Positron Emission Tomography Devices Research Articles

New Method for 18FDG generating using Geant4/ Gate7

Fluorine 18-deoxyglucose is often used in Positron Emission Tomography devices. Positron Emission Tomography imaging is one of the useful tool which is used for cancer detection and its management. Positron Emission Tomography growth is limited due to problems that depend on the production of Fluorine-18. Imaging results are strongly depending on the information of nuclear reaction cross section data. This study is presented to calculate different quantities such as stopping power, CSDA range, simulated and distributed absorbed dose of Fluorine-18 in water. In order to access these goals, we use Geant4/Gate7 simulation and the Bethe-Bloch model. The results of this simulation and theoretical model presented are in good agreement with each other. The important point of this paper is the presentation of a theoretical approach in order to the production of Fluorine-18 using protons generated through the main D(d;p)Tand side 3 He(d;p)4 He nuclear fusion reaction in which uses Helium-3 is catalyzed.

The Generation of Positrons from Mega-STN and Function as an Alternative Energy Source

Paul Dirac (1902-1984) theoretically predicted the existence of positrons for the first time in 1928, and Carl Anderson (1905-1991) found the positrons through cosmic ray observation experiments in 1932. Positrons are the antiparticle of electron, and their spin and mass are equal to electrons and they have the same electric charge but are different in sign. That is, their spin is ½ Fermion, their electric charge is base charge +e, and their mass is approximately 9.11×10−31 kg. Because positrons are the lightest particle with a positive charge, they have an infinite lifespan without collapsing into other particles. But if positron meets with another electron surrounding them, double extinction of positron and electron occurs, and positrons disappear with electrons, and then photons are generated. Because the earth has many electrons, double extinction occurs immediately in most cases even if positrons are created. There is gravity, electromagnetic force, weak interaction in the interaction of positrons, and the isotopes emitting positrons include carbon-11, nitrogen-13, oxygen-15, fluorine-18. For example, carbon- 11 turns into boron-11. These isotopes are used on positron emission tomography device. Electron capture is another way of decay that can occur competitively with positron emission, but the larger the difference of energy is, the higher the probability of decaying due to positron emission is. Researchers say that positrons are generated if there is collision between high energies by the interaction of positrons, but we think that this should be supplemented more. There is a hypothesis that positrons are generated when the unstable radioactive isotopes created during a supernova explosion collapse. It is inevitable that it will cost a lot of time and money when generating radioactive isotopes according to this hypothesis. This makes us try new methods about positrons emission breaking away from conventional fusion methods. Our new methods for generating positrons are to make artificially the fusion with micro/nanoparticles and isotopes emitting positrons and the interchangeability between them, and to create a great deal of heat energy by making micro/ nanoparticles collide into each other with using thermal energy and waves between micro/nanoparticles. We think that our new methods are the best way to generate high heat with a small energy source. To put our ideas into practice, we made a stainless steel rectangular plate using the combined materials of MEGA-STN, that is the new types fused with each of micro/nanoparticles and isotopes emitting positrons, and added MEGA-STN to materials of the existing stainless steel heater stick. We measured temperature changes depending on whether or not the materials are present and depending on the content of the materials, and checked even positrons emission in our study. We also measured the air quality and the amount of oxygen as well as humidity. Consequently, we found out obtaining high-temperature heat energy by investing less energy. The surface temperature of the existing stainless-steel heater stick did not exceed 320℃ when 3Kw electricity was supplied, but one of stainless-steel heater stick which is mixed with the materials of MEGA-STN was 1000℃. Based on these results, we think that our MEGA-STN can be replaced as a heat energy source which is necessary for all industries using fossil fuel, nuclear power, sunlight generation, wind power and so on, and this can bring good synergy to climate and environment. We expect that our emitted positrons cause the changes of the amount of oxygen and air quality, affect plants and animals including ecological growth, and so make a big difference in human life.

The Relation between MEGA-STN and Positron Wave Thermal Energy

Paul Dirac(1902-1984) theoretically predicted the existence of positrons for the first time in 1928, and Carl Anderson(1905-1991) found the positrons through cosmic ray observation experiments in 1932. Positrons are the antiparticle of electron, and their spin and mass are equal to electrons and they have the same electric charge but are different in sign. That is, their spin is ½ Fermion, their electric charge is base charge +e, and their mass is approximately 9.11×10−31 kg. Because positrons are the lightest particle with a positive charge, they have an infinite lifespan without collapsing into other particles. But if positron meets with another electron surrounding them, double extinction of positron and electron occurs, and positrons disappear with electrons, and then photons are generated. Because the earth has many electrons, double extinction occurs immediately in most cases even if positrons are created. There are gravity, electromagnetic force, weak interaction in the interaction of positrons, and the isotopes emitting positrons include carbon-11, nitrogen-13, oxygen-15, fluorine-18. For example, carbon11 turns into boron-11. These isotopes are used on positron emission tomography device. Electron capture is another way of decay that can occur competitively with positron emission, but the larger the difference of energy is, the higher the probability of decaying due to positron emission is. Researchers say that positrons are generated if there is collision between high energies by the interaction of positrons, but we think that this should be supplemented more. There is a hypothesis that positrons are generated when the unstable radioactive isotopes created during a supernova explosion collapse. It is inevitable that it will cost a lot of time and money when generating radioactive isotopes according to this hypothesis. This makes us try new methods about positrons emission breaking away from conventional fusion methods. Our new methods for generating positrons are to make artificially the fusion with micro/nanoparticles and isotopes emitting positrons and the interchangeability between them, and to create a great deal of heat energy by making micro/nanoparticles collide into each other with using thermal energy and waves between micro/ nanoparticles. We think that our new methods are the best way to generate high heat with a small energy source. To put our ideas into practice, we made a stainless steel rectangular plate using the combined materials of MEGA-STN, that is the new types fused with each of micro/nanoparticles and isotopes emitting positrons, and added MEGA-STN to materials of the existing stainless steel heater stick. We measured temperature changes depending on whether or not the materials are present and depending on the content of the materials, and checked even positrons emission in our study. Consequently, we found increasing to 200~300℃ compared to the general temperature when a constant temperature is created with minimal energy, making a marked change in temperature of our MEGA-STN and emitting positrons at a particular temperature. It is believed to have paved the way for the use of energy sources throughout the industry. Additionally, we realized that photon production caused by the double annihilation of positrons and electrons can affect plants (growth and yields) and insects (the activity of bees in winter) ecologically, cause changes in the environment such as the quality of air and water, and have a positive impact in all areas of our life.

A Narrow Optical Pulse Emitter Based on LED: NOPELED.

Light sources emitting short pulses are needed in many particle physics experiments using optical sensors as they can replicate the light produced by the particles being detected and are also an important calibration and test element. This work presents NOPELED, a light source based on LEDs emitting short optical pulses with typical rise times of less than 3 ns and Full Width at Half Maximum lower than 7 ns. The emission wavelength depends on the model of LED used. Several LED models have been characterized in the range from 405 to 532 nm, although NOPELED can work with LED emitting wavelengths outside of that region. While the wavelength is fixed for a given LED model, the intensity and the frequency of the optical pulse can be controlled. NOPELED, which also has low cost and simple operation, can be operated remotely, making it appropriate for either different physics experiments needing in-place light sources such as astrophysical neutrino detectors using photo-multipliers or positron emission tomography devices using scintillation counters, or, beyond physics, applications needing short pulses of light such as protein fluorescence or chemodetection of heavy metals.

Diagnosis of left ventricular hypertrophy using non-ECG-gated 15O-water PET

AimTo develop a method for diagnosing left ventricular (LV) hypertrophy from cardiac perfusion 15O-water positron emission tomography (PET). MethodsWe retrospectively pooled data from 139 subjects in four research cohorts. LV remodeling patterns ranged from normal to severe eccentric and concentric hypertrophy. 15O-water PET scans (n = 197) were performed with three different PET devices. A low-end scanner (66 scans) was used for method development, and remaining scans with newer devices for a blinded evaluation. Dynamic data were converted into parametric images of perfusable tissue fraction for semi-automatic delineation of the LV wall and calculation of LV mass (LVM) and septal wall thickness (WT). LVM and WT from PET were compared to cardiac magnetic resonance (CMR, n = 47) and WT to 2D-echocardiography (2DE, n = 36). PET accuracy was tested using linear regression, Bland–Altman plots, and ROC curves. Observer reproducibility were evaluated using intraclass correlation coefficients. ResultsHigh correlations were found in the blinded analyses (r ≥ 0.87, P < 0.0001 for all). AUC for detecting increased LVM and WT (> 12 mm and > 15 mm) was ≥ 0.95 (P < 0.0001 for all). Reproducibility was excellent (ICC ≥ 0.93, P < 0.0001). Conclusion15O-water PET might detect LV hypertrophy with high accuracy and precision.

Simulation Study of a Frame-Based Motion Correction Algorithm for Positron Emission Imaging.

Positron emission tomography (PET) is a functional non-invasive imaging modality that uses radioactive substances (radiotracers) to measure changes in metabolic processes. Advances in scanner technology and data acquisition in the last decade have led to the development of more sophisticated PET devices with good spatial resolution (1–3 mm of full width at half maximum (FWHM)). However, there are involuntary motions produced by the patient inside the scanner that lead to image degradation and potentially to a misdiagnosis. The adverse effect of the motion in the reconstructed image increases as the spatial resolution of the current scanners continues improving. In order to correct this effect, motion correction techniques are becoming increasingly popular and further studied. This work presents a simulation study of an image motion correction using a frame-based algorithm. The method is able to cut the acquired data from the scanner in frames, taking into account the size of the object of study. This approach allows working with low statistical information without losing image quality. The frames are later registered using spatio-temporal registration developed in a multi-level way. To validate these results, several performance tests are applied to a set of simulated moving phantoms. The results obtained show that the method minimizes the intra-frame motion, improves the signal intensity over the background in comparison with other literature methods, produces excellent values of similarity with the ground-truth (static) image and is able to find a limit in the patient-injected dose when some prior knowledge of the lesion is present.

A Real-Time, Automatic, and Dynamic Scheduling and Control System for PET Patients Based on Wearable Sensors.

Positron emission tomography (PET) is one of the commonly used scanning techniques. Medical staff manually calculate the estimated scan time for each PET device. However, the number of PET scanning devices is small, the number of patients is large, and there are many changes including rescanning requirements, which makes it very error-prone, puts pressure on staff, and causes trouble for patients and their families. Although previous studies proposed algorithms for specific inspections, there is currently no research on improving the PET process. This paper proposes a real-time automatic scheduling and control system for PET patients with wearable sensors. The system can automatically schedule, estimate and instantly update the time of various tasks, and automatically allocate beds and announce schedule information in real time. We implemented this system, collected time data of 200 actual patients, and put these data into the implementation program for simulation and comparison. The average time difference between manual and automatic scheduling was 7.32 min, and it could reduce the average examination time of 82% of patients by 6.14 ± 4.61 min. This convinces us the system is correct and can improve time efficiency, while avoiding human error and staff pressure, and avoiding trouble for patients and their families.

Quality control of small animal PET scanner: The Brazilian Scenario

This work aims to evaluate the quality control program for small animal PET (positron emission tomography) scanners in Brazil. A questionnaire focused on type of small animal PET scanner and quality assurance program was prepared and sent to all Brazilian preclinical molecular imaging services that participated in the first Brazilian microPET/SPECT/CT users meeting held at the Federal University of Rio de Janeiro. The answers were compiled and descriptive statistic was applied. There are six preclinical molecular imaging services using PET scanner in Brazil. Five are in the southeastern region and one in the southern region. All services have a single PET device, but most of them have hybrids modalities with CT (computed tomography) and/or SPECT (single photon emission computed tomography). All services have knowledge of the NEMA NU 4-2008 publication specific to small animal PET equipments. However, most of them do not have a quality assurance program in place for their imaging systems. There are few preclinical PET devices installed in Brazil and most of them are located at southeastern region. Regardless the absence of quality assurance program in many of the services, there is a consensus on the importance of quality control program implementation.

Pilot performance of a dedicated prostate PET suitable for diagnosis and biopsy guidance

BackgroundProstate cancer (PCa) represents one of the most common types of cancers facing the male population. Nowadays, to confirm PCa, systematic or multiparametric MRI-targeted transrectal or transperineal biopsies of the prostate are required. However, due to the lack of an accurate imaging technique capable to precisely locate cancerous cells in the prostate, ultrasound biopsies sample random parts of the prostate and, therefore, it is possible to miss regions where those cancerous cells are present. In spite of the improvement with multiparametric MRI, the low reproducibility of its reading undermines the specificity of the method. Recent development of prostate-specific radiotracers has grown the interest on using positron emission tomography (PET) scanners for this purpose, but technological improvements are still required (current scanners have resolutions in the range of 4–5 mm).ResultsThe main goal of this work is to improve state-of-the-art PCa imaging and diagnosis. We have focused our efforts on the design of a novel prostate-dedicated PET scanner, named ProsPET. This system has small scanner dimensions defined by a ring of just 41 cm inner diameter. In this work, we report the design, implementation, and evaluation (both through simulations and real data) of the ProsPET scanner. We have been able to achieve < 2 mm resolution in reconstructed images and high sensitivity. In addition, we have included a comparison with the Philips Gemini-TF scanner, which is used for routine imaging of PCa patients. The ProsPET exhibits better contrast, especially for rod sizes as small as 4.5 mm in diameter. Finally, we also show the first reconstructed image of a PCa patient acquired with the ProsPET.ConclusionsWe have designed and built a prostate specific PET system, with a small footprint and improved spatial resolution when compared to conventional whole-body PET scanners. The gamma ray impact within each detector block includes accurate DOI determination, correcting for the parallax error. The potential role of combined organ-dedicated prostate-specific membrane antigen (PSMA) PET and ultrasound devices, as a prebiopsy diagnostic tool, could be used to guide sampling of the most aggressive sites in the prostate.

A second-generation virtual-pinhole PET device for enhancing contrast recovery and improving lesion detectability of a whole-body PET/CT scanner.

We have developed a second-generation virtual-pinhole (VP) positron emission tomography (PET) device that can position a flat-panel PET detector around a patient's body using a robotic arm to enhance the contrast recovery coefficient (CRC) and detectability of lesions in any region-of-interest using a whole-body PET/computed tomography (CT) scanner. We constructed a flat-panel VP-PET device using 32 high-resolution detectors, each containing a 4 4 MPPC array and 16 16 LYSO crystals of 1.0 1.0 3.0mm3 each. The flat-panel detectors can be positioned around a patient's body anywhere in the imaging field-of-view (FOV) of a Siemens Biograph 40 PET/CT scanner by a robotic arm. New hardware, firmware and software have been developed to support the additional detector signals without compromising a scanner's native functions. We stepped a 22 Na point source across the axial FOV of the scanner to measure the sensitivity profile of the VP-PET device. We also recorded the coincidence events measured by the scanner detectors and by the VP-PET detectors when imaging phantoms of different sizes. To assess the improvement in the CRC of small lesions, we imaged an elliptical torso phantom measuring 316 228 162mm3 that contains spherical tumors with diameters ranging from 3.3 to 11.4mm with and without the VP-PET device. Images were reconstructed using a list mode Maximum-Likelihood Estimation-Maximization algorithm implemented on multiple graphics processing units (GPUs) to support the unconventional geometries enabled by a VP-PET system. The mean and standard deviation of the CRC were calculated for tumors of different sizes. Monte Carlo simulation was also conducted to image clusters of lesions in a torso phantom using a PET/CT scanner alone or the same scanner equipped with VP-PET devices. Receiver operating characteristic (ROC) curves were analyzed for three system configurations to evaluate the improvement in lesion detectability by the VP-PET device over the native PET/CT scanner. The repeatability in positioning the flat-panel detectors using a robotic arm is better than 0.15mm in all three directions. Experimental results show that the average CRC of 3.3, 4.3, and 6.0mm diameter tumors was 0.82%, 2.90%, and 5.25%, respectively, when measured by the native scanner. The corresponding CRC was 2.73%, 6.21% and 10.13% when imaged by the VP-PET insert device with the flat-panel detector under the torso phantom. These values may be further improved to 4.31%, 9.65% and 18.01% by a future dual-panel VP-PET insert device if DOI detectors are employed to triple its detector efficiency. Monte Carlo simulation results show that the tumor detectability can be improved by a VP-PET device that has a single flat-panel detector. The improvement is greater if the VP-PET device employs a dual-panel design. We have developed a prototype flat-panel VP-PET device and integrated it with a clinical PET/CT scanner. It significantly enhances the contrast of lesions, especially for those that are borderline detectable by the native scanner, within regions-of-interest specified by users. Simulation demonstrated the enhancement in lesion detectability with the VP-PET device. This technology may become a cost-effective solution for organ-specific imaging tasks.

Development of the fast and efficient gamma detector using Cherenkov light for TOF-PET

In this paper we present two configurations of innovative gamma detectors using Cherenkov light for time-of-flight—Positron Emission Tomography (PET). The first uses heavy crystals as a Cherenkov radiator to develop a demonstrator for a whole body PET scanner with high detection efficiency. We demonstrated a 30% detection efficiency and a 180 ps (FWHM) time resolution, mainly limited by the time transit spread of the photomultiplier. The second configuration uses an innovative liquid, the TriMethyl Bismuth, to develop a high precision brain-scanning PET device with time-of-flight capability. According to Geant4 simulation, we expect to reach a precision of 150 ps (FWHM) and an efficiency of about 25%.

Strategies of statistical windows in PET image reconstruction to improve the user’s real time experience

Nowadays, with the increase of the computational power of modern computers together with the state-of-the-art reconstruction algorithms, it is possible to obtain Positron Emission Tomography (PET) images in practically real time. These facts open the door to new applications such as radio-pharmaceuticals tracking inside the body or the use of PET for image-guided procedures, such as biopsy interventions, among others. This work is a proof of concept that aims to improve the user experience with real time PET images. Fixed, incremental, overlapping, sliding and hybrid windows are the different statistical combinations of data blocks used to generate intermediate images in order to follow the path of the activity in the Field Of View (FOV). To evaluate these different combinations, a point source is placed in a dedicated breast PET device and moved along the FOV. These acquisitions are reconstructed according to the different statistical windows, resulting in a smoother transition of positions for the image reconstructions that use the sliding and hybrid window.

Advances in digital SiPMs and their application in biomedical imaging

Similar to analog silicon photomultipliers (SiPMs), digital SiPMs (dSiPMs) essentially consist of an array of single-photon avalanche photodiodes (SPADs). Instead of a passive quench resistor, however, an active quenching circuit is locally integrated with each SPAD, making the sensor response faster and less sensitive to the gains of the individual SPADs. Moreover, additional circuits for the fully digital acquisition, processing, and readout of optical signals are integrated within the sensor. As a result, dSiPMs offer high photo-detection efficiency, high single-photon time resolution (SPTR), and high uniformity, as well as many practical advantages, such as a very compact form factor, low voltage operation, magnetic field compatibility, high stability of operation, low gain drift, and a high degree of scalability. At the same time, dSiPMs represent a new paradigm in low-level light sensing technology. That is, their fully digital operation makes them true photon counting devices, preserving at least partly the discrete spatio-temporal structure of the information embedded in the optical signal. This means that the operation of dSiPMs can be fully understood only in statistical terms, but also opens up novel possibilities for extracting information from the measured data. So far, the main driver behind the development of dSiPMs has been the detection of scintillation pulses in detectors for time-of-flight (TOF) positron emission tomography (PET). Several types of dSiPM have been developed in recent years. Moreover, first imaging devices based on dSiPMs have been realized by various groups. This review summarizes the main dSiPM concepts and technologies currently under development, provides an overview of the results obtained recently with dSiPMs-based PET and SPECT devices, and presents a critical outlook on the challenges and chances for dSiPMs in future radiomolecular imaging systems.

The role of positron emission tomography in breast cancer: a short review

Positron emission tomography (PET) provides information about abnormal metabolic features associated with cancer, and its role in breast cancer has been widely investigated. In the past several years, combined imaging systems, such as PET/CT and PET/MRI, and dedicated breast PET devices, such as PEM and MAMMI-PET, have been developed and implemented. These new techniques have become an effective oncologic tool for staging, re-staging, monitoring response to treatment, and estimation of the long-term prognosis. The aim of this review is to summarize the established and emerging PET imaging techniques and to discuss their value in the management of breast cancer patients.

TH‐C‐144‐12: On the Modelling of Facility‐Specific PET Imaging for Proton Treatment Verification: Experimental Validation and Inter‐Facility Comparison

Purpose: We report on an experiment‐driven approach to validate the Monte‐Carlo (MC) modelling for Positron‐Emission‐Tomography (PET)‐based post‐therapeutic proton treatment verification. The presented strategy was pursued to overcome (1) uncertainties in the available nuclear cross‐section data and (2) facility‐specific uncertainties due to the irradiation technique and due to the imaging characteristics of the installed PET device. Furthermore, we show a comparison of production rates of the most relevant PET radionuclides, estimated from measurements at two treatment facilities using different PET‐imaging and data processing concepts. Methods: At our hospital‐based facility, several homogeneous phantoms were irradiated with mono‐energetic proton beams. The induced PET signal was detected with a full‐ring PET/CT‐scanner shortly after beam delivery. Separation of different radionuclide contributions to the measured signal was achieved by analysing the activity decay in dynamically reconstructed time‐resolved PET images. The resulting spatially resolved activity maps were used to tune the modelling of the most relevant radionuclide production processes. These measurements were compared to data acquired at another facility with a proto‐type dual head PET camera, employing a different data processing concept. Results: The MC modelling was adjusted to accurately reproduce the measurements at our facility. The activity signal level could be predicted within a few percent and we found a range agreement of better than 0.6 mm, which constitutes a crucial property for the clinical purpose of beam range verification. The inter‐facility comparison of production rates estimated from independent PET measurements show a reasonable overall agreement. However systematic discrepancies are observed, which suggest an impact of the different imaging and data processing concepts. Conclusion: The results of the inter‐facility comparison confirm the importance of a facility‐specific experimental validation of the MC modelling. The presented experimental strategy can also be applied at other facilities to minimize uncertainties in the activity prediction for PET‐based proton treatment verification. The presented work was funded by the German Federal Ministry for Research and Education (BMBF) under the grant agreement number 01IB08002F.

Estimate of FDG Excretion by means of Compartmental Analysis and Ant Colony Optimization of Nuclear Medicine Data

[18F]fluoro-2-deoxy-D-glucose (FDG) is one of the most utilized tracers for positron emission tomography (PET) applications in oncology. FDG-PET relies on higher glycolytic activity in tumors compared to normal structures as the basis of image contrast. As a glucose analog, FDG is transported into malignant cells which typically exhibit an increased radioactivity. However, different from glucose, FDG is not reabsorbed by the renal system and is excreted to the bladder. The present paper describes a novel computational method for the quantitative assessment of this excretion process. The method is based on a compartmental analysis of FDG-PET data in which the excretion process is explicitly accounted for by the bladder compartment and on the application of an ant colony optimization (ACO) algorithm for the determination of the tracer coefficients describing the FDG transport effectiveness. The validation of this approach is performed by means of both synthetic data and real measurements acquired by a PET device for small animals (micro-PET). Possible oncological applications of the results are discussed in the final section.

Expression de l’anhydrase carbonique IX et fixation du 18F-FDG dans les cancers pulmonaires non à petites cellules

Introduction/objectivesTumoural cells develop an accelerated glycolytic metabolism for their development. Thus cancer cells have to maintain a greater glucose supply and to correct for the massive acidosis that produces glucose degradation in lactic acid at the same time. The increase of glucose transport can be estimated in vivo by positron emission tomography (PET) imaging with 18F-fluorodeoxyglucose (18F-FDG). The carbonic anhydrase IX (CAIX), an enzyme overexpressed to fight against acidosis, can be estimated ex-vivo by immunohistochemistry. The purpose of this work is to study the expression of the CAIX and the 18F-FDG uptake in primitive non small cells lung cancers (NSCLC). Material and methodsOne hundred and seven patients of the Centre Hospitalier Universitaire de Nice (CHUN, Teaching Hospital of Nice) with NSCLC surgically treated in the thoracic surgery department, having been tested for the expression of the CAIX in the department of clinical and experimental pathology, and having benefited from a PET scan with 18F-FDG in the department of nuclear medicine of the CHUN, were retrospectively included from a cohort of 555 patients. The intensity of tumoural 18F-FDG uptake was measured by 16 different methods, with in particular the calculation of “tumour on background” ratios of uptake and of values corrected from partial volume effect (PVE). This correction was made possible by calibration experiments on phantoms by the recovery coefficient method. ResultsA significative correlation between the expression of the CAIX and “maximum tumoural uptake on liver background” ratio was found. DiscussionHigh CAIX and SUV are known to be independent factors of poor prognosis for patients suffering from NSCLC. The 18F-FDG uptake reflects the expression of the glucose transporter GLUT, which is strongly increased in most of the malignant tumours. Even on modern PET devices, PVE remains an important quantitative bias in emission imaging, by provoking important underestimates of small structures uptake. Its correction appreciably improves the precision of quantification in PET imaging. At the molecular level, the transcription factor Hypoxia-Inducible Factor (HIF-1α) is the keystone of activation of numerous genes producing in particular the GLUTs, key enzymes of glycolysis and the CAIX. Thus a metabolic link is expected and found between 18F-FDG uptake and the CAIX expression via HIF-1α, what was shown in a single study carried out on a low number of patients and without PVE correction. ConclusionThe correlation suggested here between 18F-FDG uptake and expression of the CAIX seems to be in agreement with the biological hypothesis. Other studies remain necessary to show that PET with 18F-FDG, associated with the test of the tumoral expression of the CAIX, would allow refining the prognosis of these patients and estimating the prediction of the response to anti-cancerous therapies.

Detection rate of recurrent medullary thyroid carcinoma using fluorine-18 fluorodeoxyglucose positron emission tomography: a meta-analysis

Several studies evaluated the diagnostic performance of fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET), and positron emission tomography/computed tomography (PET/CT) in detecting recurrent medullary thyroid carcinoma (MTC) with conflicting results. Aim of our study is to meta-analyze published data about this topic. A comprehensive computer literature search of studies published in PubMed/MEDLINE, Scopus, and Embase databases through December 2011 and regarding FDG PET or PET/CT in patients with suspected recurrent MTC was carried out. Pooled detection rate (DR) on a per patient-based analysis was calculated to measure the diagnostic performance of FDG PET and PET/CT in this setting. A sub-analysis considering PET device used, serum calcitonin, carcino-embryonic antigen (CEA), calcitonin doubling time (CTDT), and CEA doubling time (CEADT) values was also performed. Twenty-four studies comprising 538 patients with suspected recurrent MTC were included. DR of FDG PET or PET/CT in suspected recurrent MTC on a per patient-based analysis was 59 % (95 % confidence interval: 54-63 %). Heterogeneity between the studies was revealed. DR increased in patients with serum calcitonin ≥ 1,000 ng/L (75 %), CEA ≥ 5 ng/ml (69 %), CTDT <12 months (76 %), and CEADT <24 months (91 %). In patients with suspected recurrent MTC FDG PET and PET/CT are associated with a non-optimal DR since about 40 % of suspected recurrent MTC remain usually unidentified. However, FDG PET and PET/CT could modify the patient management in a certain number of recurrent MTC because these methods are often performed after negative conventional imaging studies. DR of FDG PET and PET/CT increases in patients with higher calcitonin and CEA values and lower CTDT and CEADT values, suggesting that these imaging methods could be very helpful in patients with more aggressive disease.

Molecular Imaging in Breast Cancer: From Whole-Body PET/CT to Dedicated Breast PET

Positron emission tomography (PET), with or without integrated computed tomography (CT), using 18F-fluorodeoxyglucose (FDG) is based on the principle of elevated glucose metabolism in malignant tumors, and its use in breast cancer patients is frequently being investigated. It has been shown useful for classification, staging, and response monitoring, both in primary and recurrent disease. However, because of the partial volume effect and limited resolution of most whole-body PET scanners, sensitivity for the visualization of small tumors is generally low. To improve the detection and quantification of primary breast tumors with FDG PET, several dedicated breast PET devices have been developed. In this nonsystematic review, we shortly summarize the value of whole-body PET/CT in breast cancer and provide an overview of currently available dedicated breast PETs.

Clinical applications of positron emission tomography in hepatic tumors

Fluorodeoxyglucose (FDG), which allows the evaluation of glucose metabolism, is widely used for tumor diagnosis using positron emission tomography (PET). FDG-PET, which is used for the diagnosis of intrahepatic tumor lesions, shows high FDG accumulation in cholangiocellular carcinoma (CCC) and metastatic liver cancer. FDG-PET shows high FDG accumulation in moderately or poorly differentiated hepatocellular carcinoma (HCC) and is useful for the diagnosis of extrahepatic HCC metastases and recurrences. However, because the imaging method frequently shows low FDG accumulation in well-differentiated HCC, it is not very useful for that diagnosis. For the diagnosis of well-differentiated HCC, F-18 fluorocholine for evaluation of phospholipid metabolism and C-11 acetate for evaluation of free fatty acid metabolism are useful in the diagnosis of that HCC. It is expected that the combination of these PET agents will enhance the diagnostic performance of FDG-PET for HCC in the future. The problem of a lack of anatomical information is being resolved with the development of the use of PET in combination with computed tomography or magnetic resonance imaging. For the problem of low resolution, PET devices using semiconductors have been developed.