[The clinical impact of amino acid positron emission tomography measurements in the treatment of primary malignant brain tumors]

Despite the large-scale diagnostic and therapeutic progress of recent years, the heterogeneity and therapeutic management of adult primary malignant brain tumors pose a significant challenge to the attending physician. Based on the research and experience accumulated over the past two decades, the range of patients who can benefit the most from complex oncology treatment has been outlined, and it has been confirmed that a reliable complex diagnostic background is essential for adequate therapeutic management. However, after some necessary therapeutic steps, the "gold standard" magnetic resonance imaging (MRI) is not always able to accurately assess and diagnose post-therapeutic conditions. Thanks to the collaboration of the nuclear medicine and neuro-oncology professions, more and more types of radiotracer compounds are now available in more and more centers, including amino acid ligands and thus, positron emission tomography (PET) examinations with the radiopharmaceutical O-(2-[18F]fluoroethyl)-L-tyrosine. The metabolic state, as a kind of fourth dimension of imaging, is an essential part of adequate modern diagnostics. Combining advanced MRI techniques and PET-based (PET/CT, PET/MRI) measurements with a suitable tracer can place therapeutic decisions on a reliable basis. We present the clinical significance of amino acid-PET-based hybrid nuclear medicine imaging studies in the therapeutic management of these patients by reviewing the literature data on the practice of the method in Hungary and abroad and presenting the results of our retrospective summary research so far. Orv Hetil. 2023; 164(32): 1247-1255.

Therapy Defining at Initial Diagnosis of Primary Brain Tumor-The Role of 18F-FET PET/CT and MRI

Primary malignant brain tumors are heterogeneous and infrequent neoplasms. Their classification, therapeutic regimen and prognosis have undergone significant development requiring the innovation of an imaging diagnostic. The performance of enhanced magnetic resonance imaging depends on blood-brain barrier function. Several studies have demonstrated the advantages of static and dynamic amino acid PET/CT providing accurate metabolic status in the neurooncological setting. The aim of our single-center retrospective study was to test the primary diagnostic role of amino acid PET/CT compared to enhanced MRI. Emphasis was placed on cases prior to intervention, therefore, a certain natural bias was inevitable. In our analysis for newly found brain tumors ¹⁸F-FET PET/CT outperformed contrast MRI and PWI in terms of sensitivity and negative predictive value (100% vs. 52.9% and 36.36%; 100% vs. 38.46% and 41.67%), in terms of positive predictive value their performance was roughly the same (84.21 % vs. 90% and 100%), whereas regarding specificity contrast MRI and PWI were superior (40% vs. 83.33% and 100%). Based on these results the superiority of ¹⁸F-FET PET/CT seems to present incremental value during the initial diagnosis. In the case of non-enhancing tumors, it should always be suggested as a therapy-determining test.

Use of Diagnostic Imaging Modalities in Modern Screening, Diagnostics and Management of Breast Tumours 1st Central-Eastern European Professional Consensus Statement on Breast Cancer

Breast radiologists and nuclear medicine specialists updated their previous recommendation/guidance at the 4th Hungarian Breast Cancer Consensus Conference in Kecskemét. A recommendation is hereby made that breast tumours should be screened, diagnosed and treated according to these guidelines. These professional guidelines include the latest technical developments and research findings, including the role of imaging methods in therapy and follow-up. It includes details on domestic development proposals and also addresses related areas (forensic medicine, media, regulations, reimbursement). The entire material has been agreed with the related medical disciplines.

[Nuclear medicine techniques in the diagnosis of pancreatic cancer]

The prognosis of pancreatic cancer is closely related to the histological origin of the tumors and the stage of the disease. As recognition is advanced in most cases, treatment options are limited. The development of nuclear medicine hybrid techniques (SPECT/CT, PET/CT, PET/MRI) and new therapies plays an important role in the recognition and treatment of pancreatic tumors. These measurements are useful in characterizing biological behavior, based on which tumors can be recognized at an early stage, promote the treatment, the selection of optimal therapies (e.g., targeted therapies). The authors discuss the role of nuclear medicine techniques in the management of patients suffering from pancreatic tumors.

The role of hybrid FDG-PET/MRI on decision-making in presurgical evaluation of drug-resistant epilepsy

Background

When MRI fails to detect a potentially epileptogenic lesion, the chance of a favorable outcome after epilepsy surgery becomes significantly lower (from 60 to 90% to 20–65%). Hybrid FDG-PET/MRI may provide additional information for identifying the epileptogenic zone. We aimed to investigate the possible effect of the introduction of hybrid FDG-PET/MRI into the algorithm of the decision-making in both lesional and non-lesional drug-resistant epileptic patients.

Methods

In a prospective study of patients suffering from drug-resistant focal epilepsy, 30 nonlesional and 30 lesional cases with discordant presurgical results were evaluated using hybrid FDG-PET/MRI.

Results

The hybrid imaging revealed morphological lesion in 18 patients and glucose hypometabolism in 29 patients within the nonlesional group. In the MRI positive group, 4 patients were found to be nonlesional, and in 9 patients at least one more epileptogenic lesion was discovered, while in another 17 cases the original lesion was confirmed by means of hybrid FDG-PET/MRI. As to the therapeutic decision-making, these results helped to indicate resective surgery instead of intracranial EEG (iEEG) monitoring in 2 cases, to avoid any further invasive diagnostic procedures in 7 patients, and to refer 21 patients for iEEG in the nonlesional group. Hybrid FDG-PET/MRI has also significantly changed the original therapeutic plans in the lesional group. Prior to the hybrid imaging, a resective surgery was considered in 3 patients, and iEEG was planned in 27 patients. However, 3 patients became eligible for resective surgery, 6 patients proved to be inoperable instead of iEEG, and 18 cases remained candidates for iEEG due to the hybrid FDG-PET/MRI. Two patients remained candidates for resective surgery and one patient became not eligible for any further invasive intervention.

Conclusions

The results of hybrid FDG-PET/MRI significantly altered the original plans in 19 of 60 cases. The introduction of hybrid FDG-PET/MRI into the presurgical evaluation process had a potential modifying effect on clinical decision-making.

Trial registration

Trial registry: Scientific Research Ethics Committee of the Medical Research Council of Hungary. Trial registration number: 008899/2016/OTIG. Date of registration: 08 February 2016.

[Radiology/Nuclear Medicine Group. Use of imaging methods in the current screening, diagnostics and treatment of breast cancer - Professional guidelines. 4th Breast Cancer Consensus Conference]

Breast radiologists and nuclear medicine specialists have updated their previous recommendation/guidance at the 4th Hungarian Breast Cancer Consensus Conference. They suggest to adopt this actual protocol for the screening, diagnostics and treatment of breast tumors from now on. This recommendation includes the description of the newest technologies, the recent results of scientific research, as well as the role of imaging methods in the therapeutic processes and the followup. Suggestions for improvement of the current Hungarian practice and other related issues as forensic medicine, media connections, regulations, and reimbursement are also detailed. The guidance has been in agreement with the related medical disciplines.

[Oncology PET radiopharmaceuticals in clinic and research in 2020]

"PET based" molecular imaging has significant role in personalized medicine. New radiopharmaceuticals are continuously introduced into the daily practice of detecting diseases and assessing the effectiveness of therapy. In recent years theragnostic applications have come to the forefront of radiopharmaceutical development. This article discusses, among others, radiopharmaceuticals labelled with 18F and 68Ga isotopes required for the diagnosis of neuroendocrine and prostate tumours, furthermore the inhibitors of the fibroblast activation protein. The increasing variety of metallic radioisotopes (44Sc, 64Cu, 52Mn, 86Y, 89Zr) will help meet the need for new biomarkers and will greatly facilitate the introduction of the new generation of PET radiopharmaceuticals.

[PET-based measurements in oncology: PET/CT and PET/MRI applications]

The introduction and clinical application of 2-deoxy-2-[fluorine- 18]fluoro-D-glucose (18F-FDG) Positron Emission Tomography/Computed Tomography (PET/CT) dates back more than two decades. The method has resulted in a paradigm shift in many areas of oncology and its acceptance has grown very rapidly. The state-of-the-art PET-based hybrid measurement, PET/Magnetic Resonance Imaging (PET/ MRI), has been available since 2011 and offers additional invaluable opportunities. Various recommendations have been made to provide guidance for the standardization and harmonization of PET/MRI protocols and to support the application of the method in clinical use and research. Hopefully, with well-defined professional indications, similar to PET/CT applications, the PET/MRI technology, still somewhat mystified today, will soon become part of our everyday lives.

[Molecular imaging of Alzheimer's disease]

The ever-growing average age of the society significantly increases the occurrence of Alzheimer's disease. The increased prevalence represents considerable social and economic burden, which urges the development of diagnostic and therapeutic methods in the field. The most common cause of dementia is Alzheimer's disease, the typical histopathological abnormality of which are well known. The detection of functional changes results in the early diagnosis of the disease, which precedes the morphological changes by years. Positron-emission tomography plays an important role in the demonstration of metabolic changes. The glucose metabolic pattern differs significantly in each clinical form of dementia. The most important β-amyloid-binding radiopharmaceuticals that should be highlighted are [¹¹C]Pittsburgh compound B that is widely used in the research and [¹⁸F]florbetapir that is commonly approved in diagnostics. Tracers visualising neurofibrillary tangles consisting of tau protein appeared most recently. The development continues; newer and newer radiopharmaceuticals appear. These tracers play an important role in both the research and the diagnostics. Orv Hetil. 2019; 160(33): 1289-1295.

A PET/MR képalkotás magyarországi klinikai alkalmazásának lehetőségei, első tapasztalatai

Abstract:

Hungary’s first and still only multimodality PET/MR device is operating in the Health Center of Kaposvár University. The aim of our review article is to present the current Hungarian PET/MR imaging application opportunities, our available initial experiences with this novel multimodality imaging technique in malignant and non-malignant diseases and further potential targeted clinical fields of use are also addressed. Orv Hetil. 2018; 159(34): 1375–1384.

[Use of imaging methods in the current screening, diagnostics and treatment of breast cancer - Professional guidelines. 3rd Breast Cancer Consensus Meeting]

Breast radiologists and nuclear medical specialists have refreshed their previous statement text during the 3rd Hungarian Breast Cancer Consensus Meeting. They suggest taking into consideration this actual protocol for the screening, diagnostics and treatment of breast tumors, from now on. This recommendation includes the description of the newest technologies, the recent results of scientific research, as well as the role of imaging methods in the therapeutic processes and the follow-up. Suggestions for improvement of the Hungarian current practice and other related issues as forensic medicine, media connections, regulations, and reimbursement are also detailed. The statement text has been cross-checked with the related medical disciplines.

[New trends and novel possibilities in the management of oncologic patients: clinical uses of PET/MRI]

The most recent multimodality technique, the hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) combines two very different technologies, which is a great result of human creativity. The combined PET/MRI has significant potentials in clinical oncology providing new perspectives of functional and anatomical information. PET/MRI offers simultaneous measurements of multifunctional data such as PET mapping by different specific tracers or MRI morphologic, MR molecular (MR spectroscopy, MRS), or MR functional (fMR) information of a living system.

[New challenges and perspectives in nuclear medicine imaging]

Hybrid positron emission tomography/computer tomography (PET/CT) and single photon emission computer tomography/computer tomography (SPECT/CT) have resulted in significant advances both in medical research and routine clinical use. The most recent multimodality system that combines PET and magnetic resonance imaging (MRI) offers new potentials unthinkable before. The hybrid techniques allow obtaining simultaneous morphologic, functional, and molecular information of a living system. The proper use of multimodality imaging is of high importance as they facilitate both basic medical research and clinical practice.

[Clinical application of 18F-FDG PET/CT in the treatment of sarcomas]

[18F]-Fluoro-deoxyglucose positron emission tomography / computer tomography (18F-FDG PET/CT) is able to detect and assess the abnormal metabolism, enabling visualization and quantification in vivo with integration into CT anatomic information. The clinical usefulness of FDG PET/CT in the management of patients with sarcomas has been assessed by numerous investigators. Sarcomas are solid malignant tumors with distinct clinical and pathological features. Effective management of patients with sarcoma requires accurate diagnosis and staging. The authors discuss the major indications of PET/CT on the basis of literature data for diagnosis, staging, guidance of biopsy and monitoring response to therapy in both primary bone and soft tissue tumors. The consistent use of PET molecular imaging methods is of high importance in characterizing and understanding sarcoma behavior in clinical practice.

[Clinical use of 18F-FDG PET/CT in colorectal carcinoma]

Modern imaging techniques have an important role in the diagnostic procedures of malignancies, and assessing response to therapy. The 18F-FDG PET/CT revolutionized the evaluation of colorectal cancer in terms of preoperative staging and monitoring of recurrence. Conventional imaging techniques have limitations in early assessment of response to therapy. 18F-FDG PET has been shown to allow earlier treatment monitoring, because the metabolic change appears before any anatomic change occurs. The Response Evaluation Criteria in Solid Tumours (RECIST) are widely applied, but they have some limitations. There are new international guidelines for treatment response assessment using PET/CT in solid tumours. The authors review indications and the role of hybrid PET/CT in colorectal cancer.

[Why is PET/CT essential in urooncology?]

The wide use of molecular positron emission tomography/computed tomography (PET/CT) imaging in the tumor diagnostics has been playing an important role recently. The clinical role of hybrid imaging (PET/CT, single photon ECT/CT (SPECT/CT)) is growing continuously due to the simultaneous imaging of anatomy and function. Regarding oncology the role of (18)F-fluorodeoxyglucose ((18)F-FDG) PET is proved in several clinical questions, including urooncology. Urologic cancers are associated with low or slightly significant uptake of FDG, due to their more benign behaviour. However, alternative PET tracers have been developed which show promising clinical results and hopefully, in the near future the combination of different tracers are awaited. Additionally, in the future the use of multiparametric measurements, multitracer techniques, and the multimodal PET/magnetic resonance imaging (PET/MRI) technology is going to have a crucial clinical role.

[The role of PET-CT in detecting unknown primary tumour in patients with cervical lymph node metastases]

PET-CT examination was conducted with 440 patients treated at the Department of Head and Neck Surgery, National Institute of Oncology, Budapest, between January 1, 2006 and December 31, 2010. Out of them 77 patients were selected with whom no examination of any sort (physical, pan-endoscopy, or any of the conventional imaging techniques) succeeded in identifying the primary tumour. In each case the primary examination (aspiration cytology and histology) verified cervical metastases, most of them being squamous cell carcinoma. The significance of PET-CT was retrospectively evaluated in cases of unknown primary tumour with verified cervical metastases. We tested the sensitivity of PET-CT in detection of the primary malignant tumour, and possible distant metastases or a second primary in order to plan an optimal treatment schedule for the patient. Patients with whom the examinations specified in the treatment protocol (physical examination, pan-endoscopy, conventional imaging, biopsy) had failed to diagnose the primary tumour were referred to PET-CT. In each case 18F-FDG tracer was used. In 21/77 patients (27%), the PET-CT yielded unequivocal evidence for the primary tumour confirmed by histology, as well. With 10 others (13%), the precarious diagnoses by various imaging techniques were confirmed by the PET-CT. False positive findings with PET-CT that were not verified either by histology or control examination tests occurred but in 10 patients (13%). Concerning the primary tumour, false negative result was obtained only with 3 patients (4%). It should be noted that their retrospective evaluation proved diagnostic errors, the primary tumours were visible in all the scans. With 33 patients (43%) PET-CT furnished no additional information compared to the previous examinations. In 10 patients, asymptomatic distant metastases and in 3 patients synchronous tumours were diagnosed. We also acknowledge that the significance of PET-CT using 18F-FDG is unquestionable in the detection of unknown primary tumours. It is strongly recommended to re-include the detection of unknown primaries in the approved national indication list of PET-CT. (Note, until January 1, 2008 it had been included!) PET-CT is capable of detecting a primary tumour, after all unsuccessful diagnostic examinations till then, in 25-40% of the cases. One cannot disregard the role and significance of PET-CT in the detection of asymptomatic synchronous tumours, or distant metastases. These benefits make PET-CT a suitable tool for the refinement of individually tailored treatment strategies leading to better therapeutic results and more favourable cost-benefit ratio.

[Role of PET/CT in diagnosis and treatment of breast cancer -- review of present knowledge and perspectives for future research]

Positron emission tomography (PET) has revolutionized the diagnostic opportunities of malignances, however, it has still a controversial role at some conditions in the management of breast cancer. The article compares PET alone and PET/CT. We review the latest trends of using PET or PET/CT for diagnosis, staging, evaluation of the primary tumor and regional lymph node status, as well as early detection of recurrence and distant lesions. PET/CT provides new methods of assessment of early chemo/endocrine therapy response of locally advanced breast cancer. We discuss the development of new radiotracers and their value in predicting treatment response, identifying tumor subtypes and finding new therapeutic targets by them.

[Modern diagnostics in breast cancer: nuclear medicine techniques]

The authors discuss the role of nuclear medicine techniques in the modern diagnostics of breast cancer, including the methods currently used in Hungary and the future possibilities.

[18F-FDG PET/CT in lymphomas: assessment difficulties due to illness characteristics, and comparison with literature data]

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.

[The advantage of Positron Emission Tomography combined with Computer Tomography (PET-CT) in the diagnosis of lung cancer (experience with 408 patients)]

The authors analyzed the results of PET-CT scans made with oncological indications among 408 patients. One hundred and fifty-four PET-CTs were done to characterize pulmonary foci, after which in 59 cases lung surgery was performed. The method's sensitivity in respect to malignancy was 100%, specificity was 56%. Staging of affected lymph nodes resulted in 17 mediastinoscopies and 54 thoracotomies. In the former indications PET-CT-positive lymph nodes always need cytologic/histologic verification. M-staging done with PET-CT was performed in 141 cases, mediastinal restaging of patients having received neoadjuvant chemotherapy was done in 24 cases. The latter indications we consider superfluous because of the diagnostic inaccuracy of PET-CT. In 175 cases we analyzed the frequently determining factor of the PET-CT scan in the indication of lung surgery. The authors wish to share their experience for the better use of this method and to accelerate the inclusion of PET-CT into the diagnostic protocol.

Optimization of semi-quantification in metabolic PET studies with 18F-fluorodeoxyglucose and 11C-methionine in the determination of malignancy of gliomas

The treatment of the glioma patient depends on the nature of the lesion and on the aggressiveness of the tumor. The management of gliomas continues to be a challenging task, because morphological neuroimaging techniques do not always differentiate them from nontumoral lesions or high grade tumors from low grade lesions. Positron Emission Tomography (PET) offers the possibility of the in vivo quantitative characterization of brain tumors. Despite decades of useful application of PET in the clinical monitoring of gliomas, no consensus has been reached on the most effective image analysis approach for providing the best diagnostic performance under heavy-duty clinical diagnostic circumstances. The main objective of the present study was to find and validate optimal semi-quantitative search strategies for metabolic PET studies on gliomas, with special regard to the optimization of those metabolic tracer uptake ratios most sensitive in predicting histologic grade and prognosis. 11C-Methionine (11C-Met, n = 50) and/or 18F-Fluorodeoxyglucose (18F-FDG, n = 33) PET measurements were performed in 59 patients with primary and recurrent brain gliomas (22 high grade and 37 low grade tumors) in order to correlate the biological behavior and 11C-Met/18F-FDG uptake of tumors. Data were analyzed by region-of-interests (ROI) methods using standard uptake value calculation. Different ROI defining strategies were then compared with each other for two of the most commonly used metabolic radiotracers, 18F-FDG and 11C-Met, in order to determine their usefulness in grading gliomas. The results were compared to histological data in all patients. Both ANOVA and receiver operating characteristic (ROC) analysis indicated that the performance of 18F-FDG was superior to that of 11C-Met for most of the ratios. 18F-FDG is therefore suggested as the tracer of choice for noninvasive semi-quantitative indicator of histologic grade of gliomas. 11C-Methionine has been suggested as a complimentary tracer, useful in delineating the extent of the tumor. The best diagnostic performance was obtained by calculating the ratio of the peak 18F-FDG uptake of the tumor to that of white matter (p < 0.001; ANOVA). This metabolic tracer uptake ratio is therefore suggested as an easily obtained semi-quantitative PET indicator of malignancy and histological grade in gliomas.

Comparative overview of brain perfusion imaging techniques

Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are: Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), Xenon-enhanced Computed Tomography (XeCT), Dynamic Perfusion-computed Tomography (PCT), Magnetic Resonance Imaging Dynamic Susceptibility Contrast (DSC), Arterial Spin-Labeling (ASL), and Doppler Ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow (CBF) or volume (CBV). All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview, established by consensus among specialists of the various techniques. For clinicians, this paper should offers a clearer picture of the pros and cons of currently available brain perfusion imaging techniques, and assist them in choosing the proper method in every specific clinical setting.

Speech activation spect and plasticity of language networks

Neuronal activity might be measured by regional cerebral blood flow (rCBF) Single Photon Emission Computed Tomography (SPECT) as there is a close relationship between neuronal activity and rCBF changes. In order to study the hemispheric dominance for language and the plasticity of language networks by measuring the rCBF rest and language activation SPECT studies were performed in the presurgical evaluation of ten right-handed and two left handed patients with brain lesions of the dominant hemisphere. A special group of hemisphere-specific neuropsychologic tasks were used for activation, after a proper psychologic conditioning. The rCBF results were calculated by comparing the rest and activation SPECT data using a special regions of interest program and asymmetry index (AI). We compared the results of speech-activation to the results of clinical, morphological (MRI), and postoperative data. In controls, significant activation was found in Brodmann's area 44 and 45, contralateral cerebellum, superior middle and posterior temporal gyrus. In patients, additional regions of activation were seen in contralateral frontal and temporal regions, and in ipsilateral temporal region. AIs of the cerebellum demonstrated a negative correlation with hemispheric dominance for language. In conclusion, significant changes in rCBF in or adjacent to the eloquent areas with various patterns of rCBF changes of the additional regions demonstrate the close relationship between neuronal activity and cerebral blood flow, that can be measured by SPECT.

Comparative overview of brain perfusion imaging techniques

BACKGROUND AND PURPOSE

Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are positron emission tomography, single photon emission computed tomography, Xenon-enhanced computed tomography, dynamic perfusion computed tomography, MRI dynamic susceptibility contrast, arterial spin labeling, and Doppler ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow or cerebral blood volume. All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks.

SUMMARY OF REVIEW

This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview established by consensus among specialists of the various techniques.

CONCLUSIONS

For clinicians, this article should offer a clearer picture of the pros and cons of currently available brain perfusion imaging techniques and assist them in choosing the proper method for every specific clinical setting.

[Functional imaging of cerebrospinal fluid pathology]

The most common problem addressed by dynamic radionuclide imaging of cerebrospinal fluid (CSF) abnormalities is differentiating patients with normal-pressure hydrocephalus (NPH) from those with other forms of degenerative brain disorder who would clearly not benefit from surgical treatment by ventricular shunting. Radionuclide cisternography (RC) SPECT and regional cerebral blood flow (rCBF) SPECT are critically important for the diagnosis and therapy management of patients with chronic hydrocephalus. However, radionuclide imaging is helpful not only in identifying patients with NPH showing improvement after shunting. RC reveals tracer activity outside the intracranial cavity, indeed. The importance of establishing the diagnosis arises from the fact that untreated leaks can be followed by meningitis in up to one quarter of patients. CSF collections may communicate with the subarachnoid space. RC SPECT has proved useful in assessing the communication of the arachnoid cysts (CSF collection) with the ventricular or subarachnoid compartment. Improved anatomical detail revealed by SPECT imaging is helpful in solving problems of the CSF pathology. Sensitive and accurate assessments of normal and disordered CSF dynamics can be obtained with RC SPECT.

[Functional imaging in brain tumors]

Over the last two decades, the routine imaging methods available for the diagnosis and monitoring of intracranial tumors are computer tomography and magnetic resonance imaging. Both procedures provide precise anatomical delineation of the lesions, determine changes in tumor volume in response to therapy. However, they are not effective in differentiating low-grade from high-grade lesions and residual or recurrent tumor from radiation/chemo necrosis. Radionuclide procedures (positron emission tomography and single photon emission computer tomography), especially positron emission tomography is an example of a technique with high sensitivity and accuracy that has the potential to yield the information necessary not only to provide a means for diagnosis of tumors based on altered tissue metabolism but also to serve as a tool for monitoring the effects of the therapy. Measurements of the rate of glucose metabolism by 18F-FDG uptake in brain lesions are the most frequent applications in order to discriminate low-grade from high-grade lesions and tumor recurrence from radiation necrosis. 11C-methionine positron emission tomography is used to delineate the boundaries of tumors, providing information of value in directing stereotactic biopsy, planning the approach and extent of brain surgery, and permitting differentiation of the metabolizing neoplasm from simple disruption of the blood-brain barrier. Another substrate, 11C-thymidine has been used to measure nucleotide metabolism and utilization in DNA synthesis. Activation studies are useful in patients suffering from lesions near to or in the eloquent areas. It is likely that multiple positron emission tomography radioligands and multimodality imaging are the standards for diagnosis and monitoring of the effects of therapeutic intervention.

[Functional imaging in mental disorders]

Considerable progress has been achieved by functional brain imaging over the past 20 years in uncovering the biological basis of major psychiatric disorders and to more effectively target therapeutics. Radioligand techniques, especially the PET (positron emission tomography) method, are specific and sensitive tools for quantitative in vivo imaging of molecular pathways and molecular interactions within brain tissues. Since 1980s, advances in neuroimaging and neurophysiological techniques have provided tremendous merits for investigations into different psychiatric disorders. PET and SPECT (single photon emission computer tomography) neuroreceptor imaging, especially in schizophrenia has been an extremely fruitful area of research. Evidences from these studies suggest that schizophrenia affects various cortical and subcortical regions involved in cognitive, emotional, and motivational aspects of human behavior. PET and SPECT provide useful data in studying the fundamental neurobiology of mood disorders. Both techniques are playing a central role in studying patients with new methods and ligands for specific receptor subtypes, and are likely to increase the application of PET/SPECT in the development of new pharmacotherapies. Nuclear medicine plays an important role in studying patients with other psychiatric disorders such as obsessive-compulsive disorder (OCD), attention deficit hyperactivity disorder (ADHD), anxiety, etc. Some forms of OCD seem to share a common genetic etiology with Tourette-syndrome (TS) and to be a facultative part of the TS phenotypic spectrum. In conclusion, PET and SPECT methods seem to be helpful in the diagnosis and management of patients with different psychiatric disorders and may provide a better understanding of clinical symptomatology or the relationship of these physiological parameters to the patient's prognosis. Additionally, radionuclide techniques may improve medical therapy by demonstrating individual biochemical abnormalities of altered brain functions.

Speech activation of language dominant hemisphere:

We tested the prediction that single photon emission computed tomography (SPECT) of the blood flow distribution in speech-activated brain identifies the language-dominant hemisphere. We based the prediction on the hypothesis that language activation leads to focally increased regional cerebral blood flow (rCBF), which is reflected in the uptake of a flow tracer recorded by SPECT. We compared the results of speech activation to the results of functional transcranial Doppler (fTCD) monitoring in the same subjects. Preoperatively, 17 patients (10 women and 7 men with a mean age of 36 +/- 15 years) with diagnoses of epilepsy (n = 14) or arteriovenous malformation (AVM) (n = 3) had two SPECT and two stereo-TCD monitoring studies in each case, one at rest, and one during 3 min of speech activation. Except for two left-handed patients with right-hemisphere dominance, the subjects had the highest changes of rCBF from baseline to activation in the left posterior inferior frontal cortex and in contralateral cerebellum. The results show that changes of the level of neuronal activity reflected by the measurement of rCBF variations might be detected by SPECT. Additionally, the evaluation of hemispheric language dominance based on SPECT showed a complete agreement with the evaluation based on fTCD results (yielding a kappa coefficient equal to 1), and therefore, speech-activation SPECT mapping might be helpful in the evaluation of hemispheric language dominance, especially when fMRI and PET are not available or they are contraindicated for some reason.

[Role of SPECT scans in the diagnosis of cerebrovascular diseases]

With an incidence of 200-250 in 100,000 persons year, cerebrovascular disease (CVD) is the most common neurological disorder. In most countries, CVD is the third most frequent cause of death, exceeded only by heart disease and cancer. There are roughly 5.000 new cases per year in Hungary. Additionally, it should be emphasized that there are facts suggesting a more severe population of patients with CVD compared to the analogue group in more developed countries. There are several causes of stroke, but common to all is a critical reduction in cerebral blood flow, resulting in a focal neurological deficit. Functional imaging, particularly of cerebral perfusion, should therefore have a major role to play in the management of these patients. SPECT methods are of high importance in the diagnosis of CVD and in the patients follow-up.

[Pathophysiology of cerebrovascular disorders: PET imaging of the brain]

To understand the underlying mechanisms that occur during cerebral ischaemia and stroke one needs to assess the relationship between blood flow, oxygen and glucose metabolism, and other physiological processes as a function of the site of deficit, the time course of the tissue damage, and the etiology of the ischaemia. PET has already demonstrated its ability to provide in vivo biochemical and pathophysiological information. PET can provide the necessary understanding of the abnormal cellular biochemical processes that occur in response to perfusion insufficiencies in humans. The application of PET to cerebrovascular disease has provided information on temporal course of blood flow and volume, oxygen, and glucose utilization, as well as the respective extraction fractions for these substrates. Additionally, PET provides useful information on neurotransmission, by using receptor ligands one can measure the different receptor systems in the brain.

[Clinical positron emission tomography: brain imaging]

PET produces images of physiological functions at molecular level which can be used to measure different vital processes, including blood flow and perfusion, glucose metabolism, oxygen utilization and receptor-ligand binding rates. Unlike anatomical imaging modalities, such as CT and MR, PET allows for the assessment of biochemical and physiological changes related to any function. Recently, the clinical indications for PET have increased dramatically. PET can reduce the overall cost of medical care, because it increases the certainty of diagnosis and clinical stage of disease, and therefore eliminates the expense of unnecessary testing or treatment.

[Functional imaging (PET and SPECT) in epilepsy]

Epilepsy is one of the most prevalent neurologic disorders and affects approximately 1% of the population. Most complex seizures arise from the temporal lobes and the condition of 20-30% of these patients is refractory to medication. Many can be rendered seizure free with surgery. Epilepsy surgery requires accurate identification of the site and extent of the epileptogenic area responsible for seizures. EEG is accepted as a gold standard, however only 50% of the patients are safely diagnosed. The need for invasive monitoring with possible hemorrhage or infection has been greatly reduced by the introduction of new technologies such as PET, SPECT and MRI in the clinical practice. MRI demonstrate morphologic changes in approximately 80% of patients with epilepsy. However, structural lesions may not always correlate with clinical, EEG and pathologic localization of epileptogenic foci. Seizures are associated with pronounced changes in regional cerebral blood flow. The real power of SPECT lies in the opportunity of ictal examinations, with a sensitivity ranging from 90 to 97%. Interictal PET studies using 18F-FDG measure regional glucose metabolism, have been investigated for their value as non-invasive focus-localizing techniques. These studies have sensitivity ranging from 80 to 85%. The benzodiazepine binding site that are associated with and modulate the activity of GABA receptors have been imaged by SPECT (using 123I-iomazenil) and PET (using 11C-Flumazenil). Combined measurements of benzodiazepine binding sites and perfusion/metabolism provide a more accurate visualization of epileptogenic site than perfusion or metabolism measurements alone. Functional imaging modalities (PET and SPECT) are highly important in the presurgical evaluation of patients with medically refractory complex partial seizures.

[Functional neuroimaging in movement disorders]

Positron Emission Tomography (PET) and Single Photon Emission. Computed Tomography (SPECT) highly contribute to the management of patients with movement disorders by measuring regional cerebral metabolism/blood flow and dopamine receptors. Imaging of the dopaminergic system is a powerful tool for distinguishing patients with neurodegenerative disorders, such as Parkinson's disease. Parkinsonism is most of the time caused by idiopathic Parkinson's disease. Considering the differences in therapeutic response and prognosis, differentiation between Parkinson's disease and "parkinsonism-plus syndromes" is important. Visualisation of pre- and post-synaptic D2 dopamine receptors by using receptor ligands helps to discriminate between Parkinson's disease and "parkinsonism-plus syndromes" as Parkinson's disease is a presynaptic disease. Early disease detection in subjects suspected at risk for developing Parkinson's disease has become possible using ligands for the dopamine transporter. Functional imaging modalities are useful in the management of patients with movement disorders, are able to monitor in an objective way the efficacy of new pharmacological therapies, can document the effect of neuronal grafting for Parkinson's disease, and delineate the progression of these diseases.

[Speech activation SPECT measurements in the determination of hemispheric dominance]

Cognitive activity leads to an increased regional cerebral blood flow (rCBF) and energy metabolism in both cerebral hemispheres. In order to assess the reliability of rCBF-SPECT measurements in hemispheric dominance (Broca's area) speech activation SPECT studies were performed in nine patients. Patients (men, n = 6; women, n = 3, mean age: 33.8 +/- 13.8 years) with diagnosis of epilepsy (n = 7) and AVM (n = 2) participated in the preoperative study. Two SPECT studies were performed in each case, one in rest, and one during speech activation. 740 MBq of 99mTc-HMPAO/ECD was injected and stereo TCD monitoring was performed during the three minutes of speech activation. The acquisition was performed by a dual-head ADAC Solus Epic Atlas SPECT camera (ADAC Laboratories, Milpitas, USA). RCBF SPECT measurements were analyzed visually and by a special region-of-interest (ROI) program. The hemispheric dominance profiles were established on the basis of the respective blood flow velocity values obtained by fTCD and cortical hyperperfusion measured by SPECT. The neuropsychological test battery, used in the present study, was developed in our institute. The results of rCBF-SPECT studies highly correlated with the lateralization of hemispheric dominance measured by fTCD. There was a significant increase of rCBF in the inferior posterior frontal cortex (Broca's area, p < 0.0003). The non-invasive speech activation rCBF-SPECT measurement is a highly reliable and useful method in the determination of hemispheric dominance. SPECT studies are especially useful in cases where the performance of fTCD measurements are impossible due to the lack of temporal bone window or occlusive cerebral arterial disease.

[The place of positron-emission tomography in contemporary patient care]

Positron emission tomography (PET) is a unique method offering physicians unrivaled access to in vivo quantitative measurements. The PET studies are useful in many areas of establishing primary diagnosis, differential diagnosis, planning and monitoring therapeutical efficacy. As a clinical tool it has been shown to increase diagnostic accuracy. Unlike anatomical imaging modalities, such as CT and MR, PET permits assessment of chemical and physiological changes related to any function. PET images demonstrate pathological change long before they would be revealed by other imaging modalities like CT and MR. It produces images of molecular level of physiological function which can be used to measure many vital processes, including glucose metabolism, blood flow and perfusion, receptorligand binding rates, and oxygen utilization. The PET studies provide useful diagnostic information which may alter patient management and reduce the total cost of patient care. PET studies have made critical contributions to more cost-effective patient management in four clinical disciplines: cardiology, neurology, psychiatry and oncology. Recently, the clinical indications for PET have increased dramatically. Since Hungary's first PET center has been established at the University Medical School in Debrecen many studies additionally demonstrate that PET reduces overall cost of medical care, because it increases the certainty of diagnosis and clinical stage of disease, and therefore eliminates the expense of unnecessary testing or treatment.

[First Hungarian experiences with positron emission tomography (PET) studies. Members of the PET working group]

Diagnostic investigations commenced on the 28th of June 1994 in Hungary's and Central Europe's first PET Centre at the University Medical School of Debrecen. The Centre is equipped with a GE 4096 Plus whole body PET scanner. A metabolic tracer, 18F-deoxy-D-glucose (FDG), was used in the investigations. During the first 15 months 249 PET investigations were made in the Centre of which 242 were diagnostic and 7 normal subjects served as control for the patient studies with brain scans. The number of oncological indications (intra- and extracranial tumours, Hodgkin's lymphomas) was n = 105 (43.4% of the 242 diagnostic examinations), neurological investigations (without intracranial tumours) formed the dominant group (n = 117; 48.3%), whereas the number of cardiological indications was 20 (8.3%). The oncological studies included those of intracranial tumours (n = 76; 31.4%); thyroid tumours (n = 9; 3.7%); Hodgkin's lymphomas (n = 7; 2.9%) and other extracranial tumours (n = 13; 5.4%). The distribution of different neurological and psychiatric investigations was as follows: localization of focal epileptogen zone (n = 60; 24.8%); differential diagnosis of dementias (n = 30; 12.4%); exploration of cerebrovascular diseases (n = 10; 4.1%); and other neurological diseases (n = 17; 7.0%). The main objective of the cardiological PET investigations was the exploration of viable myocardium. The present paper overviews both the procedures (including administrative issues, as well) and the results of the first 249 FDG-PET investigations.

[Internal hydrocephalus and basal liquorrhea (radionuclide data)]

The paper shows the value of radionuclide cysternomyelography in the diagnosis of internal hydrocephalus concurrent with basal liquorrhea. The authors examined 1522 patients of whom 105 were found to have the pathology, this yielded radionuclide differential diagnostic criteria for this nosological entity. They proposed new technological conditions for enhancing its diagnostic value.

Scintigraphic study of cerebrospinal fluid shunts

This paper deals with experience gained in the study of patency of different types of shunt. Results of subsequent surgery are considered. Findings of 79 scintigraphic studies with radiotechnetium on 68 patients are presented. The method is simple, quick, easy to reproduce and means only moderate radiation load for the patient. Results obtained suggest that this study is a reliable diagnostic tool which can be used in a routine way.

Determination of nasal liquorrhoea by means of radionuclide cisternography

Ninety-two radionuclide cisternographies were performed on 88 patients with suspected nasal liquorrhoea. To identify fistulae of both traumatic and non-traumatic aetiology, 40 MBq of 169Yb-EDTA was injected to a total volume of 2 ml into the subarachnoid space usually by the cisternal route, but in some cases lumbar routes were chosen. Sixty-seven positive findings were verified by surgery, whereas no surgery was performed in 8 positive cases due to spontaneous clinical healing of the rhinorrhoea. Seventeen patients were studied who did not exhibit actual clinical signs of liquorrhoea. In each case a normal cisternogram was obtained. These cases were not operated upon. Results suggest that this investigation is a simple and reliable diagnostic tool that causes only negligible discomfort to the patient.