Patient Dose Assessment Research Articles

Assessment of patient dose and radiogenic risks during endoscopic retrograde cholangiopancreatography

Endoscopic retrograde cholangiopancreatography (ERCP) is an invasive technique that has been used for over 30 years in the diagnosis and management of pancreaticobiliary disorders. The objectives of this study were to evaluate the patient entrance surface air kerma doses (ESAK) and estimate the organ and effective doses during ERCP in three hospitals in Khartoum. A total of 55 patients were examined in three hospitals in Khartoum state, Sudan. Calibrated thermoluinescent dosimeters (TLD) were used to measure patients' ESAK. Organ and effective doses were estimated using National Radiological Protection Board (NRPB) software. The overall mean of ESAK for all ERCP procedures was 42.4mGy. The mean patient ESAK in Fedail (A), Soba (B) and Ibn sena (C) hospitals were 26.7mGy, 26.0mGy and 72.4mGy, respectively. The effective doses in three hospitals were 1.60, 1.56 and 2.67mSv in that order and the overall mean effective dose was 1.94mSv. Patient radiation doses vary widely among the hospitals. Patient ESAK is low compared to previous studies in the light of the current practice. Patient dose was decreased significantly in the last two decades.

Patient Dose Assessment for Common Digital Diagnostic Radiology Examination in Hamad Medical Corporation Hospitals in the State of Qatar

Patient Dose Assessment for Common Digital Diagnostic Radiology Examination in Hamad Medical Corporation Hospitals in the State of Qatar

Assessment of patient dose in medical processes byin-vivodose measuring devices: A review

In-vivo dosimetry (IVD) in medicine especially in radiation therapy is a well-established and recommended procedure for the estimation of the dose delivered to a patient during the radiation treatment. It became even more important with the emerging use of new and more complex radiotherapy techniques such as intensity-modulated or image-guided radiation therapy. While IVD has been used in brachytherapy for decades and the initial motivation for performing was mainly to assess doses to organs at risk by direct measurements, it is now possible to calculate 3D for detection of deviations or errors. In-vivo dosimeters can be divided into real-time and passive detectors that need some finite time following irradiation for their analysis. They require a calibration against a calibrated ionization chamber in a known radiation field. Most of these detectors have a response that is energy and/or dose rate dependent and consequently require adjustments of the response to account for changes in the actual radiation conditions compared to the calibration situation. Correction factors are therefore necessary to take. Today, the most common dosimeters for patients’ dose verification through in-vivo measurements are semiconductor diodes, thermo-luminescent dosimeters, optically stimulated luminescence dosimeters, metal-oxide-semiconductor field-effect transistors and plastic scintillator detectors with small outer diameters.

Assessment of patient dose and optimization levels in chest and abdomen CR examinations at referral hospitals in Tanzania.

The aim of this study was to evaluate the radiation doses to patient during chest and abdomen CR examinations, and assess the related level of optimization at five referral hospitals in Tanzania. The international code of practice for dosimetry in diagnostic radiology was applied to determine the entrance surface air kerma (ESAK) to patients. The level of optimization was assessed from low‐contrast objects scores of phantom images at different exposures. The results show that mean ESAK varied from 0.16 to 0.37 mGy for chest PA and from 2 to 6 mGy for abdomen AP. Assuming similar patient and phantom attenuations, the optimization performed at all facilities was consistent with phantom evaluations in terms of tube potential settings in use. However, all facilities seemed to operate at higher tube load values above 5 mAs for chest examination, which can lead to unnecessary patient doses. Inadequate initial training on CR technology explains in large proportion the inappropriate use of exposure parameters.PACS numbers: 87.50.up, 87.59bd

Monte Carlo simulation of the dose distribution of ICRP adult reference computational phantoms for acquisitions with a 320 detector-row cone-beam CT scanner

PurposeThe purpose of this study was to develop and validate a Monte Carlo (MC) simulation tool for patient dose assessment for a 320 detector-row CT scanner, based on the recommendations of International Commission on Radiological Protection (ICRP). Additionally, the simulation was applied on four clinical acquisition protocols, with and without automatic tube current modulation (TCM). MethodsThe MC simulation was based on EGS4 code and was developed specifically for a 320 detector-row cone-beam CT scanner. The ICRP adult reference phantoms were used as patient models. Dose measurements were performed free-in-air and also in four CTDI phantoms: 150 mm and 350 mm long CT head and CT body phantoms. The MC program was validated by comparing simulations results with these actual measurements acquired under the same conditions. The measurements agreed with the simulations across all conditions within 5%. Patient dose assessment was performed for four clinical axial acquisitions using the ICRP adult reference phantoms, one of them using TCM. ResultsThe results were nearly always lower than those obtained from other dose calculator tools or published in other studies, which were obtained using mathematical phantoms in different CT systems. For the protocol with TCM organ doses were reduced by between 28 and 36%, compared to the results obtained using a fixed mA value. ConclusionsThe developed simulation program provides a useful tool for assessing doses in a 320 detector-row cone-beam CT scanner using ICRP adult reference computational phantoms and is ready to be applied to more complex protocols.

Assessment of patient dose from CT localizer radiographs

With recently introduced technical innovations for CT systems, the dose of CT scan acquisitions has been substantially reduced; even effective dose values below 1 mSv have been reported. Due to this development, dose of the localizer radiograph may contribute substantially to dose of the whole CT examination. Since there are only limited data in the literature regarding patient dose for the different types of localizer radiographs, patient dose values were estimated in our study by measurements and Monte Carlo simulations and compared to dose values of typical CT examinations. First, dose distributions were measured in anthropomorphic phantoms for three different body regions (head, thorax, abdomen-pelvic) and three positions of the x-ray tube (AP, PA, and lateral views); measured values were compared to simulated data using Monte Carlo techniques for validation purposes. Second, organ and effective dose values for the various investigated localizer radiograph scenarios were calculated and compared with published dose values for standard CT and low-dose CT examinations. For the anthropomorphic phantom, deviations of the dose values between measured and calculated results were in the range of 15%. Organ and effective dose values showed a strong dependence on the tube position. The largest differences were observed for chest localizer radiographs in the female phantom for the dose to the breast (AP: 1.01 mGy vs PA: 0.24 mGy). Overall effective dose values were in the range of 0.04-0.42 mSv per localizer radiograph acquisition. In view of the technical dose-reducing innovations in CT, localizer radiographs may substantially contribute to the total dose of the whole CT examination, particularly in the case of dedicated low-dose scans used, e.g., for young patients or screening purposes. Optimization of dose in localizer radiographs should be pursued further in the same way as it was done in CT.

SU-E-P-18: Patient Dose Assessment for Common Digital Diagnostic Radiology Examination in Qatar

Purpose: The aim of this study was to estimate radiation doses to patients undergoing standard radiographic examinations using Computed Radiography and Direct Digital Radiography in two hospitals within Hamad Medical Corporation in Qatar and compared with regional and international DRLs. Methods: Data on 3391 patients were recorded from deferent X‐ray HMC hospital to provide information on Qatar patient demographic information. Entrance Skin Dose (ESD) was measured for 1046 patients for the most five common X‐ray examinations (a total of 7 projections) namely: Skull, Chest, Abdomen, Lumbar Spine and Pelvis. Exposure factors such as kV, mAs and Focal to Skin Distance (FSD) were recorded for each patient. Tube Output was measured for a range of selected kV values. ESD for each individual patient was calculated using the tube output and the technical exposure factors for each examination. Results: HMC patient demographic data evaluated from this study were: average age of 39 years, mean weight of 74 kg and mean height of 165 cm. in Qatar state. The most performed procedure during the time of this study was chest PA (52%), and the least procedure performed was skull AP/LAT (1%) examination. The mean ESD values found to be generally lower than the published values. With exception of abdomen examinations at HGH hospital, mean ESD values were found to be within the established IAEA (DRL). Conclusion: The mean ESD values at HGH were found to be much higher than that at AKH for abdomen, Lumber spine AP, Lumber Spine LAT and pelvis. The mean ESD values obtained in this was compared with values from the literature and found to be generally lower than the published values. The results will be used to optimize patient doses in all HMC and can be used with more data from other private clinics to establish national dose reference levels for Qatar.

Radiation Doses and Risks Associated with Mammographic Screening

Radiation dose and the associated risk to the breast are being studied in much detail with the aim of justifying breast cancer screening. The mean glandular dose has been proposed as the proper quantity to describe risks incurred by radiation. X. Wu (US) and D. Dance (UK) were the first authors to standardize breast dosimetry and their conversion tables have been used throughout. Doses can be calculated for specific population samples or for individual patients, in which case an accurate estimate of the glandular tissue fraction should be known. From specific DICOM tags in the digital images and access to tube output measurements from the medical physics QA, patient dose assessment can be largely automated. Other (traditional) approaches mimic clinical exposures on a Perspex phantom and use these exposures to estimate the breast dose to a typical breast. Any local data, both patient dose data and doses to Perspex, can these days be compared to an extensive amount of published dose values. Radiation dose and image quality should both be considered in screening applications. Better image quality can have a significant effect on diagnostic performance. As only a small increase in performance (ex. detected fraction) gained can mean an enormous amount of women saved, image quality settings should be optimized and not minimized. Risk benefit investigation should therefore focus on performance rather than dose. For a few screening programs, the benefits could be proven. Emerging technologies should be investigated along the same basic principles.

Screen-film versus full-field digital mammography: Radiation dose and image quality in a large teaching hospital

The objective of this paper is to measure the radiation dose and image quality in conventional screen-film mammography and full-field digital mammography in women referred to mammography examination. Participants underwent bilateral, two-view screen-film mammography or full-field digital mammography. The visibility of anatomical regions and overall clinical image quality was rated by experienced radiologists. Total of 387 women and 1548 mammograms were enrolled in the study. Image quality was assessed in terms of image quality score, whereas patient dose assessment was performed in terms of mean glandular dose. Average mean glandular dose for cranio-caudal projection was 1.5 mGy and 2.1 mGy in full-field digital mammography and screen-film mammography, respectively. For medio-lateral oblique projection, corresponding values were 2.3 and 2.1 mGy. Overall image quality criteria scoring was 0.82 and 0.99 for screen-film and digital systems, respectively. The scores were in the range from 0.11 to 1.0 for different anatomical structures. Overall, full-field digital mammography was superior both in terms of image quality and dose over the screen-film mammography. The results have indicated that phantom dose values can assist in setting the optimisation activities in mammography and for comparison between mammography units. To obtain accurate diagnostic information with an acceptable radiation dose to breast, it is necessary to periodically perform patient dose and image quality surveys in all mammography units.

Assessment of Patient Dose from CT Examinations in Khorasan, Iran

Introduction Computed Tomography scans are a very important tool for diagnosis and assessment of response to treatment in the practice of medicine. Ionizing radiation in medical imaging is undoubtedly one of the most powerful diagnostic tools in medicine. Yet, as with all medical interventions, there are potential risks in addition to the clear potential benefits. Materials and Methods Two reference dose quantities have been defined in order to promote the use of good technique in CT. These are weighted CT dose index (CTDIw) in (mGy) for a single slice in serial scanning or per rotation in helical scanning, and dose–length product (DLP) per complete examination (mGy.cm), All measurements were performed using a pencil shaped ionization chamber introduced into polymethyl methacrylate cylindrical brain and body phantoms. This survey was performed on 7 CT scanners in Khorasan Province-Iran. Results DLP for brain, chest, abdomen and pelvic examinations had a range of 255 - 1026, 76-1277, 48-737, 69-854 mGy.cm, respectively. Conclusion The results obtained in this study show that the DLP values obtained in this province are lower than European Commission reference dose levels (EC RDL), in other words performance of all the scanners were satisfactory.

Screen-film versus digital radiography of sacroiliac joints: evaluation of image quality and dose to patients

The purpose of this paper is to evaluate the image quality and dose to patients in the radiography of sacroiliac joints and to perform a clinical comparative study of digital and conventional screen-film radiography. Routine radiography of sacroiliac joint was performed in 60 patients using digital and screen-film radiography. The visibility of five anatomical regions and the overall image quality were rated by experienced radiologists. Patient dose assessment in terms of entrance surface air kerma (ESAK) was performed. The digital system showed slightly improved visualisation of specific anatomical structures. Overall image quality was significantly better in the digital when compared with the screen-film imaging system. The average ESAK was 2.4 mGy in screen-film and 3.6 mGy in digital radiography. The digital radiography provided equal or better visibility of anatomical details and overall image quality, but on higher dose levels. Therefore, the practice on digital systems must be optimised.

Assessment of patient dose and image quality for cardiac CT with breast shields

Breast shielding can reduce dose to the female breast, a radiosensitive organ receiving significant radiation during computed tomography (CT) chest examinations, particularly in cardiac CT, where Electrocardiogram dose modulation currently precludes the use of radial dose modulation to reduce breast dose. However, breast shields may produce artefacts affecting interpretation of coronary arteries. This study explores the dose savings and the effect of breast shields on image quality with torso and CT dose index body phantoms and an organ dose calculator. Change in dose calculated: 53-63 % (female breast), 82-85 % (lung), 79-84 % (oesophagus) and 76-80 % (effective dose) with larger dose reductions at lower kVp. Image quality is preserved when breast shields are placed after the scout no closer than 10 mm from the skin. Therefore, breast shields can be used in cardiac CT to reduce breast dose without compromising image quality. Revised conversion factors for dose length product to effective dose are suggested for cardiac CT without and with breast shields.

Establishment of scatter factors for use in shielding calculations and risk assessment forcomputed tomography facilities

The specification of shielding for CT facilities in the UK and many other countries hasbeen based on isodose scatter curves supplied by the manufacturers combined with thescanner’s mAs workload. Shielding calculations for radiography and fluoroscopy are linkedto a dose measurement of radiation incident on the patient called the kerma–areaproduct (KAP), and a related quantity, the dose-length product (DLP), is nowemployed for assessment of CT patient doses. In this study the link betweenscatter air kerma and DLP has been investigated for CT scanners from differentmanufacturers. Scatter air kerma values have been measured and scatter factorsestablished that can be used to estimate air kerma levels within CT scanning rooms.Factors recommended to derive the scatter air kerma at 1 m from the isocentre are0.36 µGy (mGy cm)−1 for thebody and 0.14 µGy (mGy cm)−1 for head scans. The CT scanner gantries only transmit 10% of the scatter air kerma leveland this can also be taken into account when designing protection. The factors can be usedto predict scatter air kerma levels within a scanner room that might be used in riskassessments relating to personnel whose presence may be required during CT fluoroscopyprocedures.

Patient doses using multidetector computed tomography scanners in Kenya

Assessment of patient dose attributed to multislice computed tomography (CT) examination. A questionnaire method was developed and used in recording the patient dose and scanning parameters for the head, chest, abdomen and lumbar spine examinations. The patient doses due to brain, chest and abdomen examination were above the international diagnostic reference levels (DRLs) by factors of between one and four. The study demonstrated that the use of multislice CT elevates patient radiation dose, justifying the need for local optimised scanning protocols and the use of institutional DRL for dose management without affecting diagnostic image quality.

Assessment of patient doses during mammography practice at Kenyatta National Hospital

Background Breast cancer constitutes 21% of all cancer cases and ranks third according to cancer type in Kenya. Mammography therefore remains a powerful radiographic imaging technique for detecting and managing breast cancer. However, the active and radiosensitive glandular tissue calls for the need of an effective quality assurance program. Materials and Methods A questionnaire method was developed and used in recording the displayed patient dose, compressed breast thickness and exposure factors. The average glandular dose, device performance, and film quality grading were also carried out. Results There were 3264 films taken from 1252 women between 25 to 90 years old. The AGD per film was 2.14 (range 0.27-9.43) mGy for the cranio-caudal (CC) projection and 2.44 (range 0.20-10.12) mGy for the medio-lateral oblique (MLO) projection. In this study 17% of CC and 30% of MLO films recorded doses above the 3 mGy American College of Radiology using grid diagnostic reference level. Conclusion In view of the diagnostic dose finding of this study, the variation of mammography imaging techniques revealed the need for imaging guidelines, quality assurance and optimization of mammography practice in Kenya.

Establishing a quality assurance baseline for radiological protection of patients undergoing diagnostic radiology

Background. The wide use of ionising radiation in medical care has resulted in the largest man-made cause of radiation exposure. In recent years, diagnostic departments in Kenya have adapted the high-speed film/screen combination without well-established quality control, objective image quality criteria, and assessment of patient dose. The safety of patients in terms of justification and the as-low-as-reasonably-achievable (ALARA) principle is inadequate without quality assurance measures.
 Aim. This study assessed the level of film rejects, device performance, image quality and patient dose in 4 representative hospitals using high-speed film/screen combination.
 Results. The X-ray equipment quality control tests performance range was 67% to 90%, and 63% of the radiographs were of good diagnostic value. The measured prevalent chest examination entrance surface dose (ESD) showed levels above the international diagnostic reference levels (DRLs), while lumbar spine and pelvis examination was the largest source of radiation exposure to patients.
 Conclusion. The optimisation of patient protection can be achieved with optimally performing X-ray equipment, the application of good radiographic technique, and continuous assessment of radiographic image quality.

MO‐D‐110‐01: Benefit Risk Assessment: Identifying the at Risk Patient; SYMPOSIUM‐Estimating Patient‐Specific Radiation Dose from Fluorosocpy

Radiation dose management for fluoroscopically‐ guided interventional medical procedures requires a combined effort from physicians, physicists and government regulators. Paramount to this process is an understanding of the benefits and risk for these procedures. For cardiovascular disease, despite the increasing prevalence in a setting of escalating risk factors, mortality has steadily decreased. Diagnostic and therapeutic fluoroscopic imaging has undoubtedly attributed to this as seen specifically in the areas of acute myocardial infarction, sudden cardiac arrest, and heart failure therapy. All facilities should have a radiation safety program as part of the institutional quality assurance umbrella with specific focuses on dose management as it applies to the equipment, physician, and patient. The regular interactions between the physicist and physician/staff assure proper equipment purchase and maintenance, initial and annual training, and patient dose assessment. The current challenges of the high risk patient require specific attention. As techniques and equipment advance, application of procedures expands and previously “untreatable” patients are approached. Patient factors such as morbid obesity, diabetes and repeat procedures are seen more as the norm rather than the exception. Complex anatomy in elderly, critically ill patients dictate challenging clinical decisions before, during, and after the procedure. This presentation will present a best practice approach to the challenges of benefit risk assessment in patients undergoing fluoroscopically‐guided interventional procedures.

Assessment of patient doses in CR examinations throughout a large health region.

Optimization and standardization of radiographic procedures in a health region minimizes patient exposure while producing diagnostic images. This report highlights the dose variation in common computed radiography (CR) examinations throughout a large health region. The RadChex cassette was used to measure the radiation exposure at the table or wall bucky in 20 CR rooms, in seven hospitals, using CR technology from two vendors. Exposures were made to simulate patient exposure (21 cm polymethyl methacrylate) under standard conditions for each bucky: 81 kVp at 100 cm for anteroposterior abdomen table bucky exposures (180 cm for posteroanterior chest wall bucky exposures), using the left, the right, or the center automatic exposure control (AEC) cells. Protocol settings were recorded. An average of 37% variation was found between AEC chambers, with a range between 4% and 137%. A 60% difference in dose was discovered between manufacturers, which was the result of the manufacture's image processing algorithm and subsequently corrected via software updates. Finally, standardizing AEC cell selection during common chest examinations could reduce patient dose by up to 30%. In a large health region, variation in exam protocols can occur, leading to unnecessary patient dose from the same type of examination. Quality control programs must monitor exam protocols and AEC chamber calibration in CR to ensure consistent, minimal, patient dose, regardless of hospital or CR vendor. Furthermore, this report highlights the need for communication between radiologists, technologists, medical physicist, service engineers, and manufacturers required to optimize CR protocols.

CT Dose Index and Patient Dose: They AreNotthe Same Thing

Estimates of individual patient risk, and epidemiologic studies assessing potential late effects, must use patient size–specific dose estimates—they cannot use only scanner output (volume CT dose index or dose-length product).

Radiation Exposure to Patients in a Multicenter Coronary Angiography Trial (CORE 64)

The objective of this study was to assess the exposure of patients to radiation for the cardiac CT acquisition protocol of the multicenter Coronary Artery Evaluation Using 64-Row Multidetector Computed Tomography Angiography (CORE 64) trial. An algorithm for patient dose assessment with Monte Carlo dosimetry was developed for the Aquilion 64-MDCT scanner. During the CORE 64 study, different acquisition protocols were used depending on patient size and sex; therefore, six patient models were constructed representing three men and three women in the categories of small, normal size, and obese. Organ dose and effective dose resulting from the cardiac CT protocol were assessed for these six patient models. The average effective dose for coronary CT angiography (CTA) calculated according to Report 103 of the International Commission on Radiological Protection (ICRP) is 19 mSv (range, 16-26 mSv). The average effective dose for the whole cardiac CT protocol including CT scanograms, bolus tracking, and calcium scoring is slightly higher-22 mSv (range, 18-30 mSv). An average conversion factor for the calculation of effective dose from dose-length product of 0.030 mSv/mGy · cm was derived for coronary CTA. The current methods of assessing patient dose are not well suited for cardiac CT acquisitions, and published effective dose values tend to underestimate effective dose. The effective dose of cardiac CT is approximately 25% higher when assessed according to the preferred ICRP Report 103 compared with ICRP Report 60. Underestimation of effective dose by 43% or 53% occurs in coronary CTA according to ICRP Report 103 when a conversion factor (E / DLP, where E is effective dose and DLP is dose-length product) for general chest CT of 0.017 or 0.014 mSv/mGy · cm, respectively, is used instead of 0.030 mSv/mGy · cm.