Spatiotemporal decomposition in object-space along reconstruction in emission tomography

Emission tomography has provided a new insight in brain mechanisms past years. Although reconstructions are nowadays mostly static, trend is going toward dynamic acquisitions and reconstructions. This opens a new range of investigations, for instance for drugs discovery. Indeed new drugs are studied through the dynamic ability of tissues to catch them. However, it is required to know radiotracer concentration of blood that irrigates tissues in order to draw conclusions on potentials of these drugs. This concentration is called 'input function' and this paper presents a new method for measuring it in a non-invasive way. Our new method relies on simultaneous estimations of vessels kinetics and vessels spatial distribution. These estimations are performed during the reconstruction process and take into account the statistical nature of measured signals. Indeed, this method is based on the maximisation of the likelihood of counts in detectors. It takes advantages of a non-negative matrix factorisation which separate spatial and temporal components. Results are very promising, since it estimates arterial input function accurately although object emits just a limited amount of photons, especially within the first minutes.

[Gastric motility disorders in patients after pancreatoduodenectomy]

The aim of the study was to evaluate effect of pancreatoduodenectomy on the gastric motility in patients with pancreatic carcinoma. In the patients with cancer pancreatoduodenectomy causes disorders of gastric myoelectric activity, gastric motility and autonomic nervous system function. Gastroparesis after surgery seems to depend on specific abnormalities in neurohormonal interaction of the GI tract.

Effect of low-frequency rTMS on electromagnetic tomography (LORETA) and regional brain metabolism (PET) in schizophrenia patients with auditory hallucinations

BACKGROUND

Auditory hallucinations are characteristic symptoms of schizophrenia with high clinical importance. It was repeatedly reported that low frequency (<or=1 Hz) repetitive transcranial magnetic stimulation (rTMS) diminishes treatment-resistant auditory hallucinations. A neuroimaging study elucidating the effect of rTMS in auditory hallucinations has yet to be published.

OBJECTIVE

To evaluate the distribution of neuronal electrical activity and the brain metabolism changes after low-frequency rTMS in patients with auditory hallucinations.

METHODS

Low-frequency rTMS (0.9 Hz, 100% of motor threshold, 20 min) applied to the left temporoparietal cortex was used for 10 days in the treatment of medication-resistant auditory hallucinations in schizophrenia (n = 12). The effect of rTMS on the low-resolution brain electromagnetic tomography (LORETA) and brain metabolism ((18)FDG PET) was measured before and after 2 weeks of treatment.

RESULTS

We found a significant improvement in the total and positive symptoms (PANSS), and on the hallucination scales (HCS, AHRS). The rTMS decreased the brain metabolism in the left superior temporal gyrus and in interconnected regions, and effected increases in the contralateral cortex and in the frontal lobes. We detected a decrease in current densities (LORETA) for the beta-1 and beta-3 bands in the left temporal lobe whereas an increase was found for beta-2 band contralaterally.

CONCLUSION

Our findings implicate that the effect is connected with decreased metabolism in the cortex underlying the rTMS site, while facilitation of metabolism is propagated by transcallosal and intrahemispheric connections. The LORETA indicates that the neuroplastic changes affect the functional laterality and provide the substrate for a metabolic effect.

The usefulness of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) and a comparison of (18)F-FDG-pet with (67)gallium scintigraphy in the evaluation of lymphoma: relation to histologic subtypes based on the World Health Organization classification

BACKGROUND

Although studies comparing conventional imaging modalities with (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) for the detection of lymphoma and although the relations between (18)F-FDG-PET and histologic types were reported previously, most studies were not systematic and involved relatively small numbers of patients.

METHODS

Two hundred fifty-five patients with lymphoma had their disease staged using (18)F-FDG-PET, and 191 of those patients also were assessed using gallium-67 scintigraphy ((67)Ga). Disease sites were identified on a site-by-site basis using computed tomography scans and/or magnetic resonance imaging. The results of these conventional imaging modalities were compared with the results from (8)F-FDG-PET and (67)Ga, and correlations between the imaging results and pathologic diagnoses were evaluated by using the World Health Organization classification system.

RESULTS

Of 913 disease sites in 255 patients, (18)F-FDG-PET identified >97% of disease sites of Hodgkin lymphoma (HL) and aggressive and highly aggressive non-Hodgkin lymphoma. For indolent lymphoma, the detection rate of (18)F-FDG-PET was 91% for follicular lymphoma (FL); 82% for extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue, irrespective of plasmacytic differentiation; and approximately 50% for small lymphocytic lymphoma (SLL) and splenic marginal zone lymphoma (SMZL). The results from (67)Ga were similar to those from (18)F-FDG-PET for most histologic subtypes. However, the sensitivity of (67)Ga was unexpectedly poor for FL, for mantle cell lymphoma (MCL), and for the nasal type of natural killer/T-cell lymphoma (NK/T-nasal), ranging from 30% to 38%.

CONCLUSIONS

(18)F-FDG-PET was useful for all histologic subtypes of lymphoma other than SLL and SMZL. Compared with (67)Ga, the authors strongly recommend the use of (18)F-FDG-PET in patients with FL, MCL, and NK-nasal.

Chronic electrostimulation of the trigeminal ganglion in trigeminal neuropathy: current state and future prospects

Over two decades ago, the electrostimulation of the trigeminal ganglion (TGES) was established as a treatment option for patients with trigeminopathic pain due to a (iatrogenic) lesion of the trigeminal nerve, on whom the other therapeutic methods, either neurosurgical or conservative have very limited efficacy and usually are associated with a poor outcome. The technique of TGES which uses the setup also used for the thermocoagulation lesion for trigeminal neuralgia was first published by Steude in 1984 and has not been altered substantially. After a percutaneous puncture with a 16 gage needle of the oval foramen, a monopolar electrode (diameter 0.9mm, custom-made) is placed in the postganglionic trigeminal nerve. After a successful test-stimulation phase, a permanent electrode pulse generator system is implanted. Our experience includes more than 300 patients with a minimum follow-up of one year. Of these patients, 52% showed a good to excellent analgesic effect. The TGES-induced analgesia was persistent in long term-follow-up in all patients. The impact of TGES on cerebral pain modulation was proven by electrophysiology and PET. TGES is an effective, minimally invasive and reversible treatment option in selected patients with trigeminopathic pain; it should, therefore, always be considered as the primary treatment-option. Electrodes with two leads and a diameter not exceeding the 0.9 mm, allowing bipolar stimulation might enhance the neuromodulatory efficacy and options of TGES.

Analysis of observer performance in unknown-location tasks for tomographic image reconstruction

Our goal is to optimize regularized image reconstruction for emission tomography with respect to lesion detectability in the reconstructed images. We consider model observers whose decision variable is the maximum value of a local test statistic within a search area. Previous approaches have used simulations to evaluate the performance of such observers. We propose an alternative approach, where approximations of tail probabilities for the maximum of correlated Gaussian random fields facilitate analytical evaluation of detection performance. We illustrate how these approximations, which are reasonably accurate at low probability of false alarm operating points, can be used to optimize regularization with respect to lesion detectability.

Functional imaging of working memory in Parkinson's disease: compensations and deficits

BACKGROUND AND PURPOSE

Over and above typical motor alterations, executive and working memory (WM) impairment can also occur in early idiopathic Parkinson's disease (PD). We aimed to investigate the compensatory neural processes involved in WM performance, as well as the networks involved in the long-term memory transfer from short-term stores in PD.

METHODS

Relative cerebral blood flow (rCBF) was mapped with H2O(15)-PET in eight treated nondemented PD patients while performing a WM verbal double-task (Brown-Peterson paradigm) using both short (6-second) and long (18-second) delays.

RESULTS

As compared to nine age-matched healthy subjects, performance of the PD group was only slightly reduced on the short-delay but markedly impaired on the long-delay task. Underlying the relatively preserved short-delay performance, the PD group exhibited overactivation of prefrontal and parietal areas involved in attention-demanding processes, suggestive of efficient compensatory processes. Further supporting this, significant positive correlations were found between short-delay performance and rCBF in the bilateral inferior parietal cortex. In contrast, the lack of overactivation with the long-delay task together with posterior cingulate hypoactivation would support the idea of functional disconnection impairing transfer of information from prefrontal onto (para)limbic areas. These findings suggest novel areas of investigation into early cognitive impairments in PD.

Usefulness of FDG-PET for early prediction of the response to gefitinib in non-small cell lung cancer

Increased tumor uptake of (18)F-fluorodeoxyglucose (FDG) measured by positron emission tomography (PET) reflects glucose metabolism and proliferative activity of tumor cells. We conducted a study to assess the usefulness of FDG-PET for early prediction of the response to gefitinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), in advanced non-small cell lung cancer (NSCLC). Five NSCLC patients underwent FDG-PET to evaluate changes in FDG uptake at day 2 and 4 weeks after the initiation of gefitinib therapy compared with FDG-PET prior to therapy. FDG uptake was evaluated as the maximum standardized uptake value (SUVmax) of the target lesions, which were assessable by conventional CT. Based on the CT evaluation, two patients exhibited a partial response (PR), two patients had stable disease (SD) with a minor response, and one patient had progressive disease (PD). In patients with PR and SD, SUVmax decreased by 61+/-18% (standard deviation) and 59+/-12%, respectively, on day 2, and by 26+/-6 and 43+/-10%, respectively, at 4 weeks after the initiation of gefitinib. Two patients with SD had decreased FDG uptake within 2 days of initiation of therapy, and achieved progression-free survival (PFS) of more than 12 months. In contrast, SUVmax increased up to 153+/-21% at 2 days and 232+/-73% at 4 weeks in a patient with PD. The present preliminary study suggests that FDG-PET may be able to predict response to gefitinib in the early stage of therapy in patients with advanced NSCLC and may have a potential prognostic role.

[Four patients with incidentalomas of the thyroid discovered on 18-fluoro-deoxyglucose positron-emission tomography (FDG-PET)]

In 4 patients, an incidentaloma of the thyroid was found on 18-fluoro-deoxyglucose positron-emission tomography (FDG-PET). In the first patient, a 73-year-old man, a medullary thyroid carcinoma was discovered during the staging procedure ofa laryngeal carcinoma. In the second patient, an 81-year-old woman, a follicular thyroid carcinoma was found as a result of a FDG-PET evaluation of an adenocarcinoma of the lung. In the third patient, a 64-year-old woman, a papillary thyroid carcinoma was found during dissemination investigation after curative removal of an adrenocortical carcinoma. The last patient, a 78-year-old man, was found to have a thyroid incidentaloma on FDG-PET scan during staging ofa recurrence of a gastrointestinal stromal tumour. Thyroid incidentalomas are present on 1.2-2.3% of FDG-PET scans. Further diagnostic work-up of these lesions by fine needle aspiration is warranted since up to 50% are malignant. However, whether these malignant thyroid lesions are relevant is not always clear. Treatment depends on the primary disease for which the FDG-PET scan was initially made. This requires good evaluation and discussion with the patient.

[Study on neuroreceptor imaging with radionuclide tracing in vivo]

Neuroreceptor imaging with radionuclide tracing in vivo has been greatly developed recently. Distribution, density, and activity of receptors in the brain can be visualized by the radioligands labeled for emission computed tomography (ECT), including PET (positron emission tomography) and SPECT (single photon emission computed tomography). The functional and quantitative imaging for several receptors, such as dopamine receptors, serotonin receptors, cholinergic receptors, benzodiazepine receptors, and opioid receptors, has clinical importance. The preparation of receptor imaging agents, foundation of the physio-mathematical model, and the development of nuclear medicine instruments are the main points. In the present review, we will concentrate on introducing the development of brain receptor imaging.

Imaging of cholinergic and monoaminergic neurochemical changes in neurodegenerative disorders

Positron emission tomography (PET) or single photon emission computer tomography (SPECT) imaging provides the means to study neurochemical processes in vivo. These methods have been applied to examine monoaminergic and cholinergic changes in neurodegenerative disorders. These investigations have provided important insights into disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD). The most intensely studied monoaminergic transmitter is dopamine. The extent of presynaptic nigrostriatal dopaminergic denervation can be quantified in PD and may serve as a diagnostic biomarker. Dopaminergic receptor imaging may help to distinguish idiopathic PD from atypical parkinsonian disorders. Cholinergic denervation has been identified not only in AD but also in PD and more severely in parkinsonian dementia. PET or SPECT can also provide biomarkers to follow progression of disease or evaluate the effects of therapeutic interventions. Cholinergic receptor imaging is expected to play a major role in new drug development for dementing disorders.

Scintigraphic imaging of body neuroendocrine tumors

Radionuclide imaging is often used in the diagnosis and work-up of a wide range of neoplasms, on the basis of the biologic behavior of the tumor. Neuroendocrine tumors are a subgroup of neoplasms that are generally small and slow growing, and consequently their identification with conventional anatomic imaging can be difficult. Depending on the physiologic properties of the tumor, functional images obtained with radionuclides are often complementary to anatomic images, not only in the localization of the tumor and its metastases, but also in the assessment of prognosis and response to therapy. Familiarity with the choice of the appropriate radiopharmaceutical, proper imaging protocols, and the wide range of imaging patterns will enable the radiologist to guide the clinician in case management.

Efficient liver segmentation using a level-set method with optimal detection of the initial liver boundary from level-set speed images

Automatic liver segmentation is difficult because of the wide range of human variations in the shapes of the liver. In addition, nearby organs and tissues have similar intensity distributions to the liver, making the liver's boundaries ambiguous. In this study, we propose a fast and accurate liver segmentation method from contrast-enhanced computed tomography (CT) images. We apply the two-step seeded region growing (SRG) onto level-set speed images to define an approximate initial liver boundary. The first SRG efficiently divides a CT image into a set of discrete objects based on the gradient information and connectivity. The second SRG detects the objects belonging to the liver based on a 2.5-dimensional shape propagation, which models the segmented liver boundary of the slice immediately above or below the current slice by points being narrow-band, or local maxima of distance from the boundary. With such optimal estimation of the initial liver boundary, our method decreases the computation time by minimizing level-set propagation, which converges at the optimal position within a fixed iteration number. We utilize level-set speed images that have been generally used for level-set propagation to detect the initial liver boundary with the additional help of computationally inexpensive steps, which improves computational efficiency. Finally, a rolling ball algorithm is applied to refine the liver boundary more accurately. Our method was validated on 20 sets of abdominal CT scans and the results were compared with the manually segmented result. The average absolute volume error was 1.25+/-0.70%. The average processing time for segmenting one slice was 3.35 s, which is over 15 times faster than manual segmentation or the previously proposed technique. Our method could be used for liver transplantation planning, which requires a fast and accurate measurement of liver volume.

Cross-sectional imaging of nodal metastases in the abdomen and pelvis

Accurate nodal staging is important for the management of patients with abdominal and pelvic malignancies. Local and nodal staging using cross-sectional imaging can influence treatment planning. The measurement of nodal size is still the most widely used criteria for discriminating between benign and malignant nodes. However, knowledge of the pathways of nodal spread, the treatment history, and careful analysis of nodal characteristics can improve nodal assessment. An appreciation of normal structures that may simulate nodal disease is also important. The potential for further improving nodal staging accuracy by positron emission tomography and magnetic resonance lymphography is discussed.

Nodal staging in rectal cancer

Rectal cancer is common and nodal disease is an independent adverse prognostic factor for patient survival. Accurate demonstration of the presence and location of nodal disease preoperatively may influence management strategies. In this article we review the pathways of nodal spread in rectal cancer and assessment of nodal disease using sonography, CT, and MRI. The use of morphological criteria instead of size criteria has been shown to improve nodal staging by MRI. The potential role of magnetic resonance lymphography and PET imaging in further improving nodal staging accuracy is discussed.

Harderian gland adenectomy: a method to eliminate confounding radio-opacity in the assessment of rat brain metabolism by 18F-fluoro-2-deoxy-D-glucose positron emission tomography

The 18F isotope of fluoro-2-deoxy-D-glucose (FDG) is a radiotracer commonly used in positron emission tomography (PET) for determining regional metabolic activity in the brain. However, in rats and many other species with nictitating membranes, harderian glands located just behind the eyes aggressively incorporate 18F-FDG to the extent that PET images of the brain become obscured. This radioactive spillover, or 'partial volume error,' combined with the limited spatial resolution of microPET scanners (1.5 to 2 mm) may markedly reduce the ability to quantify neuronal activity in frontal brain structures. Theoretically, surgical removal of the harderian glands before 18F-FDG injection would eliminate the confounding uptake of the radioactive tracer and thereby permit visualization of glucose metabolism in the frontal brain. We conducted a pilot study of unilateral harderian gland adenectomy, leaving the contralateral gland intact for comparison. At 1 wk after surgery, each rat was injected intravenously with 18F-FDG, and 40 min later underwent brain microPET for 20 min. Review of the resulting images showed that the frontal cortex on the surgical side was defined more clearly, with only background 18F-FDG accumulation in the surgical bed. Activity in the frontal cortex on the intact side was obscured by intense accumulation of 18F-FDG in the harderian gland. By reducing partial volume error, this simple surgical procedure may become a valuable tool for visualization of the frontal cortex of rat brain by 18F-FDG microPET imaging.

[Nuclear Medicine in the diagnosis of lower gastrointestinal bleeding]

Lower gastrointestinal bleeding appears to be a frequent problem in the every day practice. The exact localisation of the bleeding site plays a major role in treatment planning. Nuclear Medicine imaging techniques allow the diagnosis of ectopic gastric mucosa-Meckel's diverticulum (MD) and the extravasation of red blood cells. Meckel's diverticulum is the most frequent congenital anomaly of the gastrointestinal system moreover bleeding seems to be the most important clinical symptom during childhood. Scintigraphy using technetium-99m pertechnetate ((99m)TcO(4)(-)) is the method of choice for the diagnosis of ectopic gastric mucosa in MD. The use of this test in children is of high diagnostic accuracy, with a sensitivity of 85%-95% and specificity of 90%-95%. In adults, lower gastrointestinal bleeding is commonly caused by tumors, colitis, dysplasias or polyps, while MD is rare. Scintigraphic demonstration of active lower gastrointestinal bleeding contributes to risk-stratification, to prognosis, appropriate timing for angiography and to planning of surgical intervention. (99m)Tc labelled erythrocytes and (99m)Tc sulphur colloid are commonly used radiopharmaceuticals each having its own indications and used for the diagnosis of active bleeding. Moreover delayed imaging is possible using (99m)Tc labelled erythrocytes, enabling the diagnosis of intermittent bleeding. Careful interpretation of the scintiscan images is essential to avoid numerous pitfalls. The indications for using the specific nuclear medicine technique as above, for the diagnosis of lower gastroinstestinal bleeding and the indications for using other methods besides those of nuclear medicine are described.

Solitary Brain Lesions Enhancing at MR Imaging: Evaluation with Fluorine 18–Fluorocholine PET

PURPOSE

To prospectively determine whether differences between benign and malignant brain lesions can be depicted with fluorine 18 ((18)F) fluorocholine positron emission tomography (PET).

MATERIALS AND METHODS

Thirty consecutive patients (14 women, 16 men; age range, 26-79 years) with solitary brain lesions that were enhanced at magnetic resonance (MR) imaging underwent whole-brain (18)F-fluorocholine PET after giving informed consent in this institutional review board-approved, HIPAA-compliant study. Histopathologic diagnoses were made in 24 cases (13 high-grade gliomas, eight metastases to the brain, and three benign lesions). In six cases, benign lesions were diagnosed on the basis of longitudinal follow-up MR findings. The maximum standardized uptake value (SUV(max)) for lesion and peritumoral regions was measured on PET images, and a lesion-to-normal tissue uptake ratio (LNR) was calculated. Differences were assessed with one-way analysis of variance, Fisher exact, and Student t tests.

RESULTS

Differences in SUV(max) between high-grade gliomas (1.89 +/- 0.78 [mean +/- standard deviation]), metastases (4.11 +/- 1.68), and benign lesions (0.59 +/- 0.31) were significant (P < .0001). LNRs also differed significantly (5.15 +/- 2.51, 10.91 +/- 2.14, and 1.28 +/- 0.32, respectively; P < .0001). These differences were also significant at pairwise analysis. The peritumoral LNR exceeded 2.0 in seven high-grade gliomas and no metastases (P = .02). In 14 radiation-treated patients, the lesions classified as benign demonstrated significantly less uptake compared with the recurrent tumors (SUV(max): 0.72 +/- 0.38 vs 2.27 +/- 1.24, P < .01; LNR: 1.36 +/- 0.43 vs 5.88 +/- 3.66, P < .01).

CONCLUSION

High-grade gliomas, metastases, and benign lesions can be distinguished on the basis of measured fluorocholine uptake. Increased peritumoral fluorocholine uptake is a distinguishing characteristic of high-grade gliomas.

[18F]fluorodeoxyglucose positron emission tomography imaging in a case of relapsing polychondritis

Relapsing polychondritis is a rare multisystemic disease that is characterized by recurrent inflammation of the cartilaginous structures of the external ear, nose, joint, larynx, and tracheobronchial tree. Airway involvement is present in up to 50% of patients with the disease and is a major cause of morbidity and mortality. We describe a patient with relapsing polychondritis presenting with tracheal and bronchial abnormalities that were identified by an increased uptake on [18F]fluorodeoxyglucose positron emission tomography.

Role of multidetector CT and FDG-PET/CT in the diagnosis of local and distant recurrence of resected rectal cancer

PURPOSE

The aim of this study was to compare the diagnostic value of multidetector computed tomography (MDCT) and F18-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) for the detection of local and distant recurrence in patients operated on for rectal cancer.

MATERIALS AND METHODS

Sixty-seven patients who underwent radical surgery for rectal cancer and were followed up with FDG-PET/CT and MDCT were included in this retrospective study. The FDG-PET/CT and MDCT findings were independently compared with histological sampling or 2 years' follow-up.

RESULTS

Local recurrence occurred in 15/67 patients. MDCT diagnosed local recurrence in 15/15 cases and FDG-PET/CT in 14/15. Sensitivity and specificity were 100% and 98% for MDCT and 93% and 98% for FDG-PET/CT, respectively. Hepatic lesions were found in 17/67 patients. All hepatic metastases were detected by both techniques. Pulmonary metastases occurred in 8/67 patients: they were correctly identified in all cases by MDCT and in 6/8 by FDG-PET/CT.

CONCLUSIONS

MDCT and FDG-PET/CT showed high sensitivity and specificity for the detection of local recurrence of rectal cancer. Both techniques were equally accurate for the detection of hepatic metastases. MDCT showed slightly higher sensitivity and positive predictive value in detecting pulmonary metastases compared with FDG-PET/CT.

Plasma pharmacokinetic evaluation of cytotoxic agents radiolabelled with positron emitting radioisotopes

PURPOSE

This study aimed to evaluate the utility of plasma pharmacokinetic analyses of anti-cancer agents from data obtained during positron emission tomography (PET) oncology studies of radiolabelled anti-cancer agents.

PATIENTS AND METHODS

Thirteen patients were administered fluorine-18 radiolabelled 5-FU ([(18)F]5-FU) admixed with 5-FU, corresponding to a total 5-FU dose of 380-407 mg/m2 (eight patients) and 1 mg/m2 (five patients). Nine patients received 2.2-19.2 microg/m2 of carbon-11 radiolabelled N-[2-(dimethylamino)ethyl]acridine-4-carboxamide ([11C]DACA) at 1/1,000th of phase I dose, as part of phase 0 microdosing study. Radioactivity of parent drug obtained from arterial blood samples, the injected activity of the radiolabelled drug, and the total dose of injected drug were used to obtain plasma drug concentrations. Plasma pharmacokinetic parameters were estimated using model-dependent and model-independent methods.

RESULTS

5-FU plasma concentrations at therapeutic doses were above the Km and a single compartment kinetic model was best used to fit the kinetics, with a mean half-life of 8.6 min. Clearance and volumes of distribution (Vd) obtained using both model-dependent and model-independent methods were similar. Mean (SE) clearance was 1,421(144), ml min(-1) and 1,319 (119) ml min(-1) and the mean (SE) Vd was 17.3 (1.8) l and 16.3 (1.9) l by the model-independent method and model-dependent methods, respectively. In contrast, with 1 mg/m2, plasma concentrations of 5-FU were less than the Km and a two-compartment model was used to best fit the kinetics, with the mean 5-FU half-life of 6.5 min. The mean (SE) clearances obtained by the model-independent method and model-dependent methods were 3,089 (314) ml min(-1) and 2,225 (200) ml min(-1), respectively and the mean (SE) Vd were 27.9 (7.0) l and 2.3 (0.4) l, by the model independent and dependent methods, respectively. Extrapolation of AUC0-Clast to AUC0-infinity was less than 3% in both these cohort of patients. A two-compartment model with a mean half-life of 42.1 min was used to best fit the kinetics of DACA; considerable extrapolation (mean 26%) was required to obtain AUC0-infinity from AUC0-Clast. Mean (SE) clearance of DACA was 1,920 (269) ml min(-1), with the model-independent method and 1,627 (287) ml min(-1) with the model-dependent method. Similarly, Vd [mean (SE)] of DACA with the model-independent and model-dependent methods were 118 (22) l and 50 (15) l, respectively.

CONCLUSIONS

Pharmacokinetic parameters can be estimated with confidence from PET studies for agents given at therapeutic doses, whose half-lives are significantly less than the total sampling time during the scan. Tracer studies performed alone, wherein plasma levels below the Km are expected, may also provide valuable information on drug clearance for the entire range of linear kinetics. However, drugs with half-lives longer than the sampling duration are inappropriate for PET plasma pharmacokinetic evaluation.

Novel approach to stationary transmission scanning using Compton scattered radiation

Transmission scanning-based estimation of the attenuation map plays a crucial role in quantitative radionuclide imaging. X-ray computed tomography (CT) reconstructs directly the attenuation coefficients map from data transmitted through the object. This paper proposes an alternative route for reconstructing the object attenuation map by exploiting Compton scatter of transmitted radiation from an externally placed radionuclide source. In contrast to conventional procedures, data acquisition is realized as a series of images parameterized by the Compton scattering angle and registered on a stationary gamma camera operating without spatial displacement. Numerical simulation results using realistic voxel-based phantoms are presented to illustrate the efficiency of this new transmission scanning approach for attenuation map reconstruction. The encouraging results presented in this paper may suggest the possibility of proposing a new concept for emission/transmission imaging using scattered radiation, which has many advantages compared to conventional technologies.

Imaging of oral cancer

This article reviews imaging modalities commonly used to evaluate oral cavity cancers and their metastases to lymph nodes. It discusses how the studies are performed and their relative merits. It also presents new techniques for evaluating these neoplasms.

Imaging in dementia with Lewy bodies: a review

This review discusses the role of functional and structural imaging in patients with suspected dementia with Lewy bodies, with particular emphasis on SPECT and PET dopaminergic and cerebral perfusion/metabolic techniques. It is envisaged that this information may be useful to nuclear medicine physicians, radiologists, psychiatrists, neurologists, geriatricians and physicians.

Neuroimaging outcomes for clinical trials

A wide range of drugs is currently under development for treating Alzheimer's Disease (AD). Clinical trials traditionally use rating scales, such as neuropsychological tests and disability scales, as outcome measures. However, their intrinsic measurement variability, the slow disease progression, and the low effectiveness of the drugs developed so far have led to trial designs with hundreds of subjects per treatment arm. Furthermore, a key issue is to establish what effect are these compounds having on the biological progression of the disease, beyond delaying symptomatic progression. The development of imaging markers, either structural, functional, or amyloid, with proven sensitivity to disease progression has recently paved the way for their use as outcome measures in clinical trials. The use of imaging measures has the double advantage of decreasing the number of subjects per treatment arm whilst also providing a direct measure of the degree of disease modification induced by the "active" molecules. The reviewed techniques, except for the most recent amyloid imaging, are those applied to prospective studies investigating changes of imaging markers over time.

Monte Carlo simulation of energy spectra for123I imaging

(123)I is a radionuclide frequently used in nuclear medicine imaging. The image formed by the 159 keV photopeak includes a considerable scatter component due to high energy gamma-ray emission. In order to evaluate the fraction of scattered photons, a Monte Carlo simulation of a scintillation camera used for (123)I imaging was undertaken. The Monte Carlo code consists of two modules, the HEXAGON code modelled the collimator with a complex hexagonal geometry and the NAI code modelled the NaI detector system including the back compartment. The simulation was carried out for various types of collimators under two separate conditions of the source locations in air and in water. Energy spectra of (123)I for every pixel (matrix size = 256 x 256) were obtained by separating the unscattered from the scattered and the penetrated photons. The calculated energy spectra (cps MBq(-1) keV(-1)) agreed with the measured spectra with approximately 20% deviations for three different collimators. The difference of the sensitivities (cps MBq(-1)) for the window of 143-175 keV was less than 10% between the simulation and the experiment. The partial sensitivities for the scattered and the unscattered components were obtained. The simulated fraction of the unscattered photons to the total photons were 0.46 for LEHR, 0.54 for LEGP and 0.90 for MEGP for the 'in air' set-up, and 0.35, 0.40 and 0.68 for the 'in water' set-up, respectively. The Monte Carlo simulation presented in this work enabled us to investigate the design of a new collimator optimum for (123)I scintigraphy.

Diagnostic sensitivity and specificity of the radionuclide (indium)-labeled leukocyte scan

OBJECTIVE

Evaluate the sensitivity and specificity of Indium(111)-labeled leukocyte scans as used in a general, tertiary care hospital.

METHODS

Retrospective review of electronic medical records from all patients who underwent Indium(111) scan at two large Veterans Affairs Medical Centers, 1999-2005, to determine congruence between Indium(111) scan readings and final clinical diagnoses, using all available data with at least 6 months of follow-up.

RESULTS

Of 145 indium scans done for possible skeletal infection, infection was judged to be present in 52 cases. The sensitivity was 83%, and the specificity was 90%, with a diagnostic accuracy of 88%. Fifty-nine scans were done for indications other than skeletal infection. In 20 instances, when specific foci were suspected, the suspicion was correctly confirmed by indium scan in every case, without false positives or negatives (sensitivity and specificity, 100%). In 39 scans done to search for a possible source of nonspecific findings of infection (fever, leukocytosis, bacteremia), the sensitivity and specificity were 81% and 87%, respectively, with a diagnostic accuracy of 85%.

CONCLUSION

Except as a means to confirm an already-suspected clinical focus, the indium scan appears to offer relatively little definitive information that can be used for diagnosis or treatment of infection.

Hyperfast parallel-beam and cone-beam backprojection using the cell general purpose hardware

Tomographic image reconstruction, such as the reconstruction of computed tomography projection values, of tomosynthesis data, positron emission tomography or SPECT events, and of magnetic resonance imaging data is computationally very demanding. One of the most time-consuming steps is the backprojection. Recently, a novel general purpose architecture optimized for distributed computing became available: the cell broadband engine (CBE). To maximize image reconstruction speed we modified our parallel-beam backprojection algorithm [two dimensional (2D)] and our perspective backprojection algorithm [three dimensional (3D), cone beam for flat-panel detectors] and optimized the code for the CBE. The algorithms are pixel or voxel driven, run with floating point accuracy and use linear (LI) or nearest neighbor (NN) interpolation between detector elements. For the parallel-beam case, 512 projections per half rotation, 1024 detector channels, and an image of size 512(2) was used. The cone-beam backprojection performance was assessed by backprojecting a full circle scan of 512 projections of size 1024(2) into a volume of size 512(3) voxels. The field of view was chosen to completely lie within the field of measurement and the pixel or voxel size was set to correspond to the detector element size projected to the center of rotation divided by square root of 2. Both the PC and the CBE were clocked at 3 GHz. For the parallel backprojection of 512 projections into a 512(2) image, a throughput of 11 fps (LI) and 15 fps (NN) was measured on the PC, whereas the CBE achieved 126 fps (LI) and 165 fps (NN), respectively. The cone-beam backprojection of 512 projections into the 512(3) volume took 3.2 min on the PC and is as fast as 13.6 s on the cell. Thereby, the cell greatly outperforms today's top-notch backprojections based on graphical processing units. Using both CBEs of our dual cell-based blade (Mercury Computer Systems) allows to 2D backproject 330 images/s and one can complete the 3D cone-beam backprojection in 6.8 s.

Impact of instrumentation on DaTSCAN imaging: how feasible is the concept of cross-systems correction factor?

AIM

The aim of this investigation was to study the impact of applying different camera emission computed tomography (ECT) systems on semi-quantitative analysis of the novel dopamine transporter (DaT) radioligand [123I]-ioflupane (DaTSCAN) and whether applying a system-dependent correction factor is feasible to allow a migration of a ''normal'' reference data set between systems.

METHODS

Two triple-head systems, PrismXP-3000 equipped with high resolution Fan-Beam (PRISM) and Irix (Philips Medical Systems, Europe) equipped with high resolution parallel whole collimators (IRIX), were compared in phantom and patient studies. Acquisition and quantification parameters were standardized. The anthropometric striatal calibration phantom (RSD Inc., CA, USA) at rising striatum: background ratios between 2-11 was studied. Fifty-one consecutive patients (25 females, age 64.5+/-11.9 years, and 26 males, age 60.6+/-12.7 years) were randomized to both cameras for acquisition time typically beginning 3.5 to 4.5 h after i.v. injection of 123I-Joflupane at 2.06+/-0.47 MBq/kg. Striatal uptake of the radioligand was categorized as normal or abnormal, and abnormal images were further subdivided into 3 severity levels. Striatum: cerebellum ratio (SCr) was determined by applying a fixed circular or rectangular striatal and fuzzy cerebellar regions. The effect of introducing scatter compensation (Sc) on quantification and on SCr was investigated.

RESULTS

The regression coefficient (Rc) of SCr computed for both systems was close to identity (IRIX=0.999x (PRISM)+0.48 and 1.01x(PRISM)+0.86 for right and left striatum). Rc of SCr values in the phantom studies was closer to identity when Sc was added (IRIX=0.982x [PRISM]+0.724 with Sc vs 1.22x[PRISM]-0.32 without Sc). SCr values were higher for IRIX by 5-10%. Including Sc increased the percent recovery and the linear dynamic range for both systems; however, fan beam recovery decreased at low SCr values. The delineation of the striatal boundaries improved after applying Sc. Identifying the cerebellar region was easier with PRISM owing to significantly higher count statistics. Both systems performed equally well with respect to image quality. Visual scoring by 2 observers correlated significantly on the k-test (K: 0.883, T: 10, P<0.0001).

CONCLUSION

A simple linear correction is applicable to ''normal'' reference data set to migrate from one system to another; however, data acquisition and quantification parameters need to be standardized. Higher recovery values are dependent on system resolution. The spatial distribution and image quality of DaTSCAN on different high-resolution systems applying standardized acquisition and reconstruction protocols is less operator dependent and does not affect visual rating of striatal DaT loss.

Imaging of the Chest in Cystic Fibrosis

In the last 2 decades significant strides have been made in the application of chest imaging modalities to assess cystic fibrosis (CF) lung disease. This article covers current chest imaging modalities. It discusses CT, the research modality most commonly used to assess lung disease in CF, new insights regarding CF lung disease, and future directions in research and clinical care.

Contemporary imaging modalities for the surveillance of patients with renal cell carcinoma

In recent years, there have been multiple advances in imaging technologies that have improved the surveillance for recurrence of neoplasms. Multidetector row CT and dynamic contrast enhanced MRI now provide excellent anatomic detail and are beginning to show functional detail as the rapid capture of images following contrast administration improves. Positron emission tomography is emerging as a useful tool in evaluating patients with suspected metastatic disease to the abdomen and bone, particularly when combined with CT. The role of ultrasound in the surveillance of renal cell carcinoma is yet unclear, but its role may be expanding with use of newly developed contrast drugs. Herein we review the relevance of these modalities to the follow-up of patients with renal cell carcinoma.

Model-based respiratory motion compensation for emission tomography image reconstruction

In emission tomography imaging, respiratory motion causes artifacts in lungs and cardiac reconstructed images, which lead to misinterpretations, imprecise diagnosis, impairing of fusion with other modalities, etc. Solutions like respiratory gating, correlated dynamic PET techniques, list-mode data based techniques and others have been tested, which lead to improvements over the spatial activity distribution in lungs lesions, but which have the disadvantages of requiring additional instrumentation or the need of discarding part of the projection data used for reconstruction. The objective of this study is to incorporate respiratory motion compensation directly into the image reconstruction process, without any additional acquisition protocol consideration. To this end, we propose an extension to the maximum likelihood expectation maximization (MLEM) algorithm that includes a respiratory motion model, which takes into account the displacements and volume deformations produced by the respiratory motion during the data acquisition process. We present results from synthetic simulations incorporating real respiratory motion as well as from phantom and patient data.

Lungenkarzinom: Diagnostik und Staging

Despite medical advances lung cancer remains the leading cause of cancer deaths. Lung cancer is usually recognized late in its natural history and at presentation in 80 % unresectable. Smoking history is the most important risk factor. At present time, screening for lung cancer is not recommended. The only chance for cure is tumour resection in early stages, performed in about 20 % of all lung cancer cases. Histological subtypes are non-small cell lung cancer (NSCLC) (80 % of lung cancers) and 20 % small cell lung cancer (SCLC). TNM-staging has important influence on prognosis and therapy. After identification the tumour should be staged using the TNM system. Currently diagnosis and staging rely predominantly on chest radiography and computed tomography (CT) scanning. Positron emission tomography (PET) identifies the tumour by its metabolic activity and helps to find malignant nodal or systemic lesions. Flexible bronchoscopy is the key investigation in the diagnosis and staging of patients with suspected lung cancer. Endobronchial ultrasound guided transbronchial fine needle aspiration (TBNA) may be utilized to improve the bronchoscopic results in mediastinal staging. Internistic thoracoscopy or video assisted thoracoscopic surgery (VATS) may be used in malignant pleural effusions. Mediastinoscopy staging is the gold-standard for mediastinal staging.

Cluster computing software for GATE simulations

Geometry and tracking (GEANT4) is a Monte Carlo package designed for high energy physics experiments. It is used as the basis layer for Monte Carlo simulations of nuclear medicine acquisition systems in GEANT4 Application for Tomographic Emission (GATE). GATE allows the user to realistically model experiments using accurate physics models and time synchronization for detector movement through a script language contained in a macro file. The downside of this high accuracy is long computation time. This paper describes a platform independent computing approach for running GATE simulations on a cluster of computers in order to reduce the overall simulation time. Our software automatically creates fully resolved, nonparametrized macros accompanied with an on-the-fly generated cluster specific submit file used to launch the simulations. The scalability of GATE simulations on a cluster is investigated for two imaging modalities, positron emission tomography (PET) and single photon emission computed tomography (SPECT). Due to a higher sensitivity, PET simulations are characterized by relatively high data output rates that create rather large output files. SPECT simulations, on the other hand, have lower data output rates but require a long collimator setup time. Both of these characteristics hamper scalability as a function of the number of CPUs. The scalability of PET simulations is improved here by the development of a fast output merger. The scalability of SPECT simulations is improved by greatly reducing the collimator setup time. Accordingly, these two new developments result in higher scalability for both PET and SPECT simulations and reduce the computation time to more practical values.

Usefulness of FDG PET for diagnosis and radiotherapy of the patient with malignant lymphoma involving bone marrow

We experienced a case of relapsed malignant lymphoma with multiple bone marrow or bone lesions. The case was diagnosed as follicular lymphoma by cytological biopsy of the right iliac bone, with (67)Ga scintigraphy showing abnormal, intense uptake in multiple bones. After about 10 months of systemic chemotherapy, a relapse was suspected because of pain in the bilateral legs and a high level of lactate dehydrogenase. Assessment of the lesions in the patient was difficult by computed tomography because the affected sites were localized mainly in the bone marrow. (18)F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) was useful for detecting accurately the relapse sites in the bone marrow and enabled us to determine the field for radiotherapy. There are only a few reports of FDG-PET findings for such bone marrow malignant lymphomas. Therefore, we report the findings of FDG-PET for this case and review some of the literature about bone marrow lymphomas.

Potential clinical role of fluorodeoxyglucose-positron emission tomography in assessing primary or secondary lymphomas of the parotid gland

BACKGROUND

We have reviewed the utility of fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging for clinical management of primary parotid lymphoma (by applying strict criteria of primary extranodal involvement by this disease) as well as of cases in which spread of the disease to the parotid gland had occurred as a consequence of primary nodal disease.

PATIENTS AND METHODS

A total of 9 cases of parotid lymphoma (5 primary parotid lymphoma and 4 cases of combined nodal/extranodal lymphoma with parotid involvement) were identified and analyzed for this study. A retrospective review of the clinical records, radiologic data, and pathology results was carried out for assessment of the natural course and FDG-PET results in this disease. These patients had undergone conventional whole-body FDGPET or PET/computed tomography for initial or posttherapy monitoring purposes.

RESULTS

All cases in both subgroups had unilateral parotid involvement. Fluorodeoxyglucose uptake was focal, and visual assessment was sufficient to detect the disease in all the cases with a sensitivity of 100% in primary and secondary lymphoma of the parotid, independent of the histologic subtypes. The maximum standard uptake value in untreated cases of diffuse large B-cell lymphoma and follicular non-Hodgkin lymphoma of parotid was higher (10.4 and 10.2, respectively) than that of primary parotid marginal zone lymphoma (5.2). Postchemotherapeutic remission was correctly determined by PET in all 3 patients who underwent chemotherapy. The parotid involvement was noted at diagnosis in 2 cases and in the remaining ones up to 30 months after initial diagnosis. Fluorodeoxyglucose uptake was focal and distinct in all cases, and in 1 patient with a parotid nodule as small as 0.5 cm, the lesion was clearly visualized. The maximum standard uptake values in the posttreatment scenario varied from 1.3 to 1.9, which are within the range of what has been observed in the normal parotids. In 4 of 5 patients who underwent treatment monitoring, complete metabolic response in PET was noted in advance of size criteria by radiologic techniques for complete response.

CONCLUSION

Despite the known physiologic FDG uptake in parotid glands, FDG-PET appears to be of potential value in managing patients with parotid lymphoma in various stages of disease, including diagnosis and monitoring for therapeutic response.

Differentiating adrenal adenomas from nonadenomas using (18)F-FDG PET/CT: quantitative and qualitative evaluation

RATIONALE AND OBJECTIVES

We sought to assess the ability of (18)F-fluoro-2-deoxy-d-glucose (FDG) PET/CT to distinguish adrenal adenomas from nonadenomas in patients with suspected malignancy.

METHODS

Fifty-nine adrenal masses were evaluated with coregistered (18)F-FDG PET (PET/CT). Two reviewers independently graded uptake of (18)F-FDG by visual inspection of the adrenal mass in comparison to liver and background. CT attenuation value of the adrenal mass and the standardized uptake value (SUV) of the mass, liver, background, and primary neoplasm (when visible) were measured. Mean SUVs of the adrenal mass, liver, and background and ratios of the SUVs were calculated.

RESULTS

Of 47 adenomas, 43 measured <10 HU on unenhanced CT. Of 12, 12 nonadenomas measured >10 HU on unenhanced CT. Using qualitative assessment of FDG activity in the adrenal mass compared with liver, adenomas were less than, equal to, or more active than the liver in 51%, 38%, and 10%, respectively. Nonadenomas were less than, equal to, or more active than liver in 0%, 25%, and 75%, respectively. The mean SUV of adenomas (4.2) was significantly lower (P = .002) than that of their primary malignancies (9.2) but not that of liver (4.3). The mean SUV of adenomas was not significantly different than that of nonadenomas (5.2), but the mean adrenal/liver ratio (1.0) for the adenomas was significantly lower (P = .006) than that of the nonadenomas (2.1).

CONCLUSION

Adrenal adenomas were better differentiated from nonadenomas using unenhanced CT measurements in combination with ratios of the SUVs. Adrenal mass activity, which was visibly less than liver, was more specific for adenoma, whereas adrenal mass activity visibly greater than liver was more specific for malignancy.

Median-prior tomography reconstruction combined with nonlinear anisotropic diffusion filtering

Positron emission tomography (PET) is becoming increasingly important in the fields of medicine and biology. Penalized iterative algorithms based on maximum a posteriori (MAP) estimation for image reconstruction in emission tomography place conditions on which types of images are accepted as solutions. The recently introduced median root prior (MRP) favors locally monotonic images. MRP can preserve sharp edges, but a steplike streaking effect and much noise are still observed in the reconstructed image, both of which are undesirable. An MRP tomography reconstruction combined with nonlinear anisotropic diffusion interfiltering is proposed for removing noise and preserving edges. Analysis shows that the proposed algorithm is capable of producing better reconstructed images compared with those reconstructed by conventional maximum-likelihood expectation maximization (MLEM), MAP, and MRP-based algorithms in PET image reconstruction.

Effects of smoking marijuana on focal attention and brain blood flow

Using an attention task to control cognitive state, we previously found that smoking marijuana changes regional cerebral blood flow (rCBF). The present study measured rCBF during tasks requiring attention to left and right ears in different conditions. Twelve occasional marijuana users (mean age 23.5 years) were imaged with PET using [15O]water after smoking marijuana or placebo cigarettes as they performed a reaction time (RT) baseline task, and a dichotic listening task with attend-right- and attend-left-ear instructions. Smoking marijuana, but not placebo, resulted in increased normalized rCBF in orbital frontal cortex, anterior cingulate, temporal pole, insula, and cerebellum. RCBF was reduced in visual and auditory cortices. These changes occurred in all three tasks and replicated our earlier studies. They appear to reflect the direct effects of marijuana on the brain. Smoking marijuana lowered rCBF in auditory cortices compared to placebo but did not alter the normal pattern of attention-related rCBF asymmetry (i.e., greater rCBF in the temporal lobe contralateral to the direction of attention) that was also observed after placebo. These data indicate that marijuana has dramatic direct effects on rCBF, but causes relatively little change in the normal pattern of task-related rCBF on this auditory focused attention task.

Lateral hip pain: does imaging predict response to localized injection?

Lateral hip pain is a common complaint in patients with a history of lower back pain from spinal disease. These patients often are diagnosed and treated for trochanteric bursitis because of localized pain and tenderness in the lateral hip. We presumed numerous scintigraphic features could provide diagnostic criteria for diagnosing gluteus medius tendinitis and trochanteric bursitis. A study was designed to assess the scintigraphic criteria for diagnosis of trochanteric bursitis and to evaluate the relationship of trochanteric bursitis to gluteus medius tendinitis and lumbar degenerative disease in predicting relapse after injection. We evaluated 97 patients with greater trochanteric pain syndrome to find a correlation between trochanteric bursitis, gluteus medius tendinitis, and spinal degenerative disease using scintigraphy and magnetic resonance imaging. We also evaluated predictors for responding to trochanteric injection of local anesthetic/glucocorticoid injection. We found a correlation between lumbar degenerative disease, gluteus medius tendinopathy, and trochanteric bursitis. Of these, 30 of 48 patients (63%) responded to injection of local anesthetic and glucocorticoids. The major predictor of relapse of pain after injection in 18 patients was the presence of moderate to severe lumbar degenerative disease seen on scintigraphic imaging. We propose a mechanistic model of the greater trochanteric pain syndrome to explain the interrelationship and response to therapy. Scintigraphy can provide sensitive and specific diagnoses of gluteus medius tendinitis and trochanteric bursitis.

Left atrial remodelling in mitral regurgitation--methodologic approach, physiological determinants, and outcome implications: a prospective quantitative Doppler-echocardiographic and electron beam-computed tomographic study

AIMS

To define accurate and normal range of echocardiographic left atrial (LA) volume measurement and to assess the prevalence, determinants, and outcome implications of LA enlargement in mitral regurgitation (MR).

METHODS AND RESULTS

We prospectively compared LA volume obtained simultaneously by electron beam-computed tomography (EBCT) and by four echocardiographic methods in 33 test patients. Accurate echocardiographic LA volume measurements were obtained only by biplane area-length method with vertical longitudinal-length (r = 0.95, P < 0.0001; 145 +/- 57 vs. 143 +/- 55 mL, P = 0.57). Using this method, the normal range in 100 normal subjects, the physiological determinants and outcome implications of LA enlargement in 320 patients with organic MR were analysed. In normal subjects, indexed to body surface area, LA index (27 +/- 6 mL/m(2)) was not influenced by age or gender and values > or = 40 mL/m(2) were beyond the upper limit of normal. In MR, the most powerful determinants of LA enlargement were higher regurgitant volume (RVol) and atrial fibrillation (AF) (P < 0.0001), followed by older age, female gender, higher left ventricular end-systolic volume, and mass (all P < 0.001). After diagnosis in sinus rhythm, LA index > or = 40 mL/m(2) predicted superiorly and independently to LA diameter the occurrence of AF [adjusted RR 1.48 (1.06-2.16), P < 0.01] and the combined endpoint of death or need for mitral surgery [adjusted RR 1.61 (1.3-2.0), P < 0.0001].

CONCLUSION

LA remodelling can be accurately assessed by echocardiography and LA index > or = 40 mL/m(2) is beyond the normal range. In organic MR, higher LA index is the combined result of multiple physiological effects, provides independent prognostic information, and therefore should be part of a comprehensive echocardiographic examination.

Myocardial perfusion imaging protocols: is there an ideal protocol?

Is there an ideal myocardial perfusion imaging protocol? In order to answer this question and choose a protocol for clinical use, one must understand the characteristics of the available radiopharmaceuticals, the protocol variables, and the advantages and disadvantages of each. After reading this article, the technologist should be able to list the ideal characteristics of a myocardial perfusion imaging agent, describe and compare the characteristics of myocardial perfusion imaging agents, discuss the relationship between coronary blood flow and myocardial uptake of various tracers, describe imaging protocols, and discuss the advantages and disadvantages of each protocol.

Integrated PET/CT in lung cancer imaging: history and technical aspects

Integrated PET/CT is a new anatomo-metabolic imaging modality combining two different techniques: Computed Tomography (CT) that provides very detailed anatomic information and Positron Emission Tomography (PET) that provides metabolic information. Integrated PET/CT has several advantages. One of the advantages is the use of CT data for attenuation correction that is significantly faster compared to that in conventional PET systems. Due to the use of CT data for attenuation correction, artefacts can be generated on PET images related to the use of intravenous or oral CT contrast agents, CT beam-hardening artefacts due to metallic implants and motion artefacts (respiratory motion, physical bowel motion, cardiac motion). The purpose of this review is to discuss some technical considerations concerning the CT protocol that can be used for PET/CT in lung cancer imaging and to give a short overview of the initial results of staging of non-small cell lung cancer (NSCLC).

Staging of renal cell carcinoma

As in other malignant tumors, prognosis in renal cell carcinoma (RCC) depends on tumor extent and metastasis at the time of primary diagnosis. Staging systems formalize the way in which the extent of RCC is being described and classified. Primary staging of RCC aims at evaluating surgical options. Since surgical excision, which is the mainstay of therapy in non-metastatic RCC, and, recently, minimally invasive ablation methods have evolved significantly over the last decades, staging systems continue to evolve along the way. The 40-year-old Robson classification has been replaced with the TNM classification of RCC, because the latter adapts more easily to changing patterns of diagnosis and therapy. Modern cross-sectional imaging methods, such as multidetector-row computed tomography (MDCT), and magnetic resonance imaging (MRI), perform highly in T-staging of local tumor extent and M-staging of distant metastasis. However, both MDCT and MRI perform poorly in N-staging of lymphadenopathy. At present, 18-F-desoxy-glucose positron emission tomography (FDG-PET) appears to be unreliable in the detection of RCC and its metastasis. This overview of current radiological and surgical literature attempts to describe how modern staging systems for RCC are organized, and which radiological and surgical developments currently influence the way in which primary staging and prognosis of RCC depend on one another.

The role of 123I-metaiodobenzylguanidine myocardial scintigraphy in the diagnosis of Lewy body disease in patients with dementia in a memory clinic

Reduction in cardiac (123)I-metaiodobenzylguanidine (MIBG) uptake is a characteristic feature of Parkinson's disease (PD) and dementia with Lewy bodies (DLB), and is useful in distinguishing them from other neurodegenerative disorders. The aim of this study was to investigate the role of this method of scintigraphy in the differential diagnosis of dementia in our Memory Clinic. We performed MIBG scintigraphy in patients with dementia referred to the Memory Clinic and compared the heart-to-mediastinum (H/M) ratio of MIBG uptake. Thirty out of 32 patients with DLB and all 9 PD with dementia patients had reduced H/M ratios, whereas 37 out of 40 patients with Alzheimer's disease had normal H/M ratios. Most patients with vascular dementia, frontotemporal dementia, and other dementias had normal H/M ratios. The overall sensitivity to positively identify patients with Lewy body disease (including DLB and PD with dementia) was 95%, and the specificity to distinguish them from patients with other types of dementias was 87%. MIBG scintigraphy showed a high sensitivity for the detection of Lewy body disease, and also a high specificity for discrimination from other types of dementia. The scintigraphy may provide a valuable and adjunctive method in the diagnosis of Lewy body disease and a differential diagnostic tool for patients with dementias.