Correlation of signal intensity ratio on orbital MRI-TIRM and clinical activity score as a possible predictor of therapy response in Graves' orbitopathy--a pilot study at 1.5 T.

INTRODUCTION: This study seeks to describe the predictive value of the signal intensity ratio (SIR) in magnetic resonance imaging-turbo inversion recovery magnitude (MRI-TIRM) in patients with Graves' orbitopathy (GO) with regard to predictability of therapy response. METHODS: Included in this prospective pilot study were 36 consecutive patients with GO and 25 control subjects. Patients were clinically assessed according to the European Group on Graves' Orbitopathy recommendations with active GO defined by a clinical activity score (CAS) > or = 3. On magnetic resonance (MR) imaging, muscle inflammation was measured with a region of interest set within the brightest extra-ocular muscle both on coronal turbo inversion recovery magnitude (TIRM) and on fat suppressed gadolinium-enhanced T1-weighted sequences. To calculate the SIR, the measured signal intensity was set in proportion to that of the ipsilateral temporalis muscle. RESULTS: Signal intensity ratio in coronal T2-weighted TIRM sequences in either group ranged from 1.22 to 4.92 (mean 2.04) in patients with GO and from 1.18 to 2.4 (mean 1.63) in controls without GO. The observed differences were significant on the TIRM sequences (right eye p = 0.023; left eye p = 0.022), whereas, no significant differences could be detected on the T1-weighted sequences (right eye p = 0.396; left eye p = 0.498). A cut off value of SIR > 2.5 for a CAS > or = 4 to discriminate active from inactive patients was statistically calculated. CONCLUSION: T2 relaxation time is a reliable tool in detecting active GO. The difference in T2-SIR versus T1-SIR is helpful to distinguish inflammatory oedema of the extra ocular muscles from intra-orbital congestion due to reduced venous outflow.

F-18 FDG whole-body PET for the assessment of disease activity in patients with rheumatoid arthritis.

UNLABELLED: 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.

Imaging of macrophages in soft-tissue infection in rats: relationship between ultrasmall superparamagnetic iron oxide dose and MR signal characteristics.

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.

Influence of ceftriaxone treatment on FDG uptake--an in vivo [18F]-fluorodeoxyglucose imaging study in soft tissue infections in rats.

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.

18F-choline in experimental soft tissue infection assessed with autoradiography and high-resolution PET.

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.

Follow-up of women with breast cancer: comparison between MRI and FDG PET.

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.

Functional-morphologic MR imaging with ultrasmall superparamagnetic particles of iron oxide in acute and chronic soft-tissue infection: study in rats.

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.

Respiration-induced attenuation artifact at PET/CT: technical considerations.

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.

MR imaging with ultrasmall superparamagnetic iron oxide particles in experimental soft-tissue infections in rats.

PURPOSE: To investigate the feasibility of macrophage magnetic resonance (MR) imaging in rats by using an experimental soft-tissue infection model. MATERIALS AND METHODS: Thirteen rats with unilateral calf-muscle infection were imaged with a 4.7-T MR imager at an early chronic stage of infection (day 4 before contrast material injection, days 4-7 after injection). Eleven animals were imaged before and 3 and 24 hours after intravenous application of ultrasmall superparamagnetic iron oxide (USPIO), and eight animals were additionally imaged 48 hours and three animals 72 hours after USPIO application. Two infected rats served as controls. T1- and T2-weighted spin-echo and T2*-weighted gradient-echo sequences were applied. All animals were sacrificed, and histopathologic findings were correlated with findings on MR images. Electron microscopy was performed in two rats. For quantitative analysis, signal intensities on T2*-weighted images and T2 values on T2 maps were measured within regions of interest, and the temporal variation was analyzed by using the signed rank test. RESULTS: Visualization of USPIO-loaded macrophages was most sensitive with a T2*-weighted sequence. USPIO distribution pattern and quantitative analysis of T2 and T2* effects 3 hours after USPIO application were significantly different (P <.05) from those at 24 and 48 hours, reflecting the dynamic transit of the particle accumulation from the intravascular to the intracellular compartment by means of macrophage phagocytosis. Local signal intensity alterations could be correlated with iron-loaded macrophages at histopathologic examination. CONCLUSION: Activated macrophages in acute soft-tissue infection can be labeled with USPIOs and detected with MR imaging because of susceptibility effects.

Autoradiographic quantification of 18F-FDG uptake in experimental soft-tissue abscesses in rats.

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.

(18)F-FDG and (18)F-FET uptake in experimental soft tissue infection.

The aim of this study was to compare the uptake of (18)F-fluoroethyl- L-tyrosine ((18)F-FET) with that of (18)F-fluorodeoxyglucose ((18)F-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 x 10(9) CFU/ml). Four animals were intraperitoneally injected with 130-180 MBq (18)F-FDG, four with 140-170 MBq (18)F-FET and three with a mixture of 140-170 MBq (18)F-FET and 1.8 MBq (14)C-deoxyglucose. Autoradiography (10 microm 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 (18)F-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 (18)F-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 (18)F-FET in non-neoplastic inflammatory cells promises a higher specificity for the detection of tumour cells than is achieved with (18)F-FDG, since the immunological host response will not be labelled and inflammation can be excluded.

Imaging of chronic posttraumatic osteomyelitis.

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.

Chondroblastoma and clear cell chondrosarcoma: radiological and MRI characteristics with histopathological correlation.

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.