Purpose of Report: F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) can be used to image synovitis in patients with rheumatoid arthritis (RA). The aim of this study was to evaluate if a simple scoring system based on visual assessment of FDG joint uptake correlates with the clinical assessment of patients with RA undergoing antiinflammatory treatment. Materials and Methods: Seven patients with active RA underwent whole-body FDG PET and clinical assessment before and after treatment with the antitumor necrosis factor alpha antibody (infliximab). A PET total joint score, ie, the sum of all scores based on FDG uptake intensity between zero and 4 in 28 joints, was correlated with a total joint score based on the clinical disease activity in the same joints using a Spearman rank correlation. Results: The PET based total joint score was similarly high before onset as was the clinical total joint score. The decrease of FDG joint uptake in the follow-up PET scans correlated significantly with the clinical assessment. Additionally, synovial FDG uptake was found in extraarticular sites such as tendon sheaths and bursae. Conclusions: Visual assessment of FDG uptake shows a significant correlation with clinical evaluation of disease activity in patients with RA undergoing antiinflammatory treatment.

PURPOSE:To describe dose-dependent signal intensity (SI) characteristics of experimentally induced soft-tissue abscesses on 1.5-T T1- and T2*-weighted magnetic resonance (MR) images obtained 24 hours after administration of ultrasmall superparamagnetic iron oxide (USPIO) and to describe the relationship between SI and amount of USPIO uptake and macrophage iron content.MATERIALS AND METHODS:Local institutional review committee on animal care approved the experiments, which were performed according to the guidelines of the National Institutes of Health and the committee on animal research at our institution. Unilateral calf muscle abscesses were induced in 21 rats with an injection of a Staphylococcus aureus suspension. The rats were divided into three groups of seven animals each: low USPIO dose (50 micromol of iron per kilogram of body weight), high USPIO dose (150 micromol Fe/kg), and control (saline solution). All rats were imaged before and 24 hours after USPIO administration at 1.5 T (transverse T1-weighted spin-echo, T2*-weighted fast gradient-echo, and short inversion time inversion-recovery sequences). Images were analyzed quantitatively and qualitatively with regard to SI and signal pattern. Temporal variation of calculated contrast-to-noise ratios was analyzed with the Wilcoxon signed rank test. MR findings were correlated with histopathologic findings, including those of electron microscopy.RESULTS:Twenty-four hours after USPIO administration in the high-dose group, susceptibility effects were present in abscess periphery on postcontrast T2*-weighted images (P=.04), and SI enhancement was noted on postcontrast T1-weighted images within both abscess wall and abscess center (P=.04 for both). In the low-dose group, SI enhancement was noted in entire abscess on T1-weighted postcontrast images (P=.03). Neither significant SI loss (P=.09) nor susceptibility effects were detected in periphery or center of any abscess on postcontrast T2*-weighted images. There was no obvious difference in total amount of macrophages among the groups, but there was a clear difference with regard to individual iron content of iron-positive macrophages between the USPIO dose groups.CONCLUSION:At 1.5 T, SI characteristics of abscesses on T1- and T2*-weighted images obtained 24 hours after USPIO injection strongly depend on administered dose of the contrast agent. At low doses, T1 effects were stronger than T2* effects.

Our aim was to determine the influence of antibiotic treatment using ceftriaxone on [18F]-fluorodeoxyglucose (FDG) uptake in experimental soft tissue infections. PET scans were performed in two groups (treated n=4; non-treated n=4) at days 3, 5, and 6 after inoculation of the infection. Additional autoradiography was performed in four animals at day 7 and in three animals at day 11. The difference of FDG uptake on day 5 (after three days of antibiotic treatment) between both groups proved to be significant (df=6; T=2.52; p=0.045). FDG uptake determined at the other days did not reveal significant difference between the two groups. It seems to be possible that the effect of antibiotic treatment on FDG uptake is less evident than reported for therapy monitoring of cancer treatment. The change of FDG uptake over time in treated and untreated infections is complex and further in vivo experiments have to be initiated to investigate the potential value of clinical FDG PET in therapy monitoring of infection.

For each oncological tracer it is important to know the uptake in non-tumorous lesions. The purpose of this study was to measure the accumulation of fluorine-18 choline (FCH), a promising agent for the evaluation of certain tumour types, in infectious tissue. Unilateral thigh muscle abscesses were induced in five rats by intramuscular injection of 0.1 ml of a bacterial suspension ( Staphylococcus aureus, 1.2 x 10(9) CFU/ml). In all animals, FCH accumulation was measured with high-resolution positron emission tomography (PET) on day 6. Autoradiography of the abscess and ipsilateral healthy muscle was performed on day 7 (three animals) and day 11 (two animals) and correlated with histology. In addition, (18)F-fluorodeoxyglucose (FDG) PET was performed on day 5. Increased FCH uptake was noted in specific layers of the abscess wall which contained an infiltrate of mainly granulocytes on day 7 and mainly macrophages on day 11. The autoradiographic standardised uptake values in the most active part of the abscess wall were 2.99 on day 7 ( n=3) and 4.05 on day 11 ( n=2). In healthy muscle the corresponding values were 0.99 and 0.64. The abscesses were clearly visualised on the FCH and FDG PET images. In conclusion, this study demonstrated avid FCH accumulation in inflammatory tissue, which limits the specificity of FCH for tumour detection. Future studies are now needed to determine the degree of this limitation in human cancer patients.

Combined positron emission tomographic (PET)/computed tomographic (CT) scanners allow the use of CT data for attenuation correction of PET images. Eight patients with cancer underwent PET/CT scanning. Transmission scanning was performed with conventional attenuation correction and with CT scanning during maximum inspiration and normal expiration. Image quality was visually compared and fluorine 18 activities were measured in volumes of interest in the lung and myocardium. Analysis of variance for repeated measures revealed a significant decrease (P =.0001) in measured activities between PET images corrected with CT data acquired during maximum inspiration and those corrected with the conventional attenuation correction method or with CT data acquired during normal expiration. Deep inspiration during CT can result in severe deterioration in the final PET image.

PURPOSE:To investigate the use of magnetic resonance (MR) imaging enhanced with ultrasmall superparamagnetic particles of iron oxide (USPIO) to identify acute, early chronic, and late chronic abscess formation in an experimental model of soft-tissue abscess.MATERIALS AND METHODS:Experimental soft-tissue infection in 15 rats was imaged with an MR imaging unit on days 1 and 2 (acute), days 5 and 6 (early chronic), and days 8 and 9 (late chronic) after inoculation of the infectious agent. All animals were imaged without contrast enhancement and immediately and 24 hours after USPIO administration. MR and histopathologic findings were compared. The changes in relative signal intensity (SI) and in the extent and pattern of contrast enhancement (macrophage distribution) between the animal groups were analyzed. Statistical testing was performed with Kruskal-Wallis analysis of variance and the chi2 test.RESULTS:At 24 hours after USPIO administration, the relative SI of the abscess wall and the relative macrophage extent were 0.50 (0.33-0.73) and 1.03 (0.90-1.08), respectively, for acute infection; 0.11 (0.10-0.18) and 0.94 (0.93-1.01) for early chronic infection; and 0.53 (0.44-0.58) and 0.80 (0.77-0.83) for late chronic infection. The changes in enhancement pattern (P <.001), relative SI (P <.001), and relative macrophage extent (P <.05) with time were significant.CONCLUSION:The macrophage distribution pattern increases the specificity of MR findings in chronic infection and allows differentiation between areas with active inflammation and areas of reparative granulation tissue.

PURPOSE To use semiquantitative autoradiography to investigate fluorodeoxyglucose (FDG) uptake, distribution, and cellular localization in acute, early chronic, and late chronic soft-tissue infections. MATERIALS AND METHODS Unilateral calf-muscle abscesses were induced in 12 Sprague-Dawley rats by means of intramuscular inoculation of 0.1 mL of bacterial suspension (Staphylococcus aureus, 1.2 x 10(9) CFU/mL). Following injection of 130-180 MBq of fluorine 18 FDG, autoradiography of the abscess and contralateral muscle was performed (10-microm section thickness) on days 2, 5, and 9 after infection. Detailed spatial correlation of autoradiographs and histopathologic samples was performed by means of image fusion. Regions of interest were placed in the abscess wall, and measured gray values were converted to kilobecquerels per cubic centimeter according to kilobecquerels of injected activity per gram of body weight, which yielded standardized uptake values (SUVs). RESULTS Acute abscess formation was characterized by central necrosis predominantly surrounded by neutrophils and a second necrotic tissue layer that bordered neutrophil infiltrates peripherally. Areas with increased FDG uptake corresponded to cellular inflammatory infiltrates, mainly granulocytes. The corresponding SUV was calculated to be 4.08 +/- 0.65 (mean +/- SD). Early chronic phase showed mixed cellular infiltrate of granulocytes and macrophages that surrounded central necrosis with interspersed fibroblasts and only residual muscle necrosis layer within the abscess wall. FDG uptake was located where granulocytes and macrophages were present, as in acute infection (SUV = 5.32 +/- 2.30). Late chronic infection was characterized by a prominent layer of macrophages around residual central necrosis and fibroblast-enriched granulation tissue delineating the infection from muscle tissue. FDG uptake clearly coincided with the macrophages, and no substantial increase of FDG uptake was detected within fibroblast-enriched granulation tissue. The SUV was calculated as 7.97 +/- 0.21. Results of Kruskal-Wallis ANOVA demonstrated that the change in SUV with time was statistically significant (chi(2) = 7.42, P <.05). CONCLUSION The highest FDG uptake coincides with areas of inflammatory cell infiltrates, predominantly in neutrophils in the acute phase and in macrophages in the chronic phase of soft-tissue infection.

. The aim of this study was to compare MRI of the breast with 18 F-fluoro-deoxy-glucose (FDG) positron emission tomography (PET) in patients with suspected local or regional breast cancer recurrence or suspected contralateral breast cancer. Thirty-two patients (mean age 57.2 years, age range 32–76 years) with suspected loco-regional recurrence ( n =19), chest wall recurrence ( n =5), and suspected secondary tumor of the contralateral breast ( n =8) underwent MRI of the breast and FDG PET of the whole body and breast region. Cytology/histology ( n =17) or a clinical follow-up examination ( n =15) with additional imaging served as the standard of reference. A McNemar test was performed to compare PET and MRI, and kappa was determined to quantify agreement of both methods. Sensitivity was 79 and 100%, specificity was 94 and 72%, and accuracy was 88 and 84% for MRI and PET, respectively. Additional metastases outside the field of view of MRI were found in PET in 5 patients. In this study both imaging methods had comparable accuracy. The detection of distant metastases with whole-body PET imaging can influence patient management.

The aim of this study was to compare the uptake of 18F-fluoroethyl-L-tyrosine (18F-FET) with that of 18F-fluorodeoxyglucose (18F-FDG) in activated inflammatory white blood cells. Unilateral thigh muscle abscesses were induced in 11 rats by intramuscular inoculation of 0.1 ml of a bacterial suspension (S. aureus, 1.2×109 CFU/ml). Four animals were intraperitoneally injected with 130–180 MBq 18F-FDG, four with 140–170 MBq 18F-FET and three with a mixture of 140–170 MBq 18F-FET and 1.8 MBq 14C-deoxyglucose. Autoradiography (10 µm slice thickness) of the abscess and the contralateral muscle was performed and detailed spatial correlation of autoradiography and histopathology (haematoxylin-eosin staining) was obtained. Regions of interest were placed on the abscess wall and the grey values (digitised image intensities) measured were converted to kBq/cc per kBq injected activity per gram (SUV). Areas with increased 18F-FDG uptake corresponded to cellular inflammatory infiltrates mainly consisting of granulocytes. The SUV was calculated to be 4.08±0.65 (mean±SD). The uptake of 18F-FET in activated white blood cells was not increased: the SUV of the abscess wall, at 0.74±0.14, was even below that of contralateral muscle. The low uptake of 18F-FET in non-neoplastic inflammatory cells promises a higher specificity for the detection of tumour cells than is achieved with 18F-FDG, since the immunological host response will not be labelled and inflammation can be excluded.

Gross, Thomas MD; Kaim, Achim H. MD; Regazzoni, Pietro MD; Widmer, Andreas F. MD, MS Author Information

Posttraumatic osteomyelitis is frequently characterized by chronicity and recurrent activation of infection. The diagnosis is usually made on the basis of clinical, laboratory, and imaging examinations. The conventional radiograph is the basic imaging study that provides important information about skeletal deformity, bone quality, identification of metallic implants, and consolidation of the former fracture site. Other imaging techniques are required to determine the grade of activity, to define the extent of infection and to delineate small sequestra, intraosseus fistula and abscesses. A variety of more sophisticated modalities, such as modern cross-sectional imaging and radionuclide studies, are available, and the decision to choose the most suitable method can be very difficult. This review gives an overview of definition, epidemiology, and pathophysiology of chronic posttraumatic osteomyelitis and discusses the value of currently used imaging modalities.

The aim of this study was to evaluate the feasibility of three-dimensional dynamic MR hysterosalpingography (3D MR HSG) for visualization of the cavum uteri and demonstration of bilateral fallopian tube patency as an alternative to conventional hysterosalpingography. Five infertile female patients underwent 3D dynamic MR HSG prior to conventional hysterosalpingography. The MR protocol consisted of axial T1-weighted spin-echo (SE), axial/coronal T2-weighted fast SE (FSE), and 3D MR angiography sequences before, during, and after injection of a diluted gadolinium solution into the cavum uteri via a balloon catheter. Positioning of the catheter was feasible in all patients. In one patient the catheter slipped out during MRI and in one patient the catheter was placed far in the cavum uteri. In three patients catheter position was optimal at the level of the cervical canal. Evaluation of pelvic anatomy, myometrium, and ovaries was possible in all patients on the basis of T1-weighted SE and T2-weighted FSE. Three-dimensional visualization of the dilated cavum uteri was possible in four patients. In these four patients 3D MR HSG also proved bilateral fallopian tube patency which was confirmed in each patient by conventional hysterosalpingography. Three-dimensional MR HSG is feasible and further research should be done to determine if this technique can evolve into an alternative technique to conventional hysterosalpingography with the advantages of no radiation and additional visualization of the uterus wall and ovaries.

. Midgut malrotation is defined as a developmental anomaly that may cause atypical clinical symptoms in relatively common intestinal disorders due to altered anatomy. A 27-year-old woman presented with acute left-sided abdominal pain. Underlying type Ia malrotation prevented the correct clinical diagnosis of perforated, ulcerated appendicitis. Cross-sectional imaging demonstrated all the typical signs of this type of malrotation, i.e., right-sided duodenojejunal junction, left positioned cecum and ascending colon, inverted position of the superior mesenteric vessels, and hypoplasia of the uncinate process of pancreas, and surgical treatment was initiated.

Objective: To analyze and compare the radiological and magnetic resonance imaging (MRI) appearances of chondroblastoma and clear cell chondrosarcoma with histopathological correlation. Design and patients: Twelve patients with histologically proven chondroblastoma and of another four patients with clear cell chondrosarcoma were investigated by radiographs and MRI (T1-, T2-weighted sequences, intravenous gadolinium application). Additionally, the clinical and radiologic data of seven cases of clear cell chondrosarcoma without available MRI were considered. The localization, calcification of tumor matrix, periosteal reaction, cortical bone and patterns of bone destruction were analyzed according to the Lodwick radiological grading system (LRGS). The signal intensity on T1- and T2-weighted sequences, characteristics of contrast enhancement, associated bone marrow edema, soft tissue reaction and joint involvement were evaluated. Histopathological specimens were available in all cases. Results: The age of patients with chondroblastoma (range 15–59 years, mean 22.3 years) was lower than that of those with clear cell chondrosarcoma (range 19–61 years, mean 36.6 years), and the lesions were smaller in the chondroblastoma group (range 1–4 cm, mean 2.3 cm) than in patients with clear cell chondrosarcoma (range 3–7.5 cm, mean 5.2 cm). The chondroblastomas were more confined to the epiphysis (10/12) than the clear cell chondrosarcomas. All chondroblastomas and clear cell chondrosarcomas except one were classified as grade 1A or 1B according to the LRGS; one clear cell chondrosarcoma was judged as grade 2. Signal intensity of the tumors on MRI was very heterogeneous in both groups. High signal intensity on T2-weighted MR images in chondroblastoma mostly corresponded to areas with aneurysmal bone cyst components and in clear cell chondrosarcoma to islands of hyaline cartilage. Contrast enhancement occurred in all tumors and tended to be more intense with clear cell chondrosarcoma. Chondroblastoma was more frequently associated with bone marrow edema (11/12), periosteal reaction (10/12), soft tissue reaction (7/12) and synovitis (3/12). Conclusion: Chondroblastoma occurs in younger patients, is smaller than clear cell chondrosarcoma and is more confined to the epiphysis. The overlap of signal intensity and contrast enhancement patterns does not allow a reliable differentiation of the two tumors by MRI. Chondroblastomas are typically associated with bone marrow edema, periosteal reaction and soft tissue reaction.