Scintigraphic evaluation of synovial inflammation in rheumatoid arthritis with (99m)technetium-labelled human polyclonal immunoglobulin G

Use of 99mTc-anti-CD3 scintigraphy in the differential diagnosis of rheumatic diseases

OBJECTIVES

The aim of this study was to assess the use of anti-CD3, labelled with technetium-99m scintigraphy, for evaluating the joints of patients with RA, juvenile idiopathic arthritis (JIA), OA and gouty arthritis, and to establish the diagnosis parameters for each disease.

METHODS

We evaluated 2044 joints from 77 patients with rheumatic diseases. The clinical evaluation consisted of laboratory assays; examination for joint inflammation (pain and/or oedema); and for patients with RA, the disease activity score of 28 joints. To evaluate the sensitivity and specificity of 99mTc-anti-CD3 in detecting disease activity, patients received an injection of the radiopharmaceutical compound 99mTc-anti-CD3, and underwent a scintigraphy scan 1 h later. Scanning was repeated 3 h later. As a control, after 2 days, the patient was injected with 99mTc-non-specific human immunoglobulins, and scintigraphy scanning performed at 1 and 3 h after the injection. The intensity of uptake and the pattern of activity were defined, and Spearman's correlation and analysis of variance used for statistical evaluation.

RESULTS

Diagnosis criteria were established for 99mTc-anti-CD3 uptake in different diseases. RA and JIA showed joint uptake with progressive increase in late images. Gouty arthritis showed joint uptake with decrease during the late images. Joint uptake was low or absent in patients with OA, although when present the joint uptake decreased during the examination.

CONCLUSION

99mTc-anti-CD3 scintigraphy is a useful method in the differential diagnosis of rheumatic diseases.

Molecular Imaging: Integration of Molecular Imaging into the Musculoskeletal Imaging Practice

Chronic musculoskeletal diseases such as arthritis, malignancy, and chronic injury and/or inflammation, all of which may produce chronic musculoskeletal pain, often pose challenges for current clinical imaging methods. The ability to distinguish an acute flare from chronic changes in rheumatoid arthritis, to survey early articular cartilage breakdown, to distinguish sarcomatous recurrence from posttherapeutic inflammation, and to directly identify generators of chronic pain are a few examples of current diagnostic limitations. There is hope that a growing field known as molecular imaging will provide solutions to these diagnostic puzzles. These techniques aim to depict, noninvasively, specific abnormal cellular, molecular, and physiologic events associated with these and other diseases. For example, the presence and mobilization of specific cell populations can be monitored with molecular imaging. Cellular metabolism, stress, and apoptosis can also be followed. Furthermore, disease-specific molecules can be targeted, and particular gene-related events can be assayed in living subjects. Relatively recent molecular and cellular imaging protocols confirm important advances in imaging technology, engineering, chemistry, molecular biology, and genetics that have coalesced into a multidisciplinary and multimodality effort. Molecular probes are currently being developed not only for radionuclide-based techniques but also for magnetic resonance (MR) imaging, MR spectroscopy, ultrasonography, and the emerging field of optical imaging. Furthermore, molecular imaging is facilitating the development of molecular therapies and gene therapy, because molecular imaging makes it possible to noninvasively track and monitor targeted molecular therapies. Implementation of molecular imaging procedures will be essential to a clinical imaging practice. With this in mind, the goal of the following discussion is to promote a better understanding of how such procedures may help address specific musculoskeletal issues, both now and in the years ahead.

High-resolution multipinhole single-photon-emission computed tomography in experimental and human arthritis

OBJECTIVE

To image inflammatory arthritic lesions in experimental arthritis and in patients with arthritis, using a newly developed high-resolution multipinhole single-photon-emission computed tomography (MPH-SPECT) technique.

METHODS

Six interleukin-1 receptor antagonist-deficient mice with arthritis of the front and back paws and 2 control BALB/c mice were imaged with MPH-SPECT and scored macroscopically for arthritis. SPECT imaging was performed with a conventional gamma camera upgraded with a pyramidal lead collimator affixed with MPH apertures. All images were reconstructed, and uptake in the paws was quantified in counts/weight and injected activity. To transfer the imaging technique to humans we examined the clinically dominant hand of 6 individuals (3 with established rheumatoid arthritis [RA], 1 with early RA, 1 with osteoarthritis, and 1 healthy control).

RESULTS

MPH-SPECT images were high-resolution 3-dimensional tomographic images, which allowed exact localization and quantifiable observation of increased bone metabolism. MPH-SPECT counts of inflamed joints in mice correlated with macroscopic scoring and histologic joint analysis postmortem. In humans, MPH-SPECT images depicted a detailed visualization of tracer accumulation in bony structures of hand and finger joints, and were also capable of imaging increased bone metabolism that had appeared normal with other imaging modalities, e.g., magnetic resonance imaging.

CONCLUSION

The MPH-SPECT technique represents a new diagnostic tool in the detection of bone pathology in small-animal arthritis research. Compared with macroscopic scoring, this new method provides a more objective and higher-precision quantifiable measurement of bone reaction, allowing visualization of inflammatory processes of the whole skeleton in vivo. These results suggest that MPH-SPECT may be useful as a diagnostic instrument for monitoring experimental arthritis, with further potential for use in human studies of RA.