PET Scan Images Research Articles

Circulating-tumor DNA Assessment in Diffuse Large B-cell Lymphoma to Determine Up-front Stem Cell Transplantation: A Pilot Study.

This study evaluated the possibility of clinical use of circulating-tumor DNA (ctDNA) as a biomarker to determine up-front autologous stem cell transplantation (auto-SCT) for patients with high-risk diffuse large B-cell lymphoma (DLBCL) in practice. To explore the dynamics of ctDNA in DLBCL, blood samples were collected sequentially before and after treatment from patients with newly diagnosed DLBCL who received rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) chemotherapy. To conduct ctDNA genotyping and ctDNA monitoring simultaneously, targeted sequencing by cancer personalized profiling using deep sequencing was used. Ten patients between the ages of 50 and 60 years were enrolled. Based on the international prognostic index (IPI), seven patients were classified as high-IPI-risk group, and three patients were classified as low-IPI-risk group. The IPI risk group correlated with total metabolic tumor volume. All patients completed six cycles of R-CHOP chemotherapy, and seven patients achieved complete response. Changes in ctDNA mutation numbers did not correlate with changes in PET scan images and treatment response. In most high-risk patients, new mutations appeared in ctDNA after completion of chemotherapy that conceivably marked resistant clones. Notably, disease relapse did not occur in high-risk patients with poor prognostic mutations who underwent autologous SCT. ctDNA monitoring was meaningful in high-risk patients. Moreover, ctDNA and well-known prognostic factors should be considered in the decision making for auto-SCT. If a new genetic mutation in ctDNA with a negative prognosis would emerge during treatment, high-risk patients should consider auto-SCT.

Lung Cancer Detection using Fusion, CNN and YOLO in MATLAB

Abstract: Lung Cancer is one of the major causes of deaths in India. Various data analytics and classification approaches have been used to diagnose and find lung cancer in numerous cases. Lung Cancer can only be cured by early tumour diagnosis because the basis of the diseases is yet unknown, making prevention impossible. In order to classify the existence of lung cancer/tumour in a CT picture and PET image, a lung cancer detection method using image processing and deep learning is applied. Using Fusion technique, we first obtain CT scans, then PET images of the same patient, then combine both images into one. The classification carried out using image feature extraction. As a result, the combined CT and PET scan images of the patient are classified as normal or abnormal. The tumour component of the abnormal photos is the focus of the detecting process. Using YOLO and CNN, an effective strategy to identify lung cancer and its phases is one that also seeks to produce more precise results.

Chemotherapy dose per kilogram lean body mass increased dose-limiting toxicity event in male head and neck cancer with taxane and platinum-based induction therapy

BackgroundThis study aimed to determine whether drug doses per kilogram of lean body mass (LBM) were associated with dose-limiting toxicity (DLT) events in head and neck cancer (HNC) patients.MethodsThis retrospective cohort study included 179 HNC patients who underwent induction chemotherapy (IC) at a medical center from May 1, 2014, to May 31, 2021. HNC patients’ characteristics, tumor factors, IC regimen and dose, laboratory data, and body composition factors, including lean body mass (LBM) and skeletal muscle index (SMI), derived from CT, MRI, or PET scan images and drug dose per kilogram LBM were recorded. Dose-limiting toxicity (DLT) events were regarded as the primary outcome. Multivariate logistic regression was used to establish a novel risk score for DLT events by the abovementioned variables. The above-mentioned risk score was validated in another cohort.ResultsThe overall DLT events during the first cycle of IC for 179 HNC patients was 24%. After stratifying by gender, docetaxel per kilogram LBM > 2.52 mg/kg (adjusted odds ratio [aOR]: 3.18; 95% confidence interval [CI], 1.25–8.09), pre-treatment glutamic pyruvic transaminase (GPT) > 40 U/L (aOR, 2.61; 95% CI, 1.03–6.64), and history of chronic liver diseases (aOR, 3.98; 95% CI, 1.03–15.46) were significant variables in male HNC patients. The DLT events risk was categorized by summation of the above-mentioned risk factors for male HNC patients. Three risk groups were stratified by overall event of 17.6%, 25.8%, and 75%. The above-mentioned risk score had an acceptable discriminatory ability in another validation cohort.ConclusionsAmong male HNC patients treated with IC, docetaxel per kilogram LBM more than 2.52 mg/kg, pre-treatment GPT > 40 U/L, and history of chronic liver disease were significant risk factors for DLT events. Identifying high-risk patients could help physicians prevent severe/fatal complications among HNC patients undergoing IC, especially for the male individuals.

The effect of cobalt oxide nanoparticles on improving the quality of CT and PET scan medical imaging

Abstract Background: Sometimes, a patient is referred to a medical imaging center and receives a medical image that it is not good and sometimes poor quality image, which the doctor orders to re-image with a drug contrast agent (in CT scan imaging). On the other hand, small liver tumors sometimes have to reach 4 cm to be detectable. At this time, practical action is difficult to provide a proper image. Moreover, injectable tracking materials in PET scans often have short half-lives that are very expensive to maintain. Purpose: -Investigation of the effect of cobalt oxide nanoparticles on the quality of CT scan images from laboratory mice. -Evaluation of the effect of cobalt oxide nanoparticles on the quality of live PET scan images and diagnosis of small tumors in mice. Method: In this study, the coupling method was used to prepare the cobalt oxide nanoparticles. Co3O4 nanoparticle coatings are used for this purpose. They were investigated through FT-IR analysis, X-ray diffraction and magnetization curve of the crystalline sample. For this purpose a 2000 μA proton bombardment with an energy of 22 million eV and a current of 180 μA was used. The final product activity was 23 mM. A. The nanoparticles were injected into Mice with tumors in the legs, and PET images were obtained at 1, 6, 12, and 24 h intervals. Results: 1- After injection the cobalt oxide nanoparticles into the mice and CT scan imaging, the better clarity and detection Mice viscera were obtained. 2-Cobalt oxide nanoparticles showed good performance in PET scan images after injection into mice in the first first 24 hours. Conclusion: Cobalt oxide nanoparticles behave well for use as a pharmacological contrast agent in CT scan and PET scan imaging. Keywords: PET, tumor, Radiotracer, nanoparticles, CT-Scan.

An Efficient Cancer Classification Model for CT/MRI/PET Fused Images.

The aim was to study image fusion-based cancer classification models used to diagnose cancer and assess medical problems in earlier stages that help doctors or health care professionals to make the treatment plan accordingly. In this work, a novel image fusion method based on Curvelet transform is developed. CT and PET scan images of benign type tumors were fused together using the proposed fusion algorithm and the same way, MRI and PET scan images of malignant type tumors were fused together to achieve the combined benefits of individual imaging techniques. Then, the marker-controlled watershed algorithm was applied on fused images to segment cancer affected area. The various color features, shape features and texture-based features were extracted from the segmented image. Following this, a data set was formed with various features, given as input to different classifiers namely neural network classifier, Random forest classifier, and K-NN classifier to determine the nature of cancer. The results of the classifier showed normal, benign or malignant category of cancer. The performance of the proposed fusion algorithm was compared with the existing fusion techniques based on the parameters PSNR, SSIM, Entropy, Mean and Standard Deviation. Curvelet transform based fusion method performs better than already existing methods in terms of five parameters. The performances of the classifiers were evaluated using three parameters: accuracy, sensitivity, and specificity. The K-NN Classifier performed better compared to the other two classifiers and it provided an overall accuracy of 94%, sensitivity of 88% and specificity of 84%. The proposed Curvelet transform based image fusion method combined with the KNN classifier provides better results compared to other two classifiers when two input images were used individually.

An Essential Image Augmentation Processes for Pattern Based Image Retrieval System

An image retrieval system is an image search engine is most useful for human day to day life. But still, the image retrieval systems are working in the traditional manner. Nowadays increasing the image database in a huge amount of size with the heterogeneous category. At the same time increasing the demands of users in a various manner. The most demanding fields in society are healthcare, agriculture, trademark, and crime. In healthcare field diagnose the disease, in crime field investigate the criminals, in trademark field to make an analysis to recognize the right product and in agriculture field to find the disease affected fruit images. The previous image retrieval systems are working with limitations like choose any one of the fields, any one of image file format and any one of the image feature and also any one of the medical image modality. To overcome the above limitations, the Pattern Based Image Retrieval (PBIR) system has been proposed. The PBIR system works by pattern recognition techniques. A pattern is a visible entity of image. Recognition is a label learning process. It considers mainly the patterns of the image for finding a similar group of images from the heterogeneous image database. And also include all directions of image features for image retrieval processing. The PBIR system is used to find uncertain parts of the image during augmentation steps. The augmentation work is an essential to increase the quality of images and make more reliable for feature extraction. Because currently we are using streaming image data. The images are having many unknown disturbances during capture the image. In this paper, we are mainly focusing image augmentation processes are a demosaicing algorithm, gray slice, gradient magnitude and pattern detection, Viola-Jones face detection algorithm for improving the PBIR system performance. And also PBIR system working with four image file formats are.JPG, BMP, GIF, PNG. The three main medical image modalities are CT scan, MRI scan and PET scan images. The image database of PBIR system is 3D DICOM MRI image, Brand logo image, Mango fruit image and ATM crime image. Finally, Image Quality Assessment (IQA) has been carried out using various evaluation measures are found better in the performance accuracy. And also include the results of this processes for further research directions.

Cognitive Dysfunction in Drug-induced Parkinsonism Caused by Prokinetics and Antiemetics.

The use of prokinetics/antiemetics is one of the leading causes of drug-induced parkinsonism (DIP) observed in neurology clinics. Cognitive dysfunction in DIP has recently been recognized, but pathologies related with cognitive dysfunction is unknown. Among our retrospective cohort of 385 consecutive parkinsonian patients enrolled in our parkinsonism registry, 14 patients were identified who satisfied our inclusion criteria: parkinsonism caused by prokinetics/antiemetics, existing T1-weighted 3D volumetric MR images, and normal [(18)F]-N-3-fluoropropyl-2-β-carboxymethoxy-3-β-(4-iodophenyl) nortropane PET scan images. For the comparison of volumetric MR data, 30 age- and sex-matched healthy individuals were included in this study. Among 14 patients with DIP, 4 patients were diagnosed with dementia, and all other patients had mild cognitive impairment (MCI). Comparisons of MR volumetric data between DIP patients with MCI and controls show that cortical gray matter volumes are reduced bilaterally in DIP (P=0.041) without changes in either total white matter volume or total intracranial volume. Among subcortical structures, the volume of the right hippocampus is reduced in DIP patients compared with controls (P=0.011, uncorrected). In DIP, cortical thickness is reduced in the bilateral lingual (P=0.002), right fusiform (P=0.032) and part of the left lateral occipital gyri (P=0.007). Our results suggests that cognitive dysfunction in DIP caused by prokinetics/antiemetics is common. Structural changes in the brain by 3D MRI may be associated with cognitive decline in DIP.

Monitoring the early biologic response of esophageal carcinoma after irradiation with 18F-FLT: an in-vitro and in-vivo study.

The aim of our study was to explore the value of 3'-deoxy-3'-[F]fluorothymidine (F-FLT) and F-FLT PET in monitoring the early biologic response of esophageal carcinoma after irradiation in vitro and in vivo. After 2, 4, and 8 h of irradiation at different doses (0, 5, 10, and 15 Gy) of esophageal carcinoma cells in vitro, the uptake ratio of F-FLT, the relative cell survival rate, and ATP levels were measured. The tumor uptake ratio of F-FLT [tumor-to-nontumor (T/NT)] was measured through PET scans before and on the first, seventh, and 15th day after irradiation. The expression of proliferating cell nuclear antigen and Ki-67 was determined in both untreated and treated tumors. Compared with the control group, the uptake ratio changes of F-FLT after 2 h of irradiation with 5 Gy showed no statistical significance (3.65±0.17 vs. 4.00±0.17%, P>0.05), whereas the uptake ratios of the other groups decreased notably (F=33.93, P<0.01). The differences in the relative survival rates were not statistically significant (F=4.02, P>0.05). Linear regression analysis indicated a significant correlation between F-FLT and ATP levels (r=0.89, P<0.01). On F-FLT PET scan images of the xenografts, the baseline uptake ratio (T/NT) was 2.24±0.06. It decreased to 1.99±0.09, 1.85±0.04, and 1.15±0.10 at 1, 7, and 15 days after irradiation with 10 Gy. Tumor uptake of F-FLT was closely correlated with proliferating cell nuclear antigen and Ki-67 expressions (r=0.83, P<0.001, and r=0.88, P<0.001). The uptake changes of F-FLT in esophageal carcinoma cells and tumor xenografts may reflect the early biological response of esophageal carcinoma after irradiation. Thus, F-FLT PET may be potentially used to monitor the early response of esophageal carcinoma after radiotherapy.

Imaging of site specific bone turnover in osteoporosis using positron emission tomography.

The functional imaging technique of dynamic fluorine-18 labeled sodium fluoride positron emission tomography ((18)F-NaF PET) allows the quantitative assessment of regional bone formation by measuring the plasma clearance of fluoride to bone at any site in the skeleton. (18)F-NaF PET provides a novel and noninvasive method of studying site-specific bone formation at the hip and spine, as well as areas of pure cortical or trabecular bone. The technique complements conventional measurements of bone turnover using biochemical markers and bone biopsy as a tool to investigate new treatments for osteoporosis, and holds promise of a future role as an early biomarker of treatment efficacy in clinical trials. This article reviews methods of acquiring and analyzing (18)F-NaF PET scan data, and outlines a simplified approach that uses 5-minute static PET scan images combined with venous blood samples to estimate (18)F-NaF plasma clearance at multiple sites in the skeleton with a single injection of tracer.

Deep Inspiration Breath Hold [18F]FDG PET-CT on 4-rings scanners in evaluating lung lesions: Evidences from a phantom and a clinical study

ObjectiveTo investigate the clinical feasibility of a Deep Inspiration Breath Hold (DIBH) 18F-FDG PET-CT acquisition in apnea and compare the results obtained between these acts of acquisition in apnea and in Free Breathing in the evaluation of lung lesions. Material and methodsA pre-clinical phantom study was performed to evaluate the shortest simulated DIBH time according to the minimum detectable lesion that can be detected by our ultrasound scanner. This study was conducted by changing acquisition time and sphere-to-background activity ratio values and by using radioactivity densities similar to those generally found in clinical examinations. In the clinical study, 25 patients with pulmonary lesions underwent a standard whole body 18F-FDG PET-CT scan in free breathing followed by a 20s single thorax acquisition PET/CT in DIBH acquisition. ResultsThe phantom study indicated that a 20-s acquisition time provides an accurate evaluation of smallest sphere shaped lesions. In the clinical study, PET-CT scans obtained in DIBH studies showed a significant reduction of misalignment between the PET and CT scan images and an increase of SUVmax compared to free breathing acquisitions. A correlation between the %BH-index and lesion displacement between PET and CT images in FB acquisition was demonstrated, significantly higher for lesions with a displacement>8mm. ConclusionThe single 20s acquisition of DIBH PET-CT is a feasible technique for lung lesion detection in the clinical setting. It only requires a minor increase in examination time without special patient training. 20s DIBH scan provided a more precise measurement of SUVmax, especially for lesions in the lower lung lobes which usually show greater displacement between PET and CT scan images in FB acquisition.

Deep Inspiration Breath Hold [18F]FDG PET-CT on 4-rings scanners in evaluating lung lesions: Evidences from a phantom and a clinical study

To investigate the clinical feasibility of a Deep Inspiration Breath Hold (DIBH) (18)F-FDG PET-CT acquisition in apnea and compare the results obtained between these acts of acquisition in apnea and in Free Breathing in the evaluation of lung lesions. A pre-clinical phantom study was performed to evaluate the shortest simulated DIBH time according to the minimum detectable lesion that can be detected by our ultrasound scanner. This study was conducted by changing acquisition time and sphere-to-background activity ratio values and by using radioactivity densities similar to those generally found in clinical examinations. In the clinical study, 25 patients with pulmonary lesions underwent a standard whole body (18)F-FDG PET-CT scan in free breathing followed by a 20s single thorax acquisition PET/CT in DIBH acquisition. The phantom study indicated that a 20-s acquisition time provides an accurate evaluation of smallest sphere shaped lesions. In the clinical study, PET-CT scans obtained in DIBH studies showed a significant reduction of misalignment between the PET and CT scan images and an increase of SUVmax compared to free breathing acquisitions. A correlation between the %BH-index and lesion displacement between PET and CT images in FB acquisition was demonstrated, significantly higher for lesions with a displacement>8mm. The single 20s acquisition of DIBH PET-CT is a feasible technique for lung lesion detection in the clinical setting. It only requires a minor increase in examination time without special patient training. 20s DIBH scan provided a more precise measurement of SUVmax, especially for lesions in the lower lung lobes which usually show greater displacement between PET and CT scan images in FB acquisition.

Whole-body fluorodeoxyglucose positron emission tomography/computed tomography in patients with active polymyalgia rheumatica: evidence for distinctive bursitis and large-vessel vasculitis

Objectives To investigate fluorodeoxyglucose (FDG) accumulation in large joints, bursas, and large vessels in patients with polymyalgia rheumatica (PMR) using 18-FDG positron emission tomography/computed tomography (PET/CT) and to differentiate PMR from similar diseases.Methods Fourteen untreated patients with active PMR and 17 control patients with rheumatoid arthritis (n = 11) or other active rheumatic diseases (n = 6) underwent 18-FDG PET/CT. FDG uptake in large joints, bursas and vertebral spinous processes was evaluated by calculating maximum standardised uptake values and by visual scoring (scale 0–4). PET scan images were scored in seven vascular regions, and total vascular scores (range 0–21) were calculated.Results Polymyalgia rheumatica patients showed increased FDG uptake in ischial tuberosities, greater trochanters, and lumbar spinous processes. Positive results at two or more of these sites showed high sensitivity (85.7%) and specificity (88.2%) for the diagnosis of PMR, and shoulder or hip-joint involvement showed low disease specificity. High FDG accumulations were found in the aortas and subclavian arteries of two PMR patients who were asymptomatic for temporal arteritis and scanty synovium and perisynovium, based on FDG uptake. PET/CT images of the 12 PMR patients without apparent vascular involvement showed synovitis and/or perisynovitis.Conclusions Fluorodeoxyglucose-PET/CT may be useful for the detection of PMR lesions, which are difficult to identify using other methods.

Whole-body fluorodeoxyglucose positron emission tomography/computed tomography in patients with active polymyalgia rheumatica: evidence for distinctive bursitis and large-vessel vasculitis

To investigate fluorodeoxyglucose (FDG) accumulation in large joints, bursas, and large vessels in patients with polymyalgia rheumatica (PMR) using 18-FDG positron emission tomography/computed tomography (PET/CT) and to differentiate PMR from similar diseases. Fourteen untreated patients with active PMR and 17 control patients with rheumatoid arthritis (n = 11) or other active rheumatic diseases (n = 6) underwent 18-FDG PET/CT. FDG uptake in large joints, bursas and vertebral spinous processes was evaluated by calculating maximum standardised uptake values and by visual scoring (scale 0-4). PET scan images were scored in seven vascular regions, and total vascular scores (range 0-21) were calculated. Polymyalgia rheumatica patients showed increased FDG uptake in ischial tuberosities, greater trochanters, and lumbar spinous processes. Positive results at two or more of these sites showed high sensitivity (85.7%) and specificity (88.2%) for the diagnosis of PMR, and shoulder or hip-joint involvement showed low disease specificity. High FDG accumulations were found in the aortas and subclavian arteries of two PMR patients who were asymptomatic for temporal arteritis and scanty synovium and perisynovium, based on FDG uptake. PET/CT images of the 12 PMR patients without apparent vascular involvement showed synovitis and/or perisynovitis. Fluorodeoxyglucose-PET/CT may be useful for the detection of PMR lesions, which are difficult to identify using other methods.

Intérêt de la tomographie par émission de positons au fluorodéoxyglucose 18 dans la détection des neurofibrosarcomes au cours de la neurofibromatose de type 1

The appearance of malignant peripheral nerve sheath tumours (MPNST) marks a critical stage in the course of neurofibromatosis type 1 (NF1). Since the diagnostic criteria are fairly non-specific, histological examination alone can confirm malignancy. We assessed the value of 18 FDG positron emission tomoscintigraphy (PET scan) in screening for such malignant tumours. Between October 2000 and August 2006, all of our patients with NF1 and suspected MPNST underwent PET scan. Inclusion criteria consisted of clinical signs (increased tumour size or induration, pain) and/or laboratory values. Analysis of PET scan images, based upon determination of tumour/liver binding ratio with a cut-off point of 1.5 times hepatic binding, was used to classify lesions as non-suspect or pathological. In the case of suspect lesions, histological analysis was performed. For non-suspect lesions, patients either underwent monitoring or excision of the lesion where necessary and technically feasible. Thirty-eight patients with 49 tumours were included in the study. In 8 patients, PET scan showed suspect lesions (12 tumours), and histological analysis of these tumours revealed 6 MPNST. In 30 patients (37 tumours) PET scan showed non-suspect binding, and no malignant tumours were demonstrated either on histological examination or after mean follow-up of 33.5 months. PET scan thus demonstrated a sensitivity and negative predictive value of 100%, specificity of 86%, and a positive predictive value of 50%. The ratios of positive and negative probability were respectively 7.14 and 0. Our study, to our knowledge the most extensive yet performed, demonstrates the value of PET scan in detecting MPNST, particularly based on its 100% negative predictive value. To date, other than biopsy, no examinations allow diagnosis with any certainty. The literature reports 2 studies analysing the value of PET scan. The first involved 18 NF1 patients with 23 plexiform neurofibromas: of 7 tumours with hyperbinding, 5 were MPNST. The second study concerned 5 NF1 patients with a total of 15 tumours: 7 tumours showed hyperbinding, of which 6 were MPNST. Using the same evaluation criteria, our study yielded comparable results. The negative predictive value of 100% provides a strong argument in favour of a benign tumour. Our study confirms the value of PET scan in the detection of NF1 even though false positives require medical-surgical confirmation before any potentially detrimental therapeutic decisions may be made.

FDG-PET findings of vertebral compression fractures in osteoporosis: preliminary results.

The aim of this study was to evaluate FDG-PET findings in patients with osteoporosis or preclinical osteoporosis and acute vertebral compression fractures in order to determine whether FDG-PET has a value for distinction of pathological from osteoporotic vertebral fractures. 17 patients with a spontaneous compression fracture of the spine were evaluated by bone scanning with Tc-99m HDP, positron emission tomography with fluorine-18 deoxyglucose (FDG-PET) and magnetic resonance imaging (MRI). Osteoporosis had been established in all cases by X-ray and osteodensitometry. PET and bone scan images were scored independently from 0 (no pathological uptake) to 4 (definitive pathological uptake) by two blinded nuclear medicine physicians. The results of the blinded scoring were compared to MRI findings which served as gold standard. In 13 out of 17 patients, MRI demonstrated a vertebral fracture generating from osteoporosis. In 12 of these 13 cases, PET scans were scored with 0 or 1 and categorized as true negative. Standard uptake values (SUV) ranged between 1.1 and 2.4. In one of the 13 patients, PET was interpreted false positive with an uptake score of 3 (SUV = 2.9). Of the 17 patients, MRI revealed a pathological fracture caused by spondylodiscitis in three patients and by plasmacytoma in one patient. In these patients, all PET scans were highly positive with a score of 3 and 4 and SUV values between 3.8 to 9.8. The bone scans of all 17 patients were positive with scores of 3 or 4 but a differentiation between osteoporotic and pathological fractures was not possible. Our preliminary results indicate that acute vertebral fractures that originated from osteoporosis or preclinical osteoporosis tend to have no pathologically increased FDG uptake. Since a high FDG uptake is characteristic for malignant and inflammatory processes, use of FDG-PET may have potential value for differentiation between osteoporotic and pathological vertebral fractures.

Substituted benzamides as ligands for visualization of dopamine receptor binding in the human brain by positron emission tomography.

Two substituted benzamides, FLB 524 and raclopride, were labeled with 11C and examined for their possible use as ligands for positron emission tomography (PET)-scan studies on dopamine-2 (D-2) receptors in the brains of monkeys and healthy human subjects. Both ligands allowed the in vivo visualization of D-2 receptor binding in the corpus striatum caudate nucleus/putamen complex in PET-scan images. [11C]Raclopride showed a high ratio of specific striatal to nonspecific cerebellar binding, and the kinetics of binding of this ligand made it optimal for PET studies. The in vivo binding of [11C]raclopride in the striatum of cynomolgus monkeys was markedly reduced by displacement with haloperidol. This and previous in vitro data indicate that [11C]raclopride binds selectively to striatal D-2 dopamine receptors. In healthy human subjects, [11C]raclopride binding in the caudate nucleus/putamen was 4- to 5-fold greater than nonspecific binding in the cerebellum. In comparison with previously available ligands for PET-scan studies on central dopamine receptors in man, [11C]raclopride appears to be advantageous with regard to (i) specificity of binding to D-2 receptors, (ii) the high ratio between binding in dopamine-rich (caudate, putamen) and dopamine-poor (cerebellum) human brain regions, and (iii) rapid association and reversibility of specific binding. [11C]Raclopride should be a valuable tool for characterizing D-2 receptors in the brains of patients with neuropsychiatric disorders.

Imaging of [ 11C]-labelled RO 15-1788 binding to benzodiazepine receptors in the human brain by positron emission tomography

The benzodiazepine antagonist Ro 15-1788 was labelled with [ 11C] and examined for possible use as ligand for PET scan studies on benzodiazepine receptors in the brain of cynomolgus monkeys and human subjects. [ 11C] Ro 15-1788 allowed the in vivo visualization of benzodiazepine receptor binding in cerebral and cerebellar cortical areas as well as in basal brain nuclei in PET scan images. [ 11C] Ro 15-1788 exhibited a high ratio of specific benzodiazepine receptor binding (cerebral cortex) to non-specific binding (pons) and the kinetics of binding should be satisfactory for quantitative clinical PET scan studies using [ 11C]. The in vivo binding of [ 11C] Ro 15-1788 in the cerebral cortex of cynomolgus monkeys and healthy human subjects was reduced by approximately 90% within 10 min after the intravenous injection of a high dose of unlabelled Ro 15-1788 (0.5 mg/kg i.v.). Different areas of the healthy human brain showed an approximately 10-fold variation in maximal [ 11C] Ro 15-1788 binding that corresponded to the previously known distribution of benzodiazepine receptors in these regions. The highest degree of binding was obtained in the medial occipital cerebral cortex followed by frontal cortex, cerebellum, thalamus, striatum and pons. Two psychiatric patients with anxiety syndromes who had been treated for a long time with high doses of benzodiazepines had roughly the same degree of maximal [ 11C] Ro 15-1788 binding in brain regions as the healthy subjects but the rate of decline of [ 11C] Ro 15-1788 in the brain was higher. This indicates that there is measurable competition between [ 11C] Ro 15-1788 binding and clinical benzodiazepine concentrations in the body fluids of psychiatric patients. The results demonstrate that [ 11C] Ro 15-1788 should be a valuable tool for quantitative analyses of benzodiazepine receptor characteristics and receptor occupancy in the brain of patients with neuropsychiatric disorders.