Establishing the European diagnostic reference levels for interventional cardiology.

Interventional cardiac procedures may be associated with high patient doses and therefore require special attention to protect the patients from radiation injuries such as skin erythema, cardiovascular tissue reactions or radiation-induced cancer. In this study, patient exposure data is collected from 13 countries (37 clinics and nearly 50 interventional rooms) and for 10 different procedures. Dose data was collected from a total of 14,922 interventional cardiology procedures. Based on these data European diagnostic reference levels (DRL) for air kerma-area product are suggested for coronary angiography (CA, DRL = 35 Gy cm2), percutaneous coronary intervention (PCI, 85 Gy cm2), transcatheter aortic valve implantation (TAVI, 130 Gy cm2), electrophysiological procedures (12 Gy cm2) and pacemaker implantations. Pacemaker implantations were further divided into single-chamber (2.5 Gy cm2) and dual chamber (3.5 Gy cm2) procedures and implantations of cardiac resynchronization therapy pacemaker (18 Gy cm2). Results show that relatively new techniques such as TAVI and treatment of chronic total occlusion (CTO) often produce relatively high doses, and thus emphasises the need for use of an optimization tool such as DRL to assist in reducing patient exposure. The generic DRL presented here facilitate comparison of patient exposure in interventional cardiology.

Characterisation of grids of point detectors in maximum skin dose measurement in fluoroscopically-guided interventional procedures.

PURPOSE: Point detectors are frequently used to measure patient's maximum skin dose (MSD) in fluoroscopically-guided interventional procedures (IP). However, their performance and ability to detect the actual MSD are rarely evaluated. The present study investigates the sampling uncertainty associated with the use of grids of point detectors to measure MSD in IP. METHOD: Chemoembolisation of the liver (CE), percutaneous coronary intervention (PCI) and neuroembolisation (NE) procedures were studied. Spatial dose distributions were measured with XR-RV3 Gafchromic(®) films for 176 procedures. These distributions were used to simulate measurements performed using grids of detectors such as thermoluminescence detectors, with detector spacing from 1.4 up to 10 cm. RESULTS: The sampling uncertainty was the highest in PCI and NE procedures. With 40 detectors covering the film area (36 cm × 44 cm), the maximum dose would be on average 86% and 63% of the MSD measured with Gafchromic(®) films in CE and PCI procedures, respectively. In NE procedures, with 27 detectors covering the film area (14 cm × 35 cm), the maximum dose measured would be on average 82% of the MSD obtained with the Gafchromic(®) films. CONCLUSION: Thermoluminescence detectors show good energy and dose response in clinical beam qualities. However the poor spatial resolution of such point-like dosimeters may far outweigh their good dosimetric properties. The uncertainty from the sampling procedure should be estimated when point detectors are used in IP because it may lead to strong underestimation of the MSD.

Measurement of maximum skin dose in interventional radiology and cardiology and challenges in the set-up of European alert thresholds.

To help operators acknowledge patient dose during interventional procedures, EURADOS WG-12 focused on measuring patient skin dose using XR-RV3 gafchromic films, thermoluminescent detector (TLD) pellets or 2D TL foils and on investigating possible correlation to the on-line dose indicators such as fluoroscopy time, Kerma-area product (KAP) and cumulative air Kerma at reference point (CK). The study aims at defining non-centre-specific European alert thresholds for skin dose in three interventional procedures: chemoembolization of the liver (CE), neuroembolization (NE) and percutaneous coronary interventions (PCI). Skin dose values of >3 Gy (ICRP threshold for skin injuries) were indeed measured in these procedures confirming the need for dose indicators that correlate with maximum skin dose (MSD). However, although MSD showed fairly good correlation with KAP and CK, several limitations were identified challenging the set-up of non-centre-specific European alert thresholds. This paper presents preliminary results of this wide European measurement campaign and focuses on the main challenges in the definition of European alert thresholds.

Establishment of trigger levels to steer the follow-up of radiation effects in patients undergoing fluoroscopically-guided interventional procedures in Belgium.

The accumulated dose to the skin of the patient during fluoroscopically-guided procedures can exceed the thresholds for tissue reactions. In practice, interventionalists have no direct information about the local procedure-related skin doses in their patient, causing suboptimal or delayed treatment. In current study, the accumulated Kerma-Area-Product (KAP) values were registered, as well as the reference air kerma (Ka,r) values, if available, for almost 200 cases undergoing seven different procedures. A sheet filled with 50 thermoluminescent dosemeters was wrapped around each patient to measure the peak skin dose. In a significant part of the Transjugular Intrahepatic Portosystemic Shunt (TIPSS) procedures, chemo-embolizations of the liver and cerebral embolizations, the threshold values for deterministic skin damage (2 Gy) were attained. Trigger values in terms of KAP, corresponding to a peak skin dose of 2 Gy, were determined. In general, our results comply reasonably well with the values proposed in the NCRP 168 report, with a KAP value of 425 Gy cm² and a Ka,r value of 3 Gy, corresponding to a peak skin dose of 3 Gy. Only for the TIPSS procedure a considerably lower value of 2 Gy was obtained at the published Ka,r and for the RF ablations we obtained a considerably lower value of 250 Gy cm² in terms of KAP.

A study of the correlation between dose area product and effective dose in vascular radiology.

The purpose of the multi-centre study was to assess dose area product (DAP) and effective dose of patients undergoing angiography of the lower limbs in Belgium and to investigate the correlation between DAP and effective dose. DAP values were measured in 12 centres and compared with the national diagnostic reference levels (DRLs). The effective dose (E) was estimated by multiplying the DAP with case-specific conversion coefficients (CCs) that were calculated with Monte Carlo software MCNP5. As a model for the patient, a mathematical hermaphrodite phantom was used. Calculations showed that tube configurations and extra Cu filtration have a large influence on these CCs. Due to the use of Cu filtration, effective dose can be twice as high for comparable DAP values. Also the use of an over-couch tube configuration is a disadvantage when compared with the under-couch tube configuration. For centres working under-couch without the use of extra Cu-filtration, the DAP values correlate very well with effective dose (Spearman's rank correlation rho ; = 0.97). For these conditions, general CCs between DAP and E were calculated. They were 0.083 mSv Gy(-1) cm(-2) (ICRP 60) and 0.065 mSv Gy(-1) cm(-2) (ICRP 103).

Diagnostic reference levels in angiography and interventional radiology: a Belgian multi-centre study.

The purpose of this study was to determine diagnostic reference levels (DRLs) for common angiographic and interventional procedures in Belgium. Dose Area Product (DAP) measurements were performed on 21 systems, (13 angiography and 4 vascular surgery centres). Type of procedure, total DAP, patient weight and height were collected on a daily basis during 1 y. The 75th percentile of the distribution of DAP values was defined as DRL. Preliminary DRLs were calculated for the three most frequent procedures for the whole population, for a weight class of patients (65-80 kg) and normalised to the standard size patient. Among them, the DRL for angiography of the lower limbs (30% of the procedures) from the whole population was 74.6 and 63.2 Gycm2 for the size corrected. The mean DAP values of each room was then compared to these DRLs.

Evaluation of colour images printed by a thermal dye diffusion process.

Dry printing of medical images, without photochemicals, may be based on the principle of thermal dye diffusion. The Drystar (Agfa Gevaert, Mortsel, Belgium) system was evaluated in colour-coded Doppler examinations of the carotid arteries. A total of 25 consecutive patients were examined for the colour test and 37 patients for the black-and-white test. Colour and black-and-white data were available on the same view. The performances of the Drystar were tested against against laser films, matrix films and two types of glossy paper using the following criteria: grey scale, colour scale, quality of reproduction of vascular colouring, registration, endothelial layer, intraluminal echogenicity, spectral resolution, and artefacts. The overall handiness of the document was graded. A significant difference (p = 0.00005) was noted in favour of the Drystar concerning registration, grey scale, spectral resolution and vascular colouring. The global score for handiness of the colour film was 96%. Radiologists preferred the colour hard copy as compared with glossy paper prints. As in the black-and-white test, blue-base and clear-base films obtained with the Drystar were rated inferior to laser films, a double line print mode was included in the printer, giving a density of 2.3 OD.

[Evaluation of diagnostic efficacy in radiology. Literature review]. / Evaluation de l'efficacité diagnostique en radiologie. Revue de la littérature.

The recent development of new imaging procedures has lead the radiologists to assessing the diagnostic efficacy of the available examination techniques in order to reduce medical care costs. In cooperation with epidemiologists and statisticians, several methods of statistic analysis of the diagnostic efficacy of the procedures such as sensitivity and specificity evaluation, ROC analysis, disease prevalence, predictive value of tests, etc... have been developed. Benefit-cost and cost-efficiency analyses have also been performed, with a view to improving the quality of long-term medical care for the patient at a lower cost both for himself and the society.

Mach bands in mammography.

The radiologic appearance of tissue surrounding a tumor often influences the characterization of a cancerous lesion. An example is the radiolucent halo that is sometimes seen around breast cancers. Mammograms of 108 malignant tumors (74 scirrhous tumors, 17 partially scirrhous nodular tumors, and 17 nodular tumors) and eight benign tumors that showed peritumoral fat were retrospectively evaluated. All the scirrhous and partially scirrhous nodular cancers were more or less surrounded by a 5-10-mm-wide hyperlucent halo; this corona sign was also found in 14 nodular cancers. The halo sign, a hyperleucent 1-mm band, was observed around all benign lesions and immediately adjacent to sharply delineated cancers. These radiologic findings are an optical illusion (Mach band, background contrast effect). Densitometric measures and isoluminous analysis did not demonstrate the presence of a true hyperlucent zone.

[The composition of connective tissue in the normal and fibrocystic breast]. / Etude de la composition du tissu conjonctif du sein normal et mastosique.

A recent immunofluorescent study has tried to define the precise nature of the macromolecules present in the connective tissue of normal and fibrocystic breasts. Nothing abnormal has been found in the distribution of the different types of collagen and of the two glycoproteins, namely fibronectin and laminin. A quantitative approach to the research into the composition of the organ has brought us to realise that there are different amounts of the constituents of the connective tissue to be found in 80 samples which have been taken from 4 specific regions of the breast. These have been taken from 16 women aged between 28 and 82 with a mean age of 57 years. Their breasts could be ascribed to different clinical and radiological categories. We have been able to show that there is a significant rise in the water content as well as in the collagen content and, to a lesser degree, in the total proteins of the body of the breast as compared with the fatty layer in front of the breast. This increase is compensated for by a significant lessening in the percentage of lipids. It was not possible to demonstrate a statistically significant difference between these two regions as far as the concentration of proteoglycans and glycoproteins. Fibrous types of breast have, in the main body of the breast, a significant increase in the percentage of water, collagen, proteoglycans and glycoproteins as compared with fatty breasts.(ABSTRACT TRUNCATED AT 250 WORDS)