FDG PET in head and neck cancer

In our extensive experience with FDG PET imaging in head and neck cancer, we have found the technique to be of high accuracy but of limited usefulness. This seeming paradox arises from several causes. Competing techniques such as CT, MR imaging, and even clinical examination already have good accuracy. In addition, high-resolution studies such as CT and MR imaging provide information required for treatment planning that is unavailable from FDG PET images. The high cost of FDG PET militates against its use in this setting, in which only a small marginal gain can be expected. In the special problem areas in which FDG PET might be expected to offer unique advantages, such as screening for second primary lesions, searching for unknown primary lesions, or differentiating benign salivary rumors from malignant lesions, the results of FDG PET have been disappointedly poor. Of these special problem areas, only the question of accuracy in finding occult primary lesions appears unresolved and in need of further study. The single application in which FDG PET appears to be advantageous is the posttherapy setting. In this setting, the technique is definitely superior to alternative methods of determining tumor recurrence and differentiating posttherapy sequelae such as radiation necrosis from tumor recurrence. We believe that considerable opportunity remains for further research on the use of FDG PET in head and neck cancer. Other agents such as 11C-methionine for example, might improve the diagnostic accuracy of FDG PET in some of the problem areas that we have identified, such as the early postirradiation period. We currently have such a study under way. Also, because FDG PET offers a unique way to measure tumor metabolism, further investigation of the use of FDG PET tracers to evaluate various biologic parameters such as proliferation rates or tumor hypoxia are needed. Such studies could provide a noninvasive technique to identify which fractionation schemes or combinations of therapy might be useful for individual patients. A final caveat is in order. Although our findings of the usefulness (and lack thereof) of FDG PET in head and neck cancer may be disappointing to many, these results should not be generalized to other applications of FDG PET in oncology. Each tumor type and setting presents its own specific problems, and in some instances FDG PET offers unique advantages over other imaging techniques. A good example is the setting of primary lung cancer, in which FDG PET appears clearly superior to all other methods of pretherapy screening [19-20].     

FDG PET of the retroperitoneum: normal anatomy, variants, pathologic conditions, and strategies to avoid diagnostic pitfalls

Evaluation of the retroperitoneum is important to assess the extent of retroperitoneal malignancies and because the retroperitoneum is a route of nodal spread for other malignancies. Positron emission tomography (PET) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) allows detection of small malignant nodes not identified or not meeting size criteria for malignancy with computed tomography (CT) and tumor recurrences in surgical beds that are otherwise difficult to assess. However, evaluation of retroperitoneal malignancies or adenopathy with FDG PET can be complicated by urinary and colonic activity or anatomic variants. Urinary artifacts are avoided with intravenous hydration, administration of furosemide, and catheterization and retrograde filling of the bladder with saline solution. Colonic artifacts are avoided by cleansing the bowel with an isosmotic solution. FDG PET is useful in assessing the retroperitoneum for adenopathy in malignancies such as testicular cancer; lymphoma; and rectal ovarian, or cervical cancer that spread along retroperitoneal lymphatics. FDG PET is especially useful for detection of malignant nodes that do not meet size criteria at CT or when lack of retroperitoneal fat makes it difficult to identify retroperitoneal nodes with CT. FDG PET has an important role in evaluation of postoperative beds, where CT has limited useful because of altered anatomy, surgical clip artifacts, and scar issue.     

"Anatometabolic" tumor imaging: fusion of FDG PET with CT or MRI to localize foci of increased activity

Positron emission tomographic (PET) images of visceral cancers are commonly visualized as "hot spots" of increased activity with relatively little normal anatomy discernable, when 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) is used as the tracer. We describe a method by which computed tomography or magnetic resonance anatomic images can be digitally fused in three dimensions, using a rigid rotate-translate scale model with PET "metabolic" images, to simultaneously display registered anatomic and metabolic information. Such "anatometabolic" fusion images were produced in 10 patients with a variety of visceral cancers. External fiducial markers placed during both the anatomic and the metabolic study, as well as internal anatomic fiducials defined from landmarks observed on reconstructed transmission images, were used to achieve image fusion. The mean error magnitude +/- s.e.m. of fiducial registration in the nine patients with successful realignments was 5.0 +/- 0.8 mm. The mean accuracy in realignment between known anatomic structures seen on both the anatomic study and on the emission PET scan (but not used in realignment) was 6.3 +/- 0.8 mm. Localization of foci of increased FDG uptake to specific anatomic structures was achieved by this method, which represented an enhancement over the rudimentary anatomy available from the emission images alone. Anatometabolic fusion images made using this reasonably simple method should prove useful in the management of patients with cancer and other diseases.     

FDG PET and dual-head gamma camera positron coincidence detection imaging of suspected malignancies and brain disorders

The purpose of the study was to compare the diagnostic accuracy of fluorodeoxyglucose (FDG) images obtained with a dual-head coincidence gamma camera (DHC) with those obtained with a dedicated PET in a series of 26 patients. METHODS: Nineteen patients with known or suspected malignancies and 7 patients with neurological disorders underwent PET imaging after injection of approximately 10 mCi of FDG. Whole-body imaging was performed on 19 patients and brain imaging on 7 patients. DHC images were then acquired for 30 min over the region of interest using a dual-head gamma camera equipped with 3/8-in.-thick NaI(TI) crystals and parallel slit-hole collimators. The images were reconstructed in the normal mode, using photopeak/photopeak, photopeak/Compton and Compton/photopeak coincidence events. RESULTS: Although the spatial resolutions of PET with a dedicated PET scanner and of DHC are in the same range, the lesion detectability remains superior with PET (4 mm for PET versus 13.5 mm for DHC in phantom experiments) with a contrast ratio of 5:1. This is most probably attributable to the higher sensitivity of PET (2238 coincidences/min/microCi for PET versus 89 coincidences/min/microCi for DHC). The pattern of uptake and interpretation for brain imaging was similar on both PET and DHC images in all patients. In the 19 oncology patients, 38 lesions ranging from 0.7 to 5 cm were detected by PET. DHC imaging detected 28 (73%) of these lesions. Among the 10 lesions not seen with DHC, 5 were less than 1.2 cm, 2 were located centrally within the liver and suffered from marked attenuation effects and 3 were adjacent to regions with high physiological activity. The nondetectability of some lesions with DHC compared with PET can be explained by several factors: (a) start of imaging time (mean+/-SD: 73+/-16 min for PET versus 115+/-68 min for DHC, leading to FDG decay to 6.75 mCi for PET and 5.2 mCi for DHC); (b) limited efficiency of a 3/8-inch-thick Nal(TI) crystal to detect 18F photons; (c) suboptimal two-dimensional reconstruction algorithm; and (d) absence of soft-tissue attenuation correction for centrally located lesions. CONCLUSION: FDG DHC imaging is a promising technique for oncological and brain imaging.     

Diagnosis of pancreatic carcinoma: role of FDG PET

OBJECTIVE: The purpose of this study was to investigate the role of positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in differentiating benign from malignant disease in patients with possible pancreatic malignancy. SUBJECTS AND METHODS: All patients with a possible diagnosis of pancreatic carcinoma based on CT or ERCP findings were eligible for inclusion in this prospective study. PET imaging of the abdomen was performed in 37 patients and was interpreted as positive if FDG activity in the pancreas exceeded background activity and as negative if activity was less than or equal to background activity. Semiquantitative analysis was performed by calculating a standardized uptake ratio. Studies were reviewed independently by two radiologists, and results were correlated with biopsy results and with CT and ERCP findings. Sensitivity and specificity of FDG PET for revealing pancreatic malignancy was determined. RESULTS: FDG activity in the pancreas was increased in 24 patients, and adenocarcinoma was diagnosed in 22 of these patients (92%). Two patients (8%) with increased activity had benign disease, including one patient with chronic pancreatitis who showed no evidence of tumor at laparotomy and one patient with a mucinous cystic tumor who showed no malignant features at laparotomy. FDG uptake was low or normal in 13 patients, 10 of whom (77%) had benign disease. FDG uptake was also low in three patients with adenocarcinoma, whose tumor size ranged from 2 to 4 cm in diameter. The mean standardized uptake ratio value for malignant disease was 5.1 (range, 1.0-10.1) and for benign disease was 1.9 (range, 0.0-5.8) (p < .001). The sensitivity of FDG PET for revealing malignant disease in the pancreas was 88% and the specificity was 83%. CONCLUSION: FDG PET is a sensitive and specific noninvasive technique for the diagnosis of pancreatic malignancy.     

Pheochromocytomas that do not accumulate metaiodobenzylguanidine: localization with PET and administration of FDG

Many imaging methods can be used to detect pheochromocytoma, but some tumors are not detected with conventional modalities. To explore the possible usefulness of positron emission tomography (PET) after administration of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) to localize pheochromocytoma in patients with false-negative scintigrams obtained after administration of metaiodobenzylguanidine (MIBG), FDG was administered and PET was performed in two adult patients with pheochromocytomas that had never been localized despite administration of MIBG. In both patients, images were obtained dynamically for 50 minutes; then a limited truncal sequence was performed. PET enabled correct localization of the tumors. In patient 1, a tumor that had not been detected for 21 years was localized in the middle mediastinum; in patient 2, a pheochromocytoma was detected in the right adrenal gland. PET performed after administration of FDG may be useful for localization of pheochromocytomas that do not accumulate MIBG.     

Combined study with FDG PET and Tl SPECT in patients with idiopathic dilated cardiomyopathy

This study aimed to determine whether combined examinations of myocardial 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) and stress-redistribution 201Tl single-photon emission computed tomography (Tl SPECT) were useful in clarifying myocardial ischaemia and evaluating the prognosis in patients with idiopathic dilated cardiomyopathy (IDCM). Twenty-two patients with IDCM underwent echocardiography, cardiac catheterization, FDG PET, and Tl SPECT. In scintigraphic analysis, the total defect score (TDS) was semiquantitatively determined as the sum of scores of the 17 left ventricular (LV) segments with a 5-point scale (0 as normal to 4 as absent). Patients were classified according to the scintigraphic findings as follows: eight patients with small defects on Tl and FDG (TDS < or = 20) (group I), eight patients with small defects on FDG (TDS < or = 20) with FDG uptake increased relative to Tl or 'mismatch' (group II), and six patients with large defects on FDG and Tl (TDS >20) (group III). Eleven patients (50%) showed reversible defects on Tl and all showed preserved FDG uptake. The patients in group III had significantly lower LV ejection fraction (LVEF) (P<0.05, respectively) and a poorer prognosis as shown by the Kaplan-Meier event-free curve compared with those in groups I and II (P<0.01, respectively). Although patients in group II had significantly greater TDS on Tl compared with those in group I (P<0.01), no significant differences in LVEF and prognosis were found between patients in groups I and II. In multivariate analysis, a TDS on FDG revealed an independent predictor of subsequent cardiac events. In conclusion, such mismatched areas can be assumed to consist of impaired but viable myocardium, and may be associated with ischaemia of the microvasculature. Impaired myocardial glucose metabolism is a more powerful predictor of future cardiac events than perfusion abnormality in patients with IDCM.     

Lesion-to-background ratio in nonattenuation-corrected whole-body FDG PET images

The purpose of this study was to compare the diagnostic efficacy of attenuation-corrected and nonattenuation-corrected whole-body 18F-fluorodeoxyglucose (FDG) PET images to determine an adequate method that can semiquantitatively evaluate nonattenuation-corrected images. METHODS: Whole-body PET studies were performed in 24 fasting patients with various tumors (lung cancers, n = 18; mediastinal tumors, n = 4; breast cancers, n = 2) 30-40 min after a bolus injection of 18F-FDG. Transmission scans followed emission data acquisition. Reconstructed attenuation-corrected and uncorrected images were displayed simultaneously and the relative FDG uptake in lesions and corresponding background areas was evaluated by the region of interest method. Both types of images were also compared with X-CT scans and conventional nuclear medicine scans for diagnostic efficacy. RESULTS: Attenuation-corrected and uncorrected images were found to be equally sensitive for detecting lesions. There was a strong linear correlation between lesion-to-background (L/B) ratios calculated on attenuation-corrected and uncorrected images (r = 0.98; p < 0.001). Significant differences in L/B ratios between attenuation-corrected and uncorrected images were present in only 6 of 55 lesions (11%). Standardized uptake ratios (SURs) in attenuation-uncorrected images did not correlate with SURs in attenuation-corrected images nor with L/B ratios in uncorrected images. CONCLUSION: The efficacy of attenuation-uncorrected FDG PET images in evaluating tumors is similar to that using attenuation-corrected images. Uncorrected images provide not only clinically useful but also quantitative information equivalent to that provided by attenuation-corrected images. However the L/B ratio is the only available index that can be used for quantification of uncorrected images.     

Visual diagnosis of hematologic and oncologic diseases

Cancer-related problems are seen frequently by the emergency physician. More difficult presentations are seen with premonitory symptoms, paraneoplastic syndromes, and nonspecific lesions. Dermatologic paraneoplastic syndromes are numerous, nonspecific, and consist of hamartomatous growths, texture changes, new hair growth, or changes in skin color. Alteration of skin color may be of practically any color, localized or diffuse, and of sudden or indolent onset. Hormone production by tumors may lead to acne, hirsutism, gynecomastia, or a cushingoid appearance. Pruritus may herald the onset of leukemia or lymphoma and be intolerable, as with erythroderma. All suspicious presentations require thorough investigation for underlying disease. Metastasis to skin is not common and implies a poor prognosis if seen. Most metastases are seen on the head and neck, anterior chest wall, and abdomen. Basal cell and squamous cell carcinomas commonly occur in sun-exposed areas. Basal cell is locally destructive, whereas squamous cell occasionally metastasizes to local lymph nodes. Malignant melanoma is the leading fatal illness originating in skin, with a dramatic rise in incidence. It is classically described as asymmetric with irregular borders, is elevated, and shows color variegation; however, melanoma may present atypically, particularly in non-whites. Kaposi's sarcoma lesions are well-demarcated, symmetric, smooth nodules that appear purplish-brown, particularly if below the knee (owing to venous stasis). The closely interrelated structures of the eye and orbit are easily disturbed, leading to the presenting symptoms of visual disturbances, exophthalmos, pain, and ocular motility disorders. Primary tumors are not unusual and may include retinoblastoma, rhabdomyosarcoma, and melanoma. Equally common are metastatic lesions, most commonly lung and breast carcinoma. An estimation of the malignancy of bony lesions can be made by assessing the zone of transition, periosteal reaction, and bone destruction. A malignant lesion will more likely have a broad zone of transition, irregular periosteal reaction, and moth-eaten or permeative destruction of trabeculae. Metastatic bone lesions primarily occur in sites of persistent red marrow: skull, ribs, vertebrae, pelvis, and proximal humerus and femur. Bony lesions can be blastic or lytic in nature. Solitary pulmonary nodules that have not grown for 2 years can be assumed to be benign. Calcification seen on plain films are a strong (but not absolute) indication of benignancy. Lesions that are greater than 3 to 4 cm in diameter, have irregular contours, are cavitated with thick walls, have multiple peripheral nodules, and have lack of calcification are more likely malignant.     

Coregistration of FDG PET and MRI of the head and neck using normal distribution of FDG

For better localization of head and neck structures by PET with 2-(18)F-2-deoxy-D-glucose (FDG), direct incorporation of anatomical information from MRI by the coregistration of FDG PET and MRI without external markers is proposed. METHODS: Seventeen patients with neoplasms and 16 normal subjects who had both FDG PET and MRI were studied. First, the three-dimensional normal distribution of FDG was evaluated, and then the structures of the head and neck regions with normal distribution patterns of FDG were used as internal markers for the coregistration of PET and MRI. The effectiveness of the coregistration was evaluated using focal neoplasms that were identified by both PET and MRI as fiducial internal markers. RESULTS: The normal structures selected as internal landmarks for coregistration were the tonsils, salivary glands, mucosal layers of the oral cavity and pharynx, spinal cord, inferior portion of the frontal lobe, cerebellum and nasal turbinates. These structures were more easily observed in sagittal or coronal sections than in transaxial sections. All primary neoplasms were delineated by PET, whereas 4 were missed by MRI. Thirteen primary tumors and 7 cervical lymph node metastases coregistered well, with a center-of-mass distance of <2 mm, whereas 10 lymph node metastases were slightly misregistered, with a center-of-mass distance of 7.8+/-6.5 mm (mean+/-s.d.), probably due to differences in neck positions. CONCLUSION: Normal distribution of FDG uptake in the head and neck regions delineated by multidirectional sections is important for effective coregistration of FDG PET with MRI.     

Imaging of mediastinal lymph nodes: CT, MR, and FDG PET

The evaluation of mediastinal lymph nodes is an important aspect of staging in patients with non-small cell lung cancer. Anatomic imaging of lymph nodes with computed tomography (CT) and magnetic resonance (MR) imaging has been limited by the relatively low sensitivity and specificity of these techniques. Advances in physiologic imaging of mediastinal lymph nodes with 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) have resulted in improved diagnostic accuracy in the determination of nodal status. Despite the limitations of CT, this technique still plays an important role by aiding in the selection of the most appropriate procedure for staging, by guiding biopsy, and by providing anatomic information for visual correlation with FDG PET images. At present, anatomic MR imaging of lymph nodes is primarily a problem-solving tool for cases with inconclusive CT results. Physiologic MR imaging with iron oxide is an exciting area of investigation, and the accuracy of this technique is being assessed in clinical trials. Anatomic and physiologic imaging techniques should be considered complementary rather than competitive imaging strategies.     

Standardized uptake value and quantification of metabolism for breast cancer imaging with FDG and L-[1-11C]tyrosine PET

The aims of the study were to compare the value of L-[1-11C]tyrosine (TYR) and [IBF]fluoro-2-deoxy-D-glucose (FDG) as tumor tracers in patients with breast cancer, to investigate the correlation between quantitative values and standardized uptake values (SUVs) and to estimate the value of SUVs for the evaluation of therapy. METHODS: Eleven patients with one or more malignant breast lesions and two patients with one or more benign breast tumors were studied with TYR and FDG. Doses of 300 MBq of TYR and 230 MBq of FDG were given intravenously. All PET sessions were performed using a Siemens ECAT 951/31 camera. Of 10 malignant tumors and the 3 benign lesions, glucose consumption and protein synthesis rate were quantified. All lesions were studied using SUVs based on body weight, body surface area and lean body mass, with and without correction for plasma glucose or tyrosine levels. RESULTS: All malignant tumors were visualized with both FDG and TYR, but the visual contrast was better with FDG. Increased uptake of the tracers was seen in patients with fibrocystic tissue and complicated the visual assessment and the outlining of tumor tissue. Uptake in fibrocystic disease was more prominent with FDG than with TYR. No difference in tumor/nontumor ratio between the two tracers could be established. FDG showed a false-positive result in one benign lesion. No major differences between the SUVs as defined above were found, although the best correlation between glucose consumption and the SUV was observed when the SUV was based on body surface area and corrected for plasma glucose level (r = 0.85-0.87). The SUV based on lean body mass was found to correlate best with protein synthesis rate (r = 0.83-0.94). CONCLUSION: In this group of patients, TYR appears to be a better tracer than FDG for breast cancer imaging, because of lower uptake in fibrocystic disease. SUVs correlate well with quantitative values, but future studies must determine whether treatment evaluation is also reliable with SUVs.     

Radiopharmaceuticals in PET imaging

OBJECTIVE: PET isotopes are being used more commonly in nuclear medicine. This paper introduces the nuclear medicine technologist to the use of PET imaging. The major focus of this article is on the isotopes that are used in this modality and how they differ from traditional isotopes. The nuclear medicine technologist will become familiar with PET isotopes by reading about PET history, the production and availability of PET isotopes, and the use of this modality in a traditional hospital setting.     

Pitfalls in the diagnosis and management of Lyme disease

Absence of plectin, a large cytoskeleton-associated protein expressed in the skin and muscle, has been shown to underlie epidermolysis bullosa with muscular dystrophy (EB-MD), an autosomal recessive disorder (OMIM No. 226670). In the present study, we report the case of a patient who presented with neonatal blistering and late-onset muscular dystrophy with nail and tooth abnormalities, as well as severe mucocutaneous involvement including laryngeal webs and urethral strictures, features not previously reported in this syndrome. Mutation detection, based on the use of heteroduplex analysis, revealed that the proband was a compound heterozygote for two plectin mutations, 4416delC/4359ins13, both resulting in premature termination codons in the plectin rod domain. Because these mutations, and the majority of those previously reported, reside within exon 32 of the plectin gene (PLEC1), we applied the protein truncation test (PTT) to screen for mutations in the two large 3' exons (nos. 32 and 33) of PLEC1, which together comprise approximately 75% of the coding region of the gene. PTT readily detected truncated polypeptides in the proband profiled in this study, as well as in a patient in whom we have previously identified premature termination codon mutations in exon 32. Thus, PTT provides a rapid and reliable strategy to identify premature termination codon mutations from genomic DNA within PLEC1.     

Metastatic head and neck cancer: role and usefulness of FDG PET in locating occult primary tumors

OBJECTIVE: Secondary intracranial hypertension has been linked to leukocytosis. We examined our data bank containing physiologic recordings and outcome data of severely head injured patients to investigate the relationship between delayed increases in intracranial pressure (ICP), defined as occurring after a 12-hr period of normal ICP values, and leukocytosis. DESIGN: A retrospective study of observational data. SETTING: Regional neurosurgical unit and intensive care unit. PATIENTS: Sixty-four patients suffered increased ICP >20 mm Hg. Thirty-five patients fulfilled selection criteria for delayed increases in ICP (group 1). Twenty-nine patients with increased ICP with no preceding or intervening periods of normal ICP were selected as a comparison group (group 2). MEASUREMENTS AND MAIN RESULTS: Comparison of 12-month outcome revealed that 11% of group 1 patients died, with 49% remaining severely disabled, in contrast to group 2, where 35% of patients died and 14% were left severely disabled (p = .021). The pattern of outcome was independent of monitoring time, or injury severity. Regression modeling was performed for prediction of delayed increase in ICP. Of 46 patients with an initial increase then decrease in leukocyte count in the first 48 hrs, 65% experienced delayed increases in ICP, as compared with 18% of the 11 patients without this pattern p = .01 1). CONCLUSIONS: Patients with delayed increases have a significantly different pattern of outcome. Change in leukocyte count from admission to day 2 is a significant predictor of such a delayed increase.     

Pitfalls in the prenatal diagnosis of propionic acidemia

Much has been spoken about the changing nature of general practice, although little documental evidence is available to identify the nature of these changes. Such changes are said to include provision of some diagnostic services, diminishing involvement in surgical and obstetrical procedures, and a lessening of GP involvement in the hospital care of patients. Information about the range of services provided by the average general practitioner is essential knowledge required by planners of undergraduate, vocational and continuing education programmes. In view of the anticipated rapid increase in general practitioner numbers in the near future, further changes in the nature of the discipline are predicted. A survey of general practitioners was therefore proposed by four bodies concerned with medical education relevant to general practice, viz. -- the Victorian Medical Postgraduate Foundation, the Monash University Department of Social and Preventive Medicine (Section of Community Practice), the Royal Australian College of General Practitioners (Victoria Faculty) and the Victorian Academy for General Practice Limited.     

Dopamine transporter imaging with fluorine-18-FPCIT and PET

Fluorinated N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane (FPCIT) has been synthesized as a dopamine transporter ligand for PET studies. We evaluated the regional brain uptake and the plasma metabolism of [18F]-FPCIT. METHODS: PET studies were conducted on 7 normal subjects and on 10 patients with Parkinson's disease. After the [18F]-FPCIT injection (4.4+/-1.8 mCi), dynamic scans were acquired over 100 min. Plasma metabolite analysis was performed using high-performance liquid chromatography (HPLC). RESULTS: Plasma HPLC revealed two peaks corresponding to unmetabolized [18F]-FPCIT and a polar metabolite. The fraction of the parent compound decreased rapidly to 25% at 25 min. Fluorine-18-FPCIT showed a striatum-to-occipital ratio (SOR) of 3.5 at 90 min postinjection. The ratio of striatal-to-occipital distribution volume (DVR) was calculated directly by using a mean tissue-to-plasma efflux constant for occipital cortex obtained in 10 subjects (ki=0.037 min(-1)). DVR measures determined with and without plasma input function were correlated (r=0.98, p < 0.0001). In normal subjects, a significant age-related decline of DVR was observed both for caudate and putamen, corresponding to a 7.7% and 6.4% decline per decade, respectively (r > 0.85, p < 0.01). Both DVR and SOR correctly classified early-stage Parkinson's disease patients with comparable accuracy (p < 0.0001). Age-corrected DVR values correlated negatively with the Uniform Parkinson's Disease Rating Scale composite motor ratings (r=0.66, p < 0.05). CONCLUSION: The tracer characteristics are compatible with a high-affinity, reversible ligand. FPCIT/PET demonstrated age-related decline in dopamine transporter binding in normal subjects as well as significant reductions in patients with idiopathic Parkinson's disease, which correlates with the disease severity.     

Expression of glucose transporters in human pancreatic tumors compared with increased FDG accumulation in PET study

Although overexpression of GLUT-1 glucose transporter has already been reported in human cancers, the mechanism of glucose entry into pancreatic cancers remains unknown. To evaluate the relationship between GLUT glucose transporters and FDG uptake, FDG-PET was performed in 34 preoperative patients (mean age, 60.9 yr) with suspected pancreatic tumors, including 28 malignant and 6 benign tumors. METHODS: FDG uptake at 50 min after injection of 185 MBq of [18F]FDG with >5 hr of fasting was semiquantitatively analyzed as standardized uptake values (SUVs). The GLUT expression was studied by immunohistochemistry of paraffin sections from these tumors after operation using anti-GLUT-1, -2, -3, -4 and -5 antibodies to obtain immunohistochemical grading ("strong," "weak" and "negative") by three experienced physicians. RESULTS: Of 26 malignant tumors proved by histological examination, 23 (88%) tumors were positive for the expression of GLUT-1 glucose transporter, and 17 (61%) showed strong expression. On the other hand, 13 (46%), 0 (0%), 9 (36%) and 13 (46%) malignant tumors were positive for the expression of GLUT-2, -3, -4 and -5 glucose transporters, respectively. Three of six benign tumors showed strong GLUT-1 expression. Concerning GLUT-2, -3, -4 and -5, only one benign tumor showed positive GLUT-5 expression. Thus, GLUT-1 showed relatively high sensitivity but low specificity (50%) for detecting malignant tumors, whereas GLUT-2, -3, -4 and -5 had lower sensitivities but higher specificities. Correlations between SUVs and grading of GLUT immunoreactivity were significant in GLUT-1 (strong, 4.49 +/- 2.95; weak, 3.42 +/- 1.21; negative, 2.52 +/- 0.84) (p < 0.05) but not in the remaining four GLUT transporters. CONCLUSION: These data indicate that GLUT-1 has a significant role in the malignant glucose metabolism and may contribute to the increased uptake of FDG in PET imaging in patients with pancreatic tumor.