[New trends in functional medical imaging: quantitative methods]. / Újdonságok és új lehetoségek a funkcionális képalkotásban: kvantitatív módszerek.

Deriving quantitative measures from the medical imaging methods is a key issue for the optimal oncologic therapy, when the anatomical abnormalities and changes of the metabolic state of the tissues need to be characterized. In order to improve the effectiveness of the therapy, the results of medical imaging procedures should be comparable after two or more consecutive scans. There are several tomographic imaging applications (CT, MRI, SPECT and PET), but in this work we will focus on the quantitative capability of PET, because this method provides the most versatile possibilities for quantifying the resulting images.

[The role of FDG PET/CT for detecting the cause of fever of unknown origin in a clinical case]. / A (18)F-fluoro-dezoxiglükóz pozitronemissziós tomográfia/komputertomográfia szerepe az ismeretlen eredetu láz felderítésében, egy eset kapcsán.

The fever of unknown origin from time to time constitutes a serious clinical problem and nearly all diagnostic methods are involved to discover urgently its cause. According to literature data (18)F-fluoro-deoxyglucose PET/CT was successful in 25-70% of cases even in patients without any positive findings with conventional diagnostic techniques. The Hungarian National Health Fund does not include fever of unknown origin in the list of reimbursed (18)F-fluoro-deoxyglucose PET/CT indications. The authors try to illustrate the clinical problem with this case report. Fever of unknown origin persisted in a patient for a year, but conventional diagnostic procedures were unsuccessful to find the cause of the fever. Finally, (18)F-fluoro-deoxyglucose PET/CT indicated a metabolically active focus between the pancreas tail and the spleen. After a long-lasting antibiotic therapy the patient became symptomfree.

[18F-FDG PET/CT in lymphomas: assessment difficulties due to illness characteristics, and comparison with literature data]. / 18F-FDG PET/CT lymphomákban: a betegség jellegébõl adódó értékelési nehézségek és összevetés az irodalmi adatokkal.

Fluor-18-deoxy-glucose (18F-FDG or FDG) positron emission tomography - computer tomography (PET/CT) has recently become integrated into the clinical routine of patients with lymphoma in Hungary. The basic condition of risk-adapted treatment of these patients is the exact staging and early objective evaluation of the effectiveness of therapy. Between 1 May 2007 and 31 October 2010, 1862 18F-FDG PET/CT examinations were conducted for lymphoma patients at the PET/CT Center in Debrecen. This is more than 15% of the total examined patient population, and this rate shows a slight increase with each year. Based on the experience obtained from lymphoma patients by routine metabolic PET/CT scans we analyzed the difficulties of the evaluation in different time frames of patients' management. It is well known that FDG uptake of lymphomas depends on multiple factors. Although most histological subtypes are associated with uptake of FDG, the intensity of the tracer uptake is different. Different intensity of FDG uptake of the same type of lymphoma following therapeutic procedures might cause difficulties in the evaluation of the scans ensuring that primary staging by PET/CT is highly required for precise measurement and reliable comparison of data. Extranodal involvement was detected in ~40% of the patients with variable rate of prevalence. Extranodal involvement is associated with great diversity and in most cases it is not characteristic of the illness and might appear in different forms and in any organs. Additionally, because accompanying disease may produce false positive results, detailed clinical data and precise case history is highly required.

Population based ranking of frameless CT-MRI registration methods.

BACKGROUND: Clinical practice often requires simultaneous information obtained by two different imaging modalities. Registration algorithms are commonly used for this purpose. Automated procedures are very helpful in cases when the same kind of registration has to be performed on images of a high number of subjects. Radiotherapists would prefer to use the best automated method to assist therapy planning, however there are not accepted procedures for ranking the different registration algorithms. PURPOSE: We were interested in developing a method to measure the population level performance of CT-MRI registration algorithms by a parameter of values in the [0,1] interval. MATERIALS AND METHODS: Pairs of CT and MRI images were collected from 1051 subjects. Results of an automated registration were corrected manually until a radiologist and a neurosurgeon expert both accepted the result as good. This way 1051 registered MRI images were produced by the same pair of experts to be used as gold standards for the evaluation of the performance of other registration algorithms. Pearson correlation coefficient, mutual information, normalized mutual information, Kullback-Leibler divergence, L1 norm and square L2 norm (dis)similarity measures were tested for sensitivity to indicate the extent of (dis)similarity of a pair of individual mismatched images. RESULTS: The square Hellinger distance proved suitable to grade the performance of registration algorithms at population level providing the developers with a valuable tool to rank algorithms. CONCLUSIONS: The developed procedure provides an objective method to find the registration algorithm performing the best on the population level out of newly constructed or available preselected ones.