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OPTIMIZATION OF PROTECTION IN MEDICAL DIAGNOSTIC RADIOLOGY

Objective

EXPERIMENTAL STUDIES WILL BE CARRIED OUT TO DETERMINE EXPOSURE CONDITIONS AND TO ASSEESS INDIVIDUAL AND COLLECTIVE DOSES AND GLOBAL RISKS FROM MEDICAL DIAGNOSTIC RADIOLOGY, AS WELL AS OTHER DATA OF INTEREST FOR QUALITY ASSURANCE (QA) PROGRAMMES. ALONG WITH THESE STUDIES, DOSES FOR ACCOMPANYING PERSONS AND STAFF WILL BE CONSIDERED SEPARATELY FROM THOSE ON PATIENTS. DATA WILL BE OBTAINED FROM MEASUREMENTS ON DIFFERENT X-RAY EQUIPMENTS, AND THEIR VARIATIONS WILL BE STUDIED AS A FUNCTION OF RADIOLOGICAL PROCEDURES, WORKING PRACTICES AND OTHER RELATED FACTORS.
A project was devised to analyse the risks to operating staff and population in diagnostic radiology installations by area and personal dosimetry. The risks were correlated with equipment features and conditions, room workloads and training of operating staff.
The radiological risk to patient from direct dose measurement and numerical estimates and its correlation with equipment features was analysed and procedures of radiological examinations and training level of operating staff were monitored.
A pilot programme of Quality Assurance in Diagnostic Radiology was implemented and the bases for a nationwide programme of patient dosimetry and Quality Assurance in Diagnostic Radiology was set up.

With respect to personal dosimetry, more than 5000 data corresponding to 300 members of staff working with X-ray equipment have been analysed. For almost 5% of the staff effective dose equivalent values range between 0.1 and 0.3 msv; about 2% show a dose higher than 0.3; about 5% show certain anomalous dosimetric values within the year which can be caused by incorrect operating procedures or, on certain occasions, by ill functioning equipment.

In area dosimetry, 2670 data of doses corresponding to 655 different positions have been obtained, evaluated upon a total number of 104 diagnostic radiological rooms and some operating theatres.
Anomalies in protection barriers have been found out in 16 rooms (11 of which belong to the same centre, which means that nearly half of its rooms have shielding defects).
As a conclusion, area dosimetry should be applied at least once within installations, especially in those that are older, and after possible modifications to a room that involve barrier or equipment changes.

Concerning patient dosimetry, data from approximately 60,000 examinations have been obtained, and in some 3000 cases it has been possible to calculate organ and effective doses.
The results of the estimations show that in the Community of Madrid (4,800,000 inhabitants), about 680 X-ray examinations per 1000 inhabitants have been performed in 1989 (considering a yearly mean increase of 8% in the available figures over the last few years), without taking into account either military or massive labour check-ups or dental radiological examinations. This would give values of 1.21 mSv for the effective dose equivalent per inhabitant and year in the Community of Madrid and 5830 person Sv for the collective dose.

With respect to quality control of X-ray generator equipment, the following results have been obtained: 36% of the 53 pieces of equipment analysed could be considered to be in good condition, while 33% needed urgent and immediate attention and the other 33% require checking although their working order was acceptable.

Simplified procedures have been put into practice to evaluate image quality and patient dose levels in preparation for the computerization of the parameters of interest for a future expert system. Local levels of patient dose reference values were compared with the European Community (EC) values and used as sectorial indicators of priority for quality criteria (QC) actions. Also, quality controls of X-ray equipment and image devices were carried out to detect the causes of anomalies.

To evaluate the quality of images, Phantoms TORCDR were used for general Radiology, TOR-MAM for mammography and for radioscopy the 9 object set from the University of Leeds was used.
For the analysis of patient doses the simplified procedure involved dose measurements at the entrance for simple examinations or the measurement of dose x area product, apart from the number of images and the fluoroscopy time in 'complex' examinations.

Image quality in radiography has been evaluated in 57 rooms verifying a deficient quality in 13 of them. Image quality in radioscopy was evaluated in 16 units, detecting under tolerance standards and 5 in which improvements must be observed when optimizing the working parameters. Equipment under limits are being replaced.
The most frequent causes of the anomalies in image quality in 15 mammography units tested have been, among others tube potential (kVp) inaccuracies, processor malfunctioning, failures in the automatic exposure control system and in the setting of mobile grids, unsuitable (or inexisiting) filtering and unsuitable parameter selection.

Patient dose controls have been carried out in 25 rooms. 4 of them with anomalous dose values are waiting for corrective actions; in the rest, dose values are equal to or lower than the reference values.
The 3 step QC action cycle has been fulfilled in some cases when the dose values turned out to be very high and/or when the corrective actions were simple enough and of low cost. Lack of filtration, deviations and failures in the high voltage generator, use of obsolete image systems, processor malfunctioning and operating procedures not always optimized have been the most frequent causes of anomalous dose findings.
Specific evaluations at 6 paediatric rooms of 2 different hospitals have been carried out. Estimates of entrance dose values for different types of examination have been obtained for separate age groups. Image quality has been also evaluated. Corrective actions, such as change of cassette type and screens, adjustments in generators and processors, use of gonadal protectors, and similar ones have been proposed in almost all the rooms.
THE RESEARCH WORK WILL BE CARRIED OUT IN FOUR BIG HOSPITALS ASSOCIATED TO THE COMPLUTENSE UNIVERSITY OF MADRID, RESPONSIBLE FOR OVER 540,000 RADIOLOGICAL EXAMINATIONS PER YEAR, AND OVER 1,500,000 RADIOGRAPHIC FILMS. DURING THE FIRST YEAR THREE RADIOLOGICAL ROOMS PER CENTRE, HAVING SIMILAR PERFORMANCES, WILL BE EVALUATED, THE GREATER PART OF THE RADIOLOGICAL ROOMS WILL BE STUDIED DURING THE FOLLOWING TWO YEARS.
PERSONAL AND AREA DOSIMETRY WILL BE PERFORMED BY USING TL DOSIMETERS, IN ADDITION TO THOSE USED BY EACH CENTRE ITSELF FOR ITS INTERNAL DOSIMETRIC CONTROLS. ESPECIALLY SKIN DOSES WILL BE DETERMINED FOR THE MOST FREQUENT EXAMINATIONS PERFORMED IN EVERY ROOM, AND UNDER THE USUAL CONDITIONS OF FOCUS-SKIN DISTANCE, KVP, MAS, FILTRATION, ETC. THE EFFECTIVE DOSE EQUIVALENT FOR THE PATIENT WILL BE CALCULATED FROM THESE DATA. OTHER EQUIPMENT CHARACTERISTICS SUCH AS GRIDS, FILM TYPES, INTENSIFYING SCREENS, ETC., WILL BE TAKEN INTO ACCOUNT.
FOR THE MOST SIGNIFICANT EXAMINATIONS AND PRACTICES, DOSES TO SELECTED ORGANS AND TISSUES (LENSES, THYROID, GONADS, TEC.) WILL BE MEASURED INSIDE A TISSUE-EQUIVALENT PHANTOM. THE EFFECTIVE DOSE EQUIVALENT WILL THUS BE DETERMINED IN A MORE EXACT WAY. THE OBTAINED VALUES WILL BE CORRELATED WITH THE USUAL TECHNICAL PARAMETERS, EXPERIENCE OF STAFF, ETC. THE RESULTS WILL BE COMPARED TO SIMILAR CALCULATIONS AND MEASUREMENTS ALREADY CARRIED OUT IN OTHER MEMBER STATES. THIS EXERCISE WILL SUPPORT THE DETERMINATION OF REPRESENTATIVE EXPOSURE CONDITIONS AND REASONABLE DOSE RANGES.
AS SOON AS THE EQUIPMENT FOR QUALITY CONTROL WILL BE AVAILABLE, A BASIC QA PROGRAMME WILL BE CARRIED OUT,CONCENTRATING ON TECHNICAL AND PHYSICAL PARAMETERS OF THE X-RAY EQUIPMENT AND ON FILM PROCESSING TECHNIQUES AND SYSTEMS, WITH A VIEW TO IMPROVE WORKING PRACTICES, AS WELL AS EDUCATION AND TRAINING OF THE RADIOLOGICAL PERSONNEL.
FEEDBACK FROM THIS QA PROGRAMME AND THE DATA FOR EFFECTIVE DOSE EQUIVALENTS AS A FUNCTION OF WORKING PARAMETERS FOR A GIVEN RADIOLOGICAL EQUIPMENT AND EXAMINATION AND OF THE OPERATOR'S TRAINING AND EXPERIENCE WILL BE USED TO SET UP PERFORMANCE CHARACTERISTICS OF THE RADIOLOGICAL PROCEDURE AND THE TIME INTERVAL IN WHICH THEY SHOULD BE CHECKED. THE EFFICIENCY OF THE QA PROGRAMME CONCERNING EXPOSURE TO THE PATIENT, STAFF AND ACCOMPANYING PERSONS WILL BE DETERMINED.
WORKLOADS (MA.MIN/WEEK) FOR EVERY ROOM WILL BE EVALUATED, INCLUDING ALSO QUALITY OF THE X-RAY BEAMS, OPERATOR'S POSITION, TRAINING AND EXPERIENCE. THESE DATA WILL BE USED TO ESTABLISH THE RADIATION RISKS ASSOCIATED TO EVERY PROFESSIONAL WORK PLACE AND WILL HELP TO ESTIMATE RADIATION RISKS FOR ACCOMPANYING PERSONS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIVERSIDAD COMPLUTENSE DE MADRID
Address
Ciudad Universitaria Pabellon De Gobierno
28040 Madrid
Spain