Positron Emission Tomography Facility Research Articles

OPERATIONAL RADIATION SAFETY FOR PET-CT, SPECT-CT, AND CYCLOTRON FACILITIES

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are well- established and indispensable imaging modalities in modern medicine. State-of-the-art computed tomography (CT) scanners have now been integrated into multi-modality PET-CT and SPECT-CT devices, and these devices, particularly PET-CT scanners, are dramatically impacting clinical practice. 18F-fluorodeoxyglucose (FDG), by far the most widely used radiopharmaceutical for clinical PET imaging in general and oncologic PET imaging in particular, is highly accurate in detecting (approximately 90%) and staging many types of tumors, monitoring therapy response, and differentiating benign from malignant lesions. Several factors, including the relatively high administered activities [e.g., 370-740 MBq (10-20 mCi) of FDG], the high patient throughput (up to 30 patients per d), and in particular, the uniquely high energies (for a diagnostic setting) of the 511-keV positron-negatron annihilation photons, make shielding requirements, workflow, and other radiation protection issues important considerations in the design of a PET or PET-CT facility. The Report of Task Group 108 of the American Association of Physicists in Medicine (AAPM) provides a comprehensive summary of shielding design and related considerations, along with illustrative calculations. Whether in the form of a PET-CT or a SPECT-CT device, the introduction of CT scanners into a nuclear medicine setting has created new and complex radiation protection issues concerning the radiation burden and attendant risks accrued by patients undergoing such multi-modality procedures (especially in those instances in which higher-dose, diagnostic-quality CT studies are done as part of the PET-CT or SPECT-CT exam). In addition, because PET is dependent on the availability of short-lived 18F (Tp = 110 min) primarily in the form of FDG, and other short-lived positron emitters such as 11C (20 min), 13N (10 min), and 15O (2 min), cyclotrons for production of medically applied radionuclides and associated radiochemistry facilities are now widespread (well over 100 worldwide) and present their own radiation safety issues. In addition to the radioactive product, sources of exposure include neutrons and radioactive activation products in the various cyclotron components and surrounding shielding. Nonetheless, published studies have shown that the radiation doses to personnel working in cyclotron and associated radiochemistry facilities, as well as in PET or PET-CT and SPECT or SPECT-CT facilities, can be maintained below, and generally well below, the pertinent regulatory limits. This presentation will review the basic radiation safety aspects, including shielding and workflow, of these increasingly important and increasingly numerous facilities. The radiation burden accrued by the patients undergoing PET-CT or SPECT-CT exams will be considered as well.

An easy-to-use phantom and protocol for weekly PET quality assessment: A multicenter study

The authors have developed a simple phantom and dedicated software for the quality assessment of positron emission tomography (PET) scanners. The phantom is a parallelepiped box filled with a relatively low activity 18FDG solution and in which simple test objects are placed. Various image quality parameters are checked, including signal-to-noise ratio, image uniformity, slice thickness, slice sensitivity profile, spatial resolution, and dose calibration accuracy. Automatic image analysis consists in detecting surfaces and objects, defining regions of interest, acquiring reference point coordinates, and establishing gray-scale profiles. The total time needed for quality assessment (preparation and image acquisition) is less than 15 min with 37 MBq (1 mCi) 18FDG. The system's ease of use encourages frequent image quality assessment-for example, the comparison of PET scanners in interdepartment studies and the monitoring and evaluation of possible drifts over time. By way of an example, the authors present weekly quality assessment results obtained over up to 7 months at four PET facilities.

Overview of the clinical effectiveness of positron emission tomography imaging in selected cancers

To assess the clinical effectiveness of positron emission tomography (PET) using 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) in breast, colorectal, head and neck, lung, lymphoma, melanoma, oesophageal and thyroid cancers. Management decisions relating to diagnosis, staging/restaging, recurrence, treatment response and radiotherapy (RT) planning were evaluated separately. Major electronic databases were searched up to August 2005 and a survey of UK PET facilities was performed in February 2006. This assessment augments the systematic search undertaken in a previous review. Studies were limited to those using commercial dedicated PET or PET/computed tomography (CT) devices with FDG, in one of the eight cancers. The new search identified six systematic reviews and 158 primary studies. An economic model for England showed that in non-small cell lung cancer (NSCLC) FDG-PET was cost-effective in CT node-negative patients, but not in CT node-positive patients. A less robust model also showed that FDG-PET was cost-effective in RT planning for NSCLC. A model for Scotland showed that in late-stage Hodgkin's lymphoma (HL), FDG-PET was cost-effective for restaging after induction therapy. For staging/restaging colorectal cancer, FDG-PET changed patient management in a way that can impact on curative therapy. For detection of solitary pulmonary nodule (SPN) there was also impact on patient management, but the resulting effect on patient outcomes was unclear. FDG-PET had an impact on patient management across paediatric lymphoma decisions, but further study of individual management decisions is required. For other cancer management decisions, the evidence on patient management is weak. FDG-PET was accurate in detecting distant metastases across several sites, but sensitivity was variable for detection of lymph-node metastases and poor in early stage disease where sentinel lymph-node biopsy would be used and for small lesions. There were 61 studies of treatment response. These were generally small and covered all cancers except melanoma. They showed that FDG-PET imaging could be correlated with response, in some cases, but the impact on patient management was not documented. There were 17 small studies of RT planning in four cancers; here, FDG-PET led to alteration of RT volumes and doses, but the impact on patient outcomes was not studied. FDG-PET improved diagnostic accuracy compared with alternatives in a number of other cancer management decisions, but more comparative evidence is needed. There were 23 studies of PET/CT in six cancers (excluding breast and melanoma). In these FDG-PET/CT generally improved accuracy by 10-15% over PET, resolving some equivocal images. The survey of PET facilities in the UK showed that PET and PET/CT are being used for a variety of cancer indications. PET facilities are not distributed evenly across the UK and use is inconsistent. Various research studies are underway in most centres, but only a few of these are collaborative studies. There is major variation in throughput and cost per scan (635-1300 pounds). The strongest evidence for the clinical effectiveness of FDG-PET is in staging NSCLC, restaging HL, staging/restaging colorectal cancer and detection of SPN. Some of these may still require clinical audit to augment the evidence base. Other management decisions require further research to show the impact of FDG-PET on patient management or added value in the diagnostic pathway. It is likely that capital investment will be in the newer PET/CT technology, for which there is less evidence. However, as this technology appears to be slightly more accurate than PET/CT, the PET clinical effectiveness results presented here can be extrapolated to cover PET/CT. PET research could be undertaken on FDG-PET or FDG-PET/CT, using a standard cancer work-up process on typical patients who are seen within the NHS in England. For treatment response and RT planning, the need for larger studies using consistent methods across the UK is highlighted as a priority for all cancers. For all studies, consideration should be given to collaboration across sites nationally and internationally, taking cognisance of the work of the National Cancer Research Institute.

Reduced γ-Aminobutyric AcidA–Benzodiazepine Binding Sites in Insular Cortex of Individuals With Panic Disorder

Benzodiazepine drugs are highly effective anxiolytic medications, but the role of the benzodiazepine-gamma-aminobutyric acid(A)-chloride ion channel macromolecular complex in the pathophysiologic mechanism of anxiety is not well understood. Previous human imaging studies have indicated involvement of specific regions of the brain in anxiety disorders, especially the frontal-prefrontal, temporal, and cingulate cortical and the limbic areas. To identify potential abnormalities of brain benzodiazepine receptor binding number and distribution in anxiety disorders. At the University of Michigan positron emission tomography facility, 11 individuals with DSM-IV-defined anxiety syndrome panic disorder were compared with 21 unaffected healthy control subjects. Design and Main Outcome Measure In a between-group comparison, we used positron emission tomography and the benzodiazepine receptor ligand flumazenil labeled with carbon 11 to assess the regional brain pattern of receptor binding. We observed decreased binding specifically in the insular cortex bilaterally. No binding abnormality was observed in any other brain region, and there was no evidence of abnormal cerebral blood flow anywhere in the brain. Individuals with panic disorder and comorbid depression, indicative of a more severe disorder, had the lowest binding. No significant correlations were observed for binding with age, sex, or duration of disorder. A previous smaller study with the same ligand reported a probable binding abnormality in the right insula. Because gamma-aminobutyric acid is a major inhibitory neurotransmitter in the brain and because benzodiazepines facilitate this effect of gamma-aminobutyric acid, decreased benzodiazepine binding is consistent with localized brain activation (ie, loss of inhibition). Because the insula is strongly involved in visceral-somatic afferent and efferent function, activation of the insula is consistent with the occurrence of the physical symptoms prominently associated with panic disorder.

Alveolar recruitment assessed by positron emission tomography during experimental acute lung injury

To compare changes in aerated lung volumes measured by positron emission tomography (PET) and inflation volume-pressure curve (V-P) of the respiratory system, and to evaluate the reliability of PET to assess alveolar recruitment. Experimental study in six anesthetized and mechanically ventilated pigs in a PET facility in an experimental university laboratory. Lung injury was induced by oleic acid. Animals were randomly studied in four conditions: PEEP 0cmH(2)O (ZEEP) in supine position (SP), PEEP 10cmH(2)O in SP, ZEEP in prone position (PP) and PEEP in PP, each applied for 30min. With PET aerated lung volume was obtained from pulmonary density analysis using transmission scan (VA(trans)) and from nitrogen-13 kinetics on emission scan (VA(em)). Changes in VA(trans) and VA(em) were computed as the difference in aerated volume between conditions. VA(trans) and VA(em) did not differ between SP and PP, on either ZEEP or PEEP, suggesting no modification in relaxation volume of the respiratory system induced by posture. Changes in VA(trans) or VA(em) were significantly correlated with changes in aerated volume assessed from superimposed V-P curves (R (2)=0.74 and 0.75, respectively). Alveolar recruitment assessed by PET was significantly correlated with both PaO(2) (R (2)=0.61) and PaCO(2) (R (2)=0.40) variations induced by PEEP. PET is a new reliable tool of scientific interest to image lung volume and alveolar recruitment during acute lung injury.

Microdialysis versus other techniques for the clinical assessment of in vivo tissue drug distribution

Quantification of target site pharmacokinetics (PK) is crucial for drug discovery and development. Clinical microdialysis (MD) has increasingly been employed for the description of drug distribution and receptor phase PK of the unbound fraction of various analytes. Costs for MD experiments are comparably low and given suitable analytics, target tissue PK of virtually any drug molecule can be quantified. The major limitation of MD stems from the fact that organs such as brain, lung or liver are not readily accessible without surgery. Recently, non-invasive imaging techniques, i.e. positron emission tomography (PET) or magnetic resonance spectroscopy (MRS), have become available for in vivo drug distribution assessment and allow for drug concentration measurements in practically every human organ. Spatial resolution of MRS imaging, however, is low and although PET enables monitoring of regional drug concentration differences with a spatial resolution of a few millimetres, discrimination between bound and unbound drug or parent compound and metabolite is difficult. Radiotracer development is furthermore time and labour intensive and requires special expertise and radiation exposure and costs originating from running a PET facility cannot be neglected. The recent complementary use of MD and imaging has permitted to exploit individual strengths of these diverse techniques. In conclusion, MD and imaging techniques have provided drug distribution data that have so far not been available. Used alone or in combination, these methods may potentially play an important role in future drug research and development with the potential to serve as translational tools for clinical decision making.

Microdialysis Versus Other Techniques for the Clinical Assessment of In Vivo Tissue Drug Distribution

Quantification of target site pharmacokinetics (PK) is crucial for drug discovery and development. Clinical micro-dialysis (MD) has increasingly been employed for the description of drug distribution and receptor phase PK of the unbound fraction of various analytes. Costs for MD experiments are comparably low and given suitable analytics, target tissue PK of virtually any drug molecule can be quantified. The major limitation of MD stems from the fact that organs such as brain, lung or liver are not readily accessible without surgery. Recently, non-invasive imaging techniques, i.e. positron emission tomography (PET) or magnetic resonance spectroscopy (MRS), have become available for in vivo drug distribution assessment and allow for drug concentration measurements in practically every human organ. Spatial resolution of MRS imaging, however, is low and although PET enables monitoring of regional drug concentration differences with a spatial resolution of a few millimetres, discrimination between bound and unbound drug or parent compound and metabolite is difficult. Radiotracer development is furthermore time and labour intensive and requires special expertise and radiation exposure and costs originating from running a PET facility cannot be neglected. The recent complementary use of MD and imaging has permitted to exploit individual strengths of these diverse techniques. In conclusion, MD and imaging techniques have provided drug distribution data that have so far not been available. Used alone or in combination, these methods may potentially play an important role in future drug research and development with the potential to serve as translational tools for clinical decision making.

Development of a simple method to evaluate medical staff radiation dose and its application to a software system supporting PET facility operation

In recent years, positron-emitting labelled radiopharmaceuticals have come to be used in conjunction with positron emission tomography (PET) in various clinical diagnoses. Radiation exposure of the medical staff is a key issue in the design of PET facilities intended to handle large numbers of persons for PET diagnosis. As a first step, the radiation dose to individuals who received radiopharmaceuticals was calculated using a mathematical phantom model and the EGS4 electromagnetic cascade Monte Carlo code and MCNP Monte Carlo code. Dose rate behind a lead shield was also calculated for various lead thicknesses. The radiation dose distribution around a syringe containing a positron emitter was calculated. The calculated dose distributions were fitted to polynomial equations. These calculations were evaluated against measurements. The second step was to evaluate medical staff dose at a specified time by superimposing dose distribution from each person who received radioisotopes taking into account radioactive decay. In this way, we developed software to support PET facility operation, namely, planning, prediction, control of medical staff dose and facility operation. This system was also designed to schedule daily radiopharmaceuticals production and to manage radioactive wastes by taking decay time into account.

How Available is Positron Emission Tomography in the United States?

Positron emission tomography (PET) has become a major clinical diagnostic and prognostic tool for oncology and multiple other arenas. To some, however, the perception exists that PET is not available as a resource in their community. Our goal with this project was to determine how available clinical PET was in the United States. We used existing lists of PET centers, websites from PET scanner manufacturers, as well as a common Internet search engine to find clinical PET facilities. A mapping program was then used to determine area coverage with a 75-mile radius for each PET scanner found, and the United States Census website was utilized as a source of population data for covered and not covered areas. We found that 97% of the US population lives within 75 miles of a clinical PET facility. Thus, it appears that the idea of clinical PET being unavailable to many is a misconception, which may be limiting its use by some physicians who are unaware of how common it has become.

Cost-Effectiveness of Positron Emission Tomography in Recurrent Colorectal Cancer in Canada

Several studies over the past decade have demonstrated that 2-fluoro-2-D-[18F] fluorodeoxyglucose (FDG) positron emission tomography (PET) is more accurate than computed tomography (CT) for the staging of recurrent colorectal carcinoma. This study uses quantitative decision tree modeling and sensitivity analysis to assess the cost-effectiveness of a PET-based management strategy for staging recurrent colorectal carcinoma in Canada. Both management costs and life expectancy are determined. METHODS: Two patient management strategies were compared - one using CT alone and one using both CT and PET. A survey of recent literature was used to construct a meta-analyses of available studies for the accuracy of PET in staging recurrent colorectal carcinoma. Life expectancies were determined from recent Canadian statistics, and expected life expectancies with disease were calculated from published survival rates. Management costs were determined from: estimates of the installation cost of PET facilities in Canada; management costs from our institutions; and recently published Canadian cost estimates of various procedures. RESULTS: A cost savings of $1,758 per person is expected for a PET and CT strategy, along with a slight increase in life expectancy (3.8 days), when compared with a CT alone strategy. This cost savings stemmed from avoided surgeries and remained in favour of the PET strategy when subjected to a rigorous sensitivity analysis.

How should we introduce clinical positron emission tomography in the UK? Oncologists need to have a (clearer) view

It was with great interest that we read the recent editorial by Price and Laking on clinical positron emission tomography (PET) [1]. Although the article was clearly targeted at clinical oncologists in the UK, we believe that the issues raised are internationally relevant. Therefore, we wish to comment from our perspective as clinicians who work at a large cancer centre that contains the first Australian PET facility primarily dedicated to clinical service provision [2]. Over 15 000 scans in around 10 000 patients have been carried out in our institute.

The cost of positron emission tomography in six United States Veterans Affairs hospitals and two academic medical centers.

Positron emission tomography (PET) is a high-cost imaging tool primarily used in oncology, cardiology, and neuropsychiatry. Accurate estimates of the cost of PET are needed to assess its cost effectiveness and determine the appropriate role for this modality in clinical applications. We performed a survey-based cost analysis of PET with FDG by estimating direct, indirect, and capital costs from eight PET centers. A breakdown of the operational budget of PET centers and FDG-compounding facilities is presented along with the costs per scan. Differences in costs between sites that purchase FDG and those that manufacture FDG are also examined. We sent surveys to managers of eight Veterans Affairs and two non-Veterans Affairs PET scanning and FDG-compounding facilities. The survey included questions about service volume and the direct costs of equipment, personnel, space, supplies, and repairs needed for FDG compounding and PET scanning and interpretation. We estimated the indirect costs associated with FDG compounding, PET scanning, and PET interpretation. Of the eight sites that responded to our survey, three sites manufacture FDG on-site, three sites purchase FDG, and two sites do both. The total mean cost per scan using manufactured FDG is 1885 US dollars, and it is 1898 US dollars using purchased FDG. PET is expensive. The cost is similar when FDG is manufactured or purchased. Because both PET and cyclotron facilities have high fixed costs, increasing the number of scans obtained and the number of FDG doses manufactured may lead to a decrease in unit costs.

A survey of PET activity in Germany during 1999

Positron emission tomography (PET) is the most powerful molecular imaging technique currently available for clinical use. The aim of this study was to provide public health information on PET procedures carried out in Germany - a country with a very high number of PET installations. To this end, all facilities that in 1999 were running at least one dedicated PET system were contacted and requested to provide information in a questionnaire on the radiopharmaceuticals applied, the total number and age distribution of patients and volunteers examined, the main diagnostic applications and the range of administered activities. Based on the information provided by 48 of the 60 PET facilities in Germany, an annual frequency of about 0.34 PET procedures per 1,000 inhabitants was estimated, associated with an annual per capita effective dose of about 1.9 micro Sv. Averaged over all PET procedures, the mean effective dose to patients was 5.6 mSv. The age distribution of patients and volunteers was skewed markedly towards higher ages; only a very small fraction (<3%) of patients were children younger than 15 years while older patients, and especially those in the age group between 41 and 65 years, were overrepresented relative to the general population. In total, 28 different PET radiopharmaceuticals were used, with only half of these having been administered to more than 20 patients each. The most frequently applied radiotracer was the glucose analogue 2-[(18)F]fluoro-2-deoxy- D-glucose (FDG), which was utilised in more than 84% of all PET procedures. For this tracer, the median value for activities applied for examinations in the three-dimensional (3D) acquisition mode was only half of that used for two-dimensional (2D) measurements. Based on a statistical analysis of the distribution of mean FDG activities administered to patients in the 48 PET facilities who responded to our inquiry, diagnostic reference levels of 370 and 200 MBq are proposed for the 2D and the 3D mode, respectively.

The search for consistency in the manufacture of PET radiopharmaceuticals.

Nuclear Medicine is the specialty of medical imaging, which utilizes a variety of radionuclides incorporated into specific compounds for diagnostic imaging and therapeutic applications. During recent years, research efforts in this discipline have concentrated on the decay characteristics of particular radionuclides and the design of unique radiolabeled tracers necessary to achieve time-dependent molecular images. Various oncology applications have utilized specific PET and SPECT radiopharmaceuticals, which have allowed an extension from functional process imaging in tissue to pathologic processes and nuclide directed treatments. One of the most widely recognized advantages of positron emission tomography (PET) is its use of the attractive, positron-emitting biologic radiotracers that mimic natural substrates. However, a major disadvantage is that these substances are relatively short-lived and unable to be transported great distances. At this time, economic considerations and regulatory guidelines associated with the creation of a PET facility, as well as the operational costs of maintaining both the facility and the necessary procedural documentation, continue to create interesting strategic dilemmas. This commentary will focus on the current approach and anticipated impact of pending regulations, which relate to the manufacture and formulation of a variety of PET radiopharmaceuticals used in clinical research and patient management at Memorial Hospital.

The Role of the Practice of Nuclear Pharmacy in Positron Emission Tomography

As nuclear medicine evolved from an obscure research tool to a mainstream clinical diagnostic and therapeutic modality, so has the role of the practice of pharmacy in nuclear medicine also evolved. A similar evolution is unfolding today in the practice of positron emission tomography (PET). The skills of many diverse professionals, including pharmacists, are essential for the safe and efficient operation of a modern PET facility. The importance of the role of pharmacists in PET has been increasing as the use of PET radiopharmaceuticals has matured from research to clinical to commercial arenas. While it is clear that pharmacists can contribute clinical and technical skills to the operation of a PET center, perhaps one of the most important factors influencing the increased role of pharmacists in PET is their expertise and experience in the drug regulatory process. The commercial distribution of PET radiopharmaceuticals, primarily [ 18F]2-fluorodeoxyglucose (FDG), is currently being performed by a variety of corporate and institutional facility partnerships, with the likelihood of several new players entering the marketplace in the near future. This factor has served to dramatically increase the role for nuclear pharmacy in PET. The practice of nuclear pharmacy is a well-established component of PET. The role of nuclear pharmacists in PET is complementary to the many other professionals currently practicing in this specialty. With the rapidly increasing clinical demand for FDG imaging, it is likely that the number of facilities and institutions entering into the commercial distribution of PET radiopharmaceuticals will also increase. Such growth will also serve to solidify and expand the role for the practice of nuclear pharmacy in PET.

Elimination of artifactual accumulation of FDG in PET imaging of colorectal cancer.

Positron emission tomography (PET) with fluorine-18 labeled deoxyglucose (FDG) can detect tumor recurrences in surgical patients that are otherwise difficult to assess by CT, as well as distant metastases and small malignant nodes that are not identified by other imaging modalities. However, the evaluation of such malignancy is complicated by urinary and colonic concentrations of FDG. Methods and examples of the elimination of artifactual accumulation of FDG in PET imaging of the abdomen and pelvis are presented. Elimination of artifactual accumulation requires patient preparation that begins with cleansing of the colon using an isosmotic solution taken the evening prior to examination. Approximately 500 MBq of F-18 FDG is intravenously administered upon arrival at the PET facility and then the patient is hydrated. After administration of furosemide, a Foley catheter with a drainage bag is placed and the patient is then scanned. Just prior to scanning over the pelvis, normal saline is delivered retrogradely into the urinary bladder. At the end of scanning, the patient voids and repeated pelvic images are obtained. These routines yield a clean scanning field. Lesions that will generally be missed because they are obscured by FDG accumulations along the colon or in the kidneys, ureters, or bladder are better visualized and identified with greater confidence. Artifacts that lead to misinterpretation also are reduced. Elimination of artifactual accumulation of FDG in the colon and urinary system is essential if primary cancer, associated adenopathy, or subtle recurrences are to be evaluated in FDG PET imaging of the abdomen and pelvis.

Evaluation of regional myocardial perfusion in patients with severe left ventricular dysfunction: Comparison of 13N-ammonia PET and 99mTc sestamibi SPECT

Positron emission tomography (PET) scanning with 13N-ammonia and 18FDG is well established for the detection of myocardial viability. Due to the limited availability of PET facilities, recent studies have combined technetium 99m sestamibi single photon emission computed tomography (SPECT) with 18FDG PET or 18FDG SPECT. This approach enables simultaneous assessment of regional myocardial blood flow and metabolism and substantially increases the capacity for viability detection. To validate whether 99mTc-Sestamibi SPECT can replace 13N-ammonia PET, we compared these two modalities in patients with severe left ventricular dysfunction due to coronary artery disease. Thirty-one patients (mean age 57+/-8 years; mean ejection fraction 27%+/-8%) with angiographically verified coronary artery disease were included. In random order, ammonia-PET and sestamibi-SPECT scans were performed. In a 20-segment model of the left ventricle, two blinded observers scored a total of 610 segments on a five-point scale. In a subset of 20 patients, 400 segments were scored twice to evaluate the observer variations of the two techniques. Segmental score differences were used to compare the imaging modalities. The impact on viability detection was assessed by combining the two flow tracers with FDG PET. Segmental comparison of the PET and SPECT studies yielded similar (difference < or = 1) results in 74% of segments, reflecting regional concordance values in the lateral, apical, anterior, septal, and inferior myocardial walls of 86%, 82%, 71%, 66%, and 63%, respectively. The differences in the septal and inferior walls were primarily due to overestimation of perfusion defects by sestamibi SPECT, which yielded a higher proportion of mismatch patterns in those regions. The overall observer variations of the PET and SPECT studies were 7.5% and 5.8%. Myocardial perfusion imaging with 13N-ammonia PET and 99mTc-sestamibi SPECT yielded similar results in patients with severe left ventricular dysfunction, except for the septal and inferior regions. In these regions, SPECT tended to overestimate perfusion defects. Hence, attenuation correction should be considered when combining FDG PET and sestamibi SPECT for diagnosing myocardial viability to avoid overestimation of mismatch patterns in those regions.

PET imaging in soft tissue sarcomas.

Positron emission tomography (PET) was conceived in the early years of nuclear medicine; however, until about 1980 the technology was insufficiently developed to allow its routine application. Furthermore, the high cost of construction and operation of a PET facility delayed its use in the clinical arena and also limited the number of sites available for its development. Today, only 15 years later, PET instrumentation is very sophisticated, costs are decreasing relative to other clinical studies, and clinical PET procedures are proliferating rapidly. In the last few years the application of PET to oncology has proven to be very successful, and there is now a significant literature on PET imaging of many different cancers [1–18].KeywordsPositron Emission TomographyLocal Cerebral Glucose UtilizationMalignant Fibrous HistiocytomasPositron Emission Tomography TechniquePositron Emission Tomography EvaluationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Axillary lymph node metastases detection with nuclear medicine approaches in patients with newly diagnosed breast cancer

Three different tracers, Tc-99m-Sesta MIBI, In-111-Pentetreotide and F-18-FDG, were evaluated in a preliminary study in three different groups of 10 breast cancer patients programmed for breast cancer resection and axillary dissection. Planar scintigraphy and single photon emission tomography (SPET) technique were used for imaging with Tc-99m-Sesta-MIBI and In-111-Pentetreotide, positron emission tomography (PET) was used for imaging with F-18-FDG. We studied 30 breast cancer patients; their clinical stage according to the TNM classification was 30 T1-T2, 1 T4 and 1 Tx (one patient had bilateral cancer and one had bifocal cancer). The lymph nodal status ranged from NO to N2 (14 NO, 16 N1, 1 N2). Tc-99m-Sesta MIBI, In-111 Pentetreotide SPET and F-18-FDG PET were randomly performed before surgery to visualize the primary tumors and to detect axillary lymph node invasion. Tc-99m-Sesta MIBI correctly visualized 10 out of 11 primary cancers in 10 patients. In-111-Pentetreotide detected 9 out of 10 primary cancers. F-18-FDG imaged all the tumors (10). As regards the axillary nodes, Tc-99m-MIBI excluded axilla involvement in 7 out of 7 negative axillae (N-), while it was positive in 2 out of 3 positive cases (N+); In-111-Pentetreotide correctly identified 7 out of 8 negative axillae (N-), while it detected 2 of 3 positive sites. F-18-FDG visualized all positive axillary lymph nodes (4 out of 4 N+ patients) and correctly excluded involvement in all negative patients (6 out of 6 N- cases). This study demonstrated that all three tracers are adequate to be proposed as tumor seeking agents with the aim of developing non-invasive diagnostic methods for pre-operative detection of axillary metastases, so that surgical dissection can be limited to selected patients. The authors discuss the advantages and disadvantages of the different radiopharmaceuticals and conclude that in centers with PET facilities F-18-FDG is the best tumor seeking agent for the evaluation of axillary status. Between Tc-99m-Sesta MIBI and In-111-Pentetreotide the former seems to present more advantages in this kind of application, considering also its lower cost and easier availability. These results encourage further study, including the simultaneous comparison of these tracers in breast cancer staging.

Positron emission tomography: a financial and operational analysis.

Positron emission tomography (PET) is an emerging clinical imaging technique that is facing the challenges of expansion in a period of imminent health care contraction and reform. Although PET began showing utility in clinical medicine in the mid-1980s [1], its proliferation into mainstream medical practice has not matched that of other new imaging technologies such as MR imaging. Many factors have contributed to this, including the changing health care economy, the high cost of PET, the length of time it takes to develop a PET facility, and its inherent complexity. In part because of the proliferation of the use of other technologies and the general explosion of costs, insurance carriers are now holding diagnostic techniques, including PET, to stricter standards of efficacy. New techniques must show improvement in long-term outcome of patients, a difficult task for diagnostic tools. In addition to these issues, PET is an expensive technology that requires highly trained multidisciplinary personnel. Questions have also been raised about the most appropriate mechanism for regulation of PET isotope preparation, leading to speculation about future regulatory requirements. The current pioneers of PET must meet these challenges in order for it to become a routine imaging technique. Because of its clinical value, PET will probably survive despite the challenges. For many reasons, though, not every hospital should necessarily develop PET services. Conversely, many hospitals without this technology should consider acquiring PET. The purpose of this article is to identify the financial, operational, and clinical challenges facing PET centers today, describe potential organizational configurations that may enable PET to survive in an antitechnology environment, and delineate which institutions should consider this new technology.