18F-FDG PET/CT as a diagnostic tool in patients with extracervical carcinoma of unknown primary site: a literature review

BACKGROUND

Carcinoma of unknown primary (CUP) represents a heterogeneous group of metastatic malignancies for which no primary tumor site can be identified after extensive diagnostic workup. Failure to identify the primary site may negatively influence patient management. The aim of this review was to evaluate (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) as a diagnostic tool in patients with extracervical CUP.

MATERIALS AND METHODS

A comprehensive literature search was performed and four publications were identified (involving 152 patients) evaluating (18)F-FDG PET/CT in CUP patients with extracervical metastases. All studies were retrospective and heterogeneous in inclusion criteria, study design, and diagnostic workup prior to (18)F-FDG PET/CT.

RESULTS

(18)F-FDG PET/CT detected the primary tumor in 39.5% of patients with extracervical CUP. The lung was the most commonly detected primary tumor site (∼50%). The pooled estimates of sensitivity, specificity, and accuracy of (18)F-FDG PET/CT in the detection of the primary tumor site were 87%, 88%, and 87.5%, respectively.

CONCLUSIONS

The present review of currently available data indicates that (18)F-FDG PET/CT might contribute to the identification of the primary tumor site in extracervical CUP. However, prospective studies with more uniform inclusion criteria are required to evaluate the exact value of this diagnostic tool.

Melanoma

This chapter discusses the value of FDG-PET and combined FDG-PET/CT in staging and follow-up of melanoma patients. For melanoma patients, the presence or absence of regional lymph node metastases is one of the most important prognostic factors; the recent development of sentinel lymph node biopsy offers a highly sensitive staging method. FDG-PET has shown a limited sensitivity to detect microscopic lymph node metastases in this selected group of patients with stages I and II melanoma. However, for the detection of distant metastases, FDG-PET is frequently used. Although there is no consensus, some surgeons pursue surgical excision of metastatic disease if only one or a few sites of disease are apparent. Precise identification of the location and number of metastatic lesions could therefore be important for surgical planning. Even though patients with metastatic melanoma generally have a poor prognosis (5-year survival 3-16%), there is still a need for accurate staging. Firstly, to identify those patients who may benefit from a surgical procedure, while avoiding these potentially harmful surgical procedures for patients with multiple distant metastases. Secondly, accurate staging is important to improve the efficiency of clinical trials, and thirdly, to provide patients with detailed information about their prognosis. Taking the published literature together, and reasoning that FDG-PET/CT is the current standard in PET imaging, there may be a case for the combined PET/CT in the setting of metastatic melanoma. However, further research is needed as the benefit of the combined FDG-PET/CT vs. FDG-PET alone seems to be less than reported for other tumor entities, which may be due to the high avidity of melanoma for FDG, so that many of the metastases are detected with FDG-PET and the additional CT does not increase the sensitivity.

PET-CT in radiotherapy for lung cancer

For NSCLC, F-18 FDG-PET scans allow more thorough staging, thus avoiding unnecessary treatments. It reduces radiation treatment volumes because of the avoidance of mediastinal lymph nodes that are PET negative and hence reduces toxicity with the same radiation dose or enables radiation dose escalation with the same toxicity. Further research is needed to assess the effect of PET on survival. PET also reduces interobserver variability for delineating tumors and opens perspective for more automated delineation parts in radiation planning. F-18 FDG-PET-CT scans can already at present be used in routine clinical practice. It is of paramount importance that the necessary calibrations have been done and that strictly standardized protocols for every step in the treatment and planning chain are implemented. For the delineation of target volumes, a combination of PET-CT images, auto-delineation tools, and last not but least manual editing of the target volumes is necessary. The latter is needed because of resolution deficiencies of PET and any other imaging modality as well as the incorporation of other that image information (e.g., know patterns of tumor spread according to pathological studies, knowledge of endoscopic findings, and other tumor and patient factors) to come to target volume definitions that have proven their clinical efficacy.

PET and PET-CT in esophageal and gastric cancer

Esophageal cancer ranks among the ten most common malignancies in the world and is a frequent cause of cancer-related death. Almost all therapeutic modalities for esophageal cancer are associated with considerable mortality and morbidity. Consequently, there has been growing concern regarding effective management of esophageal cancer. Imaging plays an important role in the initial selection of patients. 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) is playing an increasing role in the management of esophageal cancer. The role of FDG-PET in diagnosis, preoperative staging, monitoring of response to neoadjuvant therapy, and detection of disease recurrence is evaluated in this chapter.

Sarcoma

Sarcomas are a diverse group of malignancies originating in the connective tissue. The approach of a patient with a mass suspect for sarcoma starts with performing a biopsy to obtain tissue for evaluation by pathology. The main role of the current imaging modalities, in general, is to recognize patients with typically benign disease, in whom further invasive staging can be omitted, and select patients with a suspected malignancy, who should be referred for biopsy. Since soft tissue sarcoma tends to be large and heterogeneous, there is growing interest in using imaging modalities to guide these biopsies. Together with pathology, imaging modalities are the basis for accurate staging, evaluation of locoregional extent of the primary lesion, screening for occult metastases, evaluation of response to cancer treatment, and the detection of tumor recurrence. In this chapter, an overview is given of the use of 18F-FDG PET in these settings, its strengths as well as its limitations.

Adaptive imaging for lesion detection using a zoom-in PET system

Positron emission tomography (PET) has become a leading modality in molecular imaging. Demands for further improvements in spatial resolution and sensitivity remain high with growing number of applications. In this paper we present a novel PET system design that integrates a high-resolution depth-of-interaction (DOI) detector into an existing PET system to obtain higher-resolution and higher-sensitivity images in a target region around the face of the high-resolution detector. A unique feature of the proposed PET system is that the high-resolution detector can be adaptively positioned based on the detectability or quantitative accuracy of a feature of interest. This paper focuses on the signal-known-exactly, background-known-exactly (SKE-BKE) detection task. We perform theoretical analysis of lesion detectability using computer observers, and then develop methods that can efficiently calculate the optimal position of the high-resolution detector that maximizes the lesion detectability. We simulated incorporation of a high-resolution DOI detector into the microPET II scanner. Quantitative results verified that the new system has better performance than the microPET II scanner in terms of spatial resolution and lesion detectability, and that the optimal position for lesion detection can be reliably predicted by the proposed method.

Detection of bone lesions by CT in POEMS syndrome

OBJECTIVE

To study the utility of CT for detection of small bone lesions in POEMS (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes) syndrome. For patients with a solitary bone lesion, irradiation is a first-line treatment, whereas systemic chemotherapy is indicated for patients with multiple bone lesions. Therefore it is important to correctly identify the number of bone lesions.

METHODS

We studied the sensitivity of chest/abdomen/pelvic CT to detect bone lesions in 28 patients with POEMS syndrome. (99m)Tc-HMDP bone scintigraphy was performed in 14 patients, and the results were compared with CT.

RESULTS

CT showed multiple bone lesions in 68% of the 28 patients, and 71% of the lesions had a diameter <10 mm. In 14 patients who underwent both CT and scintigraphy, bone lesions were detected in 57% by CT and in 79% by scintigraphy, but the location and nature of the identified lesions were considerably different; CT frequently showed small lesions (diameter <10 mm) in the vertebrae and pelvis, which were not detected by scintigraphy, whereas scintigraphy could show lesions in the skull and long bones. Overall, by using both examinations, multiple bone lesions were found for 86% of patients.

CONCLUSION

CT is particularly useful to detect small bone lesions. CT and bone scintigraphy are complementary, and therefore both should be performed for bone survey in POEMS syndrome.

FDG PET and PET/CT for colorectal cancer

The evaluation of patients with known or suspected recurrent colorectal carcinoma is now an accepted indication for positron emission tomography using (18)F-fluorodeoxyglucose (FDG-PET) imaging. PET and CT are complimentary, and therefore, integrated PET/CT imaging should be performed where available. FDG-PET/CT is indicated as the initial test for diagnosis and staging of recurrence, and for preoperative staging (N and M) of known recurrence that is considered to be resectable. FDG-PET imaging is valuable for the differentiation of posttreatment changes from recurrent tumor, differentiation of benign from malignant lesions (indeterminate lymph nodes, hepatic, and pulmonary lesions), and the evaluation of patients with rising tumor markers in the absence of a known source. The addition of FDG-PET/CT to the evaluation of these patients reduces overall treatment costs by accurately identifying patients who will and will not benefit from surgical procedures. This new powerful technology provides more accurate interpretation of both CT and FDG-PET images and therefore more optimal patient care. PET/CT fusion images affect the clinical management by guiding further procedures (biopsy, surgery, and radiation therapy), excluding the need for additional procedures, and changing both inter- and intramodality therapy.

PET and PET-CT of lung cancer

Accurate staging is essential to offer the patient the most effective available treatment and the best estimate of prognosis. In non-small cell lung cancer (NSCLC), surgical resection offers the best chance of cure in the early stages, either alone or in combination with chemo- or radiotherapy at the more advanced stages. However, many patients present with metastatic disease at the time of diagnosis. Both computed tomography (CT) and positron emission tomography (PET) using fluorodeoxyglucose (FDG) play an important role in the diagnosis and staging of lung cancer. CT provides excellent morphologic information but has significant limitations in differentiating between benign and malignant lesions either in an organ or in lymph nodes. FDG-PET is highly accurate in the detection of mediastinal lymph node metastases as well as extratharacic metastases. However, due to the poor anatomic information provided by PET, additional morphologic information is needed to properly locate a lesion. Imaging with PET integrated with computed tomography (PET/CT) offers essential advantages in comparison to PET alone, CT alone, or visual correlation of separate PET and CT. A combined PET/CT system provides PET and CT images perfectly coregistered so that lesions can be exactly localized.

Variability of textural features in FDG PET images due to different acquisition modes and reconstruction parameters

BACKGROUND

Characterization of textural features (spatial distributions of image intensity levels) has been considered as a tool for automatic tumor segmentation. The purpose of this work is to study the variability of the textural features in PET images due to different acquisition modes and reconstruction parameters.

MATERIAL AND METHODS

Twenty patients with solid tumors underwent PET/CT scans on a GE Discovery VCT scanner, 45-60 minutes post-injection of 10 mCi of [(18)F]FDG. Scans were acquired in both 2D and 3D modes. For each acquisition the raw PET data was reconstructed using five different reconstruction parameters. Lesions were segmented on a default image using the threshold of 40% of maximum SUV. Fifty different texture features were calculated inside the tumors. The range of variations of the features were calculated with respect to the average value.

RESULTS

Fifty textural features were classified based on the range of variation in three categories: small, intermediate and large variability. Features with small variability (range ≤ 5%) were entropy-first order, energy, maximal correlation coefficient (second order feature) and low-gray level run emphasis (high-order feature). The features with intermediate variability (10% ≤ range ≤ 25%) were entropy-GLCM, sum entropy, high gray level run emphsis, gray level non-uniformity, small number emphasis, and entropy-NGL. Forty remaining features presented large variations (range > 30%).

CONCLUSION

Textural features such as entropy-first order, energy, maximal correlation coefficient, and low-gray level run emphasis exhibited small variations due to different acquisition modes and reconstruction parameters. Features with low level of variations are better candidates for reproducible tumor segmentation. Even though features such as contrast-NGTD, coarseness, homogeneity, and busyness have been previously used, our data indicated that these features presented large variations, therefore they could not be considered as a good candidates for tumor segmentation.

The application of SPECT/CT scintigraphy with MIBI-Tc⁹⁹(m) in the diagnosis of thyroid nodules - a preliminary report

INTRODUCTION

Thyroid cancer diagnosis is based mainly on fine needle aspiration biopsy (FNAB) performed under ultrasonography guidance. Questions arise in cases of an inconclusive FNAB result - when there is no clear evidential data to support the existence of a malignant lesion or when there are any other reasons which make the decision process difficult, such as the patient's age or coexisting diseases. To clarify this issue the patient should be encouraged to undergo surgery treatment or to be followed up. Thyroid scintigraphy with an oncophilic tracer such as MIBI-Tc⁹⁹(m) may be helpful.

MATERIAL AND METHODS

The study comprised a group of 12 patients, aged 54-75 (av. 63.5) years, who, in 2009, underwent planar and SPECT/CT thyroid scintigraphy with MIBI-Tc⁹⁹(m) using washout method. The tumour/background ratio in early and delayed images was calculated and the wash-out ratio was estimated. Patients with increased focal lesion uptake were operated on and the lesions were histopathologically verified.

RESULTS

Abnormal scintigraphy results were obtained in 8 patients (10 lesions) and normal results in 4 patients (5 lesions). Out of 15 studies, in 13 cases the washout from the lesion was observed within 2 hours. It was noticed that the images obtained with SPECT/CT washout method were clearer and easier to read in comparison to planar studies. Three patients with an abnormal results underwent surgery and had benign histopathology results after the operation, in 3 patients the observation is being confirmed without any increase in malignancy suspicions, and 2 were lost for observation.

CONCLUSIONS

Our preliminary results do support the use of MIBI-Tc⁹⁹m in the evaluation of indeterminate thyroid nodules. To validate the hypothesis that MIBI-Tc⁹⁹(m) may be used to exclude malignancy in lesions indeterminate by FNAB we propose to use SPECT-CT derived images and standardized evaluation criteria.

Randomized follow-up study of resected NSCLC patients: conventional versus 18F-DG coincidence imaging

The aim of this study was to compare the utility of gamma camera using a coincidence detection system imaging (CDET) with 18-fluorodeoxyglucose to conventional imaging techniques in the detection of recurrence of non-small cell lung cancer. Sixty-nine patients were randomized into two groups for follow-up after surgery from October 2000 to December 2002. Each patient was evaluated every 6 months by conventional technique imaging in group A (n=33) or CDET imaging in group B (n=36) over two years. The direct costs of each procedure were evaluated. The major endpoint was the number of recurrences or new tumours detected. The two groups were similar. A total of 25 recurrences was detected (9 in group A and 16 in group B). Overall survival was similar in the two groups. CDET imaging was more expensive. CDET imaging provides earlier detection of recurrence, but does not modify survival outcome. Further studies are necessary to demonstrate the impact, if any, of 18-FDG imaging.

Role of 18F-DOPA PET/CT imaging in congenital hyperinsulinism

Congenital hyperinsulinism is a leading cause of severe hypoglycaemia in the newborn period. There are two (diffuse and focal) histological subtypes of congenital hyperinsulinism. The diffuse form affects the entire pancreas and if medically unresponsive will require a near total (95%-98%) pancreatectomy. The focal form affects only a small region of the pancreas (with the rest of the pancreas being normal in endocrine and exocrine function) and only requires a limited pancreatectomy. This limited section of the focal lesion has the potential for curing the patient. Thus the pre-operative differentiation of these two subgroups is extremely important. Recent advances in Fluorine-18-L-dihydroxyphenylalanine positron emission tomography ((18)F-DOPA PET/CT) have radically changed the clinical approach to patient with congenital hyperinsulinism. In most patients this novel imaging technique is able to offer precise pre-operative localisation of the focal lesion, thus guiding the extent of surgical resection.

Visual Processing Impairments and Decrements in Regional Brain Activity in Alzheimer’s Disease

The relationships between intermediate visual processes, involving object and space perception, and regional brain activity using positron emission tomography and single photon emission tomography were investigated in 16 patients with Alzheimer's disease. Significant region specific correlations were found between unfamiliar face matching and cerebral activity in the left occipito-temporal region and middle/inferior temporal regions bilaterally. Letter-word identification correlated significantly with brain activity in the angular gyri and occipital association cortices bilaterally, as well as a broad region of activation in the left hemisphere temporal, parietal and occipital lobes. Additionally, a significant correlation was found between ratings of performance of instrumental activities of daily living and brain activity in occipito-temporal and middle/inferior temporal regions. The present study demonstrates that the neuropathological distribution typically seen in Alzheimer's disease corresponds to impairments in specific aspects of intermediate visual perceptual processing, and it is related to the daily living skills of patients with Alzheimer's disease.

Radionuclide imaging of cardiac autonomic innervation

Cardiac autonomic function plays a crucial role in health and disease, with abnormalities both reflecting the severity of the disease and contributing specifically to clinical deterioration and poor prognosis. Radiotracer analogs of the sympathetic mediator norepinephrine have been investigated extensively, and are at the brink of potential widespread clinical use. The most widely studied SPECT tracer, I-123 metaiodobenzylguanidine ((123)I-mIBG) has consistently shown a strong, independent ability to risk stratify patients with advanced congestive heart failure. Increased global cardiac uptake appears to have a high negative predictive value in terms of cardiac events, especially death and arrhythmias, and therefore and may have a role in guiding therapy, particularly by helping to better select patients unresponsive to conventional medical therapies who would benefit from device therapies such as an ICD (implantable cardioverter defibrillator), CRT (cardiac resynchronization therapy), LVAD (left ventricular assist device), or cardiac transplantation. Cardiac autonomic imaging with SPECT and PET tracers also shows potential to assess patients following cardiac transplant, those with primary arrhythmic condition, coronary artery disease, diabetes mellitus, and during cardiotoxic chemotherapy. Radiotracer imaging of cardiac autonomic function allows visualization and quantitative measurements of underlying molecular aspects of cardiac disease, and should therefore provide a perspective that other cardiac tests cannot.

[Tomographic methods in the assessment of myocardial perfusion]

Myocardium visualization using the most up-to-date tomographic techniques is extremely important in clinical cardiology. Myocardial viability assessment is of particular importance in management of patients with Ischemic Heart Disease (IHD). Although rest echocardiography is the most common in assessment of heart function, nuclear cardiology (SPECT and PET), and recently cardiac computed tomography and magnetic resonance become playing important clinical roles. Determining and understanding of real capabilities of these methods is of great necessity in this regard. This review examines the current abilities of current cardiac tomographic modalities for the assessment of myocardial perfusion in patients with known IHD.

Minimising activity and dose with enhanced image quality by radiopharmaceutical administrations

Owing to the introduction of new diagnostic procedures, such as computed tomography (CT), positron emission tomography (PET) and single photon emission computed tomography (SPECT), the individual dose caused by medical exposures has grown rapidly in the last years. This is especially a subject to radiation protection for nuclear medical diagnosis, since in this case radiopharmaceuticals are administered to the patient, meaning not only a radiation exposure to the diseased tissue but also to the healthy tissues of large parts of the body. 'Minimizing Activity and Dose with Enhanced Image quality by Radiopharmaceutical Administrations' (MADEIRA) is a project cofunded by the European Commission within the Seventh Euratom Framework Programme that aims to improve three-dimensional (3D) nuclear medical imaging technologies significantly. MADEIRA is aiming to improve the efficacy and safety of 3D PET and SPECT functional imaging by optimising the spatial resolution and the signal-to-noise ratio, improving the knowledge of the temporal variation of the radiopharmaceuticals' uptake in and clearance from tumourous and healthy tissues, and evaluation of the corresponding patient dose. Using an optimised imaging procedure that improves the information gained per unit administered dose, MADEIRA aims especially to reduce the dose to healthy tissues of the patient. In this paper, an overall summary of the current achievements will be presented.

Neuroimaging in cannabis use: a systematic review of the literature

BACKGROUND

We conducted a systematic review to assess the evidence for specific effects of cannabis on brain structure and function. The review focuses on the cognitive changes associated with acute and chronic use of the drug.

METHOD

We reviewed literature reporting neuroimaging studies of chronic or acute cannabis use published up until January 2009. The search was conducted using Medline, EMBASE, LILACS and PsycLIT indexing services using the following key words: cannabis, marijuana, delta-9-tetrahydrocannabinol, THC, cannabidiol, CBD, neuroimaging, brain imaging, computerized tomography, CT, magnetic resonance, MRI, single photon emission tomography, SPECT, functional magnetic resonance, fMRI, positron emission tomography, PET, diffusion tensor MRI, DTI-MRI, MRS and spectroscopy.

RESULTS

Sixty-six studies were identified, of which 41 met the inclusion criteria. Thirty-three were functional (SPECT/PET/fMRI) and eight structural (volumetric/DTI) imaging studies. The high degree of heterogeneity across studies precluded a meta-analysis. The functional studies suggest that resting global and prefrontal blood flow are lower in cannabis users than in controls. The results from the activation studies using a cognitive task are inconsistent because of the heterogeneity of the methods used. Studies of acute administration of THC or marijuana report increased resting activity and activation of the frontal and anterior cingulate cortex during cognitive tasks. Only three of the structural imaging studies found differences between users and controls.

CONCLUSIONS

Functional neuroimaging studies suggest a modulation of global and prefrontal metabolism both during the resting state and after the administration of THC/marijuana cigarettes. Minimal evidence of major effects of cannabis on brain structure has been reported.

Some thoughts on the mechanism of cellular trapping of Cu(II)-ATSM

Cu(II)-ATSM continues to be investigated, both in the laboratory and in the clinic, as a tumor hypoxia imaging agent. However, meaningful interpretation of these images requires a more complete understanding of the mechanism by which the tracer is trapped within the cell. Cu(II)-ATSM is a simple molecule and its biochemical interaction with cells is similarly simple, mainly based upon redox chemistry. Here we suggest that the trapping mechanism is biphasic. The first phase is a reduction/oxidation cycle involving thiols and molecular oxygen. This can be followed by interaction with proteins in the mitochondria leading to more permanent retention of the tracer. The uptake mechanism is complicated by this second step because of the changes in the cell resulting from hypoxia, such as an increase in nicotinamide adenine dinucleotide (NADH) redox state and differences in cellular biochemistry and cell proteomes. These changes may lead to differences in the extent of trapping and retention of the (64)Cu in different cell types. For example, copper uptake might be increased in cells with lower pH due to the lower stability of metal bis(thiosemicarbazones) under acidic conditions. Reaction rates with cellular reductants also vary with pH, which differs between cellular organelles. For Cu(II)-ATSM to reach its full potential, more complete characterization of the mechanism of cellular trapping in different cell types is required.

Pancreatic schwannoma: a case report and literature review with special reference to imaging features

CONTEXT

We report the imaging features of pancreatic schwannomas, a rare benign type of pancreatic tumor.

CASE REPORT

A 66-year-old woman was admitted to our hospital with a pancreatic tumor indicated in medical examinations. Computed tomography (CT), magnetic resonance imaging (MRI) and endoscopic ultrasonography (EUS) revealed a solid and cystic tumor, 3 cm in diameter, within the body of the pancreas. Contrast-enhanced CT, MRI and ultrasonography showed partial enhancement in the solid component. Endoscopic retrograde cholangiopancreatography (ERCP) and angiography showed no abnormal findings. A distal pancreatectomy together with a splenectomy and lymph node dissection were performed with a tentative diagnosis of mucinous cystic neoplasm of the pancreas. The cut surface of the resected pancreas showed a well-demarcated, pale yellow, solid tumor within the pancreas parenchyma. Histopathological examination of the tumor revealed proliferation of the spindle cells showing interlacing and palisading patterns. Immunohistochemically, these spindle cells were positive for S-100 protein and vimentin, and negative for alpha-smooth muscle actin, CD34, and cytokeratin. Thus the tumor was diagnosed as a pancreatic schwannoma.

CONCLUSION

CT and US can detect pancreatic schwannomas as solid and cystic masses, and MRI shows a relatively characteristic feature. Imaging procedures such as CT, MRI and US are able to differentiate a pancreatic tumor, such as a pancreatic schwannoma.

Intraductal oncocytic papillary neoplasm of the pancreas: a radio-pathological case study

CONTEXT

An intraductal oncocytic papillary neoplasm is a rare pancreatic tumor with the potential of developing invasive carcinoma. Its differentiation from other cystic-like neoplasms of the pancreas, such as intraductal papillary mucinous neoplasms, is a challenge for pancreatic imaging.

CASE REPORT

We present the case of a 76-year-old male with painless jaundice caused by an intraductal oncocytic papillary neoplasm of the pancreas. The imaging findings on computed tomography, magnetic resonance including diffusion-weighted imaging, and (18)F-fluorodeoxyglucose positron emission tomography are presented and the radio-pathological correlations are discussed.

CONCLUSION

An intraductal oncocytic papillary neoplasm of the pancreas appears as a cystic tumor communicating with the dilated pancreatic duct featuring intraductal tumor nodules. Intraductal oncocytic papillary neoplasms show a high (18)F-fluorodeoxyglucose-uptake in positron emission tomography and low diffusion values in diffusion-weighted imaging including apparent diffusion coefficient maps which may be a valuable attribute in distinguishing these rare lesions from intraductal papillary mucinous neoplasms.

The utility of radioiodine uptake and thyroid scintigraphy in the diagnosis and management of hyperthyroidism

BACKGROUND AND OBJECTIVES

The value and practice of thyroid radionuclide imaging in the diagnosis and management of hyperthyroidism is unsettled. Our objectives were to determine the influence of thyroid uptake and scintigraphy on the diagnosis of hyperthyroidism and the prediction of outcome following radioiodine therapy.

PATIENTS AND DESIGN

We reviewed records and scintigraphic studies on 881 hyperthyroid patients carried out between 2000 and 2007. The agreement between the clinical and scintigraphic diagnosis was evaluated by kappa statistics. We determined the relationship between 4-h (123)I uptake and the outcome of (131)I treatment in 626 patients. A multiple logistic regression model was used to determine variables influencing treatment outcome in 1 year.

RESULTS

The diagnostic categories were Graves' disease (GD, n = 383), toxic multinodular goitre (n = 253), solitary toxic nodule (n = 164) and Graves' disease coexisting with nodules (n = 81). The mean age of the patients was 58 +/- 17, (M:F 160:721). There was good agreement between clinical and scintigraph diagnosis (K = 0.60, 95% CI 0.57-0.64, P < 0.001); and they were correctly matched in 74%; mismatched in 6% and indeterminate in 20% of patients. Treatment outcome was not associated with scintigraph diagnosis (P = 0.98) or radioiodine uptake at 4 h (P = 0.2). The use of antithyroid medications before treatment predicted treatment failure (odds ratio 2.0, 95% CI 1.2-3.6, P = 0.01).

CONCLUSION

Thyroid scintigraphy and uptake studies did not influence diagnosis or treatment outcomes in most cases of hyperthyroidism. Our findings in this retrospective study do not justify their routine use. Selective scanning will reduce cost and exposure to radioisotopes without compromising diagnostic accuracy or treatment outcomes.

Cardiovascular applications of hyperpolarized contrast media and metabolic tracers

Modern hyperpolarization technology enhances the recordable magnetic resonance signal four to five orders of magnitude, making in vivo assessments of tracer pathways and metabolic compartments feasible. Existing hyperpolarization instrumentation and previous tracer studies using hydroxyethylpropionate (HEP) as an extracellular marker and 14-carbon label pyruvate as examples are described and reviewed as applicable to the working heart. Future metabolic imaging based on the use of hyperpolarized pyruvate needs to consider extra- and intra-cellular label dilution due to glycolysis, lactate oxidation and protein degradation. This dilution can substantially decrease the recordable signals from PDH flux (oxidative decarboxylation of pyruvate) and other pyruvate pathways. The review of previous literature and data suggests that the (13)C-alanine signal is a better index of mitochondrially oxidized pyruvate than L-lactate. These facts and considerations will help in the interpretation of the in vivo recorded hyperpolarization signals of metabolic tracers and contrast media.

The role of integrated (18)F-FDG PET/CT in identification of ectopic ACTH secretion tumors

The role of (18)F-Flurodeoxyglucose positron emission tomography ((18)F-FDG PET) scan in localization of ectopic Cushing's syndrome (EAS) tumor is still controversial. Here, we report on the use of integrated (18)F-FDG PET and computed tomography ((18)F-FDG PET/CT) in localization of EAS tumors in patients with ectopic Cushing's syndrome. Five patients, three men and two women, were reported, whose endocrine investigations and negative pituitary imaging were suggestive of ectopic ACTH secretion. (18)F-FDG PET/CT was performed to identify the source of ACTH secretion. Then the patients were suggested to perform pathologic examination. It turned out that all of these five patients have abnormal markedly intense FDG uptake lesions on (18)F-FDG PET/CT images. Four of them underwent lesion resection, whose plasma ACTH and serum cortisol levels returned to normal after the surgery. Also, they were at last remission from all the symptoms. Pathologic results showed one thymic carcinoid, one pulmonary carcinoid, one thymoma, and one pulmonary carcinoid with upper mediastinum carcinoid. Unfortunately, one patient died due to severe infection and electrolyte disorders. (18)F-FDG PET/CT technology integrates PET and CT imaging in one device so as to increase the accuracy of tumor localization and further improve the prognosis of the patients by curative resection.

FDG PET/CT in the detection of recurrent rectal cancer

The purpose of this study was to assess the additional value of combined fluorine 18 (18F)-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in the follow-up of rectal cancer after surgery. Forty-eight examinations in 30 patients were evaluated retrospectively. CT and PET components were interpreted separately, and this was followed by a consensus reading. Sites of increased FDG uptake as well as PET/CT findings were categorized as benign (1), equivocal (2), or malignant (3). The standard of reference was histology or clinical and imaging follow-up for at least 6 months. Sensitivity, specificity, positive and negative predictive values, and accuracy for differentiating benign (14/31) from malignant (17/31) uptake sites in the small pelvis were 100%, 64%, 77%, 100%, and 84% for PET/CT, and 100%, 29%, 63%, 100%, and 68% for PET, respectively. Regarding extrapelvic abnormalities, PET/CT was able to distinguish benign (31/88) from malignant (57/88) with a sensitivity, specificity, positive and negative predictive values, and accuracy of 100%, 87%, 93%, 100%, and 95%, compared with 96%, 68%, 85%, 91%, and 86% for PET. The rare case of an FDG uptake of adrenal adenoma is documented. PET/CT is valuable in the staging of rectal cancer, particularly for excluding recurrent disease suspected by PET interpretation alone in a considerable number of patients.

Clinical and imaging follow-up after exhaustive liver resection of endocrine metastases: a 15-year monocentric experience

Liver metastases are common in gastroenteropancreatic neuroendocrine tumors and significantly impair survival. Hepatic resection is the only potential curative treatment. The records of 41 consecutive patients undergoing exhaustive resection of liver-only endocrine metastases and followed between 1992 and 2006 were reviewed. Patient's outcome and diagnostic accuracy of somatostatin receptor scintigraphy (SRS) and morphological imaging (MI) for detection of recurrences during post-operative follow-up were assessed. All identified primary had been resected. MI studies including abdominal computed tomography (CT) and/or liver magnetic resonance imaging and thoracic CT if indicated were performed every 6 months; SRS timing was decided by referring clinician. Tumor recurrences were confirmed by pathology or subsequent imaging studies. The results of 136 MI and SRS examinations performed within a 30-day interval from each other were retrospectively compared. Median post-operative follow-up was 51 months (7-165). Recurrences developed in 32 patients (78%), mainly in the liver (n=24) after a median of 19 months (2-79). Five-year overall and disease-free survival rates were 79 and 3% respectively. For recurrence detection, sensitivity, specificity, and accuracy were 89, 94, and 91% for SRS, 68, 91, and 74% for MI respectively. In 11 out of 32 patients (34%), abdominal or extra-abdominal metastases were detected 15.5 months earlier by SRS than MI. In conclusion, despite exhaustive liver surgery for endocrine metastases, hepatic or extra-hepatic recurrences are frequent and develop early. SRS is highly accurate for the detection of recurrences during post-operative follow-up and permitted early diagnosis in one third of patients; therapeutic implications of this early diagnosis remain to be determined.

FDG-PET is Superior to Gallium Scintigraphy in Staging and More Sensitive in the Follow-up of Patients withde novoHodgkin Lymphoma: A Blinded Comparison

Accurate staging of Hodgkin lymphoma (HD) allows for minimization of therapy and reduction of long-term toxicities. The present study prospectively compares FDG-PET with gallium/SPECT scintigraphy at time of diagnosis and in follow-up of 36 patients with HD. Prior to therapy, whole body FDG-PET and gallium/SPECT were performed. Follow-up scans were obtained after 3 cycles of chemotherapy (n = 22), and at the end of chemotherapy (n = 32). Two nuclear medicine physicians independently interpreted scans in blinded and random order and a consensus was obtained. Baseline scans revealed a greater number of supradiaphragmatic disease sites detected by PET, and 5 patients had splenic involvement on PET not noted by gallium (P = 0.05); 3 patients were upstaged on PET. Midway through therapy, 5 patients had positive PET (4 of whom relapsed), and 3 had positive gallium (1 relapsed). At conclusion of chemotherapy, 8 patients had a positive PET (4 relapsed) and 3 had a positive gallium (2 relapsed). In conclusion, diagnostic PET and gallium are largely concordant, with the exception of unique detection of splenic disease by PET. However, more patients have persistently positive PET at the end of chemotherapy compared with gallium (P = 0.04), although only half of these patients have relapsed.

PET Scan Evaluation of Thymic Mass After Autologous Peripheral Blood Stem-cell Transplantation in an Adult with Non-Hodgkin's Lymphoma

We report the case of a 31-year-old man with anaplastic large-cell lymphoma successfully treated with chemotherapy who showed mediastinal widening 5 months after autologous stem-cell transplantation. CT scan and PET evaluations were consistent with the diagnosis of benign thymic hyperplasia. Because of the rapid and aggressive course of this type of lymphoma, and the progressive widening of the mass at CT scan, we performed a mediastinal biopsy that confirmed these findings, showing normal thymic tissue. This is the first case of benign thymic hyperplasia defined with FDG-PET and confirmed by histologic evaluation.

The impact of PET/CT on therapeutic strategy of patients with colorectal cancer metastasis

BACKGROUND/AIMS

The study's aim was to assess the impact of the PET/CT on the therapeutic strategy of the patients with colorectal cancer metastasis.

METHODOLOGY

Fifteen patients who were suspicious of postoperative colorectal cancer metastasis were included in the study. Each patient received a positron emission tomography/computed tomography (PET/CT) after received contrast-enhanced computed tomography (ceCT). The therapeutic strategies were made before and after the PET/ CT respectively. The lesions confirmed by pathology or periodic follow up of ceCT (3 and 6 mo).

RESULTS

Intrahepatic metastases were present in 5 of the 15 patients, total 9 lesions. The specificities of the PET/CT and ceCT were 100%. The patients with intrahepatic metastases were detected by PET/CT and ceCT with a sensitivity of 100% and 80%, respectively (p = 0.0009). Extrahepatic metastases were present in 11 of the 15 patients, total 32 lesions. The specificities of the PET/CT and ceCT were 75% and 50%, respectively. PET/ CT and ceCT were with a sensitivity of 100% and 63.6%, respectively (p = 0.0177). The therapeutic strategies were changed after received PET/CT in 6 (40%) of the 15 patients.

CONCLUSIONS

PET/CT is superior to ceCT for the detection of the metastatic lesions of the colorectal cancer, and is a valuable tool to help select the correct therapeutic strategies.

Positron emission tomography/computed tomography potential pitfalls and artifacts

With the recent use of 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) for tumor staging and treatment response, it is important to recognize many pitfalls, artifacts, and benign uptakes that are commonly encountered. Normal physiology can explain many regions of increased FDG activity, as well as incidental benign tumors and benign metabolic conditions. Recognition of characterization of benign causes and physiologic variants for FDG uptake are discussed to avoid improper characterization as a malignancy. A basic understanding of PET/computed tomographic physics is also discussed, in relation to attenuation correction artifacts caused by metallic implants and contrast agents in the gastrointestinal tract, as well as artifacts caused in fused images due to patient motion. Also presented is the rationale for expected, benign uptake in various metabolic diseases, as well as pharmacologic methods for decreasing the artifacts caused by metabolic diseases. PET/computed tomographic evaluation of the thyroid, thymus, adrenal adenomas, uterus and ovaries, infection/inflammatory changes, and postradiation/chemotherapy changes are also discussed, with expected normal changes, as well as pitfalls and artifacts.

Relation of brain natriuretic peptide level to extent of left ventricular scarring in patients with chronic heart failure secondary to ischemic cardiomyopathy

Multiple factors influence brain natriuretic peptide (BNP) release in patients with heart failure. We hypothesized that extensive myocardial scarring could result in an attenuated BNP response. A total of 115 patients with New York Heart Association class III chronic heart failure and ischemic cardiomyopathy were evaluated for ischemia, hibernation, and myocardial scarring by dipyridamole-rubidium-positron emission tomographic scanning with fluorine-18, 2-fluoro-2-deoxyyglucose. Plasma BNP levels were determined within 2 weeks of the study. Left ventricular dimension and function were evaluated by echocardiography. Patients were categorized as having <33% myocardial scar (n=67) or>or=33% myocardial scar (n=48). BNP measurements were correlated with amount of myocardial scarring. Compared with patients with less scar, those with >or=33% scar had lower BNP levels (mean 317+/-364 vs 635+/-852 pg/ml, median 212 vs 357, p=0.016). Using multiple regression analysis, presence of scarring was associated with decreased BNP response (p=0.022). Further, patients with <33% scar in whom a higher BNP level was noted had more ischemia (51% vs 27%, p=0.01) and greater myocardial hibernation (22+/-14% vs 12+/-7%, p=0.02) compared with patients with >or=33% scar. In conclusion, in patients with chronic heart failure, a decreased BNP response indicated extensive myocardial scarring.

Performance of MAP reconstruction for hot lesion detection in whole-body PET/CT: an evaluation with human and numerical observers

For positron emission tomography (PET) imaging, different reconstruction methods can be applied, including maximum likelihood (ML ) and maximum a posteriori (MAP) reconstruction. Postsmoothed ML images have approximately position and object independent spatial resolution, which is advantageous for (semi-) quantitative analysis. However, the complex object dependent smoothing obtained with MAP might yield improved noise characteristics, beneficial for lesion detection. In this contribution, MAP and postsmoothed ML are compared for hot spot detection by human observers and by the channelized Hotelling observer (CHO). The study design was based on the "multiple alternative forced choice" approach. For the MAP reconstruction, the relative difference prior was used. For postsmoothed ML, a Gaussian smoothing kernel was used. Both the human observers and the CHO performed slightly better on MAP images than on postsmoothed ML images. The average CHO performance was similar to the best human performance. The CHO was then applied to evaluate the performance of priors with reduced penalty for large differences. For these priors, a poorer detection performance was obtained.

[Molecular imaging of cerebral blood flow and metabolism with SPET and PET in principal dementias]

In this review article the significance of molecular imaging techniques, single photon emission tomography and positron emission tomography (SPET and PET), in the diagnosis and differential diagnosis of various types of dementia is described. A major part of this article is focused on molecular imaging in Alzheimer's disease where parietal, temporal and posterior cingulate cortex hypoperfusion and hypometabolism are the predominant findings in molecular imaging modalities. In cases of mild amnestic cognitive impairment, molecular SPET imaging can differentiate patients converting to Alzheimer's disease from non converters. Molecular SPET imaging with pre-synaptic dopamine receptors radioligand ((123)I-ioflupane or DaTSCAN), is the method of choice in order to differentiate Alzheimer's disease from Lewy body dementia. Finally, nuclear medicine procedures support the diagnosis in fronto-temporal and multi-infarct dementia.

How to apply the evidence-based medicine concept to nuclear medicine diagnostic studies -- a review

Evidence-based medicine (EBM) is defined as using the best available evidence for managing patients in daily healthcare practice. Although this approach has been applied successfully in many medical fields, it has not been addressed fully in the radiological discipline in general and nuclear medicine in particular. In this review, the concept of EBM has been introduced briefly and four steps of EBM practice have been explained. Asking answerable questions and finding the best evidence that constitutes the first two parts of EBM practice are explained in brief. The next two steps (appraising the available evidence and applying the best evidence) are explained in more detail. Since the bulk of nuclear medicine studies are of a diagnostic nature and most of the daily practice of a nuclear medicine specialist is involved in diagnosis, we have focused on the diagnosis studies. Systematic reviews are also explained to some extent. Appraisals of other kinds of study, such as interventional or prognosis studies, are not included in this review.

[Novel imaging methods in the diagnosis of epilepsy]

The primary aim of resonance of epilepsy patients is to detect the possible structural aetiology of epilepsy. Imaging will also help in the diagnosis of the epileptic syndrome and thus in the evaluation of prognosis of epilepsy. The neuroradiologist and nuclear medicine specialist will benefit from a good referral devised by a clinician, including among other things a mention, into which brain region the EEG finding is localized. Surgical treatment of epilepsy can be contemplated in difficult epilepsy, especially if the finding in magnetic imaging is clear and compatible with the clinical seizure picture and EEG recording.

The role of radiopharmaceuticals in diagnosis of melanoma malignum

Melanoma malignum belongs to the group of neoplasms with the highest lethality. Due to the continuous increase of incidence in numerous countries, this malignance has become a serious health problem. This highly aggressive neoplasm is a source of metastases to most organs and eo ipso of bad prognosis. Early detection of the primary tumour and of metastases creates a chance for optimal therapy. The methods of nuclear medicine are becoming more popular in diagnostics of melanomas because they offer advantages over traditional methods of anatomic imaging. Functional imaging, based on the use of modern radiopharmaceuticals frequently offers more successful identification and characterization of malignant neoplasms. Over the last few decades there have been numerous attempts to utilize, in the diagnostics of melanomas, a number of compounds labelled with radioactive nuclides. An accepted role in diagnosis of melanoma found a technique of lymphoscintigraphic mapping of lymphatic nodes and of detection of the sentinel node. In addition, modern positron emission tomography (PET) with use of (18)F-fluorodeoxyglucose has found acceptance in melanoma diagnostics. The present review refers to information on the presently used and potential new radiopharmaceuticals promising effective melanoma diagnostics.

Combined imaging modalities: PET/CT and SPECT/CT

The recent development of new radiopharmaceuticals now permits molecular imaging of biologic processes at the cellular level to improve both the diagnosis and treatment of disease. Fused PET/CT and SPECT/CT imaging systems now provide metabolic and functional information from PET or SPECT combined with the high spatial resolution and anatomic information of CT. Because the two sets of images are fused, areas of normal and abnormal metabolic activity can be mapped to recognizable anatomic structures. This fusion of function and anatomy has quickly demonstrated its clinical value, especially in the field of oncology. There are also growing clinical indications in the areas of cardiology, neurology, and imaging of infection. F-18 fluorodeoxyglucose (FDG) is the PET imaging agent currently in most common use. While FDG uptake is nonspecific, it has demonstrated important applications, especially for patients with cancer. Continued progress in fused anatomic and molecular imaging can be anticipated, both in the development of more advanced instrumentation (integrated CT or MRI with PET and SPECT camera technology) and with new radiopharmaceuticals that image more specific physiologic aspects of organ and cell biology.

Therapeutic evaluation and prognostic value of interim hybrid PET/CT with (18)F-FDG after three to four cycles of chemotherapy in non-Hodgkin's lymphoma

PURPOSE

Modern risk-adapted treatment requires accurate assessment of the patient's prognosis. This study assessed the value of hybrid PET/CT with 2-[18F]fluoro-2-deoxy-d-glucose ((18)F-FDG) after 3-4 cycles of chemotherapy for early evaluation of response to therapy and prediction of progression-free survival (PFS) in non-Hodgkin's lymphoma (NHL).

METHODS

Sixty-one consecutive NHL patients (37 male and 24 female) were included. The (18)F-FDG hybrid PET/CT scans were performed prior to chemotherapy (initial scan) and after 3-4 cycles of chemotherapy (interim scan). Interim FDG findings were correlated to the PFS using Kaplan-Meier analysis. Regression analyses were employed to test for independence of established pretreatment prognostic factors.

RESULTS

After 3-4 cycles of chemotherapy, positive (18)F-FDG lesions were found in 28 patients, minimal residual uptake (MRU) in 8 and negative scans in 25 patients. In FDG-positive group, 22 patients showed progress and three died. Nine (18)F-FDG-negative patients and 4 patients from the MRU group relapsed. Survival analyses showed highly significant associations between early interim FDG imaging and PFS (P < 0.0005). The 2-year PFS rate for FDG-negative patients was 72.2 and 23.0% for FDG-positive patients. The regression model showed that the predictive value of FDG imaging owed its significance to the very high hazard ratio between patients with positive FDG imaging and patients with negative FDG imaging (P < 0.001).

CONCLUSIONS

Early interim FDG imaging is an excellent and independent predictor of PFS in NHL. An early assessment of chemotherapy response with FDG scans may provide useful information for selection of patients for alternative therapeutic strategies.

123I-metaiodobenzylguanidine (MIBG) scintigraphy for the detection of adrenal and extra-adrenal phaeochromocytomas: CT and MRI correlation

CONTEXT

Evidence regarding the accuracy of [(123)I] metaiodobenzylguanidine (MIBG) imaging for phaeochromocytoma localization is currently limited to small series.

OBJECTIVE

We present the largest series of primary phaeochromocytomas in which the performance of [(123)I]MIBG has been evaluated and correlated with cross-sectional imaging.

DESIGN

We identified 76 patients with both preoperative [(123)I]MIBG and cross-sectional imaging for confirmed primary phaeochromocytoma between 1995 and 2005 at our institution. This comprised 60 adrenal tumours in 55 patients and 33 extra-adrenal tumours in 23 patients (2 patients had both adrenal and extra-adrenal tumours). Phaeochromocytoma metastases were not evaluated.

MAIN OUTCOME MEASURE(S)

[(123)I]MIBG studies were independently reviewed and correlated with CT and MRI examinations, as well as tumour functional status, to identify features that may predict a false negative [(123)I]MIBG result.

RESULTS

The overall sensitivity of [(123)I]MIBG was 75%. Tumour detection was lower for extra-adrenal (58%) vs. adrenal (85%) phaeochromocytomas (P = 0.005). For extra-adrenal tumours, [(123)I]MIBG demonstrated 8 of 14 carotid body, 2 of 2 intrathoracic, 8 of 14 retroperitoneal and 2 of 3 pelvic phaeochromocytomas. Overall, MRI and CT demonstrated 68 of 68 and 72 of 74 primary phaeochromocytomas, respectively. Tumour size correlated with [(123)I]MIBG uptake for adrenal (P = 0.009) but not extra-adrenal tumours. When tumours were adjusted for size, no other imaging feature or functional status correlated with [(123)I]MIBG negativity, although two large [(123)I]MIBG negative adrenal tumours contained large areas of necrosis or haemorrhage.

CONCLUSIONS

Extra-adrenal and small adrenal phaeochromocytomas are more likely to result in false negatives on [(123)I]MIBG. Tumoural necrosis or haemorrhage do not consistently relate to [(123)I]MIBG uptake, although adrenal phaeochromocytomas containing minimal solid tissue due to extensive necrosis may predict a negative [(123)I]MIBG result.

Preoperative staging of colorectal cancer: CT vs. integrated FDG PET/CT

Accurate preoperative staging is essential in determining the optimal therapeutic planning for individual patients. The computed tomography (CT) in the preoperative staging of colorectal cancer, even if controversial, may be useful for planning surgery and/or neoadjuvant therapy, particularly when local tumor extension into adjacent organs or distant metastases are detected. There have been significant changes in the CT technology with the advent of multi-detector row CT (MDCT) scanner. Advances in CT technology have raised interest in the potential role of CT for detection and staging of colorectal cancer. In recent studies, MDCT with MPR images has shown promising accuracy in the evaluation of local extent and nodal involvement of colorectal cancer. Combined PET/CT images have significant advantages over either alone because it provides both functional and anatomical data. Therefore, it is natural to expect that PET/CT would improve the accuracy of preoperative staging of colorectal cancer. The most significant additional information provided by PET/CT relates to the accurate detection of distant metastases. For the evaluation of patients with colorectal cancer, CT has relative advantages over PET/CT in regard to the depth of tumor invasion through the wall, extramural extension, and regional lymph node metastases. PET/CT should be performed on selected patients with suggestive but inconclusive metastatic lesions with CT. In addition, PET/CT with dedicated CT protocols, such as contrast-enhanced PET/CT and PET/CT colonography, may replace the diagnostic CT for the preoperative staging of colorectal cancer.

A prototype instrument for single pinhole small animal adaptive SPECT imaging

The authors have designed and constructed a small-animal adaptive SPECT imaging system as a prototype for quantifying the potential benefit of adaptive SPECT imaging over the traditional fixed geometry approach. The optical design of the system is based on filling the detector with the region of interest for each viewing angle, maximizing the sensitivity, and optimizing the resolution in the projection images. Additional feedback rules for determining the optimal geometry of the system can be easily added to the existing control software. Preliminary data have been taken of a phantom with a small, hot, offset lesion in a flat background in both adaptive and fixed geometry modes. Comparison of the predicted system behavior with the actual system behavior is presented, along with recommendations for system improvements.

[Imaging in the diagnosis of colorectal liver metastases and extrahepatic abnormalities]

Imaging using ultrasonography, spiral CT, MRI and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), plays a major role at two situations during the management of patients with colorectal liver metastases: (a) at the time of the diagnosis and treatment of the primary colorectal tumour, and (b) during the follow-up for the detection of liver metastases and assessing the resectability of these metastases. At the time of the diagnosis and the treatment of the primary tumour, imaging comprising spiral CT or MRI to detect and characterize liver lesions is considered to be the modality of choice. Due to their low prevalence, imaging for the evaluation of lung metastases may be limited to conventional chest radiography. For evaluation of the extrahepatic abnormalities, abdominal and chest CT may be performed in combination with CT of the liver; alternatively a FDG-PET may be performed. During the follow-up of patients treated for colorectal carcinoma, ultrasonography is the most important imaging modality. However, if the liver cannot be adequately imaged by ultrasonography, if there is a raised level ofcarcinoembryonic antigen or irresectability cannot be determined, additional CT or MRI examination will result in more information.

Usefulness of [111In-DTPA0] octreotide scintigraphy in a family with von Hippel-Lindau disease

The identification of patients with von Hippel-Lindau (VHL) disease dictates accurate genetic counseling of family members, whereas screening for early detection of visceral and neurological involvement is usually performed by a combination of radiological and nuclear medicine techniques such as ultrasonography or contrast-enhanced computed tomography of the upper abdomen, magnetic resonance imaging of the central nervous system and 131I-metaiodobenzylguanidine-scintigraphy. The role of 111-indium-diethylenetriaminepentaacetic acid [111In-DTPA0] octreotide scintigraphy in this clinical context has never been investigated. Here, we report imaging findings in a VHL patient and in 3 consecutive family members undergoing clinical and radiological screening that included [111In-DTPA0] octreotide scintigraphy in addition to the above-mentioned procedures. Somatostatin receptor expression was investigated in vitro by immunohistochemistry in pancreatic tumor sections. On the basis of in vivo and in vitro findings, octreotide long-acting release treatment followed by 90Y-1,4,7,10-Tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA0)-Tyr3-octreotide led to a lack of progression in this patient although this result is a possibility which needs to be proved by further investigation and longer follow-up. The results of this study suggest that [111In-DTPA0] octreotide scintigraphy may be helpful in the routine work-up of VHL patients for diagnostic and therapeutic purposes.

Role of FDG-PET in the clinical management of paraneoplastic neurological syndrome: detection of the underlying malignancy and the brain PET-MRI correlates

The role of 2-deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography (FDG-PET) imaging in the clinical management of paraneoplastic neurological syndrome (PNS) is in evolution. The initial results are promising, and the potential of this modality in this setting has been demonstrated in the literature. In the setting of PNS, FDG-PET imaging can be of value from the following standpoints: (1) detection of the occult malignant focus and (2) objective assessment of the presence and extent of the functional abnormality in the brain and correlation of the imaging findings with the clinical features and disease activity. For this communication, we have not considered case reports described in the literature, while tabulating the results of the published studies. However, we have referred to important observations made in such reports. In part, this effort has been made because of the relative paucity of the existing literature on this issue. The studies investigating the role of FDG-PET imaging in detecting the sites of malignancy can be divided into two broad categories: (A) studies that incorporated FDG-PET at the initial work up of PNS along with other modalities and (B) studies where FDG-PET was applied after conventional modalities had failed to detect the offending malignancy. While majority of the studies have been of the second category, both categories have demonstrated the incremental role of FDG-PET in the detection of the primary cancer in this setting. Also, it is evident that serial studies at certain intervals should be carried out if the initial FDG-PET scan is negative. The literature describing the central nervous system findings with PET in PNS are primarily restricted to paraneoplastic limbic encephalitis (PLE) and paraneoplastic cerebellar degeneration (PCD). FDG-PET usually shows hypermetabolism in one or both temporal lobes in the setting of paraneoplastic limbic encephalitis, and the magnetic resonance imaging (MRI) findings correlate with the FDG-PET scan results in only a fraction of cases. The functional-anatomic discordance between PET and MRI in PLE needs to be examined further, which might open up new insights into the disease process and might generate further subgroups within this entity. Both modalities complement each other in PLE, and frequently, abnormalities noted on FDG-PET images can provide additional clinical information which is of great value in further patient management. In the setting of paraneoplastic cerebellar degeneration, FDG-PET generally reveals cerebellar hypometabolism similar to the cerebellar atrophy demonstrated by MRI, and FDG-PET tends to show the abnormality more often than MRI.