Τσιχλάκης Κ., Καθηγητής Οδοντιατρικής ΕΚΠΑ
Γκρίτζαλης Π., Επίκουρος Καθηγητής Οδοντιατρικής ΕΚΠΑ
Παπαδάκης Ε., Επίκουρος Καθηγητής Οδοντιατρικής ΕΚΠΑ
The achievement of radiographic image quality assurance gives multiple benefits to any radiology department, either state or private. The control of all the processes that were followed to produce digital images ensures consistently adequate diagnostic information with the minimum exposure that is reasonably achievable, so that the necessary information obtained from the dental x-ray can be used to maintain and improve the patient’s health. Simultaneously radiographic image quality can be profitable in the department’s materials and can save time during procedures.
By applying a reject and repeat analysis program of the extraoral radiographs, the produced digital images were recorded on a daily basis. Therefore an organized effort was carried out to ensure that the digital radiographs combine adequate diagnostic information with the least possible patient’s exposure to radiation and at the lowest possible cost. The analysis of rejects and repeated radiographs gives an indication of the main causes of low quality images and highlights the important sources of radiographic errors.
The purpose of this study is to provide a detailed analysis of the different parameters that lead to the rejection of the images and to assess the frequency of unacceptable radiographs in the Radiology Department of Diagnostic Radiology Oral and Dental University of Athens. This is the second study held in this Department dealing with the issue of quality assurance of extraoral radiographs, while for the first time digital imaging systems were evaluated. All digital two dimensional images, as well as the repeated and rejected film, that were performed for one consecutive month, were classified and logged into a registration form.
The staff that performed the radiographs was divided into five groups. The first group included faculty members of the Radiology Department, the second group contained first year postgraduate students of the Department of Oral Diagnosis and Radiology, the third group second year postgraduate students, the fourth group third year postgraduate students and finally in the fifth group participated other scientific partners of the clinic.
Data were collected and logged into a registration form and positioning errors were classified. Analytically, the methodology stages included: quality control of X-rays based on radiographic technique, quality control of radiographs based on film printing and quality control of the digital image based on the histogram. Operating problems of radiological equipment and other infrastructures were recorded on a daily basis and daily cleaning of work surfaces and overhead projectors was performed. The information recorded included elements concerning both the equipment and the radiographic technique. The evaluated unacceptable digital images were extraoral projections particularly panoramic and cephalometric radiographs. The selection of the repeated projections and the rejects films and their separation according to the type of error was held in a designated area.
In order to evaluate the effectiveness of a quality assurance program acceptable limits have to be established. According to the European Guidelines concerning Radiation Protection in Dental Radiology (Document No. 136), a based level “not greater than 10%” for unacceptable films has been recommended as an achievable audit standard for primary dental care. The results of this study showed that the rejection and repetition frequencies of the X-rays are within acceptable limits. The total number of extraoral radiographs, which were the sample of the present study, was 581 panoramic and 66 cephalometric projections. Specifically, the frequency of unacceptable images found during this study was 1.55% for the panoramic and 4.55% for cephalometric radiographs.
In this study the most frequent causes of unacceptable radiographic images were primarily positioning errors, foreign artifacts (dentures, metal objects) and mechanical errors (misplacement of the phosphor plate, processing and printing errors). Concerning panoramic radiographs free of positioning errors were 36.1% of the images. The most common errors observed were the tipped patient’s head (18.5%) and the asymmetry in the sagittal plane (15.5%). More specifically the positioning errors that caused repetition of the panoramic projection were closed bite and movement of the patient with 2.4% and 1.3%, respectively. Meanwhile the most common positioning error in cephalometric radiographs, that also caused rejection of the image, was the open bite with 4.55%. Foreign objects were observed in 4.3% of the extraoral projections, of which 1.9% could not be removed, causing inevitable effects in the interpretation of digital images. Finally the need of reprinting 2.3% of the total films arose due to errors while processing and printing digital images.
The evaluation of the errors that caused the non acceptance of digital images can be statistically analyzed in order to identify the main causes that led to reduction in quality. Reported findings showed that the two dimensional extraoral images performed in our Department have low unacceptable rates compared with other studies. This may be due to the fact that all extraoral projections were performed exclusively by postgraduate students and faculty members and therefore the staff has sufficient experience. Furthermore, this research took place under the uninterrupted supervision of the researcher. These general improvements may be due to the fact that conducting such research increases the attention of the staff involved and the total level of performance.
Similar quality assurance programs should ideally be applied in all private or public radiology departments and comparative tests should be held between them, so that an adequate level of imaging quality can be establish and widely accepted.
The results of this research brought the following important conclusions:
• Generally the two dimensional extraoral images performed in our Department have a normal or higher-level quality.
• The results showed that for panoramic images the overall unacceptable rate was 1,55% while the corresponding value for cefalometric radiographs was 4,55%.
• Patient positioning is a principal factor affecting image quality. Proper training according to different patient’s physical condition and appropriate attention to detail are required to ensure maximum diagnostic benefits.
• Positioning errors that affect the quality and the diagnostic information of extraoral images cannot be improved by any image processing software.
• Most importantly errors concerning dark room procedures and under/over exposed films nowadays do not affect the image quality nor the present study because digital X-ray systems do not have such limitations.
Quality, Assurance, Digital, Radiography, Panoramic, Cefalometric