Scintigraphic evaluation of the severity of inflammation of the joints with 99TCm-HIG in rheumatoid arthritis

Molecular imaging of rheumatoid arthritis: emerging markers, tools, and techniques

Early diagnosis and effective monitoring of rheumatoid arthritis (RA) are important for a positive outcome. Instant treatment often results in faster reduction of inflammation and, as a consequence, less structural damage. Anatomical imaging techniques have been in use for a long time, facilitating diagnosis and monitoring of RA. However, mere imaging of anatomical structures provides little information on the processes preceding changes in synovial tissue, cartilage, and bone. Molecular imaging might facilitate more effective diagnosis and monitoring in addition to providing new information on the disease pathogenesis. A limiting factor in the development of new molecular imaging techniques is the availability of suitable probes. Here, we review which cells and molecules can be targeted in the RA joint and discuss the advances that have been made in imaging of arthritis with a focus on such molecular targets as folate receptor, F4/80, macrophage mannose receptor, E-selectin, intercellular adhesion molecule-1, phosphatidylserine, and matrix metalloproteinases. In addition, we discuss a new tool that is being introduced in the field, namely the use of nanobodies as tracers. Finally, we describe additional molecules displaying specific features in joint inflammation and propose these as potential new molecular imaging targets, more specifically receptor activator of nuclear factor κB and its ligand, chemokine receptors, vascular cell adhesion molecule-1, αVβ₃ integrin, P2X7 receptor, suppression of tumorigenicity 2, dendritic cell-specific transmembrane protein, and osteoclast-stimulatory transmembrane protein.

Noninvasive detection of complement activation through radiologic imaging

A wealth of experimental and clinical data demonstrates that the complement system is involved in the pathogenesis of numerous inflammatory diseases. Complement activation contributes to injury in disorders that involve nearly every tissue in the body. Concerted effort has been expended in recent years to develop therapeutic complement inhibitors. Eculizumab, an inhibitory antibody to C5, was recently approved for the treatment of several diseases, and many other complement inhibitors are in clinical development. As these drugs are developed, the need for improved methods of detecting and monitoring complement activation within particular tissues will be increasingly important. We have developed a magnetic resonance imaging (MRI)-based method for noninvasive detection of complement activation. This method utilizes iron-oxide nanoparticles that are targeted to sites of complement activation with a recombinant protein that contains the C3d-binding region of complement receptor (CR) 2. Iron-oxide nanoparticles darken (negatively enhance) images obtained by T2-weighted MRI. We have demonstrated that the CR2-targeted nanoparticles bind within the kidneys of mice with lupus-like kidney disease (MRL/1pr mice), causing a decrease in the T2 signal within the kidneys. This method discriminates diseased kidneys from healthy controls, and the magnitude of the negative enhancement in the cortex of MRL/lpr mice correlates with their disease severity. This method may be useful for identifying those patients most likely to benefit from complement inhibitors and for monitoring the response of these patients to treatment. These results may open up new avenues to develop tools for the monitoring of disease progression in complement-dependent diseases.

Tc-99m HIG Scintigraphy in Detection of Active Inflammation in Ankylosing Spondylitis

OBJECTIVE

The diagnosis of active inflammation in ankylosing spondylitis (AS) is crucial for treatment to delay possible persistent deformities. There are no specific laboratory tests and imaging methods to clarify the active disease. We evaluated the value of Tc-99m human immunoglobulin (HIG) scintigraphy in detection of active inflammation.

MATERIAL AND METHODS

Twenty-nine patients were included. Tc-99m methylenediphosphonate bone (MDP) and HIG scintigraphies were performed within 2-5 day intervals. Two control groups were constituted both for MDP and HIG scintigraphies. Active inflammation was determined clinically and by serologic tests. Both scintigraphies were evaluated visually. Sacroiliac joint index values (SII) were calculated.

RESULTS

Active inflammation was considered in five (sacroiliitis in 2, sacroiliitis-spinal inflammation in 1, achilles tendinitis in 1, arthritis of coxafemoral joints in 1) patients. HIG scintigraphy demonstrated active disease in all 3 patients with active sacroiliitis. But, it was negative in the rest. The other 2 active cases were HIG negative. Right and left SII obtained from HIG scintigraphy was higher (p<0.05) in clinically active patients than inactive patients. There was not any significant difference between patients with inactive sacroiliitis and normal controls. Right and left SII obtained from bone scintigraphy was higher (p<0.05) in patient group than in control group.

CONCLUSION

Clinically inactive AS patients, behave no differently than normal controls with quantitative sacroiliac joint evaluation on HIG scintigraphy. HIG scintigraphy may be valuable for evaluation of sacroiliac joints in patients with unc

RESULTS

ertain laboratory and clinical findings.

CONFLICT OF INTEREST

None declared.

(99m)Tc-labeled-1-thio-beta-d-glucose as a new tool to temporomandibular joint inflammatory disorders diagnosis

AIM

The aim of this study was to evaluate early detection of temporomandibular joint (TMJ) inflammatory changes based on 1-thio-beta-d-glucose radiolabeled with technetium-99m.

METHOD

The method applied a TMJ inflammation model in rats followed by radiopharmaceutical synthesis, intravenous administration of (99m)Tc-1-TG and kinetic scintigraphy imaging.

RESULTS

Results show a significant difference of (99m)Tc-1-TG uptake between inflamed TMJ and the control joint. The biodistribution of (99m)Tc-1-TG by images showed the kidneys' excretion.

CONCLUSION

As conclusion, (99m)Tc-1-TG is a helpful tool in TMJ inflammatory process detection.

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.

Determination of inflammation of reflex sympathetic dystrophy at early stages with Tc-99m HIG scintigraphy: preliminary results

The pathogenesis of reflex sympathetic dystrophy (RSD) is not completely understood. However, an excessive regional inflammation, sensitization of primary somatosensory afferents, and sensitization of spinal neurons are considered to have a role in the pathogenesis of RSD. The underlying pathophysiology relating the clinical picture may help to determine the pharmacotherapeutic approach for an individual patient. Scintigraphy using radiolabelled human polyclonal non-specific immunoglobulin (HIG) has been recognized as a useful tool for the localization of inflammatory disorders. Thirty-six consecutive RSD patients associated with hemiplegia were included in this study. All the patients in this study had three phases bone scan and Tc-99m HIG scintigraphy. On admission, of 36 patients with positive bone scan, 30 had positive Tc-99m HIG scan. All the patients were symptomatic at the time of bone scanning. On the contrary, 24 out of 36 patients subsequently became asymptomatic at an 8-month re-evaluation period. Tc-99m HIG scintigraphy is a non-invasive complementary method for the determination of ongoing inflammatory reactions which also aids the clinicians to predict the response to anti-inflammatory therapy at the very early phase of RSD associated with hemiplegia. This preliminary study may be a source of inspiration for further studies with larger series and longer follow-up .

99mTc-dextran scintigraphy to detect disease activity in patients with rheumatoid arthritis

AIM

To test the applicability of Tc-dextran joint scintigraphy in the assessment of disease activity in patients with rheumatoid arthritis (RA), and to compare it with the clinical disease activity scores and laboratory parameters.

METHODS

Twenty-seven patients with RA were investigated using Tc-dextran joint scintigraphy. The images were evaluated semi-quantitatively and the regional uptakes of the radiopharmaceutical were calculated for the knee, wrist and ankle joints. The clinical and laboratory parameters were collected and fully analysed. An articular Ritchie index (a tender joint score), the number of swollen joints (Sw), the number of tender joints, the morning stiffness (h), the total Ritchie articular index (R), the visual analogue scale (VAS) and the Disease Activity Score (DAS) were determined for all patients.

RESULTS

Compared with controls, patients with RA had significantly higher regional Tc-dextran uptake in the knee, wrist and ankle joints (P=0.001). The regional Tc-dextran uptake showed no correlation with the patient's age, gender, duration of disease, number of swollen joints (Sw), number of tender joints, morning stiffness (h), VAS, total Ritchie articular index and DAS, or any laboratory parameters. There was a significant correlation between the regional Tc-dextran uptake for individual joints and the articular Ritchie index of the right and left wrist (r=0.42, P=0.03; r=0.45, P=0.02), right and left knee (r=0.66, P<0.0001; r=0.80, P<0.0001) and right and left ankle (r=0.47, P=0.014; r=0.76, P<0.0001), respectively.

CONCLUSIONS

This study demonstrates that Tc-dextran scintigraphy is a sensitive method to detect active joint inflammation and could be useful in the management of patients with RA.

Folate-targeted imaging of activated macrophages in rats with adjuvant-induced arthritis

OBJECTIVE

To determine whether overexpression of the high-affinity folate receptor (FR) on activated macrophages can be exploited to selectively target imaging agents to sites of inflammation in rats with adjuvant-induced arthritis (AIA).

METHODS

Folic acid was conjugated to a (99m)Tc chelator (the complex termed EC20), and its distribution was visualized using gamma scintigraphy in healthy rats, rats with AIA, and arthritic rats that had been depleted of macrophages. To confirm that uptake was mediated by the FR, excess folic acid competition studies were conducted, and tissue FR levels were quantitated using a radioligand binding assay. Flow cytometry was also used to investigate uptake of folate conjugates into macrophages of both arthritic and healthy rats.

RESULTS

EC20 concentrated in the arthritic extremities of diseased rats but not in the extremities of healthy rats. The intensity of images of affected tissues was greatly reduced in the presence of excess competing folic acid. The livers and spleens of arthritic animals also showed enhanced uptake of EC20 and increased levels of FR. Depletion of macrophages from arthritic animals reduced tissue FR content and concomitantly abolished uptake of EC20. In addition, macrophages isolated from livers of rats with AIA exhibited a significantly higher binding capacity for folate conjugates than did macrophages obtained from healthy rats.

CONCLUSION

Although EC20 is currently undergoing clinical evaluation for use in the imaging of ovarian carcinomas, the present results suggest that it may also be useful for assaying the participation of activated macrophages in inflammatory processes such as rheumatoid arthritis.

Technetium-99m human immunoglobulin scintigraphy in patients with adhesive capsulitis: a correlative study with bone scintigraphy

Adhesive capsulitis (AC) is a disorder that is characterized by shoulder pain and progressive limitation of both active and passive shoulder motion. Although the underlying pathological mechanisms of the disease are not well understood, the inflammatory reactions depending on the stage have been demonstrated histologically. The purpose of the study is to investigate the inflammatory changes that can be demonstrated with Tc-99m HIG in AC, and to determine the presence of correlations between scintigraphic findings and the clinical assessment. Twenty-one patients (12 females and 9 males) with a mean age of 50.57+/-8.49 were included in the study. AC was diagnosed according to recognized criteria. The planar X-ray images of the affected shoulders of all patients were normal. The patients were evaluated with the Constant Scoring System, and the functional and pain assessment parts of the American Shoulder and Elbow Surgeons' Form (ASES). Three phase bone scans and Tc-99m HIG scintigraphy were performed at least two days apart. Bone scan and Tc-99m HIG scintigraphy were evaluated visually and HIG uptake was evaluated in comparison with the contralateral normal shoulder. Bone scan demonstrated hypervascularity in 9 of the 21 patients (43%), whereas increased osteoblastic activity was detected in 19 (90%) in the affected shoulder. Tc-99m HIG uptake was positive in 12 (57%), and negative in 9 (43%) patients. All patients with increased Tc-99m HIG accumulation in the affected shoulder, also had increased osteoblastic activity on Tc-99m bone scintigraphy. A significant correlation was found between HIG uptake and constant, functional and pain scores. The difference between these scores was also statistically significant in patients with HIG positive and negative uptake. This study indicates that there is a good correlation between Tc-99m HIG scan findings and clinical scores. Tc-99m HIG accumulation in the affected shoulder may be related to continuing inflammatory reaction to AC. Tc-99m HIG scan may be a noninvasive, complementary method for demonstrating continuing inflammatory changes and may help in staging the disease.

The detection and quantitation of inflammation in the central nervous system during experimental allergic encephalomyelitis using the radiopharmaceutical 99mTc-RP128

RP128 is a novel agent which readily chelates 99mTc to form a radiopharmaceutical which binds in vivo to the tuftsin receptor located specifically on neutrophils and monocyte-macrophages, therefore removing the need for in vitro cell labelling prior to intravenous administration. We have assessed the ability of 99mTc-RP128 to detect central nervous system (CNS) inflammation in experimental allergic encephalomyelitis (EAE), an animal model of the human disease multiple sclerosis. The radiopharmaceutical was recorded at significantly increased levels in all EAE diseased CNS tissues, compared to normal and control samples, at 0.5, 1 and 3 h post-injection using a dual radioisotope technique to correct for non-extravasated tracer (P<0.05). Moreover, extravascular accumulation of the agent could be clearly demonstrated in inflammatory tissues with minimal loss of sensitivity when the secondary isotopic correction for blood volume was omitted. In addition, 99mTc-RP128 successfully monitored glucocorticoid suppression of inflammation (P<0.05), recording a typical dose-response to increasing steroid concentration. Clearly, 99mTc-RP128 can quantitatively detect CNS inflammation and assess responses to therapy indicating potential value as an imaging agent both clinically and as a research aid. Furthermore, the rapid in vivo labelling by 99mTc-RP128 of specific inflammatory cells combined with the ability to monitor the progress of anti-inflammatory therapeutics may recommend the agent for use in a variety of inflammatory conditions.