Clinical value of new SPECT CT nuclear medicine technology

By Dr Adam Tonakie, Radiologist and Nuclear Medicine specialist.

South Coast Radiology now offers identical nuclear medicine systems at both Pindara and John Flynn hospital imaging departments – the state-of-the-art GE Discovery 670 SPECT CT scanners, which offer unparalleled nuclear medicine image quality.  The new technology allows our nuclear medicine specialists to provide more accurate diagnoses leading to better outcomes for patients.

Essentially the technology blends two complementary medical imaging modalities on one scanner providing two types of medical images with one machine – Nuclear Medicine single photon emission computed tomography (SPECT) and traditional computed tomography (CT) - at the same time.

The SPECT component images the biological function of the body and often identifies disease before anatomical changes take place – it has very high sensitivity, but poor specificity.   The CT scan increases the specificity – identifying the anatomical structure involved, and when the pathology has caused changes in the organ/bone involved, it aids characterisation, and diagnosis.  Therefore, by combining these two modalities, a SPECT CT scan enables clinicians to more accurately identify and diagnose disease, and therefore plan patients’ management appropriately.  A good example is the patient with low back pain and multilevel disc and facet joint degeneration.  The bone scan SPECT component is used to identify any active arthropathy, the fused SPECT/CT images defines the actual level, and guides therapeutic steroid injection. 

The image data is presented as fused images ( SPECT + CT images) which is more easily understood and also helpful when trying to explain what the images mean to patients. Another benefit of the new scanner is a significant reduction in scanning times, which increases patient compliance, and decreases artefact from movement.   The low dose, shorter scan time improves image quality and also reduces imaging errors caused by patients who may have difficulty keeping still for long periods of time.

The CT scan is also used to eliminate attenuation artefact in myocardial perfusion studies, and this increases the specificity of these examinations.

Case study of SPECT CT for investigation of back pain

72 year old male patient presented for a nuclear medicine bones scan, post GP referral for investigation of exercise limiting back pain.  Prior CT imaging demonstrated degenerative changes at every lumbar level pain generator.

SPECT CT Bone scan was performed with images below of the lumbar spine demonstrating a facet joint arthropathy at L3/L4 only. Patient was reviewed by GP post bone scan findings and was referred back to SCR for a CT guided bilateral facet joint injections. These were performed with nil complications and patient gained 90% pain relief at 7 days post injection.

Image A) axial slice CT scan

Image B) axial fused SPECT + CT image showing active bilateral facet joint arthropathy

Image C) low does CT fluoro images of bilateral facet joint injections showing the needle placement at the edge of the facet joint.