Should Plain Films of the Lumbar Spine be Taken in the Posterior-to-Anterior or Anterior-to-Posterior Position? A Study Using Decision Analysis

The radiation dose, clinical and anatomical implications of erect lumbar spine radiography: A single centre pre-post implementation evaluation

INTRODUCTION

Lumbar radiographs remain a common imaging examination despite strategies to reduce their use. Many authors have demonstrated benefits in changing from traditional supine and recumbent lateral projections to a prone and/or erect orientation. Despite evidence of clinical and radiation dose optimisation, widespread adoption of these strategies has stalled. This article describes the single-centre implementation and evaluation of erect PA and lateral projections.

METHOD

This was an observational study pre- and post-implementation of an erect imaging protocol. Patient BMI, image field size, source image and source object distances and DAP were collected together with assessment of radiographic spinal alignment and disc space demonstration. Effective dose was calculated with organ specific doses.

RESULTS

76 (53.5%) patients were imaged in the supine AP and recumbent lateral position, 66 (46.5%) had erect PA and lateral radiographs. Despite the larger BMI of the erect cohort and similar field sizes, effective dose was lower in the PA position by an average of 20% (p < 0.05), however, no significant difference in lateral dose. Anatomical improvements were evident with greater visualisation of intervertebral disc spaces in the PA erect (t = -9.03; p < .001) and lateral (t = -10.298; p < .001) orientations. Erect PA radiographs demonstrated a leg length discrepancy in 47.0% (0.3-4.7 cm) and a scoliosis in 21.2% of cases, with a significant link between these findings (r (64) = 0.44; p < .001).

CONCLUSION

Erect lumbar spine radiography provides information on clinical outcomes not available with recumbent projections. The improvements in anatomical visualisation and radiation dose reduction supports the local change in practice.

IMPLICATIONS FOR PRACTICE

- Erect imaging can reduce effective dose with an optimised acquisition protocol - additional pathological information can be revealed by the erect posture. - postural awareness is critical to interpret images accurately.

The value of L5/S1 vertebral junction projection in diagnostic radiology

INTRODUCTION

The aim of this study was to compare the diagnostic contribution of the standard lateral and coned lumbar vertebra five and sacral vertebra one (L5/S1) projection in diagnostic radiology for specific pathologies in the digital era.

METHODS

The study used a retrospective qualitative design through a systematic stepwise process. The steps included a retrospective analysis of lumbar spine radiology reports over 20 months. The objective of this step was to identify the most common lumbar spine pathologies observed among the source population records (N=354). A radiologist identified five different pathologies on standard lateral and coned lateral L5/S1 projections (n=96). Fischer's exact test was performed to examine the significance of the association between the standard lateral and coned lateral L5/S1 projection classifications for each of the top five lumbar spine pathologies separately.

RESULTS

The five most prevalent lumbar spine pathologies indicated were degenerative disc disease (n=235; 66.4%), disc space narrowing (n=175; 49.4%), osteophytes (n=92; 26.0%), endplate sclerosis 19.21% (n=68; =9.2%) and malalignment (n=61; 17.2%). The Fisher's exact test executed to compare the top five lumbar spine pathologies visible on the standard lateral and coned lateral L5/S1 indicated that except for endplate sclerosis (p=0.0023), no significant difference in additional diagnostic information was observed between the standard lateral and coned lateral L5/S1 projections at α=0.05.

CONCLUSION

Compared to the standard lateral projection, the coned lateral L5/S1 projection did not contribute statistically significant additional diagnostic information for specific lumbar spine pathologies in the digital era.

Effective dose and image optimisation of lateral lumbar spine radiography: a phantom study

Background

To investigate lateral lumbar spine radiography technical parameters for reduction of effective dose whilst maintaining image quality (IQ).

Methods

Thirty-six radiograms of an anthropomorphic phantom were acquired using different exposure parameters: source-to-detector distance (SDD) (100, 130 or 150 cm), tube potential (75, 85 or 95 kVp), tube current × exposure time product (4.5, 9, 18 mAs) and additional copper (Cu) filter (no filter, 0.1-, 0.2-, or 0.3-mm thickness. IQ was assessed using an objective approach (contrast-to-noise-ratio [CNR] calculation and magnification measurement) and a perceptual approach (six observers); ED was estimated using the PCXMC 2.0 software. Descriptive statistics, paired t test, and intraclass correlation coefficient (ICC) were used.

Results

The highest ED (0.022 mSv) was found with 100 cm SSD, 75 kVp, 18 mAs, and without Cu filter, whilst the highest CNR (7.23) was achieved at 130 cm SSD, 75 kVp, 18 mAs, and without Cu filter. The lowest ED and CNR were generated at 150 cm SDD, 95 kVp, 4.5 mAs, and 0.3-mm Cu filter. All observers identified the relevant anatomical structures on all images with the lowest ED and IQ. The intra-observer (0.61–0.79) and inter-observer (0.55–0.82) ICC ranged from moderate to excellent.

Conclusion

All relevant anatomical structures were identified on the lateral lumbar spine radiographs despite using low-dose protocols. The lowest ED (0.002 mSv) was obtained with 150 cm SDD, 95 kVp, 4.5 mAs, and 0.3-mm Cu filter. Further technical and clinical studies are needed to verify these preliminary findings.

LUMBAR SPINE RADIOGRAPHY: LOWER ORGAN DOSE WITH THE USE OF PA PROJECTION

The purpose of the research was to determine the effect of the posteroanterior (PA) patient position in lumbar spine imaging on effective dose and the absorbed organ dose. The study was performed on 100 patients that were referred to the lumbar spine radiography that were divided into two equal groups of 50. Body Mass Index, Dose Area Product (DAP), exposure index (EXI), tube time-current (mAs), image field size and the source-patient distance were acquired for each patient. The entrance surface dose (ESD), the effective dose and the absorbed organ doses were calculated. There was no statistically significant difference in the BMI and EXI between the AP and PA projection. The results showed a significant reduction of ESD by 33% and the effective dose by 53% when the PA projection was used. Furthermore, there was a 64% average reduction of the absorbed organ doses to the selected organs.