Quality control program of the computed radiography system

Abstract

Objectives: To evaluate the correlation between the patient radiation dose and the image quality after implement the quality control program to the computed radiography system at the Department of Radiology of King Chulalongkorn Memorial Hospital, Thai Red Cross Society. Design: Experimental prospective study, prospective, before and after design by using the control (before) and experimental (after) group for QC program intervene to the CR system. Setting: Department of Radiology, King Chulalongkorn Memorial Hospital, Thai Red Cross Society. Samples: 1,384 examinations of the adult patients, age ranged from 16 to 75 years, body weight ranged from 35 to 114 kilogram of 8 types of x-ray examination, skull PA, lateral cephalometry, cervical spine AP, chest PA, abdomen AP, lumbo-sacral spine AP and lateral view and pelvis AP. Materials: Two sets of single-phase x-ray machine (Hitachi DR-155HM, Hitachi, Japan) in Room No. 4 and 5, one set of the computedradiography system, a Fuji computed radiography system model FCR 5000 (Fuji Photo Film Co. Ltd., Japan) were used during the study. Imaging phosphors were of europium doped barium fluorohalide in standard type (STVN). All soft copies were observed on Fuji CR Workstation model HI-C 655 by using Totoku high resolution monochrome liquid crystal display model ME 201L. Hard copies were made on Fuji film type 780-H (25.7 x 36.4 cm) and type LI-LM (35 x 43 cm) on Fuji wet laser imager model FL-IM D with developer (RD-20) and fixer (RF-15) were used. QC accessories were Ionization chamber (Victoreen 4000 M+ and Farmer model type 2670), FL18 phantom, wiremesh, steel ruler, resolution test tool, Sensitometer, Densitometer, Tape measurement, copper and aluminum plates and lead block. Methods: In this study, eight projections of CR images were performed under patient consent form before body weight and height measurement. The body mass index was calculated before setting the exposure factors by the radiological technologists. The radiographic dose was defined as the comparison of the reject and retake rate for the before and after QC of equipment were recorded, calculated the entrance skin dose (ESD) by application of the backscatter factor. Each machine energy entrance surface air kerma (ESAK), mAs, focus-skin-distance and focus-film distance. The matching the before and after QC CR image quality evaluation had been followed the European Commission Quality Criteria Guideline for Diagnostic Radiographic Images on CR workstation monitor by two of equivalent experience radiologists. Outcome measurements: Entrance skin dose (ESD) was determined from each general radiograph, the calculation of average radiation dose of patient would be corresponded to the reject and retake percentage and used in the statistical analysis. Results: In 1,384 examinations of the computed radiography, the examinations in two groups of study were well matched for number, age, sex, weight and height for each group. There was a significantly differences of the reject and retake rate after the quality control of the computed radiography system (P < 0.05). Conclusion: The reject and retake rate of the x-ray procedures in this study was reduced 54.55% (P < 0.05) after the implementation of the quality control of the CR system. Likewise, the patient skin dose was reduced 17.69 % in chest PA and 16.22 % in lumbosacral spine AP view. The result from the QC of x-ray equipment was shown the discrepancy of the entrance skin dose between two x-ray systems. As the QC program of the CR system was initiated using phantom, measuring devices, the result obtained shows the useful parameters benefit for the optimization of the patient dose and the image quality.