A comparison of the film density using a new computerized tool and dual energy x-ray absorptiometry

Abstract

Background: Radiographic density is a parameter that is used to determine the bone mineral density (BMD) in medical imaging; here mean pixel intensity level of radiograph is directly proportional to the BMD. BMD is an important parameter to assess metabolic diseases like osteoarthritis. Although Dual-energy X-ray Absorptiometry (DEXA) is the standard diagnostic method for BMD assessment; it is an expensive method with some diagnostic limitations. Objectives: To determine the BMD by using Antero-Posterior (AP) lumbar spine radiographs performed at standard peak kilo Voltage (kVp) range used in plain radiography. A Computer Aided system (CAD) was developed to calculate the BMD and the results were compared against the standard values. Methodology: Bone density is calculated as a 2D measurement. X-ray images (n=40) of the AP lumbar spine of the phantom were taken in the standard kVp range using conventional X-ray machine with computed radiography image processor and DEXA results of the same phantom were obtained by considering it as an average size Asian woman. Pre-processing techniques were applied before the calculation of mean pixel intensity with the aid of image processing techniques. The mean pixel intensity was used to assess BMD of a relevant vertebra. The relationship between mean T scores and Z scores of conventional image and DEXA scan was calculated using the hypothesis test and graphical representation. Results: The new CAD method showed appropriate T scores and Z scores for conventional radiographs. There was no statistically significant difference between T scores and Z scores of conventional radiographs with DEXA scan values as p<0.05. Graphically both T score and Z score coincide at the 93kVp. Conclusions: This new CAD system can be used to calculate BMD successfully using plain radiographs. It may need to be further developed with larger sample size with wide range of kVp.