Product Meter Research Articles

Pulse Fluoroscopy in ERCP: Reducing Radiation Exposure

Background: Endoscopic Retrograde Choloangio Pancreatography (ERCP) poses significant radiation risk to patients and health professionals. Radiation exposure depends mainly on fluoroscopy time which theoretically may be decreased by using pulsed fluoroscopy instead of traditional method of continuous x-ray screening. Aim: To study the fluoroscopy time and radiation exposure to patients undergoing ERCP using pulsed fluoroscopy. Methods: Three hundred consecutive ERCPs performed from January to November 2003 at a single centre in UK were retrospectively studied. Siemens Siremobil Compact mobile intensifier system was used on the endoscopy unit. A Dose Area product (DAP) meter was fitted to the Xray tube and DAP reading and fluoroscopy time was recorded for each patient. Results: A total of 300 ERCPs on 225 consecutive patients were studied during 11 month period. 278 procedures were performed and ERCP was abandoned in 22 (7.3%) cases mainly because of poor access to papillary area. The biliary ducts were adequately visualized in 262 (94.2%) cases. Out of 278 ERCPs that were performed, thirty one (11.2%) ERCPs were diagnostic and 247 (88.8%) were therapeutic. Therapeutic procedures performed were mainly sphincterotomy in 159 (64.4%), duct clearance in 163 (66%) and stent insertion or exchange in 89 (36%) cases. There were in all 13 (4.3%) complications recorded. Of which 4 (1.3%) were mild and 9 (3%) were of moderate severity. The mean fluoroscopic time was 60.19 seconds (95% C.I 46.6-73.7 sec) for diagnostic and 97.09 seconds (95% C.I 88.4-105.8 sec) for the therapeutic ERCP (p < 0.001). Average DAP was 471.3 cGray-cm2 (95% C.I 358.3-584.3) for diagnostic and 808.9 cGray-cm2 (95% C.I 730.4-887. 3) for the therapeutic ERCP (p < 0.0001). DAP showed a linear correlation with fluoroscopy time (pearson correlation 0.947). Conclusion: Use of pulsed radiation in this study resulted in smaller fluoroscopy time and radiation dose compared to published data using traditional non pulsed fluoroscopy 1. Our success rates in therapeutic procedures as well as complication rates compare favourably to most published series2. We conclude that pulse fluoroscopy can considerably reduce the screening time and radiation dose without loss of efficacy or additional risk to patients.

Optimization of dose and image quality for computed radiography and digital radiography.

The surface doses to patients during chest, abdomen and pelvis radiography were measured over a period of 3 years, during which time computed radiography (CR) and digital radiography (DR) systems were introduced to replace film-screen systems. For film-screen and CR the surface doses were measured with thermoluminescent dosimeters. For DR the surface doses were calculated from the dose-area product (DAP) meter readings. Measurements were made for each type of examination and detector type on 10 average-size patients. Measurements were made immediately after the new systems were introduced, and subsequently as adjustments were made to optimize dose and image quality. Published diagnostic reference levels were used as target values in this optimization. Initially, CR doses were the same as or higher than for film-screen, and the doses were lower for DR compared to film-screen. Subsequent clinical experience with the systems led to changes in the technique used for chest examinations both for CR and for DR. For CR, it was possible to change the algorithm and decrease the dose to one quarter of the initial value with acceptable image quality. For DR, it was decided to reduce noise by increasing the dose by a factor of two. No changes were made to abdomen or pelvic imaging techniques for either CR or DR. The final patient surface doses using CR were similar to published diagnostic reference doses; for DR, all patient doses were less than published reference levels.

X‐Ray Dose Reduction in Fluoroscopically Guided Electrophysiology Procedures

This study assessed the efficacy of a new dose reduction regime in fluoroscopically guided electrophysiology (EP) procedures, which included diagnostic electrophysiological investigations, radiofrequency ablation, and biventricular pacing. A modified dose regime for fluoroscopy was implemented in one of our cardiac electrophysiology laboratories. The x-ray system was programmed with a hierarchy of three fluoroscopy doses, and therefore image quality and settings. The default (lowest) dose mode was not expected to be suitable for all patient sizes or for the entirety of all procedures. Staff raised the dose level in a stepped manner as and when required to optimize the imaging requirements of the procedure. Phantom studies indicated that the low dose mode provided adequate image quality for visualizing EP catheters, while significantly lowering patient skin dose. In 52 clinical cases, questionnaires were used to assess the subjective clinical image quality. The mean image quality score for the low dose setting was rated between "adequate" and "good." The fluoroscopy dose level was raised from the lowest level for 6% of the total fluoroscopy time. Procedural Dose Area Product (DAP) meter readings were analyzed for patients prior to (n = 85) and after (n = 150) the implementation of the low dose regime and showed an overall reduction in DAP rate of 74%. The hierarchical dose regime proved to be acceptable in routine clinical practice for EP procedures, leading to significant reductions in patient doses.

面積線量計の基礎から臨床応用

面積線量計の基礎から臨床応用

Radiation dose exposure during cardiac and peripheral arteries catheterisation

Background Ionising radiation carries an oncogenic risk which is linearly related to the dose. An estimation of the effective dose can be obtained from the measurements of the dose–area product (DAP), which is a measure of stochastic risk and a potential quality indicator. Aim To assess radiation exposure of patients in a large volume cardiac cath-lab. Methods A retrospective analysis of adult cardiac and peripheral percutaneous procedures (April to December 2004) was carried out to determine the DAP and estimated risk of malignancy. We identified 6 groups: Group 1 ( n = 100, coronary angiography and ventriculography); Group 2 ( n = 50, carotid stenting); Group 3 ( n = 50, aortography + coronary angiography + ventriculography); Group 4 ( n = 100, inferior extremities angiography + predilatation and stenting); Group 5 ( n = 100, coronary angiography + ventriculography + direct coronary stenting); Group 6 ( n = 100, coronary angiography + ventriculography + coronary predilation and stenting). Dose–area product meter attached on the X-ray unit was used for the estimation of the radiation dose received by the patient during the procedures. Results DAP values (mean ± S.D.) ranged from 41 ± 30 Gy cm 2 in Group 1 (lowest) to 118 ± 89 Gy cm 2 in Group 6 (highest). Within each group, individual radiation exposure varies substantially: from 11 to 200 Gy cm 2 in Group 1, and from 30 to 733 Gy cm 2 in Group 6 patients. Average exposure in a Group 6 patient corresponds to a risk of mortality from a malignancy of about 1 in 1000. Conclusion The radiation dose varies substantially across different types of procedures and up to tenfold within the same procedure. The enhanced knowledge of radiation dose might help the cardiologist to implement radiation sparing procedures eventually minimizing patient and operator radiation hazards in invasive cardiology.

Entrance radiation doses during paediatric cardiac catheterisations performed for diagnosis or the treatment of congenital heart disease

The purpose of this study was to estimate the radiation exposure of children, during cardiac catheterisations for the diagnosis or treatment of congenital heart disease. Radiation doses were estimated for 45 children aged from 1 d to 13 y old. Thermoluminescent dosemeters (TLDs) were used to estimate the posterior entrance dose (DP), the lateral entrance dose (DLAT), the thyroid dose and the gonads dose. A dose-area product (DAP) meter was also attached externally to the tube of the angiographic system and gave a direct value in mGy cm2 for each procedure. Posterior and lateral entrance dose values during cardiac catheterisations ranged from 1 to 197 mGy and from 1.1 to 250.3 mGy, respectively. Radiation exposure to the thyroid and the gonads ranged from 0.3 to 8.4 mGy to 0.1 and 0.7 mGy, respectively. Finally, the DAP meter values ranged between 360 and 33,200 mGy cm2. Radiation doses measured in this study are comparable with those reported to previous studies. Moreover, strong correlation was found between the DAP values and the entrance radiation dose measured with TLDs.

Investigation of occupational radiation exposure during interventional cardiac catheterisations performed via radial artery

The purpose of this study was to determine the thyroid, sternum and hand radiation doses of radiologists who perform angiographies and angioplasties via the radial artery. Staff radiation dose was estimated for 21 cardiac interventional catheterisations. Thermoluminescence dosemeters (TLDs) were used to determine radiation dose for each procedure at the right and left wrist, at the sternum and the thyroid. A dose area product (DAP) meter was also attached to give a direct value in Gy cm2 for each procedure. Staff radiation doses varied between 34 and 235 microGy per procedure at the left wrist, 28 and 172 microGy at the right wrist, 16 and 106 microGy at the level of the thyroid and 16 and 154 microGy at the level of the sternum. The DAP values varied between 25 and 167 Gy cm2. Radiation doses in this study are comparable to those reported in previous studies. Moreover, good correlation was found between the DAP values and the occupational dose measured with TLDs.

A survey of patient doses from conventional diagnostic radiology examinations: first results from Serbia and Montenegro

Diagnostic reference levels provide framework to reduce variability. The aim of this study is to establish, for the first time, a baseline for national diagnostic reference levels in Serbia and Montenegro for the most common X-ray examination types. Measurements of patient dose using kerma-area product meter and entrance surface air kerma assessment were performed on at least ten patients for each examination type, in each of 16 randomly selected hospitals in Serbia and Montenegro, so that a total of 3,026 procedures for nine different examination categories were included in the survey. Exposure settings and individual data were recorded for each patient. Mean, median and third quartile values of patient doses are reported. Results have shown wide variation of mean hospital doses, with factor of four for barium enema to 23 for thoracic spine radiography. Entrance surface air kerma were compared with previously published diagnostic reference levels (DRL) proposed by Commission of European Communities (CEC). Doses for all studied examination types except chest radiography were within European DRL. The reasons for dose variation are discussed. Survey data are aimed to help in development of an on-going national quality assurance and quality control programme in diagnostic radiology. The findings emphasize the importance of regular patient dose measurement to ensure that patient doses are kept as low as reasonable achievable.

Impact of digital imaging on radiation doses to the patient during X-ray examination of the urinary tract

To compare radiation doses given to patients undergoing IVU (intravenous urography) before and after digitalization of our X-ray department. IVU examinations were monitored with dose area product meters before and after the X-ray department changed to digital techniques. The first step was a change from film-screen to storage phosphor plates, while the second step involved changing to a flat panel detector. Forty-two patients were included for the film-screen situation, 69 when using the storage phosphor plates, and 70 using the flat panel detector. A dose reduction from 41.8 Gycm2 to 31.5 Gycm2 was achieved with the first step when the film-screen system was replaced with storage phosphor plates. A further reduction to 12.1 Gycm2 was achieved using the flat panel detector. The introduction of the flat panel detectors made a considerable dose reduction possible.

Comparative evaluation of an II based and a flat panel based cardiovascular fluoroscopy system within a clinical environment

The image quality and dose parameters from a 2004 Siemens Axiom Artis dBC cardiac biplane with flat panel detector were evaluated and compared to similar parameters evaluated for a 1977 Toshiba DPF 2000A biplane cardiac unit with a conventional image intensifier. Image quality assessment was performed with the Westmead test object; using solid water as a patient equivalent absorber. The patient dose comparison of the two systems is based on dose area product meter readings for 1512 patient cases recorded over 6 months following installation of the Siemens flat panel digital unit. The image quality results indicate that: (a) high contrast resolution was better with the digital flat panel unit, (b) low contrast resolution is similar between systems, and (c) the threshold contrast of the flat panel system is the same or inferior to that of the image intensifier system. Input dose to the surface of the flat panel detector showed a strong dependence on field size, similar to the behaviour of image intensifier system. For the most common clinical procedure--Left Heart Study via Judkins--the average total dose area product reading was 64.0 Gy-cm2 against 67.7 Gy-cm2 for the digital and conventional units respectively (p = 0.27) indicating no significant difference in dose performance between the two x-ray machines.

Radiation Doses to Patients and Cardiologists from Permanent Cardiac Pacemaker Implantation Procedures

The purpose of this study was to determine the patient and cardiologist doses during the implantation of permanent cardiac pacemakers under fluoroscopic control. For 55 procedures concerning three different types of pacemakers (DDD, VDD, and VVI), the dose-area product (DAP) meter readings and fluoroscopy times were recorded. From these data, the dose to the operating cardiologist was estimated. The median values of DAP and fluoroscopy time for all the procedures monitored were 11.4 Gycm(2) and 6.6 minute, respectively. For the 22 DDD, 21 VDD, and 12 VVI pacemakers implanted, the respective DAP median values were 14.7, 9.9, and 7.3 Gycm(2) and the respective median fluoroscopy times were 8.4, 5, and 2.9 minutes. The median doses to the hands, chest, eyes, and legs of the cardiologist conducting the manipulations were estimated to 0.21, 0.06, 0.03, and 0.11 mGy, respectively, per procedure. Compared to the existing literature, the median DAP value of this study is almost identical to the 11.2 Gycm(2) reported from a sample of 627 patients in 17 different x-ray rooms, whereas the fluoroscopy times are within the range of values reported by other authors. Concerning the cardiologist exposure, the estimated values indicate that the implantation of pacemakers is a procedure that does not involve a severe risk, especially if it is taken into account that lead aprons and collars are routinely used.

Radiation protection in medical imaging

Radiation dose measurement in diagnostic radiology is considered to be a critical factor for optimizing radiation protection to the health care practitioners, the patient and the public. This has lead to equipment that has dose-area product meters permanently installed. In many countries and even institutions, the range of equipment is vast and with this the opportunity for radiation protection and dose recording varies considerably. Practitioners must therefore move with the changed demands of radiation protection but in many cases without the assistance of modern advancements in technology. This paper presents an overview of radiation protection in medical imaging and intends to reaffirm the importance of this aspect to practice.

Patient doses for barium meal examination in Serbia and Montenegro and potentials for dose reduction through changes in equipment settings

Patient doses for barium meal examination performed at three general hospitals in Serbia and Montenegro were measured using a kerma-area product (KAP) meter. The results were analysed in order to obtain dose-related parameters. Although the observed doses were within the range reported in other studies, intra-hospital and inter-hospital dose variations were significant. Mean KAP values for total examination in three hospitals were 8.4, 24.4 and 13.9 Gy cm2, respectively. Contribution from fluoroscopy was greater than from radiography. Factors contributing to the increased dose delivery were determined and the recommendations on radiographic techniques were made. Changes in radiography settings allowed dose reduction up to 48% in the radiographic part of examination, that is, up to 12% in total dose without loss of image quality. In addition, fluoroscopy time was noted as the second major contributor to the dose variations. The results demonstrated the need for standardisation of practice for barium meal examination in the country.

Measurement of radiation dose in dental radiology

Patient dose audit is an important tool for quality control and it is important to have a well-defined and easy to use method for dose measurements. In dental radiology, the most commonly used dose parameters for the setting of diagnostic reference levels (DRLs) are the entrance surface air kerma (ESAK) for intraoral examinations and dose width product (DWP) for panoramic examinations. DWP is the air kerma at the front side of the secondary collimator integrated over the collimator width and an exposure cycle. ESAK or DWP is usually measured in the absence of the patient but with the same settings of tube voltage (kV), tube current (mA) and exposure time as with the patient present. Neither of these methods is easy to use, and, in addition, DWP is not a risk related quantity. A better method of monitoring patient dose would be to use a dose area product (DAP) meter for all types of dental examinations. In this study, measurements with a DAP meter are reported for intraoral and panoramic examinations. The DWP is also measured with a pencil ionisation chamber and the product of DWP and the height H (DWP x H) of the secondary collimator (measured using film) was compared to DAP. The results show that it is feasible to measure DAP using a DAP meter for both intraoral and panoramic examinations. The DAP is therefore recommended for the setting of DRLs.

Radiation doses to patients from enteroclysis

The purpose of this study was to determine the patient doses during enteroclysis and compare them with the available bibliographical data. For 14 enteroclysis examinations, the dose-area product (DAP) meter readings, fluoroscopy time, number of radiographs and exposure data were recorded. From these data, the fluoroscopy and radiography contributions to DAP, the entrance surface dose (ESD) and the effective dose (E) for each examination were estimated. The mean DAP was 81 Gy cm(2) and the mean fluoroscopy time was 19.5 min. The fluoroscopy contribution to DAP was 77% and 8.7 films were acquired in each examination on average. The mean ESD and E were estimated to be 428 mGy and 21 mSv, respectively. The mean DAP and fluoroscopy time calculated in this study are quite high when compared with those reported in the literature, suggesting that the examination technique should be reviewed and the ways to reduce patient exposure without compromising the diagnostic quality should be acquired.

冠動脈インターベンション術における患者被曝線量管理システムの評価

The angiography equipment Infinix Celeve of Toshiba Corp. is a system that estimates patient absorbed dose at the skin by using a dose area product meter. This system performs incidence area compensation, which corresponds to the changes of I.I. size, FID, and FTD. We evaluated the clinical usefulness of patient entrance skin dose management by the dose area product meter of Celeve by verifying the effects of various clinical parameters on absorbed dose. We determined compensation according to the various angles usually used by clinicians, and estimated the absorbed peak dose at the skin. By using the angle compensation of the C arm, the displayed values on the dose area product meter of Celeve could be used for skin doses as they were. The skin absorbed dose was 3.0 Gy or more in 33 of the 332 examples.

Assessment of patient radiation doses during transcatheter closure of ventricular and atrial septal defects with Amplatzer devices

The purpose of this study was to estimate the radiation dose to which children are exposed during cardiac catheterizations for the treatment of ventricular and atrial septal defects. Radiation doses were estimated for 46 children aged 1-18 years. These children were treated for secundum atrial septal defects (ASD group) for perimembranous ventricular septal defects (VSD group) or underwent a routine diagnostic catheterization (diagnostic group). Thermoluminescent dosimeters (TLDs) were attached in locations, representing the lateral entrance dose, the posterior entrance dose, the thyroid dose, and the gonad dose, respectively. A dose area product (DAP) meter was also attached externally on the posterior-anterior (PA) tube to give a direct value in cGy cm(2) for each procedure. The patient's entrance dose from the PA field ranged from 1.5 to 185.0 mGy for all patients, while the lateral entrance dose varied from 0.9 to 204 mGy. Radiation exposure to the thyroid and the gonads was found to vary from 0.4 to 8.3 and 0.1 to 2.1 mGy, respectively. The DAP meter recorded DAP values for the posterior tube, between 46 and 3,700 cGy cm(2). The mean effective dose was found to be 7.7, 16.2, and 33.3 mSv for the diagnostic, the ASD, and the VSD group, respectively. Very strong correlation was found between the DAP values and the entrance radiation dose measured with TLDs. The mean entrance dose received from therapeutic cardiac catheterizations using the Amplatzer devices was found approximately twice the dose received from a diagnostic one. Even for the most complex procedures, the maximum entrance dose was at least 10 times lower than the threshold, associated with skin erythema.

Evaluation of work practices and radiation dose during adult micturating cystourethrography examinations performed using a digital imaging system

A micturating cystourethrography (MCU) examination is a specific radiological procedure that is performed under fluoroscopic screening to visualize the bladder by filling it with contrast material and to evaluate the urethral morphology during voiding. It is necessary to evaluate radiation dose during MCU examination since it involves radiosensitive organs such as the gonads. Radiation dose imparted to 109 patients undergoing MCU examination were measured using a dose-area product (DAP) meter. Patients were categorized into two groups based on whether filling of the bladder with contrast medium was done retrogradely (MCU) or by the suprapubic percutaneous route (SP-MCU). The DAP values to Group A (MCU) and Group B (SP-MCU) patients varied from 0.43 Gycm(2) to 9.26 Gycm(2) and 0.54 Gycm(2) to 9.87 Gycm(2), respectively. Reduction of radiation dose to patients was possible by the use of optimized exposure factors, precise collimation of X-ray beam, use of 0.2 mm copper filters and by acquiring images digitally.

Radiation dose measurements to the interventional cardiologist using an electronic personal dosemeter.

The aim of this study was to investigate the use of an electronic personal dosemeter (EPD) worn by a senior cardiologist in an Interventional Cardiology (IC) Laboratory of a busy cardiac centre and how the results could help in the evaluation of radiation protection equipment used. Patient samples consist of 28 patients (10 coronary angiographies (CAs) and 18 percutaneous transluminal coronary angioplasties (PTCAs)). Patient dose was measured with a dose-area product (DAP) meter. Cardiologist radiation dose value written on the EPD as well as the protective equipment used was collected. Between patient and cardiologist dose, a significant correlation was found in CA and a moderate correlation in PTCA. Mean cardiologist effective dose E per procedure was found to be 0.2 microSv in CA and 0.3 microSv in PTCA. EPD proved to be an easy, direct and straightforward way to measure the radiation dose that the cardiologist receives in an IC laboratory.

Do dose area product meter measurements reflect radiation doses absorbed by health care workers?

This study determined the correlation between radiation doses absorbed by health care workers and dose area product meter (DAP) measurements at Universitas Hospital, Bloemfontein. The DAP is an instrument which accurately measures the radiation emitted from the source. The study included the interventional radiologists, radiographers and nurses associated with radiological intervention procedures during the period 1 August 2003 - 31 August 2003. The amount of radiation produced during every procedure was measured by a dose area product meter (DAP) and routinely recorded. The absorbed doses received by health care workers were measured using a thermoluminescent dose meter (TLD). The TLDs were analysed and recorded at the end of each week. Health care workers wore TLDs on the following areas: forehead, thyroid (attached under thyroid guard), and abdomen (worn under lead jacket). A strong positive correlation (r = 0.9, p = 0.0374) was found between the radiographers’ head TLD and DAP meter readings. All other correlations between TLD and DAP readings were not statistically significant. Strong positive correlations were found between the TLD readings of the radiologists’ and nurses’ bodies, the nurses’ and radiographers’ bodies and the radiologists’ and the radiographers’ bodies, all of which were statistically significant.