Patient Entrance Surface Dose Research Articles

Assessment of radiation dose received from knee joint X-ray examinations

BackgroundMedical exposure from diagnostic X-ray machines represents the primary artificial source of human exposure to low ionizing radiation. Knee X-rays are a standard examination to diagnose multiple conditions ranging from traumatic injuries, degeneration, and cancer. In Saudi Arabia, there is a lack of available data and pertinent information regarding the assessment of the patient entrance surface dose (ESD) from knee X-rays. This study aims to estimate the ESD for adult patients undergoing knee X-ray examinations at four major medical centres in Saudi Arabia. Methods and materialsThe ESD was estimated indirectly using X-ray exposure factors for patients and directly using optically stimulated luminescence (OSL). The results were compared with previous studies conducted nationally and internationally and with international reference levels. ResultsThe results of this research showed that the mean patient ESD was 1.4 ± 0.37 mGy using the direct method and 1.12 ± 0.20 mGy using the indirect method. The estimated mean ESD values were found to be much higher than the mean ESD reference values, emphasizing the crucial requirement for optimizing radiation doses in conventional radiology to improve patient safety and diagnostic effectiveness. ConclusionThis confirms the requirement for reducing patients’ doses to the tolerable levels recommended by many international radiation protection commissions.

Analisis Indeks Paparan Radiografi Digital Pada Pemeriksaan Radiologi Thoraks Postero Anterior Sebagai Upaya Peningkatan Proteksi Radiasi Pasien

ABSTRACT Backgound: Digital radiography is an easy method of radiological examination, so many radiology technicians often use high exposure factors because they are considered to speed up when processing images, this can increase the risk of excessive radiation doses in patients, currently the exposure index (IE) is feedback to radiology technicians for optimal images and low doses for patients. Objective: evaluating Fujifilm (S-Value) exposure index and entrance surface dose (ESD) thorax posterior-anterior as an effort to increase patient radiation protection using the ALARA principle, Method: Data taken from samples with parameters 64 kVp 16 mAs to 94 kVp 2 mAs, ESD is measured using the thermoluminescent dosimeter (TLD) chip and exposure index (S-Value) from Fujifilm's direct radiography device. Result: The relationship between S-Value and ESD has an exponential trend graph. The rise of S-Value will be followed by the ESD sequence. With the BAPETEN reference value of surface radiation dose 0.40 mGy, the minimum S-value must be achieved so that the patient's ESD does not exceed S-532 at ESD 0.39. Conclusion: The results of this study indicate that Fujifilm's S-Value allows it to be used as an evaluation of the ESD values received by patients as an effort to increase patient radiation protection. Keywords: Exposure index (S-Value), ESD, chest radiography, radiation protection

Patient dosimetry in neurointerventional procedures

Neurointerventional radiology (NIR) procedures often require an extended long time to perform. Patient radiation dose is an important issue due to hazards of X-ray radiation. The aim of this work was to measure the entrance surface dose (ESD) on the patient's head during interventional neurologic procedure. A batch of solid-state dosimeters were used by mean of thermally stimulated luminescence (TSL) phenomena. Thermoluminescent dosimeters (TLDs) were placed around the head patient during interventional procedures. The ESD on the surface of the head patient was measured. The monitoring of patient's ESDs varied from 5.91 mGy up to 67.44 mGy for arteriovenous fistula (AVF) classified as diagnostic interventional radiology procedures. The highest ESD was determined for 180° with 67.44 mGy. Meanwhile, for therapeutic interventional procedures named arteriovenous malformation (AVM), the ESD measurements revealed a variation from 65.91 mGy and 600.73 mGy. The highest ESD values is attributed acquisition imaging mode during AVM therapeutic procedures. The results suggest the requirements of adopting strategies for radiation dose optimization during neurologic interventional procedures.

Diagnostic Reference Level in Frontal Chest X-Ray in Western Côte d’Ivoire

Our study aims to determine diagnostic reference levels (DRL) for chest front examination in postero anterior (PA) for optimizing patient entrance surface dose (ESD) and dose-area product (DAP) of patients in west of Cote d’Ivoire. 90 patients from three hospitals undergoing conventional radiology were considered. The ESD and DAP for each patient were obtained during chest radiography (PA) examination. The measurements were performed with the device call Dose-Area Product-meter (DAP-meter) with brand Diamentor M4-KDK, type 11017. The DRL were obtained in applying the 75th percentile statistical method to the obtained ESD and DAP. The obtained DRL in ESD for chest radiography for all rooms is 0.40 mGy and in DAP is 54.85 cGy⋅cm2. Our DRL for ESD is higher than those obtained in Abidjan District and in other countries like UK and Cameroon. Our DRL for DAP is higher than those from Abidjan and all other countries for which a similar study was made. The comparison of these values to those from Abidjan and other countries, shows us that radiology technicians can make efforts to choose radiological parameters to reduce ESD. They must use convenable the X-rays tube to reduce DAP by reducing the patient exposure surface.

Direct Anterior Hip Replacement Does Not Pose Undue Radiation Exposure Risk to the Patient or Surgeon.

The fluoroscopically assisted direct anterior approach for total hip arthroplasty has gained interest in recent years. One of the perceived advantages is the use of fluoroscopy to aid in the positioning of implants. The purpose of this study was to measure the radiation entrance surface dose to anatomically important areas of both patients and surgeons during direct anterior approach total hip arthroplasty. Radiation dosimetry badges were placed at the sternal notch and pubic symphysis of 50 patients undergoing direct anterior approach total hip arthroplasty. Badges were also placed on the surgeons outside of their lead aprons at the level of the thyroid. Three fellowship-trained arthroplasty surgeons were involved in the study. Radiation exposure of each badge was measured after each case (surgeon and patient). The cumulative dose was also calculated for the surgeons. To limit surgeon bias during the study, 50 consecutive direct anterior approach total hip arthroplasties that occurred prior to this study were analyzed for total fluoroscopic dose and time and served as a control group. Forty-five subjects met study criteria. In the study group, 1 patient had a detectable thyroid exposure equal to 1 mrem. Seven patients had a detectable radiation entrance surface dose at the pubic symphysis (range, 1 to 7 mrem). No radiation entrance surface dose was detectable in the remaining 44 patients at the sternal notch and 38 patients at the pubic symphysis. Surgeons in the study did not experience a detectable radiation entrance surface dose. The mean fluoroscopic time was 13.72 seconds (range, 6.7 to 28.7 seconds). The mean patient radiation exposure was 178 mrem (range, 54 to 526 mrem). This study demonstrates that during direct anterior approach total hip arthroplasty, the mean patient entrance surface dose at the pubic symphysis and the sternal notch is not detectable in most patients. The mean patient exposure in this study during direct anterior approach total hip arthroplasty was 178 mrem, which is less than a single pelvic radiograph (600 mrem). No surgeon in our study demonstrated a detectable radiation entrance surface dose. Our data suggest that direct anterior approach total hip arthroplasty typically results in a negligible or very low dose of absorbed radiation exposure to the patient and the surgeon. We believe this study to have clinical relevance because both patients and surgeons have evidence that utilization of fluoroscopy during direct anterior total hip replacement places both parties at a relatively low radiation exposure risk.

Institutional (local) diagnostic reference levels in fluoroscopically guided spine surgery

In this study, institutional (local) diagnostic reference levels (LDRLs) and action levels (ALs) for spine interventional procedures are reported. Fluoroscopy time (FT), kerma area product (KAP), cumulative dose (CD), as well as anatomical, clinical and technical factors affecting procedure complexity were recorded for 156 patients who underwent cervical and thoraco-lumbar interventions. Patient entrance surface dose (ESD), effective dose (ED), thyroid absorbed dose and gonadal dose were also estimated, based on KAP measurements. The LDRLs and ALs were calculated as the 75th and 10th percentile of FT, KAP and CD values for the total group of patients, as well as utilizing the weight banding method and the size correction method. For the total distribution of patients, the LDRLs for cervical and thoraco-lumbar interventions are 0.15min and 0.29min for FT values, 0.10Gycm2 and 0.71Gycm2 for KAP values, as well as 0.47mGy and 3.24mGy for CD values, respectively. The corresponding ALs are 0.03min and 0.03min, 0.01Gycm2 and 0.07Gycm2, as well as 0.05mGy and 0.33mGy for FT, KAP and CD values, respectively. The age and treated levels had a significant influence on the reference dose values only for cervical interventions, whereas none of the other included factors showed statistically significant association for both cervical and thoraco-lumbar interventions. The weight banding method resulted to reference values comparable to those obtained for the whole group of patients, while the size correction method resulted to lower values. The mean ESD values were 1.58mGy (range 0.02–13.58mGy) for cervical and 23mGy (range 0.004–390.3mGy) for thoraco-lumbar interventions. The corresponding mean ED values were 0.012mSv (range 0.001–0.097mSv) and 0.124mSv (range 0.00002–2.11mSv), respectively. The mean thyroid and gonadal doses were 0.14mGy (range 0.002–1.12mGy) and 0.044mGy (range 0.000003–1.56mGy), respectively. The LDRLs and ALs reported could contribute in the effort for establishing national DRLs and for increasing neurosurgeons awareness regarding patient dose and radiation protection issues during spine interventional procedures.

Patient Dose in Fluoroscopically Guided Cervical Discectomy and Fusion.

Cervical discectomy and fusion (CDF) is a minimally invasive procedure, where the accurate placement of the implants is accomplished using fluoroscopic guidance. Therefore, the evaluation of the radiation dose becomes mandatory. The purpose of the current study was to assess patient dose during fluoroscopically guided anterior and/or posterior CDF procedures. Thirty-three patients undergoing single or multiple-level CDF were studied using a mobile C-arm system. Data regarding fluoroscopy time (FT), air kerma area product (KAP) and cumulative dose (CD) were recorded. Patient entrance surface dose (ESD), thyroid absorbed dose and effective dose (ED) were calculated from KAP measurements, utilizing the CALDoseX software. The average FT was 0.12 min (range 0.02-0.48 min), resulting to a KAP value of 0.21 Gy cm2 (range 0.01-1.46 Gy cm2) and a CD value of 0.96 mGy (range 0.04-6.58 mGy). The ESD ranged between 0.08 and 13.58 mGy (average 1.95 mGy), the ED between 0.001 and 0.097 mSv (average 0.015 mSv), while the dose absorbed by the thyroid ranged between 0.01 and 1.12 mGy (average 0.194 mGy). The dose associated with the CDF procedure is very low, comparable to that delivered by a lateral X-ray radiograph of the cervical spine. However, higher doses can be revealed, due to the non-optimum use of the X-ray system and extended FTs, mainly affected by complex clinical conditions, as well as the experience of the neurosurgeon. Additional studies need to be conducted for further investigation of the patient dose from the CDF procedure.

Analysis of Scattered Radiation in an Irradiated Body by Means of the Monte Carlo Simulation: Back-scatter Factors of Diagnostic X-rays in the Incident Surface Which is Not Flat

To obtain patient entrance surface dose in X-ray photography, a calculation method based on measured exposure or air kerma radiated from X-ray tube is generally used. Two factors are necessary for this calculation: (1) exposure/air kerma to absorb dose conversion factor and (2) back-scatter factor (BSF) based on X-ray quality and on field size. These BSFs are commonly obtained by interpolation from existent data which were given for a water phantom whose entrance surface is flat. Since patient's surface in X-ray photograph is not flat, some error may occur when existent BSF is used in this calculation. In this article, BSF for water phantom with cylindrical surface and elliptic cylinder surface were calculated by means of the Monte Carlo simulation. And these BSFs were compared with BSF for flat surface phantom. As a result (1) radius of curvature of cylindrical phantom or horizontal axis of elliptic cylinder phantom is smaller, (2) half value layer of X-ray is larger, (3) field size is larger, difference of these BSF with that for flat surface phantom tends to be larger. Maximum difference by calculation condition assumed in this article was more than 10%. The cause of this difference is because scattering volume in irradiated body of cylindrical or elliptic cylinder phantom is smaller than flat surface phantom. To obtain patient entrance surface dose more precisely, it is necessary to use BSF respectively calculated for phantom resembling patient's body such as cylindrical or elliptic cylinder phantom by means of the Monte Carlo simulation.

Time to take the gloves off: the use of radiation reduction gloves can greatly increase patient dose.

Sterile radiation reduction gloves have been widely used over the past several decades in an effort to reduce hand doses during fluoroscopically guided procedures. While multiple studies have quantified the potential dose reduction to the fluoroscope operator from the use of such gloves, possible effects on the patient have not yet been quantified. The aim of this study was to examine the impact on patient dose when radiation reduction gloves are used. The impact on patient dose when using radiation reduction gloves in the field of view (FOV) was evaluated by measuring patient entrance surface dose rates (ESDR) using three C‐arm fluoroscopes for a range of patient sizes and different operating and magnification modes. Multiple measuring fields were used in combination with both peripheral and central glove placement. ESDR were measured with no glove in the FOV, with one radiation reduction glove, and with double gloves in the FOV, to replicate the actions of some fluoroscope operators. Compared to an ungloved hand, the use of a single radiation reduction glove in the measuring field resulted in up to a 2.8‐fold increase in ESDR. The use of double radiation reduction gloves resulted in up to a 4.9‐fold increase in ESDR. In both cases, the increase in ESDR was dependent on the size of the patient and on the operating and magnification modes used, and ranged from no increase up to the aforementioned maximum. When used in the FOV, and particularly within the measuring field, radiation reduction gloves can substantially increase ESDR. This increase in dose, when considered against the relatively small published reduction in dose to the operator's hands, may mean that the increased risks from the use of radiation reduction gloves outweigh the benefits. In any case, hands should not be placed in the FOV if not required by the goals of the procedure.PACS number: 87.59.C‐

In-house development of a neonatal chest simulation phantom.

The aim of the study was to design and construct an anatomical and radiological phantom of a neonatal chest for investigating image quality and patient entrance surface dose (ESD). The density, elemental composition, scatter, attenuation, and absorption characteristics of different possible substitute materials were compared to that of neonatal tissues for radiological equivalence. Availability and cost of possible substitute materials were also considered. The most optimal substitute materials were selected to represent neonatal muscle, bone, healthy or aerated and sick or collapsed lung. For anatomical equivalence, a computed tomography (CT) scan was performed on a neonatal cadaver. Dimensions of different organs and structures were measured with software measuring tools at different window and level settings. Simplifying assumptions, due to machining limitations, were made. The results were used to create scaled drawings, which were used to machine the structures of the phantom. The phantom was assembled in a layer‐by‐layer manner and was validated with region of interest (ROI) analyses. The neonatal chest simulation phantom was an acceptable simulation of a real neonatal chest based on ROI validation, with an overall deviation of 32.5%. The phantom was successfully used in our diagnostic radiology division for ESD and image quality investigations for chest anterior‐posterior (AP) radiographs.PACS numbers: 87.57.C‐; 87.59.B‐; 41.50.+h

Evaluation of radiation dose to neonates in a special care baby unit

The purpose of this study was to evaluate the patient entrance surface dose (ESD), organ dose and effective dose for neonates in the special care baby unit (SCBU) up to 28 days after birth. A total of 135 patients were examined during 4 months. ESDs were calculated from patient exposure parameters using DosCal software. Effective doses were calculated using software from the National Radiological Protection Board (NRPB). The mean patient ESD per procedure was 80±0.02μGy. The mean and range of the effective dose per procedure were 0.02 (0.01–0.3) mSv. The radiation dose in this study was higher compared to previous studies. A dedicated X-ray machine with additional filtration is recommended for patient dose reductions.

Patient entrance surface dose measurements using XR-QA2 Gafchromic films during micturating cystourethrography procedures

The aim of this study was to test the feasibility of using Gafchromic XR-QA2 films in the measurements of patient entrance surface dose (ESD) during the micturating cystourethrogram (MCUG) examination in paediatric patients. Radiochromic films were used to map the entrance dose and to identify the location of peak surface dose (PSD). Direct in vivo measurements of entrance dose were conducted by placing a radiochromic film between the patient and the examination table. The measured ESD values for the commonly performed MCUG fluoroscopic examinations at the authors' institution was in the range of 1.2-7.8 mGy and the PSD in the range of 1.2-8.5 mGy per MCUG procedure for patients with age ranging from 1 to 12 y old. Gafchromic films (XR-QA2) were found to be an efficient and practical dosimetry method that can be easily used to measure clinical patient entrance doses during fluoroscopically guided procedures and potentially in other diagnostic investigations.

Assessment of entrance surface dose and health risk from common radiology examinations in Iran

Medical X-ray exposures are the largest man-made source of population exposure to ionising radiation in many countries. Although information on medical exposure is already incorporated into national legislative documents, in Isfahan there is no data on the assessment of patient's entrance surface dose (ESD) and the health risk from conventional radiography in daily clinical practice. The aim of this study was to investigate ESDs and the consequent health risk for the patients undergoing routine X-ray procedures in hospitals under the control of Isfahan University of Medical Sciences, Iran, in year 2011. The values of ESDs were measured for common radiographical examinations with the highest absorbed dose to the patient in seven hospitals (Alzahra, Ashrafi-Khomeini-shahr, Feyz, Isabne-Maryam, Kashani, Nour-Aliasghar and Seyed-Al Shohada) and six stationary X-ray machines (General Electric, USA; Phillips, The Netherlands; Siemens, Germany; Shimadzu, Japan; Toshiba, Japan and Varian, USA). The results of the ESD measurements as well as the calculated effective dose values between different X-ray examinations showed values significantly greater than those recorded in some other countries especially for the high tube potential technique (such as the skull) by factors of 2.5-5.0. Based on the fatality risk of 5 % per sievert, it was estimated that, for chest and skull examinations approximately two (40.18 person-Sv×5 % per sievert) and one (2.53 person-Sv×5 % per sievert) cases of health risk, respectively, may in the future be attributable to diagnostic X rays done in year 2011 in Isfahan. Efforts should be taken to further lower patient doses while securing image quality. The need to provide relevant education and training to staff in the radiology sections is of utmost importance.

Dose Optimization for Different Medical Imaging Tasks From Exposure Index, Exposure Control Factor, and mAs in Digital Radiography

In radiographic examination, not all medical imaging tasks require the same level of image quality or diagnostic information. Criteria should be established for different imaging tasks to avoid excessive doses where there is no clear net benefit in the diagnosis or the image quality. An exposure index provided by manufacturers would be a useful tool for this purpose. This study aims to establish an optimum exposure index to be used as a guideline for clinical imaging tasks to minimize radiation exposure for chest digital radiography. A three-level classification of image quality (high, medium, and low) for chest imaging tasks was carried out. An anthropomorphic phantom was employed to establish minimum exposure index and exposure (mAs) for clinical imaging task type I (corresponding to high image quality). The exposures of medium and low quality images derived from it. Thirty patients were exposed consecutively with these optimized exposure factors, and clinical tasks were considered, while another 30 patients were exposed with the exposure factors routinely used in practice. Image quality was assessed objectively by a consensus panel. The optimized exposure provided a significant reduction of the mean exposure index from 1,556 to 1,207 (p < 0.0001) and mean patient's entrance surface dose from 0.168 mGy to 0.092 mGy (p < 0.0001). The results show that a clinical-task-determined radiographic procedure is more conducive to radiation protection of patients. In this study, the posteroanterior chest imaging examination was chosen as an example. This procedure can also apply to other body parts and views.

An evaluation of semiconductor and ionization chamber detectors for diagnostic x-ray dosimetry measurements

Dosemeters for performance testing of x-ray equipment may utilize semiconductor technology or ionization chambers (ICs). Semiconductor dosemeters incorporate several elements into the detectors from which compensation for variations in response with photon energy is derived. The design of the detectors influences their response with angle and this is different from that of ICs. The responses of semiconductor detectors (SDs) and ICs to x-ray beams with a variety of radiation qualities have been measured in order to assess differences in response. Measurements have been made with experimental arrangements simulating use of the detectors in performance testing of digital radiography and fluoroscopy equipment. Results show that differences in photon energy responses between the detectors are small, but because ICs are sensitive to radiation incident from all angles, they record more scattered radiation than SDs. Implications of differences in detector responses are discussed and recommendations made about their use. SDs are more appropriate for measurements of image receptor doses and are recommended for setting up automatic exposure control devices for digital radiography. ICs are suitable for assessment of patient entrance surface dose rate measurements. Correction factors that could be applied to allow comparisons between measurements with different dosemeters are proposed.

The importance of radiation quality for optimisation in radiology.

Selection of the appropriate radiation quality is an important aspect of optimisation for every clinical imaging task in radiology, since it affects both image quality and patient dose. Spreadsheet calculations of attenuation and absorption have been applied to basic imaging tasks to provide an assessment of imaging performance for a selection of phosphors used in radiology systems. Contrast, which is an important component of image quality affected by radiation quality, has been assessed in terms of the contrast to noise ratio (CNR) for a variety of X-ray beams. Both CNR and patient dose fall with tube potential, and selection of the best option is a compromise that will provide an adequate level of image quality with as low a radiation dose as practicable. It is important that systems are set up to match the response of the imaging phosphor, as there are significant differences between phosphors. For example, the sensitivity of barium fluorohalides used in computed radiography declines at higher tube potentials, whereas that of gadolinium oxysulphide used in rare earth screens increases. Addition of 0.2 mm copper filters, which can reduce patient entrance surface dose by 50%, may be advantageous for many applications in radiography and fluoroscopy. The disadvantage of adding copper is that tube output levels have to be increased. Application of simple calculations of the type employed here could prove useful for investigating and assessing the implications of potential changes in X-ray beam quality prior to implementation of new techniques.

Lumbar spine radiology: analysis of the posteroanterior projection.

The use of the posteroanterior (PA) technique as a means of dose reduction has been used effectively in radiology departments for chest and abdominal examinations. The aim of this investigation was to establish if the PA lumbar spine projection offers any advantages over the traditional anteroposterior (AP) view in terms of radiation dose and image quality. The contribution of tissue displacement to any dose reduction was also evaluated. The first part of the study involved the use of an anthropological phantom where entrance surface and an internal dose were measured for both the PA and AP projections. Entrance surface doses for both projections were then measured on randomly allocated female patients. Resultant image quality was assessed using CEC quality criteria. Anterior to posterior patient diameter was also recorded. The results demonstrated that with the PA compared with the AP projection, reductions of 38.6% (p = 0.016) and 38.9% (p = 0.02) in patient entrance surface dose and internal phantom dose, respectively. No significant differences in image quality were noted between the two projections. Patient diameter decreased by 1.8 cm with the PA view. The authors conclude that tissue displacement is the main factor for the patient dose reduction and recommend employment of the PA procedure for routine lumbar spine examinations.

Protocol for measurement of patient entrance surface dose rates for fluoroscopic X-ray equipment.

While patient entrance surface dose rate is an important indicator of dose performance for fluoroscopic units, there has been no standardized approach to measuring this. Since results are strongly dependent on the type of phantom used and the relative positions of the X-ray tube, intensifier and phantom, comparisons of the performance for different units are difficult to make. This document sets out a protocol for making these measurements using a standard phantom and standard configurations for different types of X-ray unit Values of dose rates which might be expected are given.

Influence of dose reduction recommendations on changes in chest radiography techniques

A previous dosimetric study on chest radiography identified ways to reduce patient entrance surface dose (ESD). This present study was designed to monitor changes that had occurred in the use of applied potential and film-screen sensitivity, after a series of recommendations were issued. The study falls into two parts: (1) an assessment of the impact of the recommendations and (2) what factors were responsible for change. Where changes had occurred, exposure factors were collected for 30 patients per tube and the mean ESD was calculated for each tube. Intercomparison (r = 0.93, p < 0.001) was made between calculated and measured (TLDs) values of mean ESD for 10 X-ray units, to ensure that the calculated values provided accurate estimates of the new mean ESDs. 89% of units previously monitored for patient ESD now use average applied potentials greater than 90 kVp and 51% are using film-screen sensitivities of 400. The mean ESD has been reduced on average by 47%, from 0.15 mGy to 0.08 mGy. It has been estimated that the annual collective dose from diagnostic radiology procedures in 30 hospitals in the West Midlands has been reduced by a value in excess of 40 man Sv. Reasons for change could be attributed to some of the following factors: (a) a knowledge of dose levels in comparison with other centres; (b) personal contact with departments; (c) feedback in terms of results and dose savings and (d) positive encouragement to make changes.

Optimization of radiographic technique for chest radiography.

Over 1500 patients undergoing chest radiography in the West Midlands have been monitored for entrance surface doses using lithium borate thermoluminescent dosemeters. In total 63 X-ray tubes were monitored from 30 hospital departments. The mean patient entrance surface dose is 0.15 mGy, and the 75th percentile entrance surface dose is 0.18 mGy. A reference level of 0.18 mGy has been recommended for PA chest radiography in the West Midlands. Image quality has been assessed on patient radiographs. Departmental radiologists were responsible for assessing radiographs taken within their hospital. Independent analysis was performed by a control radiologist. Film-screen processor sensitivity has been assessed on 48 film-screen processor combinations. Significant differences were observed between the nominally quoted sensitivities and the measured sensitivities. Only 26% of systems produced measured sensitivities within 10% of the nominal values. A four variable regression model, explaining 78% of the variance, provided the best description for the variation in patient dose. These variables were actual sensitivity, applied potential, generator waveform and radiographic quality. Four recommendations have been made to lower patient doses; these are: (1) an increase in applied potential to a minimum of 90 kVp; (2) a film-screen sensitivity of 400; (3) optimization of processor performance and (4) regular radiological audits to reduce repeat rates to a level of 5%. If all of these recommendations are followed, an estimated overall entrance surface dose saving of 53% would result. Changing the applied potential alone will see the variation in the mean entrance surface dose from non-gridded systems reduce from a factor of 4 to a factor of 2.