Neovascularization, vascular mimicry and molecular exchange: The imaging of tumorous tissue aggressiveness based on tissue perfusion.

Angiogenesis in healthy tissue and within malignant tumors differs on many levels, which may partly be explained by vascular mimicry formation resulting in altered contrast material or different radiopharmaceuticals distributions. Failed remodulation results in changes in the molecular exchange through the capillary wall and those consequences affect the behavior of contrast agents and radiopharmaceuticals. One of the most indicative signs of malignant tissue is the increased permeability and the faster molecular exchange that occurs between the extracellular and intravascular spaces. Dynamic imaging can help to assess the changed microenvironment. The fast-distribution of molecules reflects newly developed conditions in blood-flow redistribution inside a tumor and within the affected organ during the early stages of tumor formation. Tumor development, as well as aggressiveness, can be assessed based on the change to the vascular bed development, the level of molecular exchange within the tissue, and/or indicative distribution within the organ. The study of the vascular network organization and its impact on the distribution of molecules is important to our understanding of the image pattern in several imaging methods, which in turn influences our interpretation of the findings. A hybrid imaging approach (including PET/MRI) allows the quantification of vascularization and/or its pathophysiological impressions in structural and metabolic images. It might optimize the evaluation of the pretreatment imaging, as well as help assess the effect of therapy targeting neovascularization; antiVEGF drugs and embolization-based therapies, for example.

Unicentric form of Castleman´s disease, pitfalls of diagnosis and surgical treatment.

Background: Castleman´s disease is an extremely rare heterogenous lymphoproliferative pathology with a mostly benign behavior. It is a localized or generalized lymph node enlargement of an unknown aetiology. Unicentric form is typically a slow-growing solitary mass occurring mostly in the mediastinum, abdominal cavity, retroperitoneum, pelvis and neck. Aetiology and pathogenesis of CD is probably diverse, varying in different types of this heterogeneous disease. Materials and Methods: Authors present a review of this issue based on their extensive experience. The aim is to summarize the crucial factors in the management of diagnostics and a surgical treatment of the unicentric form of Castleman´s disease. One of the key issues in the unicentric form is precise preoperative diagnostics and thus choosing the right surgical treatment strategy. Authors highlight pitfalls of the diagnosis and surgical treatment. Results: All histological types such as a hyaline vascular type, plasmacytic type and a mixed type are presented as well as options of surgical and conservative treatment. Differential diagnosis and malignant potential is discussed. Conclusion: Patients with Castleman´s disease should be treated in the high- volume centers, with a great experience in major surgical procedures as well as with preoperative imaging diagnostic techniques. Specialized pathologists and oncologists focusing on this issue are also absolutely necessary to avoid misdiagnosis. Only this complex approach can lead to excellent outcomes in patients with UCD.

Assessment of Prostate Carcinoma Aggressiveness: Relation to 68Ga-PSMA-11-PET/MRI and Gleason Score.

BACKGROUND/AIM: To test the correlation of 68Ga-PSMA-11 uptake and the expression of PSMA (prostatic specific membrane antigen) with the Gleason score, apparent diffusion coefficient (ADC) and pharmacokinetic parameters obtained from dynamic contrast agent-enhanced MRI/PET. PATIENTS AND METHODS: Forty newly diagnosed, therapy naïve patients with prostatic carcinoma (PC) (mean age of 56.7, range=34-79), who were referred for 68Ga-PSMA-11-PET/MRI for primary staging and had undergone radical prostatectomy (RAPE) were included in this prospective study. Their blood samples were tested for serum levels of prostate-specific antigen (PSA) and proPSA. The patients' prostates were evaluated using whole-mount sections, which helped determine the extent and grade of the tumor; tests were performed to determine immunohistochemical PSMA expression. RESULTS: A correlation between PSMA expression and the accumulation of 68Ga-PSMA-11 was found using the Spearman correlation coefficient (p=0.0011). A stronger correlation was found between Gleason patterns 3 or 4 and PSMA expression (p=0.06). Furthermore, the correlation of Gleason score with the overall 68Ga-PSMA-11 accumulation within the tumor or non-tumor tissue was found to be significant (p=0.0157). A significant relation was found only with the Kep elimination rate constant, which was stronger in Gleason pattern 4 than in Gleason pattern 3. A weaker correlation was found between the accumulation of 68Ga-PSMA-11 and Ktrans in Gleason pattern 4: the most significant relation being between ADCmin and Gleason pattern 3 and 4 (p=0.0074). The total size of the tumor correlated with levels of proPSA (p<0.0001), and its extra prostatic extension correlated with levels of proPSA (p<0.0001). CONCLUSION: 68Ga-PSMA-11 correlates well with the expression of PSMA. Gleason pattern 3 and 4 had a higher correlation with 68Ga-PSMA-11 levels than did Gleason pattern 5. Either no correlation, or a weak correlation, was established with pharmacokinetics.

The imaging of the hypoxic microenvironment in tumorous tissue using PET/CT and PET/MRI.

Tissue hypoxia becomes the driver of the micro-environmental transformation of the malignant tumorous tissue in majority of solid tumors. Even more, during the development of solid tumors, a large amount of nutrients is consumed due to rapid proliferation of tumor cells. The way of use of nutrients could be assessed using the probes during positron emission tomography (PET), the most frequent is the use of 18F-fluorodeoxyglucose (18F-FDG) demonstrating the turn-over of glucose exploitation in a manner of Warburg phenomenon. Even tumor cells can undergo metabolic reprogramming by changing the expression of glycolysis-related proteins, development of hypoxic condition increases glucose uptake to promote their growth. The hypoxic conditions are stimulation also the development of drug and/or radiation resistance, thus, the identification of the hypoxic tissue could play an important role in therapy planning. The process that enables use of hypoxia specific PET radiopharmaceutical starts when it enters cell by passive diffusion. Intracellularly, a model substance - 18F-fluoromisonidazol (18F-FMISO) is reduced by nitroreductase enzymes to become trapped in cells within reduced tissue oxygen partial pressure. The identification of the hypoxic tissue aids to plan the target to radiotherapy in squamous cell carcinomas of head and neck or cervical carcinoma, when 18F-FMISO-PET/CT is used as a planning procedure for a target volume, while 18F-FDG-PET/MRI is being the local and whole body staging procedure. Hypoxia imaging helps to identify the high-grade component of an astrocytic tumor before stereotactic biopsy.

Computed tomography with a full FOV photon-counting detector in a clinical setting, the first experience.

OBJECTIVES: to assess the feasibility of CT with an integrated photon-counting-detector system (PC-CT) in the body imaging of clinical patients. METHODS: 120 examinations using photon counting detector CT were evaluated in six groups: 1/ a standard-dose lung, 2/ low-dose lung, 3/ ultra-high resolution (UHR) lung, 4/ standard-dose abdominal, 5/ lower-dose abdominal, 6/ UHR abdominal CTA. All CT examinations were performed on a single-source prototype device equipped with a photon counting detector covering a 50 cm scan field of view. Standard dose examinations were performed with the use of detector element size of 0.4 mm, ultra-high-resolution examinations with the detector element size of 0.2 mm, respectively. The stability of the system during imaging was tested. The diagnostic quality of the acquired images was assessed based on the imaging of key structures and the noise level in five-point scale, the effective dose equivalent, dose length product and noise level, and also relation to body mass index and body surface area were compared with three similar groups of CT images made with energy integrating high end scanner. The parameters were evaluated using Wilcoxon test for independent samples, the independence was tested using Kruskal-Wallis test. RESULTS: When PC-CT images radiation dose is compared with the similar imaging using energy integrating CT, the PC-CT shows lower dose in ultra-high resolution mode, the dose is significantly lower (p < 0.0001), the standard dose examinations were performed with the comparable radiation doses. PC-CT exhibited the significantly higher ratio between parenchyma signal and background noise both in lung and in abdominal imaging (p < 0.0001). CONCLUSIONS: PC-CT showed imaging stability and excellent diagnostic quality at dose values that are comparable or better to the quality of energy integrating CT, the better signal and improved resolution is most important advantage of photon counting detector CT over energy integrating detector CT.

Abdominal aortic aneurysm in prostate cancer patients: the "road map" from incidental detection to advanced predictive, preventive, and personalized approach utilizing common follow-up for both pathologies.

Abdominal aortic aneurysm (AAA) is often a hidden pathological process showing no clinical symptoms. Genetic burden, smoking, male gender, age > 65 years, and white race have been identified as the main risk factors. A regular screening program has been introduced but is, as yet, unclear and is not performed in most countries. Prostate cancer is the most frequent male malignant disease in Western countries. Prostate cancer is a disease of older age with a median primary diagnosis of over 60 years. In recent years, advanced imaging methods have been established as important diagnostic tools in prostate cancer diagnostics. The incidental detection of AAA during diagnostic imaging performed due to prostate cancer diagnosis could reveal some asymptomatic aneurysms. Using our experience, the incidental detection of AAA during 18F-fluoromethylcholine PET/CT imaging, performed due to the staging, follow-up, and restaging of the prostate cancer, was reworked into a regular tool of secondary prevention within the framework of personalized medicine strategies. Experience with this type of AAA detection is demonstrated by a cohort of 500 patients who underwent 18F-fluorometylcholine PET/CT examination due to the staging or restaging of prostate cancer. A total of 28 aneurysms were detected (26 aneurysms < 50 mm, 2 aneurysms > 50 mm). In 2 cases (diameter < 50 mm), serious complications were found (penetrating aortic ulcer). The detection and monitoring of AAA in patients undergoing 18F-fluorometylcholine PET/CT due to the prostate cancer offers the possibility of a secondary prevention of AAA, patient stratification, and common follow-up for both pathologies.

Hybrid imaging PET/MR in prostatic carcinoma.

Imaging of the own prostatic tissue is being not easy using standard tumour imaging approaches, contrast enhanced computed tomography and the hybrid imaging using PET/CT with the application of the 18F-fluorodeoxyglucose. Magnetic resonance imaging is useful in detection of the patients with the elevated prostatic specific antigen (PSA) and/or with the increased index of the health prostate index (PHI). The novel imaging possibilities of the imaging is hybrid positron emission tomography - magnetic resonance imaging (PET/MR) with the application of 18F-fluorocholine (FCH), 18F-natriumfluoride (18F-NaF) or 68Ga-PSMA-11 (ligand of prostatic specific membrane antigen) in detection, staging or restaging of the prostatic carcinoma. PET/MR represents current optimal method of the staging, restaging and therapy response evaluation of prostatic carcinoma.> Keywords: prostatic carcinoma, PET/MR, 18F-fluorocholine, 18F-natriumfluoride, 68Ga-PSMA-11.

18F-Fluorocholine PET/MRI in Restaging of Prostatic Carcinoma in Relation to PSA Level and Detection of Active Disease.

AIM: To evaluate our own experience with 18F- fluoromethylcholine-(FCH)-positron-emission tomography combined with magnetic resonance imaging (PET/MRI) in restaging of patients with prostatic carcinoma and elevated serum prostate-specific antigen (PSA) level. PATIENTS AND METHODS: The analysis was performed on a sample of 100 male patients who underwent 18F-FCH-PET/MRI, with a mean age of 63.2 years (range=47-78 years). The imaging was performed using an integrated PET/MRI hybrid system after intravenous application of 18F-FCH at a dose of 1.25 MBq/kg. The number and sites of pathological accumulation of FCH related to local recurrence, nodal spread and skeletal metastases were compared to corresponding MRI findings; furthermore, the relation of PSA level and presence of FCH accumulation in tumorous tissue was assessed; finally we correlated the findings of different sites of metastatic involvement. RESULTS: In patients with a PSA level up to 2 ng/ml, accumulation in tumorous tissue of local recurrence or metastases was found in 83.33% in cases of biochemical relapse, and in patients with PSA level above 5 ng/ml in 100% of cases. In general, we found any finding explained rise of PSA level in 94% of patients. CONCLUSION: 18F-FCH-PET/MRI using an integrated system with 1,25 MBq/kg dosing of FCH is a valuable tool in evaluation of restaging in patients with prostatic carcinoma, with high detection rate even in those with a low serum PSA level.

Low-dose High-resolution 18F-FDG-PET/CT Using Time-of-flight and Point-spread Function Reconstructions: A Role in the Detection of Breast Carcinoma Axillary Lymph Node Metastases.

AIM: to evaluate the performance of N-staging assessment in clinically-proven T1 breast carcinoma by high-resolution 18F-fluorodeoxyglucose-positron-emission tomography/computed tomography (18F-FDG-PET/CT) using time-of-flight with point-spread function reconstruction. PATIENTS AND METHODS: In 30 women with clinically proven T1 breast carcinoma, imaging before surgery was performed using 18F-FDG-PET/CT. The results of PET/CT in detection of lymph node metastases were compared with those obtained after pathological investigation of axillary biopsy. A four-ring PET subsystem with image reconstruction using time-of-flight and point-spread function was used with the radiopharmaceutical dose reduction to 2.5 MBq/kg. RESULTS: Axillary lymph node metastasis was confirmed by histology in 13 patients, but metastasis was suspected based on PET/CT in 12 of those patients, the absence of metastasis was surgically confirmed in 17 women, 15 of which were suspected based on PET/CT. The sensitivity for detection of axillary lymph node metastasis was 93.3%, with a specificity of 88.2% in the whole patient cohort. Additionally, distant metastatic spread was found in 13.3% of patients. CONCLUSION: The reconstruction of PET images with time-of-flight and point-spread function enabled the improvement of diagnostic performance in N-staging of breast carcinoma, even when the dose of radiopharmaceutical was reduced to 2.5 MBq/kg.

Hybrid Imaging PET/CT with Application of 18F-Fluorothymidine in Patients with Head and Neck Carcinoma Undergoing Radiotherapy.

AIM: To introduce the possible benefits of the positron-emission tomography (PET)/computed tomography (CT) with 18F-3'-deoxy-3'-fluorothymidine (18F-FLT) in patients with orofacial carcinomas and its impact to patient management. MATERIALS AND METHODS: Thirty-six patients with orofacial squamous cell carcinomas underwent 18F-FLT-PET/CT during radiotherapy. Examinations were performed after administration of 18F-FLT (1.8 MBq/kg) including full-diagnostic CT. Analysis of the radiotherapy effect was performed with possible prospect of repeated and focused irradiation. RESULTS: Complete absence of 18F-FLT uptake was found in 20 patients, thus complete response to radiotherapy was reported. Persistence of focal 18F-FLT uptake was observed in 16 patients; in 11 patients, the measured activity was only mild. In five patients, a higher level of 18F-FLT uptake was measured and additional irradiation was performed in defined regions. Repeated follow-up proved complete regression 18F-FLT uptake. CONCLUSION: It was possible to assess the effect of radiotherapy with the use of 18F-FLT-PET/CT and findings are suitable for radiation dose-escalation planning.

PET/MRI of the thorax, abdomen and retroperitoneum: Benefits of the breathing-synchronized scanning.

Hybrid imaging using various radiopharmaceuticals is currently essential not only in detection and therapy response monitoring of tumors, but also in assessment of inflammatory or systemic diseases. Combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) is still relatively new method with great prospects of comprehensive assessment using anatomical and multiple functional information. However, benefits of PET/MRI in thorax, abdomen and retroperitoneum are not completely defined. Breathing movements affect imaging of thoracic, abdominal and retroperitoneal organs and pathological structures using PET and MRI. Fast MRI sequences are performed using breath-hold technique; however, acquisition of longer sequences and PET scanning need to be breathing-synchronized. Review article summarizes concrete PET/MRI protocols and importance of concrete MRI sequences and radiopharmaceuticals in different pathological lesions with focus on benefit of breathing-synchronized techniques.

PET/MRI: Multiparametric imaging of brain tumors.

A combination of morphological imaging of the brain with microstructural and functional imaging provides a comprehensive overview of the properties of individual tissues. While diffusion weighted imaging provides information about tissue cellularity, spectroscopic imaging allows us to evaluate the integrity of neurons and possible anaerobic glycolysis during tumor hypoxia, in addition to the presence of accelerated synthesis or degradation of cellular membranes; on the other hand, PET metabolic imaging is used to evaluate major metabolic pathways, determining the overall extent of the tumor (18F-FET, 18F-FDOPA, 18F-FCH) or the degree of differentiation (18F-FDG, 18F-FLT, 18F-FDOPA and 18F-FET). Multi-parameter analysis of tissue characteristics and determination of the phenotype of the tumor tissue is a natural advantage of PET/MRI scanning. The disadvantages are higher cost and limited availability in all centers with neuro-oncology surgery. PET/MRI scanning of brain tumors is one of the most promising indications since the earliest experiments with integrated PET/MRI imaging systems, and along with hybrid imaging of neurodegenerative diseases, represent a new direction in the development of neuroradiology on the path towards comprehensive imaging at the molecular level.

18F-FDG-PET/MRI in lymphoma patients.

The introduction of hybrid PET/MRI imaging using integrated systems into clinical practice has opened up the possibility of reducing the radiation dose from hybrid imaging by eliminating the contribution from computed tomography. Studies comparing the possibilities of PET/CT and PET/MRI imaging demonstrated it is possible to use the advantages of the high contrast resolution of magnetic resonance for soft tissue and bone marrow along with PET records in a quality comparable to PET/CT imaging. The significant feature for PET imaging in Hodgkins lymphoma is that it is a tissue with high levels of radiopharmaceutical accumulation, which decreases proportionally after successful therapeutic effect, the effect of therapy is assessed using Deauville score system on interim examinations. While the efficacy of prognosis determined using the Deauville scale in HL is widely accepted, it turns out that in DLBCL, the prognostic value of PET imaging is bound to the evaluation of subtypes. PET/MRI scanning can be used to evaluate a relapse if follicular lymphoma has already been treated, or to confirm transformation into more aggressive forms. In children and adults with Burkitt's lymphoma, negative findings after induction therapy have a high negative predictive value for relapse prognosis.

The role of 18F-FDG accumulation and arterial enhancement as biomarkers in the assessment of typing, grading and staging of hepatocellular carcinoma using 18F-FDG-PET/CT with integrated dual-phase CT angiography.

AIM: The purpose of the present study was to evaluate the possibility of detection, staging and differentiation assessment of hepatocellular carcinoma (HCC) using a combination of dual-phase computed tomography (CT)-angiography in the arterial and portal phase with positron emission tomography (PET) imaging using (18)F-fluorodeoxyglucose ((18)FDG). PATIENTS AND METHODS: From a set of 10,000 patients who underwent (18)FDG-PET/CT, we examined a total of 65 patients (52 males, 13 females; mean age=61.7 years, ranging from 35-82 years) with HCC. The imaging included CT data acquisition after intravenous application of iodinated contrast material in arterial and portal phases, allowed to obtain data in CT angiography quality. Histological diagnosis of the resection sample (21), biopsy (37) or necropsy (7), including the evaluation of the hepatocytary origin of the tumor and the grade of its differentiation, was determined in all patients. RESULTS: The most sensitive sign in the detection of HCC was the alternative presence of hypervascularity or hyperaccumulation of (18)F FDG that reached 93.8%. The high level of (18)F-FDG accumulation showed sensitivity of 84.1% and specificity of 75.0% for distinguishing between well- and poorly differentiated HCC. CONCLUSION: The combination of the dual-phase CT angiography with (18)FDG PET helps in the assessment of staging and differentiation of HCC and has an important role in treatment decision-making.

Assessment of grading in newly-diagnosed glioma using 18F-fluorothymidine PET/CT.

AIM: To evaluate the proliferation activity in gliomas using 18F-fluorothymidine (18F-FLT)-positron emission tomography/computed tomography (PET/CT). PATIENTS AND METHODS: Samples of 26 tumors were analyzed (mean age=51.6; range=26-72 years; 16 males, 10 females). All examinations were performed using a PET/CT scanner equipped with lutetium oxyorthosilicate (LSO) detectors. All data were acquired with a delay of 15 min, following intravenous application of 18F-FLT (dosed 2 MBq/kg of body weight). The PET/CT contained CT after intravenous application of iodinated contrast agent and high-resolution brain PET acquired during 15 min in one position. PET/CT was performed before confirmation of the histological diagnosis and the level of 18F-FLT accumulation was compared to the grading of the tumor evaluated using immunohistochemistry staining of Ki-67. Samples were obtained by stereotactic biopsy (5×) or surgical resection (21×). RESULTS: Five tumors of grade IV, 7 tumors of grade III and 14 tumors of grade II were found. Pre-bioptical discrimination between high-grade and low-grade tumors reached accuracy 92.3% (24/26), sensitivity 92.3% (12/13) and specificity 92.9 (13/14). The mean maximum standardized uptake value (SUVmax) in high-grade tumors was 2.23, significantly different from low-grade tumors (mean SUVmax 0.61, T=7.803, p<0.0001). CONCLUSION: 18F-FLT-PET/CT enables to estimate the proliferation activity of glioma before biopsy.

18F-FDG-PET/CT in potentially advanced renal cell carcinoma: a role in treatment decisions and prognosis estimation.

AIM: to assess the influence of positron emission tomography/computed tomography with (18)F-fluorodeoxyglucose ((18)F-FDG-PET/CT) on the treatment decision in renal cell carcinoma and to assess the prognostic value of the (18)F-FDG accumulation assessments. PATIENTS AND METHODS: Data from 60 patients were included. The cohort consisted of 43 males, 17 females, mean age 66.2 years (range=49-86 years). All patients underwent (18)F-FDG-PET/CT including two-phase CT-angiography of the kidneys. Locally advanced or generalized renal cell carcinoma was suspected in all patients. The level of the (18)F-FDG accumulation within the tumor was compared with the histological grading and the development of the disease was assessed 12 months after (18)F-FDG-PET/CT. RESULTS: Overall mortality reached 46.7%, the highest (18)F-FDG accumulation showed tumor of grade 4 (mean SUV(max)=10.7, range=5-23), the highest mortality was found for tumors exceeding SUV(max) value of 10 (mortality 62.5%). New information was brought by (18)F-FDG-PET/CT in 85% of cases. CONCLUSION: (18)F-FDG-PET/CT has the potential to estimate the patient's survival according to the (18)F-FDG accumulation measured in SUV(max). Depiction of occult metastatic disease has an emerging role in decision making regarding surgery.

Pulmonary imaging using dual-energy CT, a role of the assessment of iodine and air distribution.

AIM: The aim of the study is to present the feasibility of using dual-energy CT and the evaluation of iodine and air distribution in differentiation of pathological conditions. MATERIAL AND METHOD: We used the data of 50 CT examinations performed due to suspected pulmonary embolism with any pathological finding except consolidation of the parenchyma. The patients underwent CT angiography of the pulmonary arteries on a dual-source CT (DSCT), with the two tubes independently operated at 140 and 80 kV. By exploiting the dual-energy information, iodine distribution maps were obtained in addition to the conventional CT images which served as a marker of pulmonary perfusion. Minimum intensity projections (MinIP) were used as a marker of air content. RESULTS: By comparing the iodine distribution maps and MinIP images, it was possible to differentiate between the following templates of lung parenchyma: A--normal iodine and air distribution; B--iodine content deficit with minimal or with no redistribution of air; C--reduced iodine content and increased content of air; D--deficit of iodine content and increased content of air; E--increased iodine content and normal content of air; F--increased iodine content and reduced content of air; G--reduced perfusion and reduced content of air. The type A (five cases) was typical for the pulmonary embolism with preserved normal conditions of perfusion and ventilation. Type B (18 cases) occurred in pulmonary embolism; type C was found in case of inflammation of small respiratory airways (five cases); emphysema was typical for type D (nine cases); increased perfusion was observed in the parenchyma preserved from emphysema or preserved from embolism in cases of emphysema or pulmonary embolism; type F occurred in pulmonary interstitial edema (four cases) both with pulmonary infection; finally type G was found in interstitial lung diseases (five cases). CONCLUSION: Imaging of the pulmonary circulation by means of dual-energy CT opens the potential to study pathological changes of circulatory and pulmonary perfusion impairments, our presented work signs the important relations between iodine and air distribution which have to be thought in the interpretation of dual-energy perfusion imaging of the lungs.

Fever of unknown origin: a value of (18)F-FDG-PET/CT with integrated full diagnostic isotropic CT imaging.

AIM: The aim of presented work is to evaluate the clinical value of (18)F-FDG-PET/CT in patients with fever of unknown origin (FUO) and to compare PET/CT finding with the results of the following investigation. MATERIAL AND METHOD: 48 patients (24 men, 24 women, mean age 57.6 years with range 15-89 years) underwent (18)F-FDG-PET/CT due to the fever of unknown origin. All examinations were performed using complex PET/CT protocol combined PET and whole diagnostic contrast enhanced CT with sub-millimeter spatial resolution (except patient with history of iodine hypersensitivity or sever renal impairment). CT data contained diagnostic images reconstructed with soft tissue and high-resolution algorithm. PET/CT finding were compared with results of biopsies, immunology, microbiology or autopsy. RESULTS: The cause of FUO was explained according to the PET/CT findings and followed investigations in 44 of 48 cases-18 cases of microbial infections, nine cases of autoimmune inflammations, four cases of non-infectious granulomatous diseases, eight cases of malignancies and five cases of proved immunity disorders were found. In 46 cases, the PET/CT interpretation was correct. Only in one case, the cause was overlooked and the uptake in atherosclerotic changes of arteries was misinterpreted as vasculitis in the other. The reached sensitivity was 97% (43/44), and specificity 75% (3/4) respectively. CONCLUSION: In patients with fever of unknown origin, (18)F-FDG-PET/CT might enable the detection of its cause.

Diffusion tensor magnetic resonance imaging of glial brain tumors.

AIM: To evaluate the author's experience with the use of diffusion tensor magnetic resonance imaging (DTI) on patients with glial tumors. METHODS: A retrospective evaluation of a group of 24 patients with glial tumors was performed. There were eight patients with Grade II, eight patients with Grade III and eight patients with Grade IV tumors with a histologically proven diagnosis. All the patients underwent routine imaging including T2 weighted images, multidirectional diffusion weighted imaging (measured in 60 non-collinear directions) and T1 weighted non-enhanced and contrast enhanced images. The imaging sequence and evaluation software were produced by Massachusetts General Hospital Corporation (Boston, MA, USA). Fractional anisotropy (FA) maps were calculated in all patients. The white matter FA changes were assessed within the tumorous tissue, on the tumorous borderline and in the normally appearing white matter adjacent to the tumor. A three-dimensional model of the white matter tract was created to demonstrate the space relationship of the tumor and the capsula interna or corpus callosum in each case using the following fiber tracing parameters: FA step 0.25 and a tensor declination angle of 45 gr. An additional assessment of the tumorous tissue enhancement was performed. RESULTS: A uniform homogenous structure with sharp demargination of the Grade II tumors and the wide rim of the intermedial FA in all Grade III tumors respectively, were found during the evaluation of the FA maps. In Grade IV tumors a variable demargination was noted on the FA maps. The sensitivity and specificity for the discrimination of low- and high-grade glial tumors using FA maps was revealed to be 81% and 87% respectively. If the evaluation of the contrast enhancement was combined with the evaluation of the FA maps, both sensitivity and specificity were 100%. CONCLUSION: Although the evaluation of the fractional anisotropy maps is not sufficient for glioma grading, the combination of the contrast enhancement pattern and fractional anisotropy maps evaluation improves the possibility of distinguishing low- and high-grade glial tumors. Three-dimensional models of the white matter fibers in the corpus callosum and the internal capsule may be used in the presurgical planning.