Catherine Beckers

(18)F-FDG PET imaging of rheumatoid knee synovitis correlates with dynamic magnetic resonance and sonographic assessments as well as with the serum level of metalloproteinase-3.

PurposeThe aim of this study was to assess rheumatoid arthritis (RA) synovitis with positron emission tomography (PET) and 18F-fluorodeoxyglucose (18F-FDG) in comparison with dynamic magnetic resonance imaging (MRI) and ultrasonography (US).MethodsSixteen knees in 16 patients with active RA were assessed with PET, MRI and US at baseline and 4 weeks after initiation of anti-TNF-α treatment. All studies were performed within 4 days. Visual and semi-quantitative (standardised uptake value, SUV) analyses of the synovial uptake of FDG were performed. The dynamic enhancement rate and the static enhancement were measured after i.v. gadolinium injection and the synovial thickness was measured in the medial, lateral patellar and suprapatellar recesses by US. Serum levels of C-reactive protein (CRP) and metalloproteinase-3 (MMP-3) were also measured.ResultsPET was positive in 69% of knees while MRI and US were positive in 69% and 75%. Positivity on one imaging technique was strongly associated with positivity on the other two. PET-positive knees exhibited significantly higher SUVs, higher MRI parameters and greater synovial thickness compared with PET-negative knees, whereas serum CRP and MMP-3 levels were not significantly different. SUVs were significantly correlated with all MRI parameters, with synovial thickness and with serum CRP and MMP-3 levels at baseline. Changes in SUVs after 4 weeks were also correlated with changes in MRI parameters and in serum CRP and MMP-3 levels, but not with changes in synovial thickness.Conclusion18F-FDG PET is a unique imaging technique for assessing the metabolic activity of synovitis. The PET findings are correlated with MRI and US assessments of the pannus in RA, as well as with the classical serum parameter of inflammation, CRP, and the synovium-derived parameter, serum MMP-3. Further studies are warranted to establish the place of metabolic imaging of synovitis in RA.

SPECT/CT workflow and imaging protocols

PurposeIntroducing a hybrid imaging method such as single photon emission computed tomography (SPECT)/CT greatly alters the routine in the nuclear medicine department. It requires designing new workflow processes and the revision of original scheduling process and imaging protocols. In addition, the imaging protocol should be adapted for each individual patient, so that performing CT is fully justified and the CT procedure is fully tailored to address the clinical issue. Such refinements often occur before the procedure is started but may be required at some intermediate stage of the procedure. Furthermore, SPECT/CT leads in many instances to a new partnership with the radiology department. This article presents practical advice and highlights the key clinical elements which need to be considered to help understand the workflow process of SPECT/CT and optimise imaging protocols.MethodsThe workflow process using SPECT/CT is complex in particular because of its bimodal character, the large spectrum of stakeholders, the multiplicity of their activities at various time points and the need for real-time decision-making.ResultsWith help from analytical tools developed for quality assessment, the workflow process using SPECT/CT may be separated into related, but independent steps, each with its specific human and material resources to use as inputs or outputs. This helps identify factors that could contribute to failure in routine clinical practice. At each step of the process, practical aspects to optimise imaging procedure and protocols are developed. A decision-making algorithm for justifying each CT indication as well as the appropriateness of each CT protocol is the cornerstone of routine clinical practice using SPECT/CT.ConclusionIn conclusion, implementing hybrid SPECT/CT imaging requires new ways of working. It is highly rewarding from a clinical perspective, but it also proves to be a daily challenge in terms of management.

Néphropathie tubulo-interstitielle aigue avec uvéite: à propos d'un cas

We report another case of acute interstitial nephritis with uveitis (TINU syndrome) in a 35-year-old woman. About thirty cases were described since the first ones 20 years ago. We discuss the assessment needed to reach the diagnosis. The evolution is unusually favourable with steroid therapy.

Fluoride PET-CT

[18F]fluoride was first introduced in 1962, and rapidly proposed as a radiotracer for bone exploration. The complex [18 F]NaF is injected intravenously, and it dissociates in the blood into Na + and [18 F]fluoride ion. The uptake of [18 F]fluoride results from ionic exchanges between hydroxyl groups of hydroxylapatite to form fluoroapatite and is thus directly related to bone metabolism. Both the blood flow and the osteoblastic activity influence the [18 F] fluoride accumulation, in proportions that are still discussed. [18 F]NaF-PET imaging, using appropriate modeling, can thus noninvasively assess bone metabolism. The advantage of [18 F]fluoride compared to other PET tracers is the synthesis, which is extremely simple and relatively inexpensive: [18 F]fluoride is rendered isotonic with a NaCl solution to form [18 F]NaF. Since the early sixties, the mechanism of uptake of [18 F]fluoride has been extensively studied. The accumulation of [18 F]fluoride in osteoform-ing areas of bone metastases was demonstrated in autopsy series and in rabbit experimental models. In mice, [18 F] NaF-PET clearly identified fractures as increased uptake foci up to 7 weeks after the initial trauma, human bone grafts 2 months after the implantation, and osteoblastic lesions induced by human prostate cancer cells. Lytic lesions from human prostate cancer cells (CL-1 et PC-3) were visualized either as foci of globally increased activity or, most frequently, as rim-like foci, surrounding the edge of the lesions. Quantitative uptake, measured as cps/ pixel/min, was fairly reproducible in femoral and humeral ROIs drawn on four studies over a period of 4 weeks. The relationship between [18 F]NaF uptake and bone formation was clearly established using quantitative modeling in mini pigs, showing correlations of bone blood flow and metabolic activity, with histomorphometric indices of bone formation in the normal bone tissue. Furthermore, in patients with secondary hyperparathyroidism, the [18 F] NaF incorporation rate was correlated with the plasma parathormone level and with the bone formation rate.