Dosimetry In Diagnostic Radiology Research Articles

X-Ray Dose Audit and Potential Local Diagnostic Reference Levels in Select Hospitals In Kaduna State, Nigeria


 
 
 
 
 Background: Dosimetry in diagnostic radiology is fundamental to providing information to practitioners regarding the level of their doses and to ensure adequate optimization of the protection of patients presenting for radiological examinations. The introduction and implementation of diagnostic reference levels (DRLs) in diagnostic radiology has proven to be a potent tool for quality control and dose reduction. This has not been comprehensively addressed in Nigeria.
 Objective: To carryout dose audit of patients presenting for common radiographic projections in select hospitals in Kaduna State, Nigeria.
 Methodology: Thermoluminescent dosimeters (TLDs) were used to measure entrance surface dose (ESD) on 420 randomly selected adult patients presenting for x-ray examination of the chest PA/Lateral, skull PA/Lateral, lumbar spine AP/Lateral, abdomen and pelvic AP, respectively. Results were compared with existing literature.
 Results: The range of the mean ESD determined for the study population on various x-ray examinations were: chest PA (0.44 – 0.9 mGy), and lateral (0.9 – 1.5 mGy); skull PA (2.0 – 4.7 mGy), and lateral (1.7 – 3.4 mGy); lumbar spine AP (3.4 -7.8 mGy), and lateral (6.8 –11.3 mGy); abdomen AP (3.6 – 6.2 mGy); and pelvic AP (2.4 – 6.9 mGy). Comparison showed dose levels were below IAEA recommendations.
 Conclusion: In the absence of arbitrary high doses, practice is generally safe and will not result in unwarranted hazards to the patients.
 
 
 
 

X-Ray Dose Audit and Potential Local Diagnostic Reference Levels in Select Hospitals In Kaduna State, Nigeria


 
 
 
 
 Background: Dosimetry in diagnostic radiology is fundamental to providing information to practitioners regarding the level of their doses and to ensure adequate optimization of the protection of patients presenting for radiological examinations. The introduction and implementation of diagnostic reference levels (DRLs) in diagnostic radiology has proven to be a potent tool for quality control and dose reduction. This has not been comprehensively addressed in Nigeria.
 Objective: To carryout dose audit of patients presenting for common radiographic projections in select hospitals in Kaduna State, Nigeria.
 Methodology: Thermoluminescent dosimeters (TLDs) were used to measure entrance surface dose (ESD) on 420 randomly selected adult patients presenting for x-ray examination of the chest PA/Lateral, skull PA/Lateral, lumbar spine AP/Lateral, abdomen and pelvic AP, respectively. Results were compared with existing literature.
 Results: The range of the mean ESD determined for the study population on various x-ray examinations were: chest PA (0.44 – 0.9 mGy), and lateral (0.9 – 1.5 mGy); skull PA (2.0 – 4.7 mGy), and lateral (1.7 – 3.4 mGy); lumbar spine AP (3.4 -7.8 mGy), and lateral (6.8 –11.3 mGy); abdomen AP (3.6 – 6.2 mGy); and pelvic AP (2.4 – 6.9 mGy). Comparison showed dose levels were below IAEA recommendations.
 Conclusion: In the absence of arbitrary high doses, practice is generally safe and will not result in unwarranted hazards to the patients.
 
 
 
 

Characterization of cost-efficient OPT101 PIN photodiode as relative dosimetry in diagnostic radiology: An IOT application

OPT101 photodiode sensor dosimetry properties were investigated for various parameters to observe its capability as a relative dosimeter. Its characterization was done with PTW semiconductor detector for diagnostic radiology as a benchmark. OPT101 presented excellent output linearity relative to dose measured by PTW semiconductor for energy dependency and reproducibility test. A significant high sensitivity was observed against dose rates and mean energies and linear response against different source-to-detector distance, SDD. Results suggest the use of an Arduino IDE microcontroller as potential of utilizing an IoT application in input/output communication with the sensor and data processing.

Development and characterization of an LED-based detector for dosimetry in diagnostic radiology

Light-emitting diodes (LEDs) could be a potential dosimetry candidate because they are radiation hard, spectrally selective, direct band gap, and low-cost devices. Thus, an LED-based detector prototype was designed and characterized for dosimetry. A 20 × 20 cm2 array of surface mount device LED chips was sandwiched in photovoltaic mode between two intensifying screens to form a dosimetric system. The system was enclosed in a light-tight air cavity using black vinyl tape. The screens converted diagnostic x-ray beams into fluorescent blue light. LEDs, applied in detector mode, converted the fluorescent light into radiation-induced currents. A digital multimeter converted the analog currents into digital voltage signals. Prototype characterization was executed using (a) IEC 61267’s RQR 7 (90 kVp) and RQR 8 (100 kVp) beam qualities, and (b) low (25 mAs) and high (80 mAs) beam quantities. A standard dosimeter probe was simultaneously exposed with the prototype to measure the prototype’s absorbed dose. In all exposures, the x-ray beams were perpendicularly incident on both the dosimeter and prototype, at a fixed source to detector distance-60 cm. The LED array prototype’s minimum detectable dose was 0.139 mGy, and the maximum dose implemented herein was ∼13 mGy. The prototype was 99.18% and 98.64% linearly sensitive to absorbed dose and tube current–time product (mAs), respectively. The system was ±4.69% energy, ±6.8% dose, and ±7.7% dose rate dependent. Two prototype data sets were 89.93% repeatable. We fabricated an ultrathin (5 mm), lightweight (130 g), and a relatively low-cost LED-based dosimetric prototype. The prototype executed a simple, efficient, and accurate real-time dosimetric mechanism. It could thus be an alternative to the current passive dosimetric systems.

Determination of Calibration Factors and Uncertainties Associated with the Irradiation of MTS-N (LiF: Mg, Ti) Chips with Cesium-137 and X-ray Sources Under Low Doses for Personal Dosimetry in Diagnostic Radiology

Purpose: The purpose of this study was to compare calibration factors for deep dose equivalent Hp (10) and shallow dose equivalent Hp (0.07) between Cesium (Cs)-137 and X-ray sources when they are exposed to same dose and to determine uncertainties with MTS-N (LiF: Mg, Ti) chips when they are exposed to low dose ≤ 2mGy. Material and Methods: Thermoluminescent (TL) chips were annealed at 400oC for one hour and allowed to cool and were subjected to a temperature of 100oC for another two hours using a TLD Furnace Type LAB-01/400. They were then taken to a Secondary Standard Dosimetry Laboratory (SSDL) for irradiation using a Cs-137 source at known doses (0.2-2mGy). A RadPro Cube 400 manual TLD Reader was used to determine corresponding TL signal. The above process was replicated but with a calibrated X-ray unit as the source for calibration. Results: The calibration factors (CF) from the line graph of dose (mGy) against TL signal (count) for Cs-137 source with Hp (10) and Hp (0.07) were 3.72 x 10-6 and 5.97x10-6 mGy/count respectively. Those with X-ray source for Hp (10) and Hp (0.07) were 3.44x10-6 and 4.05x10-6 mGy/count respectively with an overall coefficient of determination (R2) = 0.99. The adjusted maximum percentage deviation between the actual and calculated dose for both sources was -2.74%. The percent (%) deviation of the mean with both sources for Hp (10) and Hp (0.07) was 3.9% and 19% respectively. Conclusion: Adjusted percent deviation from both sources were within the recommended dose limit of ±30% by the Radiological Protection Institute of Ireland (RPII) and within the International Commission on Radiological Protection (ICRP) limit respectively. Better accuracy was seen for Hp (10) with both sources compared to Hp (0.07). Calibration of the MTS-N chips using both sources was successful and can be used for personal dosimetry.

Establishment and Dissemination of Radiological Standards in the Field of Diagnostic Radiology in India.

Background:The increased use of ionizing radiation for diagnostic purpose has resulted in an increase in the world population dose. Patient dosimetry in X-ray diagnostic radiology is required to establish diagnostic reference levels (DRLs) and to assess the average dose received by organs and tissues. International bodies have recommended DRLs to be based on dosimetric quantities.Aim:To cater to the increased requirement for dosimetry in diagnostic radiology, international guidelines are provided to establish and disseminate traceable calibration for dosimeters used in X-ray diagnostic radiology. X-ray diagnostic beams established are standardized using a diagnostic range free-air ionization chamber (DFAIC) (20-150 kV).Materials and Methods:Characterization of the DFAIC and determination of the correction factors for the air kerma measurements were evaluated experimentally and by theoretical calculations.Results:The paper details the establishment of 18 diagnostic beam qualities using DFAIC along with the associated uncertainties. The overall uncertainty for the air kerma measurements was within ±0.5% at 1 sigma level. Eight diagnostic range air kerma measurements using DFAIC were compared with the medium energy primary standard FAIC (50–300 kV) maintained in the laboratory.Conclusion:The air kerma rates agreed within ±1% and are within the overall standard uncertainty of both the chambers at the time of the comparison. Dissemination to the users in the field of diagnostic radiology in the country has been carried out by calibrating their ionization chambers and solid-state detector-based instruments against the DFAIC. The methodology followed to standardize the beams using DFAIC and calibration of dosimeters is presented in this work.

A Study of Entrance Surface Air Kerma for Patients Undergoing Chest and Abdomen from Digital Radiography at Chulabhorn Hospital

Objective: The main purpose of this study was to investigate the typical dose for standard-sized patients in chest (posteroanterior; PA) and abdomen (anteroposterior; AP) digital radiography.Material and Methods: The air kerma was measured by the ionization chamber (Radical Corporation, model 10X6-6) in X-ray equipment manufactured by General Electric Healthcare Definium 8000 System for different kilovoltage peak (kVp) settings in each X-ray examination. The entrance surface air kerma (ESAK) was determined in 422 mediumsized patients in different projections: chest (PA) and abdomen (AP), according to the recommended protocol of the International Atomic Energy Agency Technical Report Series Number 457 (Technical Reports Series No. 457 “Dosimetry in Diagnostic Radiology: An International Code of Practice).Results: The mean entrance surface air kerma values for chest (PA) radiography in female and male patients were 0.08 milligray (mGy) and 0.09 mGy, respectively and for abdomen (AP) radiography for both genders were 0.98 mGy and 1.06 mGy, respectively.Conclusion: The mean entrance surface air kerma values of this study were less than the diagnostic reference levels from the IAEA 1996, Korea 2007, United Kingdom 2010 and Japan 2015, in all projections. Patient doses (ESAK) in chest (PA) and abdomen (AP) digital radiography at Chulabhorn Hospital were less than the other guidelines, because of the use of a high kVp technique for the chest and the automatic exposure control for the abdomen. Furthermore, Thai people are smaller than Westerners. We studied in digital radiography only that literally provides lowest radiation dose compares with screen film and computed radiography.

Radioluminescence sensing of radiology exposures using P-doped silica optical fibres

In previous work we investigated the real-time radioluminescence (RL) yield of Ge-doped silica fibres and Al2O3 nanodot media, sensing electron- and x-ray energies and intensities at values familiarly obtained in external beam radiotherapy. The observation of an appreciable low-dose sensitivity has given rise to the realisation that there is strong potential for use of RL dosimetry in diagnostic radiology. Herein use has been made of P-doped silica optical fibre, 2 mm diameter, also including a 271 µm cylindrical doped core. With developing needs for versatile x-ray imaging dosimetry, preliminary investigations have been made covering the range of diagnostic x-ray tube potentials 30 kVp to 120 kVp, demonstrating linearity of RL with kVp as well as in terms of the current-time (mAs) product. RL yields also accord with the inverse-square law. Given typical radiographic-examination exposure durations from tens- to a few hundred milliseconds, particular value is found in the ability to record the influence of x-ray generator performance on the growth and decay of beam intensity, from initiation to termination.

Intensities of Incident and Transmitted Ultraviolet-A Rays through Gafchromic Films.

Gafchromic films have been applied to X-ray dosimetry in diagnostic radiology. To correct nonuniformity errors in Gafchromic films, X-rays in the double-exposure technique can be replaced with ultraviolet (UV)-A rays. Intensities of the incident and transmitted UV-A rays were measured. However, it is unclear whether the chemical color change of Gafchromic films affects the UV-A transmission intensity. Gafchromic EBT3 films were suitable to be used in this study because non-UV protection layers are present on both sides of the film. The film is placed between UV-A ray light-emitting diodes and a probe of a UV meter. Gafchromic EBT3 films were irradiated by UV-A rays for up to 60 min. Data for analysis were obtained in the subsequent 60 min. Images from before and after UV-A irradiation were subtracted. When using 375 nm UV-A, the mean ± standard deviation (SD) of the pixel values in the subtracted image was remarkably high (11,194.15 ± 586.63). However, the UV-A transmissivity remained constant throughout the 60 min irradiation period. The mean ± SD UV-A transmission intensity was 184.48 ± 0.50 μm/cm2. Our findings demonstrate that color density changes in Gafchromic EBT3 films do not affect their UV-A transmission. Therefore, Gafchromic films were irradiated by UV-A rays as a preexposure.

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

Characterization of a low-cost PIN photodiode for dosimetry in diagnostic radiology

A commercial silicon PIN-photodiode was tested and characterized as ionizing radiation detector for radiological applications. A current-to-voltage amplification stage was designed and realized in order to acquire the photodiode signal in current mode. The system was tested with clinical beams routinely used for radiography and mammography. A Monte Carlo simulation of the detector was performed with the MCNPX code in order to model and fully understand, in particular, the impact of the sensor casing on the low energy response of the device. A reproducible output linearity was found over the dose range 0.03–4.5 mGy of great clinical relevance. The system sensitivity was found to be stable at 0.2 V s Gy−1 for effective X-ray energies between 17 and 40 keV. The batch-to-batch reproducibility of the diodes was also experimentally investigated for two different batches of 14 diodes each. An inter-comparison with dosimeters routinely used in medical physics (i.e. Barracuda MPD RTI) showed a linear correlation between PIN-photodiode readout and absorbed dose measured with Barracuda, in the range of doses received by mammography and radiology patients.

SU‐E‐I‐24: Design and Fabrication of a Multi‐Functional Neck and Thyroid Phantom for Medical Dosimetry and Calibration

Purpose:The purpose of this study is the design and fabrication of a multipurpose anthropomorphic neck and thyroid phantom for use in medical applications (i.e. quality control of images in nuclear medicine, and dosimetry).Methods:The designed neck phantom is composed of seven elliptic cylindrical slices with semi‐major axis of 14 and semi‐minor axis of 12.5 cm, each having the thickness of 2cm. Thyroid gland, bony part of the neck, and the wind pipe were also built inside the neck phantom.Results:The phantom contains some removable plugs,inside and at its surface to accommodate the TLD chips with different shapes and dimensions, (i.e. rod, cylindrical and cubical TLD chips)for the purpose of medical dosimetry (i.e. in radiology, radiotherapy, and nuclear medicine). For the purpose of quality control of images in nuclear medicine, the removable thyroid gland was built to accommodate the radioactive iodine. The female and male thyroid glands were built in two sizes separately.Conclusion:The designed phantom is a multi‐functional phantom which is applicable for dosimetry in diagnostic radiology, radiotherapy, and quality control of images in nuclear medicine.

Introducing a simple tissue equivalent anthropomorphic phantom for radiation dosimetry in diagnostic radiology and radiotherapy

It is important to measure organ dose in diagnostic radiology & radiotherapy. Because measurement on patients has some limitations, phantoms are being constructed to be implemented. One kind of several phantoms which is being used so far is anthropomorphic phantom which is similar to a man. In this work, using human natural bone as phantom skeletal tissue & paraffin plus NaCl (as impurity) as soft tissue substitute an anthropomorphic phantom was constructed which consists of three parts: 1. head & neck 2.torso 3.hip. Phantom dimensions were selected from the standard man. To measure absorbed dose in tissues, at the sites of parotid, thyroid, sternum, diaphragm, abdomen and hip some cylinders were inserted which were constructed from phantom material and had some cavities to insert TLDs in different depths. Due to importance of photoelectric effect in diagnostic radiology & Compton effect in radiotherapy, two important parameters which should be considered in construction of a phantom is effective atomic number and electronic density were6.57& 3.36×10 23 electron.gr -1 , respectively.

Feasibility of calibrating thermoluminescent dosimeters in a mammography unit for patient dosimetry

Abstract Solid state thermoluminescent dosimeters are widely used for beam dosimetry in diagnostic radiology. Accurate dosimetry in mammography requires that dosimeters should be calibrated in X-ray beams produced by a molybdenum target tube, which is not available in many metrology laboratories. In this work the feasibility of using a mammography unit to calibrate dosimeters was investigated. Calibration results were compared for Mo/Mo, Mo/Rh and W/Rh target/filter conditions.

A study in Europe of patient dosimetry in diagnostic radiology: protocol development and findings

In a multi-centre study more than 600 patient measurements of patients receiving thorax radiography were performed in five European cities. Participating centres were Fulda, Liverpool, Nicosia, Passau and Sofia. The dose quantities measured were the air kerma-area product (AKAP), incident air kerma and entrance surface air kerma (ESAK). In addition, for each patient sex, age, weight, height, focus-to-film distance, focus-to-skin distance, patient thickness, kV, mAs, field size and the nominal film speed were registered. Different X-ray machines were used in the participating centres--Thoravision, flat panel detector and film screen combinations in two centres (analogue system). The tube voltages employed varied between 60 and 150 kV and the nominal film speed between 200 and 400/800. All mean dose values (ESAK and AKAP) for the different centres showed a different value for female and male populations. The differences were up to 100 % and always higher for the mean AKAP. For a thorax posteroanterior examination, the mean ESAK varied between 0.06 and 0.46 mGy and the mean AKAP varied between 60 and 690 mGy cm(2). The differences in the results obtained as well as the methodologies for multi-national, multi-centre studies will be discussed. Future perspectives for this type of study within the framework of radiation protection and quality assurance in Europe will also be discussed as well as the role and function of multi-national radiological data sets including patient dose values.

A clinical audit programme for diagnostic radiology: the approach adopted by the International Atomic Energy Agency

The International Atomic Energy Agency (IAEA) has a mandate to assist member states in areas of human health and particularly in the use of radiation for diagnosis and treatment. Clinical audit is seen as an essential tool to assist in assuring the quality of radiation medicine, particularly in the instance of multidisciplinary audit of diagnostic radiology. Consequently, an external clinical audit programme has been developed by the IAEA to examine the structure and processes existent at a clinical site, with the basic objectives of: (1) improvement in the quality of patient care; (2) promotion of the effective use of resources; (3) enhancement of the provision and organisation of clinical services; (4) further professional education and training. These objectives apply in four general areas of service delivery, namely quality management and infrastructure, patient procedures, technical procedures and education, training and research. In the IAEA approach, the audit process is initiated by a request from the centre seeking the audit. A three-member team, comprising a radiologist, medical physicist and radiographer, subsequently undertakes a 5-d audit visit to the clinical site to perform the audit and write the formal audit report. Preparation for the audit visit is crucial and involves the local clinical centre completing a form, which provides the audit team with information on the clinical centre. While all main aspects of clinical structure and process are examined, particular attention is paid to radiation-related activities as described in the relevant documents such as the IAEA Basic Safety Standards, the Code of Practice for Dosimetry in Diagnostic Radiology and related equipment and quality assurance documentation. It should be stressed, however, that the clinical audit does not have any regulatory function. The main purpose of the IAEA approach to clinical audit is one of promoting quality improvement and learning. This paper describes the background to the clinical audit programme and the IAEA clinical audit protocol.

SENSITIVITY COMPARISON OF TWO L-ALANINE DOPED BLENDS TO DIFFERENT PHOTON ENERGIES

Blends of L-alanine (85% weight proportion) with KI (10%) and with PbI2 (10%), these last two compounds acting as dopants, and with PVA (5%) acting as binder, were prepared in water at 80 degrees C. A blend of pure L-alanine (95%) with PVA (5%) was also prepared. The three blends were irradiated with photon beams of different energies (120 kV, Co, and 10 MV) to a unique dose of 30 Gy to compare their sensitivities for those three energies. EPR spectra of the three irradiated blends were recorded in a K-Band spectrometer (24 GHz) taking aliquots of about 4 mg for each blend. The energy sensitivity of a blend was defined as the peak-to-peak amplitude of its EPR spectrum central line. For the Co energy (1.25 MeV) the blends presented practically the same sensitivity, indicating that the presence of the dopants does not affect the sensitivity of L-alanine. For 10 MV x-rays, there was an increment (around 10%-20%) in sensitivity for the two L-alanine doped blends compared with the pure L-alanine blend (not doped). In the case of 120 kV x-rays, the blends ala+KI and ala+PbI showed increments of 10 and 20 times more sensitivity than the pure L-alanine blend. It is concluded that the dopants KI and PbI2 produce a great enhancement of the L-alanine sensitivity to low-energy photons. For the same dopant's content (10%) in the blend, PbI2 showed a better performance. Increasing the PbI2 proportion (30%) in the blend allows the detection of radiation dose as low as 10 mGy for 120 kV x-rays. These results encourage the authors to try to enhance the sensitivity of L-alanine even more by increasing the dopant's content in the blend and diminishing the lower limit detection. Application of these L-alanine doped blends in the dosimetry in diagnostic radiology could be possible.

Computed tomography dose measurements with radiochromic films and a flatbed scanner

Gafchromic XR-QA films were developed for patient dosimetry in diagnostic radiology. A possible application of these films is the measurement of doses in computed tomography. In this study a method to evaluate the CTDI using Gafchromic XR-QA film and a flatbed scanner was developed and tested. Film samples were cut to dimensions of 6 x 170 mm2 in order to have an integration area similar to that of a pencil ionization chamber, with the possibility of changing the integration length. Prior to exposing these films to a computed tomography beam, the angular dependence of the film dose response was investigated by exposing film strips to a static x-ray beam at different angles in the range 0 degrees-180 degrees. A difference of 49% was found between the response with the axis beam parallel to the film surface (90 degrees) and with the axis beam perpendicular (0 degrees and 180 degrees). Integrating over a 360 degrees exposure like the one in computed tomography, a difference of less than 2% was estimated, which is comparable with the measurement error obtainable with XR-QA film. A calibration with a CT beam in the scout mode was performed and film strips were then exposed to single axial scans and to helical scans both in air and in phantoms. Two different types of flatbed scanners were used to read the film samples, a Microtek ScanMaker 9800XL scanner and an Epson Expression 10000 XL scanner, and the accuracy of the results were compared. For beam collimations above 10 mm differences between CTDI measured by film and CTDI measured by ionization chamber below 9% were found for the Epson scanner, with an average estimated error at 1 sigma level of 5%. For the Microtek scanner and for the same film samples, differences below 11% with an average error at 1 sigma level of 8% were founded. The 1 sigma uncertainty of the measured CTDI was provided by the method for each measurement, and it was shown that about the 95% of the differences between the CTDI measurements with radiochromic films and with the ionization chamber were below the estimated 2 sigma uncertainty, for both scanners. After an accurate calibration procedure and the consideration of the uncertainty associated with the measurement, Gafchromic XR-QA films can be used to evaluate the CTDI.

A method for the production of composite scintillators for dosimetry in diagnostic radiology

Plastic scintillators are used in the dosimetry of photons in radiotherapy. Their use in diagnostic radiology is affected by the drop in response at lower photon energies due to inadequate composition (effective atomic number) and chemical quenching. To compensate for this deficiency, a method for the production of composite polystyrene-based plastic scintillators was devised allowing the incorporation of inorganic scintillation powder. Disks of 10 mm diameter and 1 mm thickness optimized for a flat energy response referred to kerma in air were produced using CaWO4, ZnS:Ag and CaF2:Eu as additives. In an HVL range of 2.26–13.69 mmAl, the response was within an interval of ±2.8% for CaF2:Eu as additive, ±3.2% for CaWO4 and ±10.9% for ZnS:Ag, respectively. The response of a commercial plastic scintillator (BC470) stays within ±13.6%. The temperature dependence of the composite scintillator using CaF2:Eu is lowest with a variation of +3.7% to −3.6% in an interval from 5 °C to 45 °C. The deficiency in photon absorption at lower energies due to the effective atomic number is reduced but not fully compensated by the additive scintillators. The optimized concentrations were established for the scintillator dimensions used.

Overview of patient dosimetry in diagnostic radiology in the USA for the past

This review covers the role of medical physics in addressing issues directly related to patient dosimetry in radiography, fluoroscopy, mammography, and CT. The sections on radiography and fluoroscopy radiation doses review the changes that have occurred during the last 50 to 60 years. A number of technological improvements have contributed to both a significant reduction in patient and staff radiation doses and improvements to the image quality during this period of time. There has been a transition from film-screen radiography with hand dip film processing to electronic digital imaging utilizing CR and DR. Similarly, fluoroscopy has progressed by directly viewing image intensifiers in darkened rooms to modern flat panel image receptor systems utilizing pulsed radiation, automated variable filtration, and digitally processed images. Mammography is one of the most highly optimized imaging procedures performed, because it is a repetitive screening procedure that results in annual radiation exposure. Mammography is also the only imaging procedure in the United States in which the radiation dose is regulated by the federal government. Consequently, many medical physicists have studied the dosimetry associated with screen-film and digital mammography. In this review, a brief history of mammography dose assessment by medical physicists is discussed. CT was introduced into clinical practice in the early 1970s, and has grown into one of the most important modalities available for diagnostic imaging. CT dose quantities and measurement techniques are described, and values of radiation dose for different types of scanner are presented. Organ and effective doses to adult patients are surveyed from the earliest single slice scanners, to the latest versions that include up to two x-ray tubes and can incorporate as many as 256 detector channels. An overview is provided of doses received by pediatric patients undergoing CT examinations, as well as methods, and results, of studies performed to assess the radiation absorbed by the conceptus of pregnant patients.