An evaluation of the effect of tube potential on clinical image quality using direct digital detectors for pelvis and lumbar spine radiographs

Abstract

Introduction: High kVp techniques, 15% or 10-kVp rules, are well-known dose reduction methods. Traditionally, the use of high tube potential (i.e. increased kVp) is associated with decreased radiographic contrast and overall image quality. Recent studies suggest contrast and image quality are not heavily reliant on kVp with digital systems. This study aims to assess the effects of the high tube potential technique on clinical radiographic image quality when using digital systems, to validate high kVp as a dose saving technique. Methods: A selection of comparable pelvis and lumbar spine radiographs were collected from the hospital's picture archiving and communication system (PACS), with technical factors recorded. All clinical radiographs were assessed by 5 senior radiographers using a 15-point visual grading analysis (VGA) rubric. Results: For 40 AP pelvis radiographs and 40 lateral lumbar spine radiographs, reduction in the dose area product (DAP) with higher kVp is seen. Average pelvis DAP at 75 kVp = 14.06 mGy.cm 2 ; 85 kVp = 7.47 mGy.cm 2. Average lumbar spine DAP at 80 kVp = 15.76 mGy.cm 2 ; 90 kVp = 14.83 mGy.cm 2. Image quality and contrast scores showed no statistically significant difference between the high and low kVp groups (z = 0.06 and 0.12, respectively). Average pelvis VGA score at 75 kVp = 11.26; 85 kVp = 12.55. Average lumbar spine VGA score at 80 kVp = 9.23; 90 kVp = 10.64. Conclusions: The high tube potential techniques allowed for reduced patient radiation doses whilst showing no degradation of diagnostic image quality in a clinical setting. This study successfully validates the high kVp technique as a useful tool for reducing patient radiation doses whilst maintaining high diagnostic image quality for digital pelvis and lumbar spine radiography.

An explanation of the limitations relating to ‘An evaluation of the effect of tube potential on clinical image quality using direct digital detectors for pelvis and lumbar spine radiographs’ and the reasoning behind the study – Authors response to letter to the editor

“…Our study is very much set around clinical changes made within our department and as such we fully accept a large number of limitations with it, which we sought to list in the article. 1 Our study follows a previous basic pilot study that aimed to investigate image acquisition protocols established for film-screen technology as they now relate to digital radiography. 2 Following this study, our results suggested that there did not appear to exist an overwhelming difference in image contrast between exposures utilising a difference of 15% in kVp.…”

“…We did exclude a small number of images that would lead to such aberrations, an example of which Alzyoud et.al reference from our article as figure 1B. 1 Alzyoud et.al also raise interest in the variation of the VGA results that exist across the different images in the study and concern at the variation, and however, we are not necessarily surprised by the variation given the varied patient presentations we see within our department, which we have stipulated is a limitation of this retrospective study. This limitation was described in the article, in that we had no control over image acquisition conditions and patient size.…”

“…We wish to thank our colleagues for their interest in our study. Our study is very much set around clinical changes made within our department and as such we fully accept a large number of limitations with it, which we sought to list in the article 1 . Our study follows a previous basic pilot study that aimed to investigate image acquisition protocols established for film–screen technology as they now relate to digital radiography 2 .…”

“…Alzyoud et.al also correctly point out the effect of accurate positioning to ensure that the AEC provides correct exposure, citing scoliosis as an example. We did exclude a small number of images that would lead to such aberrations, an example of which Alzyoud et.al reference from our article as figure 1B 1 …”

The complete evaluation of tube potential on clinical image quality when using direct digital detectors for pelvis and lumbar spine radiography

“…We read with interest a recent submission to the Journal of Medical Radiation Sciences entitled ‘An evaluation of the effect of tube potential on clinical image quality using direct digital detectors for pelvis and lumbar spine radiographs’ by Peacock, Steward and Riley 1 . We would like to thank the authors for their valuable contribution and acknowledge that they have attempted to assess an important issue and to provide further validation of high tube potential as a dose‐saving technique.…”