Nuclear Medicine Modalities Research Articles

Development of GATE Monte Carlo simulation for a CsI pixelated gamma camera dedicated to high resolution animal SPECT.

GATE is currently considered in scintigraphic imaging as a powerful tool to develop, design and optimize nuclear medicine modalities. This paper describes the GATE simulation of a pixelated gamma camera which is dedicated to high resolution of small animals imaging. It consists of a CsI(Na) crystal array coupled to position sensitive photomultiplier tube. The simulation model includes photon tracking through low energy high resolution hexagonal parallel holes collimator, CsI(Na) pixelated crystal, back-compartment, and camera shielding. Simulations were compared with experimental results by some criteria such as energy spectrum, energy resolution, spatial resolution, sensitivity and count profiles obtained from line and point sources imaging. The acquired energy resolution show good agreement with measured spectra. Difference between calculated and experimental values is about 0.3% for absolute sensitivity measurement. The result of the image uniformity is more consistent after implementation of non-uniformity correction. These values were about 1.3 and 1.2% for experimental and simulation study in the central field of view, respectively. Measurements showed that the spatial resolutions differences at the head surface along the long dimensions of gamma camera for simulation and experimental differed by no more than 4%.Differences along the short axis were about 6%. The FWHMs of images of point and line sources show good consistency between experimental images and corresponding simulated ones. The difference between experimental and simulated system parameters was within 11%. Our results demonstrate the ability and flexibility of the Monte Carlo simulation for modeling pixelated gamma camera with position sensitive detector by selecting the appropriate parameters for digitizer chain and collimator position on the detector surface.

Nuclear medicine for the investigation of canine behavioral disorders

The aim of this review was to report the current literature concerning the use of nuclear imaging modalities for the investigation of the neurobiology of canine behavioral disorders. The conventionally used nuclear medicine modalities are positron emission tomography and single photon emission (computed) tomography. At this moment, information is scarce about their application in veterinary behavioral medicine and only present for single photon emission tomography studies in dogs, mainly using 99mTc-ethyl cysteinate dimer to assess brain perfusion (and indirectly neuronal function) and 123I-5-I-R91150 to evaluate the 5-hydroxytryptamine-2A receptor binding. Current results suggest that functional nuclear imaging provides useful noninvasive in vivo information about the neurobiology and therapeutic evaluation of canine behavioral disorders. Due to striking similarities with neurobiological alterations in human disorders, the dog also represents an interesting natural animal model for human neuropsychiatric diseases.

The EANM practice guidelines for bone scintigraphy.

PurposeThe radionuclide bone scan is the cornerstone of skeletal nuclear medicine imaging. Bone scintigraphy is a highly sensitive diagnostic nuclear medicine imaging technique that uses a radiotracer to evaluate the distribution of active bone formation in the skeleton related to malignant and benign disease, as well as physiological processes.MethodsThe European Association of Nuclear Medicine (EANM) has written and approved these guidelines to promote the use of nuclear medicine procedures of high quality.ConclusionThe present guidelines offer assistance to nuclear medicine practitioners in optimizing the diagnostic procedure and interpreting bone scintigraphy. These guidelines describe the protocols that are currently accepted and used routinely, but do not include all existing procedures. They should therefore not be taken as exclusive of other nuclear medicine modalities that can be used to obtain comparable results. It is important to remember that the resources and facilities available for patient care may vary.

Diagnostic imaging to detect and evaluate response to therapy in bone metastases from prostate cancer: current modalities and new horizons.

Different therapeutic options for the management of prostate cancer (PC) have been developed, and some are successful in providing crucial improvement in both survival and quality of life, especially in patients with metastatic castration-resistant PC. In this scenario, diverse combinations of radiopharmaceuticals (for targeting bone, cancer cells and receptors) and nuclear medicine modalities (e.g. bone scan, SPECT, SPECT/CT, PET and PET/CT) are now available for imaging bone metastases. Some radiopharmaceuticals are approved, currently available and used in the routine clinical setting, while others are not registered and are still under evaluation, and should therefore be considered experimental. On the other hand, radiologists have other tools, in addition to CT, that can better visualize bone localization and medullary involvement, such as multimodal MRI. In this review, the authors provide an overview of current management of advanced PC and discuss the choice of diagnostic modality for the detection of metastatic skeletal lesions in different phases of the disease. In addition to detection of bone metastases, the evaluation of response to therapy is another critical issue, since it remains one of the most important open questions that a multidisciplinary team faces when optimizing the management of PC. The authors emphasize the role of nuclear modalities that can presently be used in clinical practice, and also look at future perspectives based on relevant clinical data with novel radiopharmaceuticals.

Nuclear medicine imaging of posttraumatic osteomyelitis.

IntroductionEarly recognition of a possible infection and therefore a prompt and accurate diagnostic strategy is essential for a successful treatment of posttraumatic osteomyelitis (PTO). However, at this moment there is no single routine test available that can detect osteomyelitis beyond doubt and the performed diagnostic tests mostly depend on personal experience, available techniques and financial aspects. Nuclear medicine techniques focus on imaging pathophysiological changes which usually precede anatomical changes. Together with recent development in hybrid camera systems, leading to better spatial resolution and quantification possibilities, this provides new opportunities and possibilities for nuclear medicine modalities to play an important role in diagnosing PTO.AimIn this overview paper the techniques and available literature results for PTO are discussed for the three most commonly used nuclear medicine techniques: the three phase bone scan (with SPECT-CT), white blood cell scintigraphy (also called leukocyte scan) with SPECT-CT and 18F-fluorodeoxyglucose (FDG)-PET/CT. Emphasis is on how these techniques are able to answer the diagnostic questions from the clinicians (trauma and orthopaedic surgeons) and which technique should be used to answer a specific question. Furthermore, three illustrative cases from clinical practice are described.

Accessory spleen mimicking pancreatic tumour: evaluation by 99mTc-labelled colloid SPECT/CT study. Report of two cases and a review of nuclear medicine methods utility.

The accessory spleen is a common congenital anomaly, typically asymptomatic and harmless to the patient. However, in some clinical cases, this anomaly beco-mes significant as it can be mistaken for a tumour or lymph node and be missed during a therapeutic splenectomy. There are nuclear medicine modalities which can be applied in the identification and localisation of an accessory spleen. They include scintigraphy with radiolabelled colloids or heat damaged red blood cells, which are trapped in the splenic tissue. Modern techniques, including hybrid imaging, enable simultaneous structure and tracer distribution evaluations. Additionally, radiation-guided surgery can be used in cases where the accessory spleen, which is usually small (not exceeding 1 cm) and difficult to find among other tissues, has to be removed. In the study, we would like to present 2 cases of patients in which the malignancy had to be excluded for the reason that the multiple accessory spleens were very closely related to the pancreas. There was a lack of certainty in the multi-phase computed tomography (CT) evaluation; however, this situation was clearly resolved by using the 99mTc-stannous colloid single photon emission computed tomography/ CT study. We would also like to briefly analyse the clinical applications of nuclear medicine in case of an accessory spleen.

Pheochromocytomas in Multiple Endocrine Neoplasia Type 2.

Pheochromocytoma (PC) is a neuroendocrine tumor that originates from chromaffin cells of the adrenal medulla. The production of catecholamines, including epinephrine, norepinephrine and dopamine, may lead to haemodynamic instability. Over 30% of PCs are associated with germline mutations, including re-arranged in transfection (RET) mutations seen in multiple endocrine neoplasia type 2 (MEN2) syndromes. Around 40% of individuals with MEN2 develop PC, though it is rarely the presenting feature. Compared to sporadic PC, MEN2-associated PC is more likely to be epinephine secreting and demonstrate bilateral adrenal involvement, and is less likely to be malignant. The diagnosis of PC requires clinical suspicion and biochemical testing, followed by imaging studies. Novel nuclear medicine modalities, including FDG positron emission tomography (PET) and 68Ga DOTATATE PET have added to the conventional techniques of 123I-metaiodobenzylguanindine (MIBG) scintigraphy, computer tomography and magnetic resonance imaging. Treatment of PC is surgical and requires peri-operative alpha and, frequently, beta blockade. Novel surgical techniques, such as adrenal sparing surgery and a laparoscopic approach, have decreased peri-operative morbidity. Surveillance for PC is life long, due to the risk of metastatic disease.

Myocardial metastases on 6-[18F] fluoro-L-DOPA PET/CT: a retrospective analysis of 116 serotonin producing neuroendocrine tumour patients.

PurposeThis study evaluates the prevalence of cardiac metastases in patients with serotonin producing neuroendocrine tumours (NET), examined with 18F-FDOPA PET/CT, and the relationship of these metastases to the presence of carcinoid heart disease (CHD) based on echocardiography.BackgroundCHD occurs in patients with serotonin producing NET. The diagnostic method of choice remains echocardiography. The precise prevalence of cardiac metastases is unknown given the limitations of standard technologies. Nuclear medicine modalities have the potential to visualize metastases of NET.MethodsAll patients who underwent 18F-FDOPA PET/CT because of serotonin producing NET between November 2009 and May 2012 were retrospectively analyzed. The presence of cardiac metastasis was defined as myocardial tracer accumulation higher than the surrounding physiological myocardial uptake. Laboratory tests and transthoracic echocardiography (TTE) results were digitally collected.Results116 patients (62 male) underwent 18F-FDOPA PET/CT, mean age was 61±13 years. TTE was performed in 79 patients. Cardiac metastases were present in 15 patients, of which 10 patients also underwent TTE. One patient had both cardiac metastasis (only on 18F-FDOPA PET/CT) and echocardiographic signs of CHD. There were no differences in echocardiographic parameters for CHD between patients with and without cardiac metastases. TTE in none of the 79 patients showed cardiac metastases.ConclusionThe prevalence of cardiac metastases detected with 18F-FDOPA PET/CT in this study is 13%. 18F-FDOPA PET/CT can visualize cardiac metastases in serotonin producing NET patients. There appears to be no relationship between the presence of cardiac metastases and TTE parameters of CHD.

An analytic reconstruction method for PET based on cubic splines

PET imaging is an important nuclear medicine modality that measures in vivo distribution of imaging agents labeled with positron-emitting radionuclides. Image reconstruction is an essential component in tomographic medical imaging. In this study, we present the mathematical formulation and an improved numerical implementation of an analytic, 2D, reconstruction method called SRT, Spline Reconstruction Technique. This technique is based on the numerical evaluation of the Hilbert transform of the sinogram via an approximation in terms of 'custom made' cubic splines. It also imposes sinogram thresholding which restricts reconstruction only within object pixels. Furthermore, by utilizing certain symmetries it achieves a reconstruction time similar to that of FBP. We have implemented SRT in the software library called STIR and have evaluated this method using simulated PET data. We present reconstructed images from several phantoms. Sinograms have been generated at various Poison noise levels and 20 realizations of noise have been created at each level. In addition to visual comparisons of the reconstructed images, the contrast has been determined as a function of noise level. Further analysis includes the creation of line profiles when necessary, to determine resolution. Numerical simulations suggest that the SRT algorithm produces fast and accurate reconstructions at realistic noise levels. The contrast is over 95% in all phantoms examined and is independent of noise level.

Antimicrobial peptides: their role as infection-selective tracers for molecular imaging.

Antimicrobial peptides (AMPs) are a heterogeneous class of compounds found in a variety of organisms including humans and, so far, hundreds of these structures have been isolated and characterised. They can be described as natural microbicide, selectively cytotoxic to bacteria, whilst showing minimal cytotoxicity towards the mammalian cells of the host organism. They act by their relatively strong electrostatic attraction to the negatively charged bacterial cells and a relatively weak interaction to the eukaryote host cells. The ability of these peptides to accumulate at sites of infection combined with the minimal host's cytotoxicity motivated for this review to highlight the role and the usefulness of AMPs for PET with emphasis on their mechanism of action and the different interactions with the bacterial cell. These details are key information for their selective properties. We also describe the strategy, design, and utilization of these peptides as potential radiopharmaceuticals as their combination with nuclear medicine modalities such as SPECT or PET would allow noninvasive whole-body examination for detection of occult infection causing, for example, fever of unknown origin.

The EANM and SNMMI practice guideline for lymphoscintigraphy and sentinel node localization in breast cancer

The accurate harvesting of a sentinel node in breast cancer includes a sequence of procedures with components from different medical specialities, including nuclear medicine, radiology, surgical oncology and pathology. The aim of this document is to provide general information about sentinel lymph node detection in breast cancer patients. The Society of Nuclear Medicine and Molecular Imaging (SNMMI) and the European Association of Nuclear Medicine (EANM) have written and approved these guidelines to promote the use of nuclear medicine procedures with high quality. The final result has been discussed by distinguished experts from the EANM Oncology Committee, the SNMMI and the European Society of Surgical Oncology (ESSO). The present guidelines for nuclear medicine practitioners offer assistance in optimizing the diagnostic information from the SLN procedure. These guidelines describe protocols currently used routinely, but do not include all existing procedures. They should therefore not be taken as exclusive of other nuclear medicine modalities that can be used to obtain comparable results. It is important to remember that the resources and facilities available for patient care may vary.

The Role of Nuclear Medicine in The Diagnosis and Management of Solitary Pulmonary Nodules

Solitary pulmonary nodule (SPN) is a frequent finding on the chest x-ray and computed tomography. Nuclear medicine techniques play an important role in the diagnosis and management of SPN. In the current review, we briefly will explain the different nuclear medicine modalities in this regard including positron emission tomography (PET) using 18-F-FDG, and 11-C-Methionine, and single photon emission computerized tomography (SPECT) using somatostatin receptor scintigraphy, 201-Thallium, and 99m-Tc-MIBI.

A Clinician's Guide to Nuclear Medicine

A. Taylor, D.M. Schuster, and N. Alazraki Reston, VA: Society of Nuclear Medicine and Molecular Imaging, 2006, 424 pages, $51 Compared with diagnostic imaging modalities such as CT, MR imaging, radiography, and sonography, nuclear medicine modalities are often less familiar to referring

Nanosized multifunctional liposomes for tumor diagnosis and molecular imaging by SPECT/CT

Among currently used cancer imaging methods, nuclear medicine modalities provide metabolic information, whereas modalities in radiology provide anatomical information. However, different modalities, having different acquisition times in separate machines, decrease the specificity and accuracy of images. To solve this problem, hybrid imaging modalities were developed as a new era, especially in the cancer imaging field. With widespread usage of hybrid imaging modalities, specific contrast agents are essentially needed to use in both modalities, such as single-photon emission computed tomography/computed tomography (SPECT/CT). Liposomes are one of the most desirable drug delivery systems, depending on their suitable properties. The aim of this study was to develop a liposomal contrast agent for the diagnosis and molecular imaging of tumor by SPECT/CT. Liposomes were prepared nanosized, coated with polyethylene glycol to obtain long blood circulation, and modified with monoclonal antibody 2C5 for specific tumor targeting. Although DTPA-PE and DTPA-PLL-NGPE (polychelating amphilic polymers; PAPs) were loaded onto liposomes for stable radiolabeling for SPECT imaging, iopromide was encapsulated into liposomes for CT imaging. Liposomes [(DPPC:PEG2000-PE:Chol:DTPA-PE), (PL 90G:PEG2000-PE:Chol:DTPA-PE), (DPPC:PEG2000-PE:Chol:PAPs), (PL 90G:PEG2000-PE:Chol:PAPs), (60:0.9:39:0.1% mol ratio)] were characterized in terms of entrapment efficiency, particle size, physical stability, and release kinetics. Additionally, in vitro cell-binding studies were carried out on two tumor cell lines (MCF-7 and EL 4) by counting radioactivity. Tumor-specific antibody-modified liposomes were found to be effective multimodal contrast agents by designating almost 3–8 fold more uptake than nonmodified ones in different tumor cell lines. These results could be considered as an important step in the development of tumor-targeted SPECT/CT contrast agents for cancer imaging.

Synthesis of oncological [11C]radiopharmaceuticals for clinical PET

Positron emission tomography (PET) is a nuclear medicine modality which provides quantitative images of biological processes in vivo at the molecular level. Several PET radiopharmaceuticals labeled with short-lived isotopes such as (18)F and (11)C were developed in order to trace specific cellular and molecular pathways with the aim of enhancing clinical applications. Among these [(11)C]radiopharmaceuticals are N-[(11)C]methyl-choline ([(11)C]choline), l-(S-methyl-[(11)C])methionine ([(11)C]methionine) and 1-[(11)C]acetate ([(11)C]acetate), which have gained an important role in oncology where the application of 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) is suboptimal. Nevertheless, the production of these radiopharmaceuticals did not reach the same level of standardization as for [(18)F]FDG synthesis. This review describes the most recent developments in the synthesis of the above-mentioned [(11)C]radiopharmaceuticals aiming to increase the availability and hence the use of [(11)C]choline, [(11)C]methionine and [(11)C]acetate in clinical practice.

Diagnostic accuracy of combined 99mTc-sulesomab and 99mTc-nanocolloid bone marrow imaging in detecting prosthetic joint infection

Autologous-labeled leukocytes combined with sulfur colloid bone marrow scan is the current nuclear medicine gold standard for the diagnosis of prosthetic joint infection. The goal of this study is to assess the diagnostic accuracy of a new nuclear medicine modality for detecting infection in this context. Twenty-seven patients with suspicious hip and knee arthroplasties were enrolled prospectively and underwent nuclear medicine testing using 99mTc-sulesomab and 99mTc-nanocolloids sequentially. These results were then crossed with the final diagnosis to determine the test(s) diagnostic accuracy. An isolated 99mTc-sulesomab scan shows 100% sensitivity (0.40-1) and negative predictive value (0.31-1) but only 20% specificity (0.05-0.48). Combining it with a 99mTc-nanocolloid bone marrow scan increases the specificity (0.75-1) and the positive predictive value (0.40-1) to 100%. Furthermore, the combined test has fewer equivocal readings and higher interreader agreement: κ test value 0.59 vs. 0.44. The results support the hypothesis that these technically simpler and ready-to-use products may be an alternative to autologous-labeled leukocytes/sulfur colloid marrow scan.

131I/123I-Metaiodobenzylguanidine (mIBG) scintigraphy: procedure guidelines for tumour imaging

The aim of this document is to provide general information about mIBG scintigraphy in cancer patients. The guidelines describe the mIBG scintigraphy protocol currently used in clinical routine, but do not include all existing procedures for neuroendocrine tumours. The guidelines should therefore not be taken as exclusive of other nuclear medicine modalities that can be used to obtain comparable results. It is important to remember that the resources and facilities available for patient care may vary from one country to another and from one medical institution to another. The present guidelines have been prepared for nuclear medicine physicians and intend to offer assistance in optimizing the diagnostic information that can currently be obtained from mIBG scintigraphy. The corresponding guidelines of the Society of Nuclear Medicine (SNM) and the Dosimetry, Therapy and Paediatric Committee of the EANM have been taken into consideration, and partially integrated into this text. The same has been done with the most relevant literature on this topic, and the final result has been discussed within a group of distinguished experts.

Assessment and Optimization of Cell Engraftment After Transplantation Into the Heart

Myocardial regeneration using stem and progenitor cell transplantation in the injured heart has recently become a major goal in the treatment of cardiac disease. Experimental studies and clinical applications have generally been encouraging, although the functional benefits that have been attained clinically are modest and inconsistent. Low cell retention and engraftment after myocardial delivery is a key factor limiting the successful application of cell therapy, irrespective of the type of cell or the delivery method. To improve engraftment, accurate methods for tracking cell fate and quantifying cell survival need to be applied. Several laboratory techniques (histological methods, real-time quantitative polymerase chain reaction, radiolabeling) have provided invaluable information about cell engraftment. In vivo imaging (nuclear medicine modalities, bioluminescence, and MRI) has the potential to provide quantitative information noninvasively, enabling longitudinal assessment of cell fate. In the present review, we present several available methods for assessing cell engraftment, and we critically discuss their strengths and limitations. In addition to providing insights about the mechanisms mediating cell loss after transplantation, these methods can evaluate techniques for augmenting engraftment, such as tissue engineering approaches, preconditioning, and genetic modification, allowing optimization of cell therapies.

Computerized tomographic pulmonary angiography versus ventilation perfusion lung scanning for the diagnosis of pulmonary embolism

The purpose of this review is to focus on recent research that has addressed the relative merits of computed tomographic pulmonary angiography (CTPA) and ventilation perfusion (V/Q) scanning for the diagnosis of pulmonary embolism. Computed tomographic pulmonary angiography is the most sensitive test for the diagnosis of pulmonary embolism and its use has been associated with a rising incidence of the condition. Diagnostic algorithms using either CTPA or V/Q scanning have proven to be comparably safe to exclude the diagnosis of pulmonary embolism. Negative multidetector CTPA study results essentially ruled out the diagnosis of pulmonary embolism without the need to routinely exclude the presence of deep vein thrombosis. Use of multidetector CTPA was associated with significant radiation exposure that potentially increases risk of secondary malignancies. This is particularly a concern for young women given the risk of breast cancer. Single photon emission tomography (SPECT) V/Q and modified diagnostic criteria for V/Q scan interpretation increased their diagnostic accuracy compared with V/Q scanning and offer nuclear medicine modalities that are alternatives to CTPA in at least some patients with suspected pulmonary embolism at a fraction of the risk of radiation exposure. Excluding low risk patients for pulmonary embolism as defined by clinical scoring systems and D-dimer testing would enhance the yield of diagnostic testing. Computed tomographic pulmonary angiography is the most reliable test for diagnosis of pulmonary embolism. However, diagnostic algorithms using V/Q scanning are safe and may be preferred in some patient populations.

Multimodality Imaging in a Patient With Adrenocortical Carcinoma Leading to Peptide Receptor Radionuclide Therapy

In the recommended staging system for adrenocortical carcinoma, nuclear medicine modalities are optional. In cases of distorted postoperative anatomy and when postoperative infection/inflammation mimics malignancy, functional imaging is helpful. We present a case of a patient with adrenocortical carcinoma where F-18 FDG dual time point imaging and somatostatin receptor scintigraphy were used in the diagnostic work up after surgery complicated by infection, until end-stage palliative peptide receptor radionuclide therapy. The estimated uptake on somatostatin receptor scintigraphy is traditionally done visually on planar images. We suggest a more objective, semiquantitative approach by comparing the tumor uptake with a standard reference.