Effect of x-ray tube potential on image quality and patient dose for lumbar spine computed radiography examinations

Abstract

A study was conducted to investigate the effect of increasing x-ray tube voltage on patient dose and image quality during computed radiography (CR) examination of the lumbar spine. Images of a pelvis - lumbar spine phantom were obtained at three different tube voltages using two CR systems. The images were evaluated by image scores (IS) using the image quality criteria proposed by the Commission of the European Communities (CEC), by measuring the signal-to-noise ratio and the contrast-to-noise ratio. The entrance surface dose (ESD) to the phantom was also measured using ionisation chambers and the resulting gonad dose (G) and effective dose (E) were calculated. The CEC recommended tube voltages can be exceeded with CR systems for lumbar spine radiography. The ESD, G and E decreased by 25%-50% with both CR systems when tube voltage was increased. Although the decrease in IS was statistically significant (P < 0.05) the images obtained with the 3 tube voltages were diagnostically acceptable. The balance between image quality and patient dose can be optimised by using higher x-ray tube voltages for lumbar spine CR examinations.

Optimisation of Radiographic Procedures – Lumbar Spine Imaging in General Radiography

“…Papers describing optimisation techniques in lumbar spine radiography have been studied in several countries around the world. Those countries are Finland (16), Australia (17,34,39,41), Ireland (18,19,21,22,25), China (20), Sweden (24,26,33), Kuwait (23), United Kingdom (27,30,36), Slovenia (28,35,37), Iran (29,32), Israel (31), Croatia (38) and Malta (40).…”

“…The research methodology was experimental in almost all studies, except for three studies (16,32,39) in which the research methodology was a retrospective study of lumbar spine images. In most cases, the research was performed on an anthropomorphic phantom (17,20,34,41,(22)(23)(24)(25)(29)(30)(31)33), in a few studies the research was performed on patients only (27,(36)(37)(38), and some of them performed a combined study fi rst on a phantom and then on patients (18,19,21,26,28,35,40). The sample size of the examined patient studies varied from study to study.…”

“…The investigators studied the radiation dose to the patient and/ or phantom in all papers, but the measurement tool for the dose measurements varied from study to study. The dose was measured using TLDs (16,(18)(19)(20)(21)(22)25,28,33), ionization chambers (17,26,30), with some mathematical formulas and using conversion factors (21,23,32), DAP meters (27,35,36,38,40), based on calculations with the PCXMC program and Monte Carlo simulation (24,(29)(30)(31)(35)(36)(37)(38)41) and other ways (24,29,34). Image quality was not checked in a large number of the papers examined (17,20,34,37,(25)(26)(27)(28)(29)(31)(32)(33).…”

“…There were several ways to achieve dose optimisation in lumbar spine radiography. In 7 papers, the researchers used diff erent tube potentials (kV) (21)(22)(23)(24)34,39,41), diff erent mAs (41), in 5 papers they used alternative positioning of the patient, in which the patient or phantom was rotated to diff erent positions (19,27,(29)(30)(31)(35)(36)(37), and 2 studies used lead shielding as a method of radiation dose reduction (25,28). Four papers investigated increasing the distance (focus-fi lm distance and source-to-image distance) on the radiation dose to the patient during lumbar spine radiography (17,18,22,41), and some of the papers evaluate the eff ect of proper collimation (32,33,38).…”

“…Of the 26 reviewed papers, 14 (16,18,(38)(39)(40)(41)19,(21)(22)(23)(24)30,35,36) examined the eff ect of the optimisation procedure on image quality. In eleven papers, the researchers found no statistically signifi cant diff erence between image quality before and after optimisation (16,18,41,19,22,30,35,36,(38)(39)(40).…”