Dual-Energy CT Diagnosis of Gouty Arthritis in the Foot
Cleveland Clinic Abu Dhabi, UAE

By Dr. Esat Memisoglu, MD.
Jorge Guerra RT
Lynda Sullivan RT
Imaging Institute, Cleveland Clinic Abu Dhabi
Dr. Abhay Joshi, MD.
Rheumatology, Cleveland Clinic Abu Dhabi
 |  2018-01-29

History

A 49 year old male patient with past history of skin psoriasis and hyperuricemia complains of recurrent bilateral knee, ankle and foot pain. He appears to have bilateral patellofemoral osteoarthritis and has no family history of gout. There is suspicion of psoriatic arthritis versus gout. Further investigation with Dual-Energy CT (DECT) was requested to look for uric acid crystals.

Methodology

Non-contrast DECT scan of the feet was performed. Standard bone window and color rendered multi planar
reconstructed images as well as 3D volume rendering were obtained using the syngo.via DECT gout application.
Monosodium Urate (MSU) deposition was coded green in the color maps.

Diagnosis

DECT images disclosed extensive bone erosions and MSU deposition with calcifications in the periarticular soft tissues and tendons.

CT (Fig. 1a-1d).

DECT images disclose there are monosodium urate crystal (in green) deposition in the hind foot, midfoot and forefoot. Cinematic rendering and MPR images delineate foot erosions strikingly involve the right first MTP joint and left second MTP joint with juxta-articular erosions.

Findings

There are striking juxta-articular erosions involving the right first MTP joint, left second MTP joint, intertarsal and tarsometatarsal joints and right lateral malleolus demonstrating overhanging edges and sclerotic margins. 
Secondary osteoarthritic changes are seen as well. The adjacent areas of calcific soft tissue tophi demonstrate green color labeling, consistent with MSU crystal deposition. Calcification in tophi is due to coexisting calcium pyrophosphate crystals. Diffuse bilateral anterior tibial tendon thickening is also seen with multifocal green color deposits, consistent with intratendinous gout.

Comments

Gout is a painful and potentially debilitating condition. Definitive diagnosis of gout has been historically achieved with aspiration of synovial fluid from an affected joint to look for urate crystals. This however is an invasive procedure which sometimes can yield false negative results. Dual-Energy Computed Tomography (DECT) could essentially change the diagnostic approach to tophaceous and non-tophaceous gout, facilitating a rapid and accurate noninvasive examination. This can also be helpful in anatomic areas where aspiration can be challenging to perform. The chemical composition of uric acid lends itself to behave differently with varying energy x-ray spectra.
Simultaneous DECT acquisition of high and low energy datasets in a single scan and further auto post-processing with syngo.via workstation allow visualization of MSU deposition in color coded maps.

Examination Protocol

ScannerSOMATOM Definition flash  
Scan areaBoth footRotation time0.33 s
Scan modeDECT –Dual energyPitch0.7
Scan length232 mmSlice collimation64 × 0.6 mm
Scan directionCranio-caudalSlice width1 mm
Scan time5.6 sReconstruction increment0.5 mm
Tube voltage80 kv / sn 140 kvReconstruction kernelD30f
Effective mAs225 mAsSAFIRE Strength0
Dose modulationCARE Dose4DEffective dose2.98 mSv
CTDIvol10.51 mGyDLP213 mGy

 


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