Endoscopic retrograde cholangiopancreatography (ERCP) is an important tool for the diagnosis and treatment of the hepatobiliary system. The use of fluoroscopy to aid ERCP places both the patient and the endoscopy staff at risk of radiation-induced injury. Radiation dose to patients during ERCP depends on many factors, and the endoscopist cannot control some variables, such as patient size, procedure type, or fluoroscopic equipment used. Previous reports have demonstrated a linear relationship between radiation dose and fluoroscopy duration. When fluoroscopy is used to assist ERCP, the shortest fluoroscopy time possible is recommended. Pulsed fluoroscopy and monitoring the length of fluoroscopy have been suggested for an overall reduction in both radiation exposure and fluoroscopy times. Fluoroscopy time is shorter when ERCP is performed by an endoscopist who has many years experience of performing ERCP and carried out a large number of ERCPs in the preceding year. In general, radiation exposure is greater during therapeutic ERCP than during diagnostic ERCP. Factors associated with prolonged fluoroscopy have been delineated recently, but these have not been validated.
Endoscopic retrograde cholangiopancreatography; Radiation dose; Fluoroscopy; Radiation exposure; X-ray
Although image quality (IQ) is the ultimate goal for accurate diagnosis and treatment, minimizing radiation dose is equally important. This is especially true when pediatric patients are examined, because their sensitivity to radiation-induced cancer is two to three times greater than that of adults. DoseWise is an ALARA-based philosophy within Philips Medical Systems that is active at every level of product design. It encompasses a set of techniques, programs and practices that ensures optimal IQ while protecting people in the X-ray environments. DoseWise methods include management of the X-ray beam, less radiation-on time and more dose information for the operator. Smart beam management provides automatic customization of the X-ray beam spectrum, shape, and pulse frequency. The Philips-patented grid-controlled fluoroscopy (GCF) provides grid switching of the X-ray beam in the X-ray tube instead of the traditional generator switching method. In the examination of pediatric patients, DoseWise technology has been scientifically documented to reduce radiation dose to <10% of the dose of traditional continuous fluoroscopy systems. The result is improved IQ at a significantly lower effective dose, which contributes to the safety of patients and staff.
Pediatric dose management; Fluoroscopic equipment; Technical advances
This software tool locates and computes the intensity of radiation skin dose resulting from fluoroscopically guided interventional procedures. It is comprised of multiple modules. Using standardized body specific geometric values, a software module defines a set of male and female patients arbitarily positioned on a fluoroscopy table. Simulated X-ray angiographic (XA) equipment includes XRII and digital detectors with or without bi-plane configurations and left and right facing tables. Skin dose estimates are localized by computing the exposure to each 0.01 × 0.01 m2 on the surface of a patient irradiated by the X-ray beam. Digital Imaging and Communications in Medicine (DICOM) Structured Report Dose data sent to a modular dosimetry database automatically extracts the 11 XA tags necessary for peak skin dose computation. Skin dose calculation software uses these tags (gantry angles, air kerma at the patient entrance reference point, etc.) and applies appropriate corrections of exposure and beam location based on each irradiation event (fluoroscopy and acquistions). A physicist screen records the initial validation of the accuracy, patient and equipment geometry, DICOM compliance, exposure output calibration, backscatter factor, and table and pad attenuation once per system. A technologist screen specifies patient positioning, patient height and weight, and physician user. Peak skin dose is computed and localized; additionally, fluoroscopy duration and kerma area product values are electronically recorded and sent to the XA database. This approach fully addresses current limitations in meeting accreditation criteria, eliminates the need for paper logs at a XA console, and provides a method where automated ALARA montoring is possible including email and pager alerts.
Peak skin dose; sentinal event; DICOM structured report dose; patient entrance reference point; fluoroscopy; interventional radiology; Joint Commission (JC); radiation dose; Digital Imaging and Communications in Medicine (DICOM)
Interventional and fluoroscopic imaging procedures for pediatric patients are becoming more prevalent because of the less-invasive nature of these procedures compared to alternatives such as surgery. Flat-panel X-ray detectors (FPD) for fluoroscopy are a new technology alternative to the image intensifier/TV (II/TV) digital system that has been in use for more than two decades. Two major FPD technologies have been implemented, based on indirect conversion of X-rays to light (using an X-ray scintillator) and then to proportional charge (using a photodiode), or direct conversion of X-rays into charge (using a semiconductor material) for signal acquisition and digitization. These detectors have proved very successful for high-exposure interventional procedures but lack the image quality of the II/TV system at the lowest exposure levels common in fluoroscopy. The benefits for FPD image quality include lack of geometric distortion, little or no veiling glare, a uniform response across the field-of-view, and improved ergonomics with better patient access. Better detective quantum efficiency indicates the possibility of reducing the patient dose in accordance with ALARA principles. However, first-generation FPD devices have been implemented with less than adequate acquisition flexibility (e.g., lack of tableside controls/information, inability to easily change protocols) and the presence of residual signals from previous exposures, and additional cost of equipment and long-term maintenance have been serious impediments to purchase and implementation. Technological advances of second generation and future hybrid FPD systems should solve many current issues. The answer to the question ‘how much better are they?–is ‘significantly better– and they are certainly worth consideration for replacement or new implementation of an imaging suite for pediatric fluoroscopy.
Flat-panel detectors; Fluoroscopy; Interventional radiology
Imaging for urolithiasis has evolved over the past 30 years. Currently, non-contrast computed tomography (NCCT) remains the first line imaging modality for the evaluation of patients with suspected urolithiasis. NCCT is a dominant source of ionizing radiation for patients and one of its major limitation. However, new low dose NCCT protocols may help to reduce the risk. Fluoroscopy use during operating room (OR) surgical procedures can be a substantial source of radiation for patients, OR staff and surgeons. It is important to consider the amount of radiation patients are exposed to from fluoroscopy during operative interventions for stones. Radiation reduction can be accomplished by appropriate selection of imaging studies and multiple techniques, which minimize the use of fluoroscopy whenever possible. The purpose of this manuscript is to review common imaging modalities used for diagnosing and management of renal and ureteral stones associated with radiation exposure. We also review alternatives and techniques to reduce radiation exposure.
Calculi; imaging computed tomography scan; nephrolithiasis
To test the hypothesis that replacing the antiscatter grid with an air gap will reduce patient radiation exposure without significant compromise of image quality.
457 patients having either uncomplicated diagnostic studies or a single vessel angioplasty (percutaneous transluminal coronary angioplasty (PTCA)) on a flat plate system (GE Innova) were studied. For two months their total dose–area product score was recorded on standard gridded images and then for two months on images made with the grid out, with an air gap used to reduce scatter. Detector magnification was reduced one step when an air gap was used to achieve the same final image size. A sample set of studies was reviewed blind by five observers, who scored sharpness and contrast on a non‐linear scale.
The average dose–area product was significantly reduced, both in the diagnostic group (n = 276), from a mean (SD) of 26.2 (14.7) Gy·cm2 with the grid in to 16.1 (12) Gy·cm2 with the grid out (p = 0.01), and in the PTCA group (n = 181), from 48.2 (36.2) to 37 (27.5) (p = 0.01). The mean image quality scores of the gridless cohort were not significantly different from those of the gridded cohort.
With the use of a flat plate detector, air gap gridless angiography reduces the radiation dose to the patient and, in consequence, to the operator without significantly affecting image quality. It is proposed that gridless imaging should be the default technique for adults and children and in most installations.
radiographic magnification; coronary angiography; x rays; scattering, radiation
The increasing use of fluoroscopy-based surgical procedures and the associated exposure to radiation raise questions regarding potential risks for patients and operating room personnel. Computer-assisted technologies can help to reduce the emission of radiation; the effect on the patient’s dose for the three-dimensional (3-D)-based technologies has not yet been evaluated.
We determined the effective and organ dose in dorsal spinal fusion and percutaneous transsacral screw stabilization during conventional fluoroscopy-assisted and computer-navigated procedures.
Patients and Methods
We recorded the dose and duration of radiation from fluoroscopy in 20 patients, with single vertebra fractures of the lumbar spine, who underwent posterior stabilization with and without the use of a navigation system and 20 patients with navigated percutaneous transsacral screw stabilization for sacroiliac joint injuries. For the conventional iliosacral joint operations, the duration of radiation was estimated retrospectively in two cases and further determined from the literature. Dose measurements were performed with a male phantom; the phantom was equipped with thermoluminescence dosimeters.
The effective dose in conventional spine surgery using 2-D fluoroscopy was more than 12-fold greater than in navigated operations. For the sacroiliac joint, the effective dose was nearly fivefold greater for nonnavigated operations.
Compared with conventional fluoroscopy, the patient’s effective dose can be reduced by 3-D computer-assisted spinal and pelvic surgery.
Level of Evidence
Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
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.
Radiography; digital radiography; dose calculation; image quality; tube potential
During the last 15 years, developments in X-ray technologies have substantially improved the ability of practitioners to treat patients using fluoroscopically guided interventional techniques. Many of these procedures require a greater use of fluoroscopy and more recording of images. This increases the potential for radiation-induced dermatitis and epilation, as well as severe radiation-induced burns to patients. Many fluoroscope operators are untrained in radiation management and do not realize that these procedures increase the risk of radiation injury and radiation-induced cancer in personnel as well as patients. The hands of long-time fluoroscope operators in some cases exhibit radiation damage—especially when sound radiation protection practices have not been followed. In response, the Center for Devices and Radiological Health of the United States Food and Drug Administration has issued an Advisory calling for proper training of operators. Hospitals and administrators need to support and enforce the need for this training by requiring documentation of credentials in radiation management as a prerequisite for obtaining fluoroscopy privileges. A concerted effort on the part of professional medical organizations and regulatory agencies will be required to train fluoroscopy users to prevent physicians from unwittingly imparting serious radiation injuries to their patients.
Credentialing fluoroscopist; Fluoroscopist radiation dose
Radiography using film has been an established method for imaging the internal organs of the body for over 100 years. Surveys carried out during the 1980s identified a wide range in patient doses showing that there was scope for dosage reduction in many hospitals. This paper discusses factors that need to be considered in optimising the performance of radiographic equipment. The most important factor is choice of the screen/film combination, and the preparation of automatic exposure control devices to suit its characteristics. Tube potential determines the photon energies in the X-ray beam, with the selection involving a compromise between image contrast and the dose to the patient. Allied to this is the choice of anti-scatter grid, as a high grid ratio effectively removes the larger component of scatter when using higher tube potentials. However, a high grid ratio attenuates the X-ray beam more heavily. Decisions about grids and use of low attenuation components are particularly important for paediatric radiography, which uses lower energy X-ray beams. Another factor which can reduce patient dose is the use of copper filtration to remove more low-energy X-rays. Regular surveys of patient dose and comparisons with diagnostic reference levels that provide a guide representing good practice enable units for which doses are higher to be identified. Causes can then be investigated and changes implemented to address any shortfalls. Application of these methods has led to a gradual reduction in doses in many countries.
Radiography; dental radiography; X-ray film; automatic exposure control; anti-scatter grid
In this article, we present GE Healthcare’s design philosophy and implementation of X-ray imaging systems with dose management for pediatric patients, as embodied in its current radiography and fluoroscopy and interventional cardiovascular X-ray product offerings. First, we present a basic framework of image quality and dose in the context of a cost–benefit trade-off, with the development of the concept of imaging dose efficiency. A set of key metrics of image quality and dose efficiency is presented, including X-ray source efficiency, detector quantum efficiency (DQE), detector dynamic range, and temporal response, with an explanation of the clinical relevance of each. Second, we present design methods for automatically selecting optimal X-ray technique parameters (kVp, mA, pulse width, and spectral filtration) in real time for various clinical applications. These methods are based on an optimization scheme where patient skin dose is minimized for a target desired image contrast-to-noise ratio. Operator display of skin dose and Dose-Area Product (DAP) is covered, as well. Third, system controls and predefined protocols available to the operator are explained in the context of dose management and the need to meet varying clinical procedure imaging demands. For example, fluoroscopic dose rate is adjustable over a range of 20:1 to adapt to different procedure requirements. Fourth, we discuss the impact of image processing techniques upon dose minimization. In particular, two such techniques, dynamic range compression through adaptive multiband spectral filtering and fluoroscopic noise reduction, are explored in some detail. Fifth, we review a list of system dose-reduction features, including automatic spectral filtration, virtual collimation, variable-rate pulsed fluoroscopic, grid and no-grid techniques, and fluoroscopic loop replay with store. In addition, we describe a new feature that automatically minimizes the patient-to-detector distance, along with an estimate of its dose reduction potential. Finally, two recently developed imaging techniques and their potential effect on dose utilization are discussed. Specifically, we discuss the dose benefits of rotational angiography and low frame rate imaging with advanced image processing in lieu of higher-dose digital subtraction.
Pediatric dose management; Fluoroscopic equipment; Technical advances
Image intensifier screening is commonly used in orthopaedic theatres. There has been concern regarding the cumulative radiation dose to surgeons and theatre personnel. The mini C-arm intensifier has been reported to scatter less radiation and have a reduced radiation dose to patients and theatre staff.
MATERIALS AND METHODS
A 2-month prospective survey of usage of radiographer-operated large intensifier and surgeon-operated mini C-arm image intensifier in a district general hospital orthopaedic theatre department.
A total of 153 cases required image intensifier screening – 63% used the large intensifier and 37% the mini C-arm intensifier. There were difficulties with equipment with the large intensifier in 16% of cases. There were delays in 11% of cases using the large intensifier. The total radiographer attendance time was 123 h. For the mini C-arm intensifier, there were no equipment difficulties or delays. The minimum radiographer time saved by using this machine was 21.9 hours.
The mini C-arm intensifier has saved 15% of the radiographer workload with its current pattern of usage in our department. There have been no problems or delays as a result of its usage in theatre. Usage of the large image intensifier resulted in a 16% problem rate and 11% delay rate. Other departments are encouraged to consider acquisition of a mini C-arm intensifier to facilitate theatre throughput, reduce risk to the patient and theatre personnel, and reduce demands on the radiology department.
Image intensifier; Orthopaedics; Radiology
Fluoroscopic systems have excellent temporal resolution, but are relatively noisy. In this paper we present a recursive temporal filter with different weights (lag) for different user selected regions of interest (ROI) to assist the neurointerventionalist during an image guided catheter procedure. The filter has been implemented on a Graphics Processor (GPU), enabling its usage for fast frame rates such as during fluoroscopy.
We first demonstrate the use of this GPU-implemented rapid temporal filtering technique during an endovascular image guided intervention with normal fluoroscopy. Next we demonstrate its use in combination with ROI fluoroscopy where the exposure is substantially reduced in the peripheral region outside the ROI, which is then software-matched in brightness and filtered using the differential temporal filter. This enables patient dose savings along with improved image quality.
Although the risk of radiation-induced spontaneous malignancy and genetic anomalies from occupational radiological procedures is relatively low – and perhaps slightly lower still for the general population – patients and endoscopists in particular, should be aware of the cumulative risk associated with all exposure. Radiation dose has a direct linear relationship with fluoroscopy duration; therefore, limiting fluoroscopy time is one of the most modifiable methods of reducing exposure during fluoroscopic procedures. This retrospective study analyzed more than 1000 endoscopic retrograde cholangiopancreatography procedures and aimed to determine the specific patient, physician and procedural factors that affect fluoroscopy duration.
Fluoroscopy during endoscopic retrograde cholangiopancreatography (ERCP) has a logarithmic relationship with radiation exposure, and carries a known risk of radiation exposure to patients and staff. Factors associated with prolonged fluoroscopy duration have not been well delineated.
To determine the specific patient, physician and procedural factors that affect fluoroscopy duration.
A retrospective analysis of 1071 ERCPs performed at two tertiary care referral hospitals over an 18-month period was conducted. Patient, physician and procedural variables were recorded at the time of the procedure.
The mean duration of 969 fluoroscopy procedures was 4.66 min (95% CI 4.38 to 4.93). Multivariable analysis showed that the specific patient factors associated with prolonged fluoroscopy duration included age and diagnosis (both P<0.0001). The endoscopist was found to play an important role in the duration of fluoroscopy (ie, all endoscopists studied had a mean fluoroscopy duration significantly different from the reference endoscopist). In addition, the following procedural variables were found to be significant: number of procedures, basket use, biopsies, papillotomy (all P<0.0001) and use of a tritome (P=0.004). Mean fluoroscopy duration (in minutes) with 95% CIs for different diagnoses were as follows: common bile duct stones (n=443) 5.12 (3.05 to 4.07); benign biliary strictures (n=135) 3.94 (3.26 to 4.63); malignant biliary strictures (n=124) 5.82 (4.80 to 6.85); chronic pancreatitis (n=49) 4.53 (3.44 to 5.63); bile leak (n=26) 3.67 (2.23 to 5.09); and ampullary mass (n=11) 3.88 (1.28 to 6.48). When no pathology was found (n=195), the mean fluoroscopy time was 3.56 min (95% CI 3.05 to 4.07). Comparison using t tests determined that the only two diagnoses for which fluoroscopy duration was significantly different from the reference diagnosis of ‘no pathology found’ were common bile duct stones (P<0.0001) and malignant strictures (P<0.0001).
Factors that significantly affected fluoroscopy duration included age, diagnosis, endoscopist, and the number and nature of procedures performed. Elderly patients with biliary stones or a malignant stricture were likely to require the longest duration of fluoroscopy. These identified variables may help endoscopists predict which procedures are associated with prolonged fluoroscopy duration so that appropriate precautions can be undertaken.
ERCP; Fluoroscopy time; Radiation
Fluoroscopic guidance is frequently utilized in interventional pain management. The major purpose of fluoroscopy is correct needle placement to ensure target specificity and accurate delivery of the injectate. Radiation exposure may be associated with risks to physician, patient and personnel. While there have been many studies evaluating the risk of radiation exposure and techniques to reduce this risk in the upper part of the body, the literature is scant in evaluating the risk of radiation exposure in the lower part of the body.
Radiation exposure risk to the physician was evaluated in 1156 patients undergoing interventional procedures under fluoroscopy by 3 physicians. Monitoring of scattered radiation exposure in the upper and lower body, inside and outside the lead apron was carried out.
The average exposure per procedure was 12.0 ± 9.8 seconds, 9.0 ± 0.37 seconds, and 7.5 ± 1.27 seconds in Groups I, II, and III respectively. Scatter radiation exposure ranged from a low of 3.7 ± 0.29 seconds for caudal/interlaminar epidurals to 61.0 ± 9.0 seconds for discography. Inside the apron, over the thyroid collar on the neck, the scatter radiation exposure was 68 mREM in Group I consisting of 201 patients who had a total of 330 procedures with an average of 0.2060 mREM per procedure and 25 mREM in Group II consisting of 446 patients who had a total of 662 procedures with average of 0.0378 mREM per procedure. The scatter radiation exposure was 0 mREM in Group III consisting of 509 patients who had a total 827 procedures. Increased levels of exposures were observed in Groups I and II compared to Group III, and Group I compared to Group II.
Groin exposure showed 0 mREM exposure in Groups I and II and 15 mREM in Group III. Scatter radiation exposure for groin outside the apron in Group I was 1260 mREM and per procedure was 3.8182 mREM. In Group II the scatter radiation exposure was 400 mREM and with 0.6042 mREM per procedure. In Group III the scatter radiation exposure was 1152 mREM with 1.3930 mREM per procedure.
Results of this study showed that scatter radiation exposure to both the upper and lower parts of the physician's body is present. Protection was offered by traditional measures to the upper body only.
Patients undergoing ERCP receive nontrivial doses of radiation, which may increase their risk of developing cancer, especially young patients. Radiation doses to patients during ERCP correlate closely with fluoroscopy time.
The aim of this study was to determine whether endoscopist experience is associated with fluoroscopy time.
Retrospective analysis of a prospectively collected database.
Data from 69 providers from 6 countries.
9,052 entries of patients undergoing ERCP.
Main Outcome Measurements
Percent difference in fluoroscopy time associated with endoscopist experience and fellow involvement.
For procedure types that require less fluoroscopy time, compared with endoscopists who performed > 200 ERCPs in the preceding year, endoscopists who performed < 100 and 100 to 200 ERCPs had 104% (95% confidence interval [CI], 85%–124%) and 27% (95% CI, 20%–35%) increases in fluoroscopy time, respectively. Every 10 years of experience was associated with a 21% decrease in fluoroscopy time (95% CI, 19%–24%). For fluoroscopy-intense procedures, compared with endoscopists who performed > 200 ERCPs in the preceding year, endoscopists who performed < 100 and 100 to 200 ERCPs had 59% (95% CI, 39%–82%) and 11% (95% CI, 3%–20%) increases in fluoroscopy time, respectively. Every 10 years of experience was associated with a 20% decrease in fluoroscopy time (95% CI, 18%–24%).
Database used is a voluntary reporting system, which may not be generalizable. Data is self-reported and was not verified for accuracy.
Fluoroscopy time is shorter when ERCP is performed by endoscopists with more years of performing ERCP and a greater number of ERCPs in the preceding year. These findings may have important ramifications for radiation-induced cancer risk.
Although many clinicians know about the reducing effects of the pulsed and low-dose modes for fluoroscopic radiation when performing interventional procedures, few studies have quantified the reduction of radiation-absorbed doses (RADs). The aim of this study is to compare how much the RADs from a fluoroscopy are reduced according to the C-arm fluoroscopic modes used.
We measured the RADs in the C-arm fluoroscopic modes including 'conventional mode', 'pulsed mode', 'low-dose mode', and 'pulsed + low-dose mode'. Clinical imaging conditions were simulated using a lead apron instead of a patient. According to each mode, one experimenter radiographed the lead apron, which was on the table, consecutively 5 times on the AP views. We regarded this as one set and a total of 10 sets were done according to each mode. Cumulative exposure time, RADs, peak X-ray energy, and current, which were viewed on the monitor, were recorded.
Pulsed, low-dose, and pulsed + low-dose modes showed significantly decreased RADs by 32%, 57%, and 83% compared to the conventional mode. The mean cumulative exposure time was significantly lower in the pulsed and pulsed + low-dose modes than in the conventional mode. All modes had pretty much the same peak X-ray energy. The mean current was significantly lower in the low-dose and pulsed + low-dose modes than in the conventional mode.
The use of the pulsed and low-dose modes together significantly reduced the RADs compared to the conventional mode. Therefore, the proper use of the fluoroscopy and its C-arm modes will reduce the radiation exposure of patients and clinicians.
fluoroscopy; radiation; radiation dosage; radiographic image enhancement
Fluoroscopy has been an integral part of modern interventional pain management. Yet fluoroscopy can be associated with risks for the patients and clinicians unless it is managed with appropriate understanding, skill and vigilance. Therefore, this study was designed to determine the amount of radiation received by a primary operator and an assistant during interventional pain procedures that involve the use of fluoroscopy
In order to examine the amount of radiation, the physicians were monitored by having them wear three thermoluminescent badges during each single procedure, with one under a lead apron, one under the apron collar and one on the leg during each single procedure. The data obtained from each thermoluminescent badge was reviewed from September 2008 to November 2008 and the annual radiation exposure was subsequently calculated.
A total of 505 interventional procedures were performed with C-arm fluoroscopy during three months. The results of this study revealed that the annual radiation exposure was relatively low for both the operator and assistant.
With proper precautions, the use of fluoroscopy during interventional pain procedures is a safe practice.
fluoroscopy; interventional pain management; radiation exposure
Computed Tomography (CT) examinations have rapidly increased in number over the last few years due to recent advances such as the spiral, multidetector-row, CT fluoroscopy and Positron Emission Tomography (PET)-CT technology. This has resulted in a large increase in collective radiation dose as reported by many international organisations. It is also stated that frequently, image quality in CT exceeds the level required for confident diagnosis. This inevitably results in patient radiation doses that are higher than actually required, as also stressed by the US Food and Drug Administration (FDA) regarding the CT exposure of paediatric and small adult patients. However, the wide range in exposure parameters reported, as well as the different CT applications reveal the difficulty in standardising CT procedures. The purpose of this paper is to review the basic CT principles, outline the recent technological advances and their impact in patient radiation dose and finally suggest methods of radiation dose optimisation.
Patient doses in computed tomography (CT); dose management in CT; dose optimisation in CT
Factors that may reduce the dose of radiation, from diagnostic and therapeutic x-ray procedures, to the patient and to the occupational and non-occupational worker are outlined. Suitable basic radiation measuring apparatus is described. It is recommended that, in diagnostic radiography, relatively high kilovoltage, proper cones, collimation and adequate filtration be used. Some specific recommendations are made concerning fluoroscopic, photoroentgen and portable x-ray examinations. Film monitoring of personnel is advisable. Examples are given of protective devices to lessen the dosage to the occupational worker. It is the responsibility of the radiologist or physician in charge to ensure that the x-ray equipment is safe to operate and the radiation dose to the patient is kept to a minimum. The roentgen output for all radiographic examinations should be known by the responsible user.
Computed tomography (CT) fluoroscopy is able to give real time images to a physician undertaking minimally invasive procedures such as biopsies, percutaneous drainage, and radio frequency ablation (RFA). Both operators executing the procedure and patients too, are thus at risk of radiation exposure during a CT fluoroscopy.
This study focuses on the radiation exposure present during a series of radio frequency ablation (RFA) procedures, and used Gafchromic film (Type XR-QA; International Specialty Products, USA) and thermoluminescent dosimeters (TLD-100H; Bicron, USA) to measure the radiation received by patients undergoing treatment, and also operators subject to scatter radiation.
The voltage was held constant at 120 kVp and the current 70mA, with 5mm thickness. The duration of irradiation was between 150-638 seconds.
Ultimately, from a sample of 30 liver that have undergone RFA, the study revealed that the operator received the highest dose at the hands, which was followed by the eyes and thyroid, while secondary staff dosage was moderately uniform across all parts of the body that were measured.
radiofrequency ablation; Gafchromic film; thermoluminescent dosimeter; computed tomography fluoroscopy
Recent advances in medical X-ray imaging have enabled the development of new techniques capable of assessing not only bone quantity but also structure. This article provides (a) a brief review of the current X-ray methods used for quantitative assessment of the skeleton, (b) data on the levels of radiation exposure associated with these methods and (c) information about radiation safety issues. Radiation doses associated with dual-energy X-ray absorptiometry are very low. However, as with any X-ray imaging technique, each particular examination must always be clinically justified. When an examination is justified, the emphasis must be on dose optimisation of imaging protocols. Dose optimisation is more important for paediatric examinations because children are more vulnerable to radiation than adults. Methods based on multi-detector CT (MDCT) are associated with higher radiation doses. New 3D volumetric hip and spine quantitative computed tomography (QCT) techniques and high-resolution MDCT for evaluation of bone structure deliver doses to patients from 1 to 3 mSv. Low-dose protocols are needed to reduce radiation exposure from these methods and minimise associated health risks.
Osteoporosis; Bone densitometry; DXA; QCT; Bone structure
The C-arm fluoroscope is known as the most important equipment in pain interventions. This study was conducted to investigate the completion rate of education on radiation safety, the knowledge of radiation exposure, the use of radiation protection, and so on.
Unsigned questionnaires were collected from the 27 pain physicians who applied for the final test to become an expert in pain medicine in 2011. The survey was composed of 12 questions about the position of the hospital, the kind of hospital, the use of C-arm fluoroscopy, radiation safety education, knowledge of annual permissible radiation dose, use of radiation protection, and efforts to reduce radiation exposure.
In this study, although most respondents (93%) had used C-arm fluoroscopy, only 33% of the physicians completed radiation safety education. Even though nine (33%) had received education on radiation safety, none of the physicians knew the annual permissible radiation dose. In comparing the radiation safety education group and the no-education group, the rate of wearing radiation-protective glasses or goggles and the use of radiation badges or dosimeters were significantly higher in the education group. However, in the use of other protective equipment, knowledge of radiation safety, and efforts to reduce radiation exposure, there were no statistical differences between the two groups.
The respondents knew very little about radiation safety and had low interest in their radiation exposure. To make the use of fluoroscopy safer, additional education, as well as attention to and knowledge of practices of radiation safety are required for pain physicians.
education; fluoroscopy; radiation; radiation monitoring; radiation protection
Uterine artery embolization (UAE) is a minimally invasive procedure performed under fluoroscopy for the treatment of uterine fibroids and accompanied by radiation exposure.
To compare ovarian radiation doses during uterine artery embolization (UAE) in patients using conventional digital subtraction angiography (DSA) with those using digital flat-panel technology.
Patients and Methods
Thirty women who were candidates for UAE were randomly enrolled for one of the two angiographic systems. Ovarian doses were calculated according to in-vitro phantom study results using entrance and exit doses and were compared between the two groups.
The mean right entrance dose was 1586±1221 mGy in the conventional and 522.3±400.1 mGy in the flat panel group (P=0.005). These figures were 1470±1170 mGy and 456±396 mGy, respectively for the left side (P=0.006). The mean right exit dose was 18.8±12.3 for the conventional and 9.4±6.4 mGy for the flat panel group (P=0.013). These figures were 16.7±11.3 and 10.2±7.2 mGy, respectively for the left side (P=0.06). The mean right ovarian dose was 139.9±92 in the conventional and 23.6±16.2 mGy in the flat panel group (P<0.0001). These figures were 101.7±77.6 and 24.6±16.9 mGy, respectively for the left side (P=0.002).
Flat panel system can significantly reduce the ovarian radiation dose during UAE compared with conventional DSA.
Uterine Artery; Embolization, Therapeutic; Radiation; Angiography
Region-of-interest (ROI) fluoroscopy takes advantage of the fact that most neurovascular interventional activity is performed in only a small portion of an x-ray imaging field of view (FOV). The ROI beam filter is an attenuating material that reduces patient dose in the area peripheral to the object of interest. This project explores a method of moving the beam-attenuator aperture with the object of interest such that it always remains in the ROI. In this study, the ROI attenuator, which reduces the dose by 80% in the peripheral region, is mounted on a linear stage placed near the x-ray tube. Fluoroscopy is performed using the Microangiographic Fluoroscope (MAF) which is a high-resolution, CCD-based x-ray detector. A stainless-steel stent is selected as the object of interest, and is moved across the FOV and localized using an object-detection algorithm available in the IMAQ Vision package of LabVIEW. The ROI is moved to follow the stent motion. The pixel intensities are equalized in both FOV regions and an adaptive temporal filter dependent on the motion of the object of interest is implemented inside the ROI. With a temporal filter weight of 5% for the current image in the peripheral region, the SNR measured is 47.8. The weights inside the ROI vary between 10% and 33% with a measured SNR of 57.9 and 35.3 when the object is stationary and moving, respectively. This method allows patient dose reduction as well as maintenance of superior image quality in the ROI while tracking the object.
Dose reduction; Region-of-interest (ROI) fluoroscopy; object tracking; adaptive temporal filtering