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Effective dose (E) has been developed by the International Commission on Radiological Protection (ICRP) as a dose quantity with a link to risks of health detriment, mainly cancer. It is based on reference phantoms representing average individuals, but this is often forgotten in its application to medical exposures, for which its use sometimes goes beyond the intended purpose. There has been much debate about issues involved in the use of E in medicine and ICRP is preparing a publication with more information on this application. This article aims to describe the development of E and explain how it should be used in medicine. It discusses some of the issues that arise when E is applied to medical exposures and provides information on how its use might evolve in the future. The article concludes with responses to some frequently asked questions about uses of E that are in line with the forthcoming ICRP publication. The main use of E in medicine is in meaningful comparison of doses from different types of procedure not possible with measurable dose quantities. However, it can be used, with appropriate care, as a measure of possible cancer risks. When considering E to individual patients, it is important to note that the dose received will differ from that assessed for reference phantoms, and the risk per Sv is likely to be greater on average in children and less in older adults. Newer techniques allow the calculation of patient-specific E which should be distinguished from the reference quantity.

Purpose In interventional cardiology, patients may be exposed to high doses to the skin resulting in skin burns following single or multiple procedures. Reviewing and analysing available software (online or offline) may help medical physicists assessing the maximum skin dose to the patient together with the dose distribution during (or after) these procedures. Method and results Capabilities and accuracy of available software were analysed through an extensive bibliography search and contacts with both vendor and authors. Their markedly differed among developers. In total, 22 software were identified and reviewed according to their algorithms and their capabilities. Special attention was dedicated to their main features and limitations of interest for the intended clinical use. While the accuracy of the 12 software products validated with measurements on phantoms was acceptable (within±25%), the agreement was poor for the two products validated on patients (within±43% and±76%, respectively). In addition, no software has been validated on angiographic units from all manufacturers, though several software developers claimed vendor-independent transportability. Only one software allows for multiple procedures dose calculation. Conclusion Large differences among vendors made it clear that work remains to be done before an accurate and reliable skin dose mapping is available for all patients.

This investigation is aimed to study the feasibility of size-specific dose estimate (SSDE) to patient dosimetry in pediatric head CT scans and to establish typical values in a hospital in Tunja, Colombia. The volumetric computed tomography index (CTDIvol) and the dose-length product of 468 pediatric patients from newborn to 15-year-olds, who underwent non-contrast head CT scans, were collected retrospectively. For 186 cases only, SSDE was estimated using patient attenuated-based size metrics and CTDIvol,16-to-SSDE conversion factors reported in AAPM report 293. Results showed that SSDE is an accurate metric that can be used to establish typical dose values from pediatric head CT scans. Median SSDE values of 33.5, 31.6, 36.2 and 57.9 mGy were established as typical dose values for the 0–

The aim of this study was to present the results of organ and effective doses for paediatric patients for different types of interventional cardiology procedures for age and weight groups, derived from a patient dosimetry pilot programme carried out in Chile, under the auspices of the International Atomic Energy Agency. Over seven years, a retrospective collection of demographic and patient dose data was obtained: age, gender, weight, height, number of cine series, total number of cine frames, fluoroscopy time, dose-area product (DAP) and cumulative dose at patient entrance reference point. Monte Carlo software was used to calculate organ and effective doses. 1506 procedures were divided into four age and seven weight groups. Organ doses (median values) for diagnostic and therapeutic procedures were: active bone marrow 0.90 and 0.64mGy; heart 1.99 and 1.46mGy; lungs 3.56 and 2.59mGy; thyroid 1.27 and 0.83; and breast (in the case of females) 1.78 and 1.36mGy. The ranges for effective doses (median values) and weight bands were 1.2-3.9mSv for diagnostic procedures and 1.0-2.5mSv for therapeutic procedures. The resulting conversion factors (median values) to estimate effective dose from DAP (in mSv/Gy.cm2) were: 1.70; 0.89; 0.58; and 0.40, for age groups of1year, 1-5years, 5-10years and 10-16years, respectively. The obtained set of dose values will enable comparisons with other imaging procedures (comparing the same age bands) for justification and optimization purposes.

Advantages of Cone Beam Computed Tomography (CBCT) include high-quality 3D imaging and reduced radiation exposure with relatively low cost. In this study, patient radiation exposure in CBCT implant planning dentistry was measured in terms of Kerma Area Product (KAP). Data were obtained from 217 CBCT scans on 168 individuals using a CS9300 Carestream system. Scans were made using 80–90 kVp, 4–5 mA, 8 and 13.3 s exposure time (depending on voxel size) and a fixed field of view (FOV) of 10 × 10 cm2 (medium). Mean KAP was estimated using two voxel sizes 180 × 180 × 180 μm3 and 200 × 200 × 200 μm3 and found to be 399 and 314 mGycm2, respectively. Corresponding KAP values found in literature ranged between 210 and 2140 mGycm2. Mean E was estimated using conversion coefficient factors found in literature, according to FOV size and tube voltage value and found to range between 24 and 161 μSv.

Real time radiation dose monitoring in the cath lab may provide immediate feedback for potential dose reduction during PCI. Radiation dose monitoring to predict potential tissue injury utilizes equipment measured air Kerma at the interventional reference point (IRP) with then calculated specific tissue peak skin dose. The role of the cath lab Quality Committee is not only to assess individual high dose radiation cases but also to create processes and assess new technologies to assure radiation dose is best utilized in all cases.

International audience; OBJECTIVES:A national retrospective survey on patient doses was performed by the French Society of Medical physicists to assess reference levels (RLs) in interventional radiology as required by the European Directive 2013/59/Euratom.METHODS:Fifteen interventional procedures in neuroradiology, vascular radiology and osteoarticular procedures were analysed. Kerma area product (KAP), fluoroscopy time (FT), reference air kerma and number of images were recorded for 10 to 30 patients per procedure. RLs were calculated as the 3rd quartiles of the distributions.RESULTS:Results on 4600 procedures from 36 departments confirmed the large variability in patient dose for the same procedure. RLs were proposed for the four dosimetric estimators and the 15 procedures. RLs in terms of KAP and FT were 90 Gm.cm2 and 11 mins for cerebral angiography, 35 Gy.cm2 and 16 mins for biliary drainage, 75 Gy.cm2 and 6 mins for lower limbs arteriography and 70 Gy.cm2 and 11 mins for vertebroplasty. For these four procedures, RLs were defined according to the complexity of the procedure. For all the procedures, the results were lower than most of those already published.CONCLUSIONS:This study reports RLs in interventional radiology based on a national survey. Continual evolution of practices and technologies requires regular updates of RLs.KEY POINTS:• Delivered dose in interventional radiology depends on procedure, practice and patient. • National RLs are proposed for 15 interventional procedures. • Reference levels (RLs) are useful to benchmark practices and optimize protocols. • RLs are proposed for kerma area product, air kerma, fluoroscopy time and number of images. • RLs should be adapted to the procedure complexity and updated regularly.

One measurement and an algebraic formula are used to calculate the incident air kerma (Ka,i) at the skin after any CT examination, including cone-beam CT (CBCT) and multi-slice CT (MSCT). Empty scans were performed with X-ray CBCT systems (dental, C-arm and linac guidance scanners) as well as two MSCT scanners. The accumulated Ka,i at the flat panel (in CBCT) or the maximum incident air kerma at the isocentre (in MSCT) were measured using a solid-state probe. The average Ka,i(skin), at the skin of a hypothetical patient, was calculated using the proposed formula. Additional measurements of dose at the isocentre (DFOV) and kerma-area product (KAP), as well as Ka,i(skin) from thermoluminiscence dosimeters (TLDs) and size-specific dose estimates are presented for comparison. The Ka,i(skin) for the standard head size in the dental scanner, the C-arm (high dose head protocol) and the linac (head protocol) were respectively 3.33 ± 0.19 mGy, 15.15 ± 0.76 mGy and 3.23 ± 0.16 mGy. For the first MSCT, the calculated Ka,i(skin) was 13.1 ± 0.7 mGy and the TLDs provided a Ka,i(skin) between 10.3 ± 1.1 mGy and 13.8 ± 1.4 mGy. Estimation of patient air kerma in tomography with an uncertainty below 7% is thus feasible using an empty scan and conventional measurement tools. The provided equations and website can be applied to a standard size for the sake of quality control or to several sizes for the definition of diagnostic reference levels (DRLs). The obtained incident air kerma can be directly compared to the Ka,i from other X-ray modalities as recommended by ICRU and IAEA.

Purpose The protocol for quality control of CBCT devices was produced as consensus among active MPEs of EFOMP, ESTRO and IAEA. It is available on-line since September 2017. In the beginning of 2018 we published an update including an appendix on patient dosimetry by EURADOS, comments by the German institute of standards (DIN) and remarks by users from countries that were not involved in the first edition, such as Austria, Costa Rica and Australia. This contribution gives a general overview of the guideline including insights about this recent update. Methods The guideline focuses on the measurement of objective image quality parameters and radiation output from any kind of CBCT device, including applications in dental radiology, C-arms and guidance systems in radiotherapy. Indications to use commercial or non-commercial phantoms and software are given, as well as to use ionization chambers or solid state dosemeters. The new EURADOS appendix includes an extensive review of patient dose data from recent research papers, organized by application and dose indicators: CTDI, DAP, effective dose, entrance surface dose, CTDIw, absorbed dose, D1-D2 and air kerma. The DIN has reviewed the details of the standards 6868–161 and 6868–15 for acceptance and constancy tests in dental CBCT. Individual comments have helped to clarify the measurements of radiation output and the methods to measure the modulation transfer function. Some colleagues have stressed the informative value of the appendices. Results The comments received were reviewed by the authors of the corresponding sections and discussed by the group in virtual meetings before being published as an update. The mentioned additions are meant to keep the document alive. They respond to questions raised by physicists that are starting to use the protocol inside and outside Europe. Conclusions The first presentation in the ECMP in Athens was followed by international presentations at ESTRO, ECR, IOMP and IRPA and national presentations in Italy, Spain, UK, Germany and other countries. Thanks to these voluntary efforts, physicists around the world are using and improving the document together. We also welcome your participation in this session and your feedback.

Introduction To reduce exposure to the workers in interventional radiology, Collective Protection Equipment (CPE) are used (low lead curtains and their vertical extension, ceiling suspended screen …). For the same purpose, radio-attenuator soft screens (RADPAD®) have been developed. The objective of this study is to evaluate the influence of the CPE and the RADPAD® on the operator’s dosimetry in coronary angiography; we also measured patient’s skin-dose without and with the utilization of the RADPAD®. Methods Firstly, the interventional radiology equipment has been positioned at the tube incidence LAO 0°. The dose at different heights along the operator’s body (50, 75, 100, 125, 150 and 175 cm) was measured without the use of any CPE, and then by adding them successively (low curtains, vertical extension of the low curtains, ceiling suspended screens and then the radio-attenuator screen RADPAD®). Secondly, the skin dose of a phantom placed on the patient’s table was measured at three different distances from the ceiling screen, with and without RADPAD® at a tube voltage of 68 kVp in LAO 0° and then at 125 kVp in LAO 0° and LAO 30°. Results The use of the three CPE shows an attenuation of the radiation dose by 76% at the height of 175 cm along the operator’s body, it increases by 3.8% when using the RADPAD®. At low voltage, the use of the RADPAD® increases patient’s dose by 13% in the region near the ceiling screen. However, it attenuates the dose by 85.5% at 26 cm form this latter. At high voltage, the dose decreases at all of the three measure points; the effect of the RADPAD® varies depending on the distance from the screen and the tube angle. Conclusions Collective Protection Equipment are effective to decrease operator’s exposure in coronary angiography. The RADPAD® allows a significant reduction of the patient’s dose far the ceiling screen.

Cardiac interventions often result in high radiation dose to patient's skin, so a reliable indicator in terms of a commonly used dose descriptor is required to monitor skin exposures. In the present study, Gafchromic XR-RV3 film was used to measure the peak skin dose (PSD) during 40 coronary angiography (CA) and 50 percutaneous transluminal coronary angioplasty (PTCA) procedures. Corresponding values of kerma-area product (PKA), fluoroscopy time (FT) and reference air-kerma (Ka,r) were recorded and correlated with PSD. Doses to patient's eyes and thyroid were also measured by using thermoluminescent dosimeters (TLDs) during PTCA procedures. The average dose to thyroid was about six times higher than the average dose to eyes. The mean values of PSD, PKA and FT were 1140 mGy, 97 Gy cm2 and 15.7 min for PTCA and 290 mGy, 21.1 Gy cm2 and 2.4 min for CA procedures, respectively. One in seven patients of PTCA procedure received PSD >2 Gy. With respect to FT, PKA may be used as a better predictor of skin exposures because the correlation of PSD with PKA was found better than with FT for both CA and PTCA procedures.

Radioiodine therapy is an effective and safe treatment of hyperthyroidism due to Graves' disease, toxic adenoma, toxic multinodular goiter. We compared the outcomes of a traditional calculation method based on an analytical fit of the uptake curve and subsequent dose calculation with the MIRD approach, and an alternative computation approach based on a formulation implemented in a public-access website, searching for the best timing of radioiodine uptake measurements in pre-therapeutic dosimetry. We report about sixty-nine hyperthyroid patients that were treated after performing a pre-therapeutic dosimetry calculated by fitting a six-point uptake curve (3-168h). In order to evaluate the results of the radioiodine treatment, patients were followed up to sixty-four months after treatment (mean 47.4±16.9). Patient dosimetry was then retrospectively recalculated with the two above-mentioned methods. Several time schedules for uptake measurements were considered, with different timings and total number of points. Early time schedules, sampling uptake up to 48h, do not allow to set-up an accurate treatment plan, while schedules including the measurement at one week give significantly better results. The analytical fit procedure applied to the three-point time schedule 3(6)-24-168h gave results significantly more accurate than the website approach exploiting either the same schedule, or the single measurement at 168h. Consequently, the best strategy among the ones considered is to sample the uptake at 3(6)-24-168h, and carry out an analytical fit of the curve, while extra measurements at 48 and 72h lead only marginal improvements in the accuracy of therapeutic activity determination.

The aims of this study were to estimate the effective radiation doses from CT examinations of both adults and children in Japan and to study the impact of various scan parameters on the effective doses.A questionnaire, which contained detailed questions on the CT scan parameters employed, was distributed to 3000 facilities throughout Japan. For each scanner protocol, the effective doses for head (non-helical and helical), chest and upper abdomen acquisitions were estimated using ImPACT CT Patient Dosimetry Calculator software v. 1.0.4 (St George's Hospital, London, UK).The mean effective doses for chest and abdominal examinations using 80-110 kV were significantly lower than those using 120 kV. However, there was no statistically significant difference in the mean effective doses for head scans between facilities employing 80-110 kV and 120 kV. In chest and abdominal examinations, the mean effective doses using CT scanners from Western manufacturers [Siemens (Forchheim, Germany), Philips (Eindhoven, Netherlands) and GE Medical Systems (Milwaukee, WI)] were significantly lower than those of examinations using Japanese scanners [Hitachi (Kashiwa, Japan) and Toshiba (Otawara, Tochigi, Japan)], except for in paediatric chest examinations.The mean effective doses for adult head, chest and abdominal CT examinations were 2.9, 7.7 and 10.0 mSv, respectively, whereas the corresponding mean effective doses for paediatric examinations were 2.6, 7.1 and 7.7 mSv, respectively.Facilities using CT scanners by Western manufacturers commonly adopt low-tube-voltage techniques, and low-tube-voltage CT may be useful for reducing the radiation doses to the patients, particularly for the body region.

Purpose: The aim of this study was to present the results of a pilot program on patient dosimetry carried out in Chile during the last 5 yr, using a biplane x-ray angiography system settled for pediatrics. This research was conducted in Latin America under the auspices of the International Atomic Energy Agency (IAEA) supporting programs on radiological protection (RP) of patients. Methods: Patient age, gender, weight, height, number of cine series, total number of cine frames, fluoroscopy time, and two dosimetric quantities [air kerma-area product (P{sub ka}) and cumulative dose (CD) at the patient entrance reference point] were recorded for each procedure. Results: The study includes 544 patients grouped into four age groups. The distributions by age group were 150 for

This work investigates the validity of estimating effective dose for cone beam CT (CBCT) exposures from the weighted CT dose index (CTDIW) and irradiated length.Measurements were made within cylindrical poly(methyl methacrylate) (PMMA) phantoms measuring 14 cm and 28 cm in length and 32 cm in diameter for the 200° DynaCT acquisition on the Siemens Artis zee fluoroscopy unit (Siemens Medical Solutions, Erlangen, Germany). An interpolated average dose was calculated to account for the partial rotation. Organ and effective doses were estimated by modelling projections in the Monte Carlo software programme PCXMC (STUK, Helsinki, Finland).The CTDIW was found to closely approximate the interpolated average dose if the positions of the measured doses reflected the X-ray beam rotation. The average dose was found to increase by 8% when the phantom length was increased from 14 to 28 cm. Using the interpolated average dose and the irradiated length for effective dose calculations gave similar values to PCXMC when a double-length (28-cm) CT dose index phantom was irradiated. Simplifying the estimation of effective dose with PCXMC by modelling just 4 projections around the abdomen gave effective doses that were only 7% different to those given when 41 projections were modelled. Calculated doses to key organs within the beam varied by as much as 27%.Estimating effective dose from the CTDIW and the irradiated length is sufficiently accurate for CBCT if the chamber positions are considered carefully. A conversion factor can be used only if a single CT dose index phantom is available. The estimation of organ doses requires a large number of modelled projections in PCXMC.

Monitoring of professionally exposed workers in Bosnia and Herzegovina started in 1960s. Doses received by patients and professionals in interventional cardiology are high in comparison with other practices in medicine. The purpose of this study is to present personal and patient dosimetry data. Results show increase in doses of personnel in interventional cardiology. Total collective dose for four cardiology centres in Bosnia and Herzegovina increased from 15 person mSv in 2007 to 52 person mSv in 2010. This increase mainly corresponds to higher number of personnel and increase in the number of procedures. Average monthly dose has increased from 0.40 to 0.72 mSv in the same period. The results of occupational and patient doses in interventional cardiology are similar to results reported in the literature. It is of great importance for professionals working in this field to be educated in radiation protection and proper use of X-ray equipment.

The purpose of this study was to investigate how the choice of the scanned region affects organ doses in CT. ImPACT CT Patient Dosimetry Calculator (version 1.0) was used to compute absorbed doses to eight organs of interest in medical radiation dosimetry. For 13 dosimetry data sets, the authors calculated the maximum organ dose (D(max)) as well as the corresponding organ dose for a scan with selected length D(L). These data permitted the relative dose (D(r) = D(L)/D(max)) to be determined for varying scan lengths. Computations were performed for a nominal X-ray tube current of 100 mA, a rotation time of 1 s and a CT pitch of 1. The authors also determined values of D(max)/CTDI(vol), where CTDI(vol) is obtained in a 32-cm diameter CT dosimetry phantom using the same radiographic techniques. For each organ, D(r) was independent of the type of scanner, and increased monotonically to unity with increasing scan length. Relative doses for a scan restricted to the organ length ranged from 0.65 D(max) for the bladder to 0.86 D(max) for the lungs. There was good correlation (r = 0.64) between relative organ dose and the corresponding organ length. At 120 kV, the lowest value of D(max)/CTDI(vol) was 1.23 for the breast and the highest was 2.22 for the thyroid. Varying the X-ray tube voltage between 100 and 130 kV results in changes in D(max)/CTDI(vol) of no more than 4 %. CT scans limited to the direct irradiation of an average-sized organ results in an absorbed dose of ~0.75 D(max).

The study aims to analyse the effects of beam energy, dose fractionation, response homogeneity, long-term fading and response sensitivity of radiochromic films. It also investigates the effect of the scanner, ambient temperature and storage conditions on the response of the films. The radiochromic films were irradiated at various air kerma from 20 mGy to about 8 Gy. Results showed that the response of the films is not energy dependent for low doses ranging from 300 to 700 mGy (coefficient of variation = 5-12%) but starts to show a slight dependence for high doses above 2 Gy (coefficient of variation = 20%). There is no significant difference (4%) in optical densities (OD) and pixel values when doses were fractionated and when using scanner with and without warm-up lamp. The curve fitting of OD and pixel values for the sensitivity test at different kilovolt potential gave an r(2) value of 0.99.

Purpose Cone beam CT (CBCT) is an advanced imaging technique compared to panoramic radiography and of lower cost than a conventional CT procedure. Its advantages are the focused imaging of the maxillofacial region and a reduced radiation exposure with relatively low cost. CBCT produces three-dimensional information on the facial skeleton and teeth in a few seconds time. The purpose of the study was to measure patient radiation exposure in terms of Kerma Area Product (KAP) in implant planning dentistry, to estimate effective dose (Ef) and to compare patient radiation doses with corresponding values from CT and conventional panoramic radiography, in clinical practice. Methods The X-ray system used was a CS9300 Carestream system. Patient sample included 168 individuals undergoing 211 CBCT examinations. Data recorded included: KAP, tube voltage, tube current, exposure time, field of view (FOV), patient age and clinical indication. Five examination types were selected in order to keep protocol settings as similar as possible. Results Patient mean age was 55 years. Patients underwent either 1 (80.2%), 2 (14.7%), 3 (2.5%) or >3 (2.3%) CBCT examinations. Protocol details were: 80–90 kV, 4–5 mA, 8 s exposure time and fixed FOV of 10*10 cm2. Mean (SD) KAP was 533 (112) mGy*cm2. Median KAP value was 530 mGy*cm2. A conversion factor of 0.08 mSv/Gycm2 was used to calculate Ef. Mean (SD) Ef was found 42.7 (9.0) μSv (median 42.4 μSv). A broad comparison was done with international data from dental dosimetry studies using different modalities, showing that CBCT requires 4–10 times lower radiation exposure than corresponding CT images, depending on examination type. At the same time, CBCT patient radiation exposure is 3–6 times higher than panoramic radiography. Conclusions CBCT is an accurate and useful tool for many clinical oral-maxillofacial indications. Although CBCT doses are significantly lower than conventional CT, yet they are higher than those from conventional imaging used in dentistry. Therefore, a risk/benefit analysis must be carried out before a CBCT investigation is requested.

Biological effects induced by exposure to radiation made evident the need for an accurate dosimetry from the early days of X-ray use in medicine. Later the scientific interest turned also to the estimation of risks of radiation-induced cancer and genetic effects. Various dosimetric quantities have been used in diagnostic radiology and sometimes confusion is caused because the same name is used for different quantities. The question arises: what is patient dose and what is not? It’s common practice to indicate the dose received by a patient in radiology using the dosimetric indexes defined for the different imaging modalities. However, dosimetric indexes are a useful tool for practices optimization and comparison, but certainly they don’t describe patient dose. To accurately estimate patient dose there is the need to collect a lot of information concerning patient characteristics and irradiation events in order to obtain organ or tissue dose. Nowadays, thanks to the digital technology used in medical imaging, various ways of collecting these data are available. The information is communicated using specific standards (i.e. DICOM), such as the non-image information object definitions. These objects are carrying information about equipment output and other dose related information which allow the user to provide a more accurate estimate of patient dose. The standards are in continuous development, to provide more and more detailed information and to include most recent modalities (e.g. CBCT). This talk will review the basic concepts on patient dosimetry as well as the existing DICOM objects and IHE profiles used to monitor patient exposure, highlighting pros and cons and introducing to the future developments.

To investigate the relationship between radiographic techniques (i.e. kilovolt and milliampere-second) and the corresponding volume computed tomography dose index (CTDI(vol)). Data were obtained for CTDI(vol) for head and body phantoms from the ImPACT CT patient dosimetry calculator for 43 scanners from four major vendors of medical imaging equipment (i.e. GE, Philips, Siemens and Toshiba). CTDI(vol) were obtained with the largest X-ray beam width, and using a CT pitch of unity. For each scanner, relative values of CTDI(vol) were also computed as a function of X-ray tube voltage, normalised to unity at 120 kV. The average CTDI(vol) for 43 commercial scanners was 167 + or - 44 microGy (mA s)(-1) for the head phantom and 78 + or - 22 microGy (mA s)(-1) for the body phantom. The 90th percentile CTDI(vol) values are approximately twice the corresponding 10th percentile values for both head and body phantoms. Over the last 20 y, the head phantom CTDI(vol) has increased approximately 50 % and the body phantom CTDI(vol) has increased approximately 90 %. For both, the head phantom and the body phantom, CTDI(vol) is proportional to kilovolt(2.6). CT output must be specified using CTDI(vol) because for a fixed kilovolt and milliampere-second, CT scanner outputs (CTDI(vol)) differ by about a factor of 2. Increasing the X-ray tube voltage from 80 to 140 kV increases CTDI(vol) by about a factor of 4.

The purpose of this article is to develop a method for estimating embryo doses in CT.Absorbed doses to the uterus (embryo) of a 70-kg woman were estimated using the ImPACT CT Patient Dosimetry Calculator. For a particular CT scan length, relative uterus doses and normalized plateau uterus doses were determined for a range of commercial CT scanners. Patient size characteristics were obtained from cross-sectional axial images of 100 consecutive patients (healthy women undergoing unenhanced pelvic CT examinations). For each patient, the diameter of a water cylinder with the same mass as the patient's pelvis was computed. Relative dose values were generated for cylinder diameters ranging from 16 to 36 cm at x-ray tube voltages between 80 and 140 kV.Values of relative uterus dose increased monotonically with increasing scan length, independently of scanner model, and reached a plateau for scan lengths greater than approximately 50 cm. The average normalized plateau uterus dose for all scanners was approximately 1.4 and showed interscanner differences of less than 10% for modern scanners operated at 120 kV. Normalized plateau doses show little dependence on the x-ray tube voltage used to perform the CT examination. Our results show that the uterus dose estimate in an abdominal or pelvis CT examination performed on a 70-kg patient is about 40% higher than the reported value of the volume CT dose index (CTDI(vol)). The pelvis of a 70-kg patient may be modeled as a water cylinder with a diameter of 28 cm and has an average anteroposterior dimension of 22 cm. For constant CT technique factors, embryo dose estimates for a 45-kg patient would be approximately 18% higher than those for a 70-kg patient, whereas the corresponding dose estimates in a 120-kg patient would be approximately 37% lower.Embryo doses can be estimated using relative uterus doses, normalized plateau uterus doses, and CTDI(vol) data with correction factors for patient size.

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

Background: Since computed tomography (CT) urography began to replace excretory urography as the primary imaging technique in uroradiology, the collective radiation dose to the patients has increased. Purpose: To examine the changes in the CT urography protocol for investigating suspected urinary tract malignancy between the years 1997 and 2008, and how these changes have influenced the mean effective dose. Material and Methods: The study was based on 102 patients (mean age 66.1±14.8 years, range 31–89 years; 30 female, 72 male) divided into five groups (groups A–E) corresponding to the time points at which changes were made to the CT urography protocol. The mean effective doses were estimated using the ImPACT CT Patient Dosimetry Calculator. Results: The number of scan phases at CT urography was reduced from four to three in 1999, resulting in a reduction of the mean effective dose from 29.9/22.5 (female [F]/male [M]) mSv (group A) to 26.1/18.9 (F/M) mSv (group B). In 2001, mAs settings were adapted to patient size, and the mean effective dose was reduced to 16.8/12.0 (F/M) mSv (group C). In 2005, scans were performed with a multidetector-row CT equipped with automatic tube current modulation in the x- and y-axis (CARE Dose). The effective mAs was also lowered in the unenhanced and excretory phase, yet the mean effective dose increased to 18.2/13.1 (F/M) mSv (group D), since the effective mAs had to be increased in the corticomedullary phase to maintain image quality. In 2008, as tube current modulation in the x-, y-, and z-axis was introduced (CARE Dose4D), the mean effective dose was reduced to 11.7/8.8 (F/M) mSv (group E). Conclusion: This study shows that the individual mean effective dose to patients undergoing CT urography has decreased by 60%, from 29.9/22.5 (F/M) mSv in 1997 to 11.7/8.8 (F/M) mSv in 2008.

Interventional cardiology procedures result in substantial patient radiation doses due to prolonged fluoroscopy time and radiographic exposure. The procedures that are most frequently performed are coronary angiography, percutaneous coronary interventions, diagnostic electrophysiology studies and radiofrequency catheter ablation. Patient radiation dose in these procedures can be assessed either by measurements on a series of patients in real clinical practice or measurements using patient-equivalent phantoms. In this article we review the derived doses at non-pediatric patients from 72 relevant studies published during the last 22 years in international scientific literature. Published results indicate that patient radiation doses vary widely among the different interventional cardiology procedures but also among equivalent studies. Discrepancies of the derived results are patient-, procedure-, physician-, and fluoroscopic equipmentrelated. Nevertheless, interventional cardiology procedures can subject patients to considerable radiation doses. Efforts to minimize patient exposure should always be undertaken.

The introduction of routine patient dosimetry to Brazilian radiological institutions is very necessary in order to meet national and international standard requirements for radiation protection. This work presents a survey of the air kerma-area product (P(KA)), the entrance surface air kerma (K(e)) and the effective dose (E) in common radiographic examinations during the routine of a large public hospital in the city of Belo Horizonte, Brazil. Results draw attention to the use of field sizes larger than the cassette dimension, the lack of both the collimation X-ray beam and the standardisation of the exposure parameters by radiology technicians.

Application of a quality control (QC) programme is very important when optimisation of image quality and reduction of patient exposure is desired. QC surveys of diagnostics imaging equipment in Republic of Srpska (entity of Bosnia and Herzegovina) has been systematically performed since 2001. The presented results are mostly related to the QC test results of X-ray tubes and generators for diagnostic radiology units in 92 radiology departments. In addition, results include workplace monitoring and usage of personal protective devices for staff and patients. Presented results showed the improvements in the implementation of the QC programme within the period 2001 - 2005. Also, more attention is given to appropriate maintenance of imaging equipment, which was one of the main problems in the past. Implementation of a QC programme is a continuous and complex process. To achieve good performance of imaging equipment, additional tests are to be introduced, along with image quality assessment and patient dosimetry. Training is very important in order to achieve these goals. Workshop on Safety and Efficacy for New Techniques and Imaging using New Equipment Supporting European Legislation, Apr 18-20, 2007, Delft, Netherlands

A detailed study of radiation doses received by 83 patients who underwent coronary angiography (CA) and 26 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) by the femoral route in two hospitals in Mashhad-Iran is presented. All procedures were undertaken with Siemens angioscope X-ray equipment. Thermoluminescent dosimeters (TLD-100), suitably calibrated, were used to measure the dose received at five locations on the patient's skin (on the thyroid, gonads and lens of eyes). A dose area product (DAP) meter was also used. DAP values and fluoroscopy times were recorded for each patient. The mean values for DAP were 32.47 ± 4.03 and 44.49 ± 5.64 Gy cm 2 for CA and PTCA, respectively. The patient dosimetry results revealed the thyroid receives the highest dose in CA and PTCA examinations. Also, in this study, DAP to effective dose conversion factors were estimated by means of a Rando phantom and the effective dose received by the patients was estimated for CA and PTCA examinations. The estimated mean values of effective dose were 6.75 ± 0.85 and 9.61 ± 1.24 mSv, respectively.

SummaryAim: Dosimetry in 131I-lipiodol therapy for hepatocellular carcinoma (HCC) in the hitherto largest existing patient cohort. Patients, methods: 38 courses of intra-arterial 131I-lipiodol therapy with a total activity up to 6.7 GBq were performed in 18 patients with HCC. Liver and tumour volume were measured by computed tomography (CT) and 131I activity by scintigraphy on day 3, 6, 14, 28 and 42 after injection. Lipiodol deposition in tumour nodules as shown by CT rendered definite attachment to scintigraphic data possible. The radiation dose in tumour nodules, liver and lungs was calculated according to the MIRD concept and the tumour dose related to pre-therapeutic tumour volume, response and survival. Results: Mean tumour dose was 23.6 ± 3.6 Gy (14.2 ± 2.1 mGy/MBq) with maximal 162 Gy (90.1 mGy/MBq) after one and 274 Gy after three courses. The dose to nontumourous liver was 1.9 ± 0.2 Gy (1.2 ± 0.1 mGy/MBq) and the mean dose ratio of tumour / nontumourous liver 11.1 ± 1.7 (max. 82). The pulmonary dose was 25.9 ± 1.8 mGy (16.3 ± 1.2 μGy/MBq) and therefore much lower. There was a reciprocal relation between tumour dose and pretherapeutic tumour volume. Tumour dose had no effect on response or survival. Conclusion: High radiation doses are particularly in small tumour nodes achievable but not necessarily related to tumour response. The dose of non-tumourous liver and lungs is much lower.

The importance and methodology of contemporary patient dosimetry in well-established radionuclide therapies are reviewed. The different protocols used for radioiodine treatment of thyrotoxicosis are discussed. Special attention is paid to patient dosimetry in the largest safe dose approach for curative radioiodine therapy of thyroid remnants and metastases in the post-surgical treatment of differentiated thyroid cancer. Nowadays, meta-[131I]iodobenzylguanidine (131I-MIBG) therapy for neuroblastoma relies on bone marrow dose levels. Issues related to whole-body and tumour dosimetry in this type of radionuclide therapy, where, traditionally, dosimetry has played an important role, are discussed. A relatively large number of patients are treated with radiolabelled Lipiodol for hepatocellular carcinoma. Administered activities are restricted to 2.22 GBq (60 mCi) when using 131I-lipiodol because of the radioprotection measures to be taken. These radiation protection issues can be avoided by using 188Re labelled Lipiodol allowing further dose escalation. The follow-up of these patients also necessitates whole-body dosimetry. It is concluded that for treatment of malignant diseases reliable patient dosimetry is now a keystone of high quality radionuclide therapy. Where dosimetry of present medical applications focuses generally on the critical organs, in the near future accurate 3-dimensional tumour dosimetry also will become feasible by the introduction of the combined SPECT-CT and PET-CT imaging systems in the dosimetric methodology. This will allow treatment protocols based on tumour dose prescriptions as performed in external beam radiotherapy.

The aim of this study was to demonstrate the advantages of patient dosimetry using voxel models and to present sets of dose estimates for patients of different gender and size. These models offer greater realism with respect to organ shape and topology than the well-established Medical Internal Radiation Dose (MIRD)-type mathematical models. At the National Research Centre for Environment and Health (GSF), specific absorbed fractions have been previously calculated for 4 male and 3 female voxel models, representing different age and stature, for a wide range of source organs. For this study, estimates both for established and new radiopharmaceuticals were performed using biokinetic data from International Commission on Radiological Protection (ICRP). The above calculations allowed for comparison to the MIRD technique in relation to the resulting absorbed organ and effective doses. Furthermore, data sets representing a range of voxel phantoms were investigated. It was found that dose differences among the voxel models can amount up to a factor of 3.

A single-use dosimeter, designed for in vivo patient dosimetry, has been evaluated. Key dosimetric characteristics of the dosimetry system have been measured for high-energy photon and electron beams commonly used in external beam therapy. Under the measurement conditions utilized, dose accuracy was within 5% for all data points, and inter-batch uniformity was acceptable, with a standard deviation of 1.7%. Dose linearity was confirmed for doses ranging from 2 to 400 cGy. The dosimeter readings were independent of dose rate for rates ranging from 80 to 480 cGy/min. When used as instructed, the dosimeter readings were accurate across the tested range of energy and modality. These measurements show that the dosimetry system's performance may be acceptable for in vivo dosimetry of entrance d{sub max} doses.

Effective dose is an important quantity in relation to assessment of radiation risk. Organ and effective doses to paediatric patients undergoing diagnostic and therapeutic heart catheterization procedures can be assessed by combining relatively simple measurements, e.g. of dose-area product (DAP), and calculated dose conversion factors (DCF). This also holds for the radiation dose to the hospital staff, e.g. the cardiologist. Monte Carlo (MC) simulation of radiation transport in mathematical anthropomorphic phantoms is used to obtain the DCFs, which strongly depend on beam quality and geometrical parameters. The performance of a dedicated fast MC code (PCXMC) for patient dosimetry is compared with that of a more elaborate general purpose MC code (MCNP). Resulting organ doses sometimes may differ considerably, partly due to phantom differences. While MCNP uses separate male and female mathematical phantoms, PCXMC uses a hermaphrodite. However, both codes yield effective doses that agree rather well, so PCXMC can be used for convenience. The MCNP code is used to calculate the effective dose to the cardiologist exposed to radiation scattered from the patient. Without protective clothing, effective dose per procedure to the cardiologist is at least two orders of magnitude lower than that to the patient. The effectiveness of various types and thickness of protective clothing has been evaluated for one view of one cardiac catheterization. The results of the calculations do not contradict experimental studies from the literature. MC simulation may serve as a useful tool to improve the accuracy of estimating occupational effective dose from personal dose monitors.

To establish a system for patient dosimetry audit and setting of local diagnostic reference levels (LDRLs) for nuclear medicine (NM) CT.Computed radiological information system (CRIS) data were matched with NM paper records, which provided the body region and dose mode for NMCT carried out at a large UK hospital. It was necessary to divide data in terms of the NM examination type, body region and dose mode. The mean and standard deviation dose-length products (DLPs) for common NMCT examinations were then calculated and compared with the proposed National Diagnostic Reference Levels (NDRLs). Only procedures which have 10 or more patients will be used to suggest LDRLs.For most examinations, the mean DLPs do not exceed the proposed NDRLs. The bone single-photon emission CT/CT lumbar spine data clearly show the need to divide data according to the purpose of the scan (dose mode), with mean (±standard error) DLPs ranging from 51 ± 5 mGy cm (low dose) to 1086 ± 124 mGy cm (metal dose).A system for NMCT patient dose audit has been developed, but there are non-trivial challenges which make the process labour intensive. These include limited information provided by CRIS downloads, dependence on paper records and limited number of examinations available owing to the need to subdivide data. Advances in knowledge: This article demonstrates that a system can be developed for NMCT patient dose audit, but also highlights the challenges associated with such audit, which may not be encountered with more routine audit of radiology CT.

In recent years, dose justification and optimization have been attempted in percutaneous coronary intervention (PCI); however, deterministic effects have been reported. To prevent radiation skin injuries in PCI, it is necessary to measure the patient entrance skin dose (ESD), but an accurate dose measurement method has not yet been established. In this study, we developed a dosimetry gown that can measure the ESD during PCI using multiple radiophotoluminescence dosimeters (RPLDs). The RPLDs were placed into 84 pockets that were sewn into a dosimetry gown. Patients wear the original dosimetry gown during the procedures, after which we obtain accurate ESD measurements. We believe that this method using RPLDs and a newly-designed dosimetry gown provides accurate ESD measurements during PCI. We expect this system to become a standard method for measuring ESD during PCI.

Some dosimetry instruments and products are reviewed, the main emphasis being on patient dosimetry, recommendations for accuracy in different measurement applications and the results of some intercomparisons, It seems to be a common problem that the users of the general purpose air kerma (K a ) meters, dose-area product (DAP) meters or products such as thermoluminescence (TL) dosemeters are not always able to select the correct ionisation chamber, the calibration factor of a DAP meter or the TL dosemeter material and type, respectively, for different radiation conditions. The combined DAP and K a meters developed recently, as well as the exposure data acquisition systems designed for monitoring one or more quantities or for determining the effective dose of a complicated examination, are described briefly. The most advanced software of these systems is able to display the dose distributions for the most exposed areas of the skin, on-line.

Dosimetry requirements and protocols for performing measurements in digital and interventional radiology are discussed. Calculated entrance surface dose (ESD) is predicted to be of increasing interest in the future, replacing direct measurement with thermoluminescence (TL) dosemeters. The quantities proposed for establishment of reference values for interventional radiology are reviewed briefly, and the methods of collecting the data required for estimation of their values by means of traditional manual and new automatic methods are compared. It is concluded that the manufacturers of X ray units can largely solve the dosimetry problems of interventional radiology in machines with fully digital control systems after they have received sufficient data on patient dosimetry requirements.

The Council Directive 97/43/EURATOM requires Member States to guarantee the establishment of diagnostic reference levels in radiodiagnostics. Patient dosimetry and image quality are basic controls in quality assurance programmes, according to the predictive capability to diagnose the correct behaviour of an X ray facility, including both X ray equipment and examination protocol. This paper addresses the role of both items in the framework of optimisation and the approach of the quality assurance programmes to interventional and digital radiology, fields where the reference levels are scarcely developed and a number of practical challenges must be solved. Expertise in the use of diagnostic reference levels and foresights on quality assurance in an X ray department of a university hospital with digital equipment are described.

Electronic portal imaging devices (EPIDs) can be used for non-imaging applications in radiotherapy such as patient dosimetry. Of the systems available, the fluoroscopic camera-based EPID Theraview (InfiMed Inc.) has not been studied to date, and a review of the dosimetric properties of the system is presented here. In the "single set-up" mode of image acquisition, pixel intensity increases sublinearly with applied dose. The response was dependent on the system's video signal gain and showed a threshold dose to the detector in the range 0.05-0.35 cGy, and pixel saturation at detector doses in the range 1.2-1.6 cGy. Repeated exposures of the EPID were observed to be extremely reproducible (standard deviation 0.5%). The sensitivity of the system showed a linear decline of 0.04% day-1 over a 68-day period, during which time the relative off-axis response within 10 x 10 cm2 field was constant to within a standard deviation of 0.56%. The system shows spatial non-uniformity, which requires correction for application to dose measurements in two-dimensions. Warm-up of the camera control unit required a period of at least 40 min and was associated with an enhancement in pixel intensity of up to 12%. A radiation dose history effect was observed at doses as low as 0.2 Gy. Camera dark current was shown to be negligible at normal accelerator operation. No discernible image distortion was found. Mechanical stability on gantry rotation was also assessed and image displacement of up to 5 mm at the isocentre was observed. It was concluded that the device could be used for dosimetry provided necessary precautions were observed and corrections made.

The purpose of this study was to quantify patient exposure to X rays in arteriography of the lower limbs and to derive hitherto unavailable characteristics of common projections. In a study of 455 patients three types of arteriography have been monitored: Seldinger catherisation for arteriography of both legs, percutaneous needle puncture arteriography of one leg and intravenous digital subtraction arteriography of peripheral vessels. Using a microcomputer-controlle automatic data acquition system, information was obtained on fluoroscopy time focus-to-patient distance, position and direction of the X ray beam. lield size, X ray tube voltage, dose-area product (DAP), digital subtraction arteriography (DSA) runs, DSA frames, conventional cut film runs, and cut films. Exposure parameters needed for the definition of X ray projections in peripheral arteriography have been derived, as well as associated DAP values and entrance dose estimates.

X ray projection data (see Part I) and GSF phantoms ADAM and EVA were used as input for the GSF Monte Carlo transport code to calculate hitherto unavailable dose conversion coefficients (DCCs) for common projections in arteriography of the lower limbs. These DCCs served to estimate organ equivalent doses and effective dose in a study of 455 patients. The effective dose caused by percutaneous needle puncture arteriography of one leg was on average I mSv, by Seldinger catherisation for arteriography of both legs 4 mSv, and by intravenous digital subtraction arteriography (DSA) 5 mSv, For needle puncture and Seldinger arteriography the effective dose attributable to fluoroscopy was about 50% for male and 60% for female patients. The contribution of DSA was between 15 and 35%, that of cut films between 17 to 28%, depending on gender and procedure. The effective dose in intravenous arteriography was mainly due to DSA (91-93%).

A programme of patient dose measurements in radiography and fluoroscopy has been ongoing for the past 5 years in accordance with the National Protocol for Patient Dosimetry. Dose measurements for radiography are carried out at approximately 3-yearly intervals with thermoluminescence dosemeters (TLDs) used to measure skin entrance dose for up to 10 common examinations. Dose-area product meters (DAPMs) are used for the assessment of dose in complex examinations including barium enemas and meals. Data have been collected from a number of hospitals across the region. The data from the initial round of measurements over 1992-1995 has been used in the setting of local reference dose levels against which, in addition to National Reference levels, all subsequent survey results can be compared. The results are presented, identifying the local reference levels set for the various examinations. The local figures act as a tighter constraint than the original national figures. The use of locally set reference levels has been a success with more relevance for participating hospitals, consequently having a greater impact on the optimisation programme.

There are two main approaches to the establishment of reference doses for digital fluoroscopy/fluorography equipment. One involves the measurement of dose/image and dose rate when a suitable patient-equivalent phantom is placed in the primary beam. The other is based on the analysis of the results of a series of patient dose measurements for different examinations. Both methods have their advantages and disadvantages. The former can he incorporated into a programme of quality assurance measurements and facilitates comparison between different digital fluoroscopy units. Unfortunately there is no international scientitic agreement on measurement protocols or standards, and the measured values are also critically dependent on the settings used by the automatic exposure control. Patient dosimetry measurements can be performed and have the advantage that risk and detriment can be determined for specific individuals. However, the effect of patient variability in terms of size and composition makes comparisons difficult. The results of a regional survey of digital fluoroscopy/fluorography equipment is presented and discussed in relation to the overall context of the meeting objectives (i.e. reference doses and quality assurance).

The investigations deal with the search for a passive dosemeter applicable to patient dosimetry in diagnostic radiology, which meets particularly the requirements of a low detection limit and an adequate energy response, as well as sufficiently high precision and reliability A thermoluminescence dosimetry (TLD) technology is reported that fits these requirements. The detector material consists of lithium fluoride co-doped with copper (LiF:Mg.Cu.P) The detectors, originating from China, are shown to exhibit high radiation sensitivity exceeding that of conventional lithium fluoride. LiF:Mg,Ti (TLD- 100), by far. Based on the new technology a detection threshold of 0. 1 μGy, precision as low as ≤1 % (1σ rel ) and strict linearity of the TL signal-dose relationship were found, for dose up to at least 1 mGy.

A collaborative national survey initiated by the University of Malaya and the Ministry of Health was conducted from 1993 to 1995 to establish baseline patient dose data for seven common types (12 projections) of X-ray examinations in Malaysia. A total of 12 randomly selected public hospitals and 867 patients were included in this survey. The entrance surface doses (ESD) received by the patients were measured using thermoluminescent dosemeters (TLDs) attached to the patient's skin. Histograms are presented showing wide, positively skewed distributions of measured entrance surface doses for each examination. Mean, median, first and third quartile values of ESD and median effective dose are reported. Survey results are generally comparable with those reported in the UK, USA and by the International Atomic Energy Agency (IAEA). The results also provide information on dose level for a lower weight population (mean weight 60 kg) compared with the international reference dose values based on a 70 kg standard. The findings support the importance of the on-going national quality assurance programme to ensure doses are kept to a level consistent with optimum image quality. The data will also be useful for the formulation of national guidance levels as recommended by the IAEA. Furthermore, this study provides patient dosimetry information on healthcare level II countries.

The Harshaw 6600 reader is designed for personal monitoring using whole body cards and extremity dosemeters. The latter have the potential for use in performing a large scale patient dose survey during radiographic procedures but have not previously been used for this purpose. This system has several potential advantages: fast read-out rate, reproducible time temperature profile, no mechanical contact with the dosemeter and barcode identification. This allows individual elemental correction coefficients to be applied to each chip which thereby improves the measurement precision. This system was rigorously tested prior to use for patient dosimetry. Reproducibility, batch uniformity and minimum detectable dose were found to be 2.9%, 3.1% and 0.1 mGy respectively. Signal fading after receiving a radiation dose was found to be 25% over a three month period whilst the fading before exposure was found to be 12% over three months. The energy response of the dosemeters relative to that measured using 137Cs gamma rays was found to vary between 1.3 and 1.6 over the range 45 - 104 keV. The overall uncertainty of the results was assessed and compared with the value recommended by the National Patient Dosimetry Protocol. It was concluded that the system could be used with extremity dosemeters for large scale patient dosimetry surveys.

OBJECTIVE. This article describes the different automatic approaches used to collect and process patient dose values and other procedural data during diagnostic and interventional radiology and discusses their benefits for clinical practice and quality control online. Approaches for automatic processing of patient dose and other procedural data for computed radiography and for flat-panel detectors extracting information from DICOM headers or via DICOM services are described. The method to perform image retake analysis is also discussed. CONCLUSION. Automatic systems to manage patient doses and procedural data are feasible and will improve radiation safety and quality in radiology. The current level of technology makes such systems achievable at a reasonable cost and with great benefit to clinical practice.