Patient Dose Management Research Articles

WE‐B‐213CD‐02: NCRP‐168 as a Training and Operational Resource

NCRP Report 168 provides guidance on facilities as well as on patient and worker radiation safety during fluoroscopically guided interventions (FGI). Fluoroscopy is widely used in surgical settings in ways that can be comparable to its use in other FGI procedures. Surgical fluoroscopes range from simple mobile analog C‐arms, heavy mobiles with most of characteristics of a fixed system, to state of the art fixed systems. Patient and worker radiation safety concerns along with training, credentialing, and privileging of surgical staff are similar to those for all other FGI procedures. Recommendations relevant to the surgical setting will be reviewed. Two key recommendations are: An FGI procedure shall be performed or supervised only by a physician or other medical professional with fluoroscopic and clinical privileges appropriate to the specific procedure. An FGI procedure shall be performed or supervised only by a physician or other medical professional with fluoroscopic and clinical privileges appropriate to the specific procedure. Other topics such as responsibilities of all workers for their own radiation protection, those of the attending surgeon for patient dose management and follow‐up, and those of the facility for providing necessary resources will also be briefly discussed.Learning Objectives:1. To understand the responsibilities of surgeons and others working in a FGI environment toward patient and worker radiation safety.2. To understand radiation protection requirements and actions necessary for personal safety while radiation is in use in a surgical environment3. To gain familiarity with the knowledge base needed to safely perform or supervise FGA procedures in the surgical environment.

Establishing an individual dosing system for patients undergoing interventional transcatheter arterial embolization: Radiochromic film and Monte Carlo simulation

Less invasive imaging-guided vascular interventions with fluoroscopy and digital subtraction angiography have recently become widespread and have been successfully used for treating various diseases. However, interventional fluoroscopy procedures may present deterministic and stochastic radiation risks. The International Commission on Radiological Protection (ICRP) and the Food and Drug Administration have requested identifying procedures that may involve patient doses greater than the recommended thresholds. In this study, radiochromic dosimetric media, known as self-developing films, and measurement-based Monte Carlo simulations were used to establish an interventional radiology dosing system for individual patients undergoing interventional transcatheter arterial embolization. The peak skin dose, evaluated from the entrance surface dose distribution, was 21% less than the cumulated dose reported from the console. A 3D dose map incorporated into CT images was established. The organ doses and effective doses for individual patients were evaluated using this dosing system. This system could be applied very well to other fluoroscopic or interventional procedures for patient dose management.

Management of patient dose in radiology in the UK

Programmes to manage patient dose in radiology are becoming a higher priority as the number of imaging examinations and the proportion of higher dose computed tomography (CT) and complex interventional procedures all continue to rise. Such programmes have a number of components and their implementation in UK hospitals, which have been developing such programmes over two decades, is described. As part of any programme to manage patient doses, elements should be in place for both justification and optimisation. The system for justification needs to be robust in order to minimise the number of unnecessary procedures and requires the provision of training in radiation protection for medical and other staff to ensure that they understand the risks. Optimisation of X-ray techniques requires performance tests on equipment at installation and regularly thereafter, linked to surveys of patient doses. Confirming the performance of the available options on fluoroscopy and CT equipment is essential and the information obtained should be available to radiographers and radiologists, so they can make informed choices in developing imaging protocols. Patient doses should be compared with diagnostic reference levels set in terms of measured dose quantities to allow the identification of equipment that is giving higher doses. Taking the next step of analysing results to determine the reasons for high doses is crucial and requires a link with the equipment performance tests and an understanding of the underlying physics. Medical physics services play an important role at the hub of the dose management programme for carrying out tests, organising surveys, making recommendations on optimisation strategies and training other staff in radiation protection, performance testing and dose reduction. Programmes for management of patient doses in UK hospitals were first set up in the late 1980s by medical physicists and have been developed since that time to keep pace with the developments in technology. Regional departments serving several hundred or a thousand X-ray units form the model followed in most regions. This paper describes the form of patient dose management programmes in the UK. It also gives guidance that might be useful to others that are now embarking on the same journey.

WE‐B‐110‐01: Application of Medical Informatics to Patient Dose Management in Interventional Radiology

Tools for measurement and validation of radiation dose, including ALARA Policies for Fluoroscopically Guided Interventions (FGI) have been being developed using medical informatics. Informatics, primarily DICOM and Hl7 are rich content data sources that provide the potential for determination of peak skin dose, as well as a direct and immediate source of conventional metrics such as KAP, cumulative AK at the RP, and fluoroscopy duration. Newly purchased equipment may provide Radiation Dose Structured Reports which includes each radiation episode (fluoroscopy, DSA, Digitial Spots, or Cine) as separate records. For each of these data files, table position, exposure at the RP, collimation, etc. are available for use. A database has been created that uses DICOM exchange to capture dose related information for FGI. These data are used in conjunction with simulated C‐arm devices that more and mimic that which is encountered in a lab. When the desired physics parameters are included (backscatter factor, table attenuation, calibration of the vendors AK, etc) it is possible to re‐ create the exposure irradiations actually used, to compute and locate on a virtual patient the skin dose distribution and determine the Peak Skin Dose. This dose is saved to the data base for future QA uses.

Radiation dose and image quality for paediatric interventional cardiology systems. A national survey in Chile

Radiation dose and image quality for paediatric protocols in all five X-ray fluoroscopy systems used for interventional cardiology procedures existing in Chile have been evaluated. Entrance surface air kerma (ESAK) and image quality using a test object (TO) and polymethyl methacrylate (PMMA) phantoms have been measured for the typical paediatric patient thicknesses (4-16 cm of PMMA). Images from fluoroscopy (low (FL), medium and high) and cine (CI) modes have been archived in DICOM format. Signal-to-noise ratio (SNR), figure of merit (FOM) and high-contrast spatial resolution (HCSR) have been computed from the images. The ratio between the maximum and the minimum value of ESAK per frame for a given fluoroscopy mode between the five systems ranges from 2 to 5 and from 14 to 38 for CI mode. SNR, FOM and HCSR showed a great variability for the different acquisition modes (AMs) and PMMA thickness. In the near future, it is urgent to upgrade Chilean legislation on radiation protection to incorporate quality assurance programmes that will allow us to evaluate and optimise the X-ray systems used in medical applications. Increments in doses per frame when increasing phantom thickness and when used CI runs instead of FL runs can be considered by the cardiologist in the good management of patient dose and allow them to select the best imaging AM during clinical procedures.

Management of patient doses and diagnostic reference levels in X-ray radiography in Lithuania

Management of patient doses and determination of national or local diagnostic reference levels (DRLs) are important parts of a quality control program in X-ray diagnostics. In Lithuania, national DRLs for specific radiographic examinations are comparatively higher than those recommended by the European Commission (EC) and the International Atomic Energy Agency (IAEA). A survey of entrance surface doses (ESDs) was performed to investigate the reasons for exceeding the European and the IAEA DRLs. The first measurements showed that the average ESD for standard patients and for all examinations exceeded DRLs at approximately 25 % of the hospitals. The main problems were the use of low kilovolt technique, the lack of automatic exposure control systems or improper adjustment of them as well as inadequate training of the staff. After corrective actions, the ESD measurements were repeated. The results showed that the average patient doses were reduced almost everywhere. An additional patient dose survey for establishing new DRLs in radiography taking into account the advantages of new equipment to indicate directly the kerma area product (KAP) values was done. The ESD values were calculated from the KAP-values. The data were analysed, and the average and third quartile values were calculated. The new DRLs, in terms of ESDs, were reduced significantly in almost all radiography examinations. They are equal or lower than the IAEA and EC DRLs. Especially at thorax spine LAT, lumbar spine LAT, hip joint AP, pelvis AP and abdomen AP they are half the IAEA DRLs.

Radiation Exposure to Patients During Interventional Procedures in 20 Countries: Initial IAEA Project Results

The purpose of our study was to investigate the level of radiation protection of patients and staff during interventional procedures in 20 countries of Africa, Asia, and Europe. In a multinational prospective study, information on radiation protection tools, peak skin dose (PSD), and kerma-area product (KAP) was provided by 55 hospitals in 20 mainly developing countries (nine mostly in Eastern Europe, five in Africa, and six in Asia). Nearly 40% of the interventional rooms had an annual workload of more than 2,000 patients. It is remarkable that the workload of pediatric interventional procedures can reach the levels of adult procedures even in developing countries. About 30% of participating countries have shown a 100% increase in workload in 3 years. Lead aprons are used in all participating rooms. Even though KAP was available in almost half of the facilities, none had experience in its use. One hundred of 505 patients monitored for PSD (20%) were above the 2-Gy threshold for deterministic effects. Interventional procedures are increasing in developing countries, not only for adults but also for pediatric patients. The situation with respect to staff protection is considered generally acceptable, but this is not the case for patient protection. Many patients exceeded the dose threshold for erythema. A substantial number (62%) of percutaneous transluminal coronary angioplasty procedures performed in developing countries in this study are above the currently known dose reference level and thus could be optimized. Therefore, this study has significance in introducing the concept of patient dose estimation and dose management.

Dose assessment during the commissioning of flat detector imaging systems for cardiology

Incident air kerma (IAK) and entrance surface air kerma (ESAK) have been measured for a range of copper (Cu) absorbers (1-10 mm) and polymethylmethacrylate (PMMA) slabs (12-28 cm) with kilovolt values ranging from 61 to 120 during the commissioning of an X-ray system equipped with a flat detector used in interventional cardiology procedures. Numerical parameters on image quality have also been measured for different X-ray beam qualities using the plastic wall of the ionisation chamber. When moving from 1 to 10 mm of Cu, IAK per frame increased to a factor of 38 for cine and 27 for fluoroscopy. A cine frame requires 60-116 times more IAK than a fluoroscopy frame. As for PMMA, when the backscatter factor is included (simulating real conditions with patients), and when moving from 12 to 28 cm, the increases in ESAK are 16 times for cine and 10 times for fluoroscopy. Because of the differences in X-ray beam quality for cine and fluoroscopy modes, the Cu thicknesses necessary to drive the generator to equivalent kilovolts resulted in the following values (cine and fluoroscopy, respectively): 12 cm of PMMA (1 and 1.5 mm Cu), 20 PMMA (2.5 and 3.5 mm Cu) and 28 cm PMMA (4.5 and 8.5 mm Cu). With the analysis of IAK, ESAK and image quality, one can verify the appropriate settings of the X-ray system and obtain baseline information for constancy checks and help cardiologists in the management of patient doses by knowing the dose increase factors and image quality changes when increasing patient thickness or using different C-arm projections.

新しいＩＶＲ線量分布作成方法の開発

Recently, the angiography system used for interventional radiology (IVR) provides a device for measuring dose-area product (DAP), which is compulsory in European countries. The usefulness of DAP is that one can observe patient dose in real time during IVR and can obtain an integral dose by overall IVR procedure without a dosimeter directly placed on a patient. It is important to know the most irradiated region (hot spot) of the patient's skin and its maximum value in the dose management of IVR, but this information cannot be obtained only in DAP. In this paper, we describe a new method to estimate patient surface dose distributions in IVR. We devised a sheet dubbed the "Number map", which does not obstruct the IVR procedure, to confirm the hot spot, and we developed software (named PIETA "Patient Information on Exposure Total Dose Analysis in IVR") to analyze the data from the Number map. Using this system, dose distributions of patient's skin were easily obtained, and we could easily perform patient dose management in IVR.

Radiation dose and image quality for paediatric interventional cardiology

Radiation dose and image quality for paediatric protocols in a biplane x-ray system used for interventional cardiology have been evaluated. Entrance surface air kerma (ESAK) and image quality using a test object and polymethyl methacrylate (PMMA) phantoms have been measured for the typical paediatric patient thicknesses (4–20 cm of PMMA). Images from fluoroscopy (low, medium and high) and cine modes have been archived in digital imaging and communications in medicine (DICOM) format. Signal-to-noise ratio (SNR), figure of merit (FOM), contrast (CO), contrast-to-noise ratio (CNR) and high contrast spatial resolution (HCSR) have been computed from the images. Data on dose transferred to the DICOM header have been used to test the values of the dosimetric display at the interventional reference point. ESAK for fluoroscopy modes ranges from 0.15 to 36.60 µGy/frame when moving from 4 to 20 cm PMMA. For cine, these values range from 2.80 to 161.10 µGy/frame. SNR, FOM, CO, CNR and HCSR are improved for high fluoroscopy and cine modes and maintained roughly constant for the different thicknesses. Cumulative dose at the interventional reference point resulted 25–45% higher than the skin dose for the vertical C-arm (depending of the phantom thickness). ESAK and numerical image quality parameters allow the verification of the proper setting of the x-ray system. Knowing the increases in dose per frame when increasing phantom thicknesses together with the image quality parameters will help cardiologists in the good management of patient dose and allow them to select the best imaging acquisition mode during clinical procedures.

Image Retake Analysis in Digital Radiography Using DICOM Header Information

A methodology to automatically detect potential retakes in digital imaging, using the Digital Imaging and Communications in Medicine (DICOM) header information, is presented. In our hospital, neither the computed radiography workstations nor the picture archiving and communication system itself are designed to support reject analysis. A system called QCOnline, initially developed to help in the management of images and patient doses in a digital radiology department, has been used to identify those images with the same patient identification number, same modality, description, projection, date, cassette orientation, and image comments. The pilot experience lead to 6.6% and 1.9% repetition rates for abdomen and chest images. A thorough analysis has shown that the real repetitions were 3.3% and 0.9% for abdomen and chest images being the main cause of the discrepancy being the wrong image identification. The presented methodology to automatically detect potential retakes in digital imaging using DICOM header information is feasible and allows to detect deficiencies in the department performance like wrong identifications, positioning errors, wrong radiographic technique, bad image processing, equipment malfunctions, artefacts, etc. In addition, retake images automatically collected can be used for continuous training of the staff.

Digital radiography detectors – A technical overview: Part 2

Digital X-ray detector technologies provide several advantages when compared with screen-film (SF) systems: better diagnostic quality of the radiographic image, increased dose efficiency, better dynamic range and possible reduction of radiation exposure to the patient. The transition from traditional SF systems to digital technology-based systems highlights the importance of the discussion around technical factors such as image acquisition, the management of patient dose and diagnostic image quality. Radiographers should be aware of these aspects concerning their clinical practice regarding the advantages and limitations of digital detectors. New digital technologies require an up-to-date of scientific knowledge concerning their use in projection radiography. This is the second of a two-part review article focused on a technical overview of digital radiography detectors. This article provides a discussion about the issues related to the image acquisition requirements and advantages of digital technologies, the management of patient dose and the diagnostic image quality.

The IAEA's activities in radiological protection in digital imaging

The success achieved to minimise the radiation exposure to staff to levels much below the prescribed dose limits encourages a similar approach in patient protection where dose limits do not exist but where reference levels are provided. A number of radiation injuries among patients have been reported, per capita dose is increasing and medical exposure has become the largest contributor to population dose. The International Atomic Energy Agency (IAEA) has supported a number of research projects, produced a wide range of guidance publications, conducted over 60 training courses in the past 5 y, produced for free dissemination training CDs on radiation protection and established a dedicated Web site on the radiological protection of patients (http://rpop.iaea.org). The number of countries that is currently receiving assistance in this field exceeds 80, as compared to about half a dozen 5 y ago. Significant results on patient dose management, demonstrating dose reduction of more than 30% while maintaining image quality, have been made available through IAEA projects.

Patient dose management in digital radiography

Purpose:To present the experience in patient dose management and the development of an online audit tool for digital radiography.Materials and methods: Several tools have been developed to extract the information contained in the DICOM header of digital images, collect radiographic parameters, calculate patient entrance doses and other related parameters, and audit image quality.Results: The tool has been used for mammography, and includes images from over 25,000 patients, over 75,000 chest images, 100,000 computed radiography procedures and more than 1,000 interventional radiology procedures. Examples of calculation of skin dose distribution in interventional cardiology based upon information of DICOM header and the results of dosimetric parameters for cardiology procedures in 2006 are presented.Conclusion: Digital radiology has great advantages for imaging and patient dose management. Dose reports, QCONLINE systems and the MPPS DICOM service are good tools to optimise procedures and to manage patient dosimetry data. The implementation of the ongoing IEC-DICOM standard for patient dose structured reports will improve dose management in digital radiology.

ICRP Special radiation protection issues in interventional radiology, digital and cardiac imaging

The International Commission on Radiological Protection (ICRP) has published two reports giving recommendations dealing with the avoidance of deterministic injuries in interventional radiology and the management of patient dose in digital radiology in 2001 and 2004, respectively. Another document, on radiation protection for cardiologists performing fluoroscopically guided procedures, will be produced during 2005. This paper highlights some of the topics of the published reports, their relevance to European legislation on medical exposures and the importance of radiation protection research in underpinning the ICRP task groups' work in to producing these documents. It is also anticipated that the results, obtained in the cardiology work package of the European research project, will be used in the new document on radiation protection for cardiologists.

Skin dose measurements on patients for diagnostic and interventional neuroradiology: a multicentre study

The present study reports on the skin dose measurements on patients undergoing diagnostic and interventional neuroradiology procedures. Grids of thermoluminescence dosemeters were attached on the head of the patient. The exposure parameters of the X-ray systems and the clinical procedures were fully documented. While for the diagnostic procedure, the dose threshold of 2 Gy for deterministic effects was not reached, this situation was much different for the embolisations. For angiography of the carotid arteries, no skin doses were measured >320 mGy. For the cerebral embolisations, maximum skin doses up to 5.4 Gy were measured. Doses to the patients varied largely between different hospitals and within the same hospital for similar procedures. On the one hand, the complexity of the pathology for interventional procedures was responsible for the large variability in dose. On the other hand, large differences in clinical protocol and technical parameters of the X-ray systems, explaining the dose variations, were also observed. A correlation was found between the maximum skin dose measured on a patient and the total dose-area product (DAP) value for cerebral embolisations. This correlation makes it possible to estimate the maximum skin dose from these DAP values and to determine a trigger level. In conclusion, management of patient doses in interventional radiology requires training, specialisation and well-documented procedure guidelines.

Guest Editorial, Preface, Main Points, Glossary and Chapter 1

Digital techniques have the potential to improve the practice of radiology but they also risk the overuse of radiation. The main advantages of digital imaging, i.e. wide dynamic range, post processing, multiple viewing options, and electronic transfer and archiving possibilities, are clear but overexposures can occur without an adverse impact on image quality. In conventional radiography, excessive exposure produces a 'black' film. In digital systems, good images are obtained for a large range of doses. It is very easy to obtain (and delete) images with digital fluoroscopy systems, and there may be a tendency to obtain more images than necessary. In digital radiology, higher patient dose usually means improved image quality, so a tendency to use higher patient doses than necessary could occur. Different medical imaging tasks require different levels of image quality, and doses that have no additional benefit for the clinical purpose should be avoided. Image quality can be compromised by inappropriate levels of data compression and/or postprocessing techniques. All these new challenges should be part of the optimisation process and should be included in clinical and technical protocols. Local diagnostic reference levels should be re-evaluated for digital imaging, and patient dose parameters should be displayed at the operator console. Frequent patient dose audits should occur when digital techniques are introduced. Training in the management of image quality and patient dose in digital radiology is necessary. Digital radiology will involve new regulations and invoke new challenges for practitioners. As digital images are easier to obtain and transmit, the justification criteria should be reinforced. Commissioning of digital systems should involve clinical specialists, medical physicists, and radiographers to ensure that imaging capability and radiation dose management are integrated. Quality control requires new procedures and protocols (visualisation, transmission, and archiving of the images).

Creation and clinical application of real-time dose monitor using dose area product meter

The management of patient dose has become more of an issue in recent years. Dose can be determined non-invasively and in real time through the use of a dose area product meter, but it is the area dose value that is obtained. Therefore, we created a program that estimates entrance skin dose (ESD) in real time from area dose values obtained during procedures. We used Microsoft Visual C++ 6.0 (Standard Edition) for the programming language and C language for the programming environment. The value was a maximum 285.4 mGy at ileus tube insertion when measuring ESD for radiography of the digestive organ and non-vascular type IVR using the created program and seeking the average according to the procedures. The program that we created can be considered valid for monitoring ESD correctly and in real time.

Fluoroscopy: patient radiation exposure issues.

Fluoroscopic procedures (particularly prolonged interventional procedures) may involve high patient radiation doses. The radiation dose depends on the type of examination, the patient size, the equipment, the technique, and many other factors. The performance of the fluoroscopy system with respect to radiation dose is best characterized by the receptor entrance exposure and skin entrance exposure rates, which should be assessed at regular intervals. Management of patient exposure involves not only measurement of these rates but also clinical monitoring of patient doses. Direct monitoring of patient skin doses during procedures is highly desirable, but current methods still have serious limitations. Skin doses may be reduced by using intermittent exposures, grid removal, last image hold, dose spreading, beam filtration, pulsed fluoroscopy, and other dose reduction techniques. Proper training of fluoroscopic operators, understanding the factors that influence radiation dose, and use of various dose reduction techniques may allow effective management of patient dose.