-ray in the diagnostic energy regions. Comparative measurements of percentage depth and surface doses in Rhizophora spp. binderless particleboard phantom and similarly shaped Perspex and water phantoms were performed. Measurements were conducted in the diagnostic X-ray energy range of 50kVp to 90kVp. Results showed that the binderless particleboard phantom can be used for dosimetric measurements. For the X-ray beam at 90kVp, the binderless particleboard and water phantom showed data agreement of 1.6%, 2.7%, and 4.3% at depths of 1, 2, and 4cm, respectively, whereas the measurements in water and Perspex were 1.8%, 2.7%, and 4.4%. The surface dose differences were due to difference in the backscattering material. The doses measured at the surface were within 0.4% for binderless particleboard and water and within 0.9% for Perspex and water.

Radiation-associated circulatory disease mortality in a pooled analysis of 77,275 patients from the Massachusetts and Canadian tuberculosis fluoroscopy cohorts

High-dose ionising radiation is associated with circulatory disease. Risks associated with lower-dose (<0.5 Gy) exposures remain unclear, with little information on risk modification by age at exposure, years since exposure or dose-rate. Tuberculosis patients in Canada and Massachusetts received multiple diagnostic x-ray fluoroscopic exposures, over a wide range of ages, many at doses <0.5 Gy. We evaluated risks of circulatory-disease mortality associated with <0.5 Gy radiation exposure in a pooled cohort of 63,707 patients in Canada and 13,568 patients in Massachusetts. Under 0.5 Gy there are increasing trends for all circulatory disease (n = 10,209; excess relative risk/Gy = 0.246; 95% CI 0.036, 0.469; p = 0.021) and for ischaemic heart disease (n = 6410; excess relative risk/Gy = 0.267; 95% CI 0.003, 0.552; p = 0.048). All circulatory-disease and ischaemic-heart-disease risk reduces with increasing time since exposure (p < 0.005). Over the entire dose range, there are negative mortality dose trends for all circulatory disease (p = 0.014) and ischaemic heart disease (p = 0.003), possibly due to competing causes of death over this dose interval.These results confirm and extend earlier findings and strengthen the evidence for circulatory-disease mortality radiation risk at doses <0.5 Gy. The limited information on well-known lifestyle/medical risk factors for circulatory disease implies that confounding of the dose trend cannot be entirely excluded.

A CMOS-based high resolution fluoroscope (HRF) detector prototype with 49.5 μm pixels for use in endovascular image guided interventions (EIGI).

X-ray detectors to meet the high-resolution requirements for endovascular image-guided interventions (EIGIs) are being developed and evaluated. A new 49.5-micron pixel prototype detector is being investigated and compared to the current suite of high-resolution fluoroscopic (HRF) detectors. This detector featuring a 300-micron thick CsI(Tl) scintillator, and low electronic noise CMOS readout is designated the HRF-CMOS50. To compare the abilities of this detector with other existing high resolution detectors, a standard performance metric analysis was applied, including the determination of the modulation transfer function (MTF), noise power spectra (NPS), noise equivalent quanta (NEQ), and detective quantum efficiency (DQE) for a range of energies and exposure levels. The advantage of the smaller pixel size and reduced blurring due to the thin phosphor was exemplified when the MTF of the HRF-CMOS50 was compared to the other high resolution detectors, which utilize larger pixels, other optical designs or thicker scintillators. However, the thinner scintillator has the disadvantage of a lower quantum detective efficiency (QDE) for higher diagnostic x-ray energies. The performance of the detector as part of an imaging chain was examined by employing the generalized metrics GMTF, GNEQ, and GDQE, taking standard focal spot size and clinical imaging parameters into consideration. As expected, the disparaging effects of focal spot unsharpness, exacerbated by increasing magnification, degraded the higher-frequency performance of the HRF-CMOS50, while increasing scatter fraction diminished low-frequency performance. Nevertheless, the HRF-CMOS50 brings improved resolution capabilities for EIGIs, but would require increased sensitivity and dynamic range for future clinical application.

Estimation of Radiation Dose for Adult Patients Undergoing Diagnostic X-ray Examinations of the Skull and Cervical Spine

Estimation of Radiation Dose for Adult Patients Undergoing Diagnostic X-ray Examinations of the Skull and Cervical Spine

Development of Functional Material for Simultaneous Shielding X-ray and EMI Radiations Using Inorganic–Organic Hybrid Gel

We report an unique method for the development of functional, non-toxic, flexible and moldable, simultaneous X-ray and EMI radiation shielding material, capable of simultaneous X-ray and EMI radiations shielding by exploring the multi elemental, multi componental phases present in red mud. The ceramic treatment of red mud leads to the formation of tailored radiation shielding powder having multilayered and multi shielding phases. Further, the shielding powder was treated with rheological and chemical compatible silicone polymer i.e. Polydimethylsiloxane (PDMS) to make inorganic–organic hybrid gel, which was further used to develop functional radiation shielding material of varying desire dimensions. The process basically involves sorption of PDMS on to the surface of particles of tailored radiation shielding powder via functional groups at interface which helps in achieving excellent dispersibility in the developed functional shielding material. The developed functional shielding material was evaluated for its diagnostic X-ray attenuation as well as electromagnetic shielding effectiveness (EMSE) characteristics and found to posses highly effective properties. X-ray attenuation was studied using Nomex Multimeter from PTW for energies of 80 kVp and 100 kVp X-ray photons. Evaluation of EMSE of the developed shielding material was done using vector analyzer in the frequency range of 8.2 GHz to 12.4 according to ASTM D4935. Also, the developed material was characterized by using various complementary techniques like FTIR, TGA, DSC, FESEM, XRD and EDXA for studying the chemical compatibility of PDMS with shielding powder. The developed functional material can be used in broad application spectrum ranging from diagnostic X-ray and CT scanner room to other strategic radiation shielding installation and other electronic devices simultaneously.

3D measurements in conventional X-ray imaging with RGB-D sensors

A method for deriving 3D internal information in conventional X-ray settings is presented. It is based on the combination of a pair of radiographs from a patient and it avoids the use of X-ray-opaque fiducials and external reference structures. To achieve this goal, we augment an ordinary X-ray device with a consumer RGB-D camera. The patient’ s rotation around the craniocaudal axis is tracked relative to this camera thanks to the depth information provided and the application of a modern surface-mapping algorithm. The measured spatial information is then translated to the reference frame of the X-ray imaging system. By using the intrinsic parameters of the diagnostic equipment, epipolar geometry, and X-ray images of the patient at different angles, 3D internal positions can be obtained. Both the RGB-D and X-ray instruments are first geometrically calibrated to find their joint spatial transformation. The proposed method is applied to three rotating phantoms. The first two consist of an anthropomorphic head and a torso, which are filled with spherical lead bearings at precise locations. The third one is made of simple foam and has metal needles of several known lengths embedded in it. The results show that it is possible to resolve anatomical positions and lengths with a millimetric level of precision. With the proposed approach, internal 3D reconstructed coordinates and distances can be provided to the physician. It also contributes to reducing the invasiveness of ordinary X-ray environments and can replace other types of clinical explorations that are mainly aimed at measuring or geometrically relating elements that are present inside the patient’s body.

Energy dependence measurement of small-type optically stimulated luminescence (OSL) dosimeter by means of characteristic X-rays induced with general diagnostic X-ray equipment

Energy dependence measurement of small-type optically stimulated luminescence (OSL) dosimeter by means of characteristic X-rays induced with general diagnostic X-ray equipment

Unintended and accidental medical radiation exposures in radiology: guidelines on investigation and prevention

This paper sets out guidelines for managing radiation exposure incidents involving patients in diagnostic and interventional radiology. The work is based on collation of experiences from representatives of international and national organizations for radiologists, medical physicists, radiographers, regulators, and equipment manufacturers, derived from an International Atomic Energy Agency Technical Meeting. More serious overexposures can result in skin doses high enough to produce tissue reactions, in interventional procedures and computed tomography, most notably from perfusion studies. A major factor involved has been deficiencies in training of staff in operation of equipment and optimization techniques. The use of checklists and time outs before procedures commence, and dose alerts when critical levels are reached during procedures, can provide safeguards to reduce the risks of these effects occurring. However, unintended and accidental overexposures resulting in relatively small additional doses can take place in any diagnostic or interventional x-ray procedure and it is important to learn from errors that occur, as these may lead to increased risks of stochastic effects. Such events may involve the wrong examinations, procedural errors, or equipment faults. Guidance is given on prevention, investigation, and dose calculation for radiology exposure incidents within healthcare facilities. Responsibilities should be clearly set out in formal policies, and procedures should be in place to ensure that root causes are identified and deficiencies addressed. When an overexposure of a patient or an unintended exposure of a foetus occurs, the foetal, organ, skin, and/or effective dose may be estimated from exposure data. When doses are very low, generic values for the examination may be sufficient, but a full assessment of doses to all exposed organs and tissues may sometimes be required. The use of general terminology to describe risks from stochastic effects is recommended rather than the calculation of numerical values, as these are misleading when applied to individuals.

Diagnostic Reference Levels of Adults CT-Scan Imaging in Cameroon: A Pilot Study of Four Commonest CT-Protocols in Five Radiology Departments

CT-scan is the most irradiating tool in diagnostic radiology. For 5% - 10% of diagnostic X-ray procedures, it is responsible for 34% of irradiation according to UNSCEAR. Patients radiation protection must therefore be increased during CT-scan procedures. This requires the rigorous application of optimization principle which imposes to have “diagnostic reference levels”. Objective: The aim of this study was to determine the diagnostic reference levels (DRLs) of the four most frequent CT-scans examinations of adults in Cameroon. Material and Method: It was a cross-sectional pilot study carried out from April to September 2015 in five health facilities using CT-scan in Cameroon. The studied variables were: patients age and sex, type of CT-scan examination (cerebral, chest, abdomino-pelvic, lumbar spine), Used of IV contrast (IV﹣/ IV+), acquisition length, time of tube rotation, voltage (kV), mAs, pitch, thickness of slices, CTDIvol and DLP. For each type of examination, at least 30 patients were included per center, consecutively on the randomly predetermined days. The DRL for each type of examination was defined as the 75th percentile of its PDL and CTDIvol. Results: Of the 696 examinations, 41.2% were cerebral, 26.9% abdomino-pelvic, 17.7% lumbar spine and 14.2% chest. The mean age of patients was 52 ± 15 years [20 - 90 years], 58.9% were 50 years and older. The sex-ratio was 1.26 (55.9% males). The CT machines were 4, 8 and 16 multidetectors. The 75th percentile of DLP or DRLs [standard deviation] was: [1150 ± 278 mGy·cm], [770 ± 477 mGy·cm], [720 ± 170 mGy·cm] and [715 ± 187 mGy·cm] respectively for cerebral, lumbar spine, abdominopelvic and chest CT-scans. Taking in consideration the number of detectors, the 75th percentile of the Dose-Length product decreased with the increase number of detectors for cerebral examinations but was the highest with 16 MDCT for the abdominopelvic, lumbar spine and chest CT-scans. For the chest and lumbar spine examinations, there was a significant increase in patient-dose with the increase in the number of detectors. Conclusion: Our DRLs values lie between the norms of some European countries and those of some African countries. There is remarquable variation in dose for the commonest CT-scans examinations in Cameroon, requiring then an optimization process from these determined DRLs and establishment of national DRLs. Special attention to optimization should be paid when using 16 MDCT.