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Nuclear Instruments and Methods in Physics Research A 652 (2011) 794797Contents lists available at ScienceDirectNuclear Instruments and Methods inPhysics Research A0168-90
E-mjournal homepage: www.elsevier.com/locate/nimaInfluence of physical parameters on radiation protection and imagequality in intra-oral radiologyW. Belinato a,b, D.N. Souza b,n
a Instituto Federal de Ensino Basico, Tecnico e Tecnologico da Bahia, Av. Amazonas, 1350-45030220, Zabele, Vitoria da Conquista, BA, Brazilb Departamento de Fsica, Universidade Federal de Sergipe, Av. Marechal Rondon s/n, 49100-000 Rosa Elze, S ~ao Cristov~ao, SE, Brazila r t i c l e i n f o
Available online 13 October 2010
Image quality02/$ - see front matter & 2010 Elsevier B.V. A
esponding author. Tel.: +55 79 2105 6725; fa
ail addresses: [email protected], divanizia@gmaa b s t r a c t
In the world of diagnostic imaging, radiography is an important supplementary method for dental
diagnosis. In radiology, special attentionmust be paid to the radiological protection of patients and health
professionals, and also to image quality for correct diagnosis. In Brazil, the national rules governing the
operation of medical and dental radiology were specified in 1998 by the National Sanitary Surveillance
Agency, complemented in 2005 by the guide Medical radiology: security and performance of
equipment. In this study, quality control tests were performed in public clinics with dental X-ray
equipment in the State of Sergipe, Brazil, with consideration of the physical parameters that influence
radiological protection and also the quality of images taken in intra-oral radiography. The accuracy of the
exposure time was considered acceptable for equipment with digital timers. Exposure times and focal-
spot size variations can lead to increased entrance dose. Increased dose has also been associated with
visual processing of radiographic film, which often requires repeating the radiographic examination.
& 2010 Elsevier B.V. All rights reserved.1. Introduction
In the world of diagnostic imaging, radiography is an importantsupplementary method for dental diagnosis. Radiology requiresthat special attention be given to the radiological protection ofpatients and practitioners alike, as well as to image quality forcorrect diagnosis.
The essential aspects of correct diagnosis in radiology are relatedto radiation beam and image quality as well as to the radiologicalprotection of patients and practitioners. International standards forradiation protection have been published by several organizations;one of these documents is Dosimetry in diagnostic radiology: aninternational code of practice, printed by the International AtomicEnergy Agency . This standard presents the main dosimetricparameters to be investigated in diagnostic radiology, includingsome related to dental X-rays. In Brazil, the national standardgoverning the operation of medical and dental radiologyequipment was issued in 1998 by the National Health MonitoringAgency, amended in 2005 by means of a supplementary document,Medical radiology: safety and equipment performance [2,3].
In Brazil, in recent years, there has been growing concern aboutthe methods used in dental radiography, especially with regard toequipment, as evidenced mainly by research conducted in post-graduation programs. Examples of this can be seen in surveysll rights reserved.
x: +55 79 2105 6708.
il.com (D.N. Souza).conducted in Brazil by Spyrides , Oliveira  and Arguiropulo and also in other countries at the same time . Brazilianresearchers have sought to evaluate, amongst other things, thelevel of knowledge of dentists from two southeastern states ofBrazil, Rio de Janeiro and S~ao Paulo, on factors related to theacquisition of periapical radiographs in their offices, including theoperating parameters of X-ray apparatus and knowledge andpreventive attitudes of these professionals in relation to ionizingradiation. In addition, the authors sought to encourage theestablishment of programmes to control the quality of imagesproduced in these offices. Theirwork pointed to inadequacies in theradiological procedures in many of the clinics studied such asinappropriate methods of disclosure, lack of use of lead apronsresulting in patient entrance skin air kerma higher than thoseconsidered adequate. The authors also showed that adherence to aprogramme of quality control has enabled an improvement in thequality of images produced and a reduction in entrance skin airkerma (ESAK). Although exposure of the population to dentalX-rays contributes approximately 1% of the total absorbed dosefrom clinical radiological examinations , suitable procedures arenecessary to maintain dental radiation exposures ALARA .
So in this study, a few years after the publication of theseresearch reports and standards, we have extracted the parametersof beams from dental X-ray equipment and of film processing in allpublic health services in a state in northeastern Brazil, Sergipe, andlooked at the physical parameters that interfere with radiologicalprotection and also those that affect the quality of imagesperformed in intra-oral conventional radiography. The goal of
W. Belinato, D.N. Souza / Nuclear Instruments and Methods in Physics Research A 652 (2011) 794797 795this study is to show that continuous quality control programmesenable images of sufficient quality to be produced for correct dentalradiodiagnosis.2. Materials and methods
In all, 22 dental public health services in Sergipe, Brazil, wereinvestigated. Quality control tests were performed on the dentalX-ray equipment using a Radcals ACCU-PRO toolkit, a device thatmeasures the focal point of the X-ray tube, manufactured by MRA(model CQ-06), and a dental phantom, shown in Fig. 1, that wasdeveloped from low costmaterials and had the same pattern as the76-025 phantom from Flukes Biomedical.
The radiation field size check was performed by exposing fourperiapical films, as shown in Fig. 2(a), and measuring the diameterof the exposed field after processing, shown in Fig. 2(b).
Analyses of patient entrance skin air kerma were carried outusing a variety of exposure times, considering that differentexposure times are used in offices. Using a dental X-ray with anFig. 1. Dental phantom reproduced with acrylic, showing an E film inserted.
Fig. 2. (a) Exposure of E films and (baccelerating voltage of 70 kVp, the tests were made with exposuretimes ranging from0.2 to 0.8 s. In other equipmentwith a voltage of60 kVp, the exposure times ranged from 0.4 to 1.0 s.
The quality of images obtained from dental offices was assessedby a 0.8 s exposure of E film, produced by Kodak, in a 60 kVpequipment and using 70 kVp for 0.5 s. The ideal exposure timewasbased on parameters that gave a satisfactory image quality. Foreach X-ray equipment, three radiographsweremade: The first filmwas developed at the dentists office in accordancewith the routinemethod; the second filmwas processed under standard conditionsusing the Kodak GBXs processing solution diluted in the propor-tion of 3.8 l of solution to 9.0 l of water at room temperature,limiting the time in the developer to 1.5 min and the time in thefixer to 3.0 min; the third film was developed in the pattern, usingready-made solutions fromKodaks, leaving it for 2 min and 30 s inthe developer, and 4 min in the fixation solution, as recommendedby the manufacturer.
Radiographs developed at the dentists offices were visuallycompared to those that were processed in two other types ofdeveloping solution under standard conditions in order to detectany significant changes in image quality obtained from the clinicssuch as veiling and excessive development or those resulting frominsufficient development time. After processing, the radiographswere scanned using an HP Scanjet G2710s at 300 DPI. The imageswere analyzed by measuring the IGL of the three regions of lowcontrast film using graphics software. From IGL analyses, it waspossible to compare whether the quality of the images obtainedfrom the clinics was satisfactory compared to the others processedunder standard conditions. Fig. 3 shows an example of IGL analysis.
Using IGL, it was possible to compare the quality of imagesobtained from the clinics compared to those developed understandard solutions.3. Results and discussion
Of the 22 clinics studied, none of them keep records of thequality control procedures and only in some of them there wereconcerns about the need for such a control.
Considering that the actual kV voltage should not vary from thevalue indicated on the kit by more than 10% over the range oftechniques normally used, only one X-ray dental device actuallydelivered the output voltage with the proper accuracy, as shown in) radiation field measurement.
Fig. 3. Example of IGL analysis.
Fig. 4. Accuracy output of X-ray devices.
W. Belinato, D.N. Souza / Nuclear Instruments and Methods in Physics Research A 652 (2011) 794797796Fig. 4, confirming the large voltage swing of this single-phaseequipment.
Considering that 2.0 mm is themaximumvariation expected forthe diameter of the radiation field on the patients skin, only in 50%of the equipment the diameter of the radiation field present valuesbetween 5.8 and 6.2 cm.
In the set of equipment studied, it was observed that 73.7% haddigital timers. It was observed that for selected times higher than0.3 s, all digital equipment showed accurate exposure times.Devices with analog timers did not indicate the recommendedvalues of accuracy.
The values of entrance skin air kerma to exposure times greaterthan 0.7 s were proportional to exposure time in 91% of theequipment, being approximately linear in two of the devicesstudied. In 39% of the 70 kVp equipment, it was observed thatwhen an ESAK higher than the recommended limit value of3.5 mGy was used, the exposure time was greater than or equalto 8.0 s; although such values exceed the recommended limit, itwas observed that for exposure times less than 0.7 s all ESAK valueswere within the limit recommended for radiography. Half of thenominal 60 kVp X-ray machines also exceeded the recommendedESAK limit, and one equipment set delivered doses above 7.0 mGyfor exposure times exceeding 7.0 s.
Dimensions of the effective X-ray focal point were a little abovethose recommended in three of the tested equipment, compromis-ing resolution and image quality and increasing the ESAK releasedby these two 60 kVp devices.
Table 1 presents information on the parameters for thedevelopment of intra-oral radiographs in the clinics surveyed.This table shows informationabout the type of developing chamber(darkroom), the quality of processing chemical solutions, the datesof replacement of the solutions, and the use of thermometer andtimer to control the development process. It was observed that inall dental services, conventional manual film processing was used
Table 1Parameters of development processes in clinics surveyed.
Parameters (material or device) Percentage observed (%)
DarkroomConventional manual processing in box with
transparent acrylic red walls
Conventional manual processing in box with
acrylic opaque walls
No darkroom 4.5
Quality processing chemicalsTrademark 89.9
Manufacturer unknown 9.1
Schedule for the chemical replacementYes 77.3
Control of development timeYes 4.5
Control of development temperatureYes 9.0
Table 2Comparison of the IGL developed film in dental services and in standard solutions.
Solution compared Percentage (%)
SERVGBXLarge IGL 47.0
Small IGL 18.0
Proportional values of IGL 35.0
SERVRESOSmall IGL 59.0
Proportional values of IGL 41.0
GBXRESOSmall IGL 32.0
Proportional values of IGL 68.0
W. Belinato, D.N. Souza / Nuclear Instruments and Methods in Physics Research A 652 (2011) 794797 797and in one of the 22 clinics therewas no adequate chamber for filmprocessing. Two other services did not have information about thequality of processing chemical solutions and they had no recordeddates for the replacement frequency of these solutions. In only 9.0%of the clinicswas a thermometer used to control the temperature ofthe developing solutions. The film development time should bechosen according to the temperature of the solutions, becauseinappropriate film processing is a cause of under- or over-development, consequently impairing the radiographic imagingquality. Furthermore, if the professional uses an inappropriateexposure methodology, there is no doubt that to obtain images ofhigh enough quality it will be necessary to apply exposure timesgreater than those considered safe, and these factors can certainlycontribute to the patient being exposed to an unnecessaryradiation dose.
A comparison of inverted gray level (IGL) of the three areas of lowcontrast in radiographic images obtained by dental services usingthe solutions prepared in the service (SERV), diluted solutions (GBX)and ready-made solutions (RESO) is shown in Table 2. It can beobserved that the images developed in dental services presented anIGL higher than those developed in standard solutions for 47% ofservices. When the solutions of services were compared with RESO,it could beobserved that the IGL obtained fromSERVprocessedfilmswas higher in 59% of them. As one would expect, the best ratio wasobtained in a comparison of the IGL of radiographs obtained withstandard solutions. The lowest proportions of the SERVGBS andSERVRESO comparisons are probably due to the developmentprocess performed in dental services without control of either thedevelopment time or temperature. Furthermore, one shouldconsider that some equipment had inadequate output.
Observations were made for beam absorption by lead aprons,proper storage of these aprons, and also whether a lead thyroidcollar existed. Itwas observed that 32%of the lead aprons examinedhad radiation absorption levels three times less than thoseconsidered appropriate for this type of personal protection; theseaprons had damage that could be associated with age or improperstorage, because in 81.8% of installations there was no support forsuch storage. It was also observed that 36.4% of services had noprotective thyroid collar.4. Conclusions
The exposure timewasmore accurate for X-ray equipmentwithdigital timers, confirming the recommendation of the NationalSanitary Surveillance Agency of Brazil.
The tube voltage for single-phase equipment can vary by up to30% of its peak value, which was confirmed by calculating theaccuracy of the voltage, which showed variations greater than 10%in 95.5% of the equipment.
The values of the focal spots were a little above the recom-mended level, not affecting resolution or image quality, butaffecting the ESAK in dental X-rays with values higher thanrecommended.
Entrance skin air kerma was proportional to the exposure timein 91% of the equipment, being approximately linear for two of theclinics evaluated. The ESAK value exceeded the recommended limitof 3.5 mGy when an exposure time greater than 0.7 s was used, in39% of the 70 kVp equipment. For exposure times less than 0.7 s, allvalues were within the limit of 3.5 mGy per radiograph.
Tubes with a nominal voltage of 60 kVp and greater focal pointalso exceeded the recommended value of entrance dose, reachingvalues above 8.0 mGy for intra-oral radiography.
A comparison of inverted gray level in images processed in theclinical services with those developed in standard solutionsindicates that visual processing reduces image quality.
Thus, as expected,wecould confirmthat the lackof quality controlprocedures compromise the quality of radiographic images and favorthe use of inadequate parameters for dental radiodiagnosis.References
 International Atomic Energy Agency, Dosimetry in diagnostic radiology: aninternational code of practice, Technical Report Series, TRS no. 457, Interna-tional Atomic Energy Agency, Vienna, 2007.
 Ministerio da Saude, Brazil, Diretrizes de protec- ~ao medico e odontologico.Portaria 453.1 de junho de 1998 MS/SVS, 1998.
 Ministerio da Saude, Brazil, Radiodiagnostico medico: Desempenho de equi-pamentos e seguranc-a. Ministerio da saude, Agencia Nacional de VigilanciaSanitaria, Brazil, 2005.
 K. S. Spyrides, Doctoral Thesis, Universidade Estadual de Campinas, 2002. G. F., Oliveira, Doctoral Thesis, Universidade Estadual de Campinas, 2002. A. Y. Arguiropulo, . Doctoral Thesis, Universidade Federal doRio de Janeiro, 1999. E.N. Yakoumakis, C.E. Tierris, E.P. Stefanou, I.G. Phanourakis, C.C. Proukakis, Oral
Surg. Oral Med. Oral Pathol. Oral Radiol. Endod. 91 (2001) 362. F. Shannoun, H. Zeeb, C. Back, M. Blettner, Health Phys. 91 (2006) 154.
Influence of physical parameters on radiation protection and image quality in intra-oral radiologyIntroductionMaterials and methodsResults and discussionConclusionsReferences