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Musculoskeletal bone, Musculoskeletal joint, Cone beam CT, MR, Comparative studies, Cost-effectiveness, Arthritides
E. Trajcevska, C. Owen, R. Buchanan, R. B. Zwar; Melbourne/AU
Cone Beam Computed tomography (CBCT) of the wrist demonstrates more erosions in patients with a diagnosis of Rheumatoid Arthritis (RA) when compared to the current gold standard of Magnetic Resonance Imaging (MRI).
CBCT is potentially a highly valuable technique and its benefits are highlighted by the results of this retrospective audit.
results for the pisiform and the fourth and fifth metacarpal bases demonstrate marked difference in the number of erosions detected on CBCT compared to MRI.
We propose that this marked difference may be explained by the three plane,
high resolution of CBCT,
which allows assessment of the pisiform and metacarpal bases in planes that best account for their shape,
the sagittal plane.
Standard inflammatory disease MRI sequences,
on the other hand,
have limited sagittal data sets available for review (Fig. 5).
The ability of CBCT to produce three plane,
high resolution imaging is believed to also account for the overall higher number of erosions and bone involvement scores detected by the use of CBCT compared to MRI across the carpal bones (Fig. 6; Fig. 7; Fig. 8).
This exploratory study does demonstrate CBCT to have a very high sensitivity to erosive change,
what also needs to be considered is that this high sensitivity does not necessarily correlate to a high specificity.
Due to the high resolution of CBCT,
structures that are not often seen are being well delineated and there is a real potential pitfall in mistaking normal anatomical structures and variants for erosive change.
An example noted during the course of this study is the varying appearances of the metacarpal bases at the site of the intermetacarpal ligament insertion.
In some patients this was much deeper than generally recognized and inferred to be erosion.
A second potential pitfall is the interpretation of prominent nutrient foramina as erosive change (Fig. 6; Fig. 9).
For future purposes,
clear distinctions and definitions would need to be set prior to commencement,
including ensuring a clear understanding of the common sites of nutrient foramina in the carpal bones.
The results presented currently lack an associated analysis of background demographics.
This additional information would make a positive contribution to the value of the data presented and is anticipated to be addressed for future presentations.
This study is also innately limited by its retrospective nature and the small cohort of patients assessed.
It is a preliminary,
exploratory work anticipated to form the basis of a larger,
prospective research project on this topic.
In this future study we will assess plain film radiography as well as MRI and CBCT.
the findings of this retrospective audit support our proposal that CBCT is more sensitive and at least comparable to the current gold standard of MRI in the assessment of erosions in RA.
CBCT has the potential to provide a readily accessible,
cost effective and efficient imaging alternative for RA patients and subsequently reduce the strain on MRI resources and expedite treatment decisions in this population.