Murat Tuncel

Gamut: soft tissue uptake of bone radiopharmaceuticals

XTRASKELETAL UPTAKE OF bone-seeking radiopharmaceuticals is an unexpected finding. oft tissue uptake of bone scanning agents is caused y chemisorption on the surface of calcium salts and ydroxyapatite crystals. Metastatic calcification and eterotrophic bone formation are the most common auses. The recognition of patterns of soft-tissue ccumulation of bone-seeking agents has an important mplication in the differential diagnosis.

Osteopoikilosis: a major diagnostic problem solved by bone scintigraphy

Osteopoikilosis (OPK) is a rare disease with an unknown etiology. Although a benign condition, it may lead to diagnostic problems when the patient undergoes diagnostic imaging of the skeletal system due to various reasons like malignancy. Herein, we report 2 cases with OPK causing difficulties in the final diagnosis of the cases which was resolved with the contribution of bone scintigraphy and clinical follow-up.

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.

Gastroesophageal reflux scintigraphy: interpretation methods and inter-reader agreement

BackgroundScintigraphic imaging is a useful screening tool for patients with suspected gastroesophageal reflux. New scintigraphic interpretation methods have recently been introduced. This study was undertaken to evaluate the efficiency of various scintigraphic interpretation methods in the detection of gastroesophageal reflux and to measure their influence on inter-reader agreement.MethodsScintigraphic images of 49 children with suspected gastroesophageal reflux were interpreted by three different methods: visual interpretation, time activity curves, and condensed images. The readings were performed by three specialists and a resident. The discordant results were resolved by a consensus reading done together by all interpreters based on the three different methods. The gastroesophageal refluxes were grouped according to their number, location and intensity.ResultsGastroesophageal reflux scintigraphy revealed 22 patients with negative results and 27 with positive results. The sensitivity, positive predictive value and specificity for each of the three specialists vs. the resident were 96%, 96% and 81% vs. 96%; 93%, 90% and 96% vs. 81%; and 90%, 86%, and 95% vs. 73%, respectively. The mean inter-observer reproducibility (κ value) was 0.910 for visual interpretation, 0.652 for time activity curves and 0.789 for condensed images. Twenty-seven percent of the results were discordant and most of these refluxes were of low grade (92%), low intensity (77%) and localization in the distal esophagus (54%).ConclusionGastroesophageal scintigraphy is a useful tool for detecting patients with suspected reflux, and visual interpretation is better than the other two methods in terms of accuracy and inter-observer reproducibility.

Osteoid osteoma of the rib detected on bone scintigraphy: Importance of pattern recognition

Osteoid osteoma is a bone-forming neoplasm that occurs most often in the long bones. The occurrence of an osteoid osteoma in a rib is very rare. The authors describe a patient with an isolated osteoid osteoma of the sixth rib detected on Tc-99m MDP bone scintigraphy. Protrusion of the area of increased tracer uptake in the rib lesion was observed on bone imaging, which suggested a primary bone tumor. The case reported indicates the importance of pattern recognition, which, in certain instances, helps to narrow the differential diagnosis.

Nuclear Medicine in Pediatric and Adolescent Tumors.

Nuclear medicine has an important role in the management of many cancers in pediatric age group with multiple imaging modalities and radiopharmaceuticals targeting various biological uptake mechanisms. 18-Flourodeoxyglucose is the radiotracer of choice especially in patients with sarcoma and lymphoma. (18)FDG-PET, for sarcoma and lymphomas, is proved to be superior to conventional imaging in staging and therapy response. Although studies are limited in pediatric population, (18)FDG-PET/CT has found its way through international guidelines. Limitations and strengths of PET imaging must be noticed before adapting PET imaging in clinical protocols. Established new response criteria using multiple parameters derived from (18)FDG-PET would increase the accuracy and repeatability of response evaluation. Current data suggest that I-123 metaiodobenzylguanidine (MIBG) remains the tracer of choice in the evaluation of neuroblastoma (NB) because of its high sensitivity, specificity, diagnostic accuracy, and prognostic value. It is valuable in determining the response to therapy, surveillance for disease recurrence, and in selecting patients for I-131 therapy. SPECT/CT improves the diagnostic accuracy and the interpretation confidence of MIBG scans. (18)FDG-PET/CT is an important complementary to MIBG imaging despite its lack of specificity to NB. It is valuable in cases of negative or inconclusive MIBG scans and when MIBG findings underestimate the disease status as determined from clinical and radiological findings. F-18 DOPA is promising tracer that reflects catecholamine metabolism and is both sensitive and specific. F-18 DOPA scintigraphy provides the advantages of PET/CT imaging with early and short imaging times, high spatial resolution, inherent morphologic correlation with CT, and quantitation. Regulatory and production issues currently limit the tracers availability. PET/CT with Ga-68 DOTA appears to be useful in NB imaging and may have a unique role in selecting patients for peptide receptor radionuclide therapy with somatostatin analogues. C-11 hydroxyephedrine PET/CT is a specific PET tracer for NB, but the C-11 label that requires an on-site cyclotron production and the high physiologic uptake in the liver and kidneys limit its use. I-124 MIBG is useful for I-131 MIBG pretherapeutic dosimetry planning. Its use for diagnostic imaging as well as the use of F-18 labeled MIBG analogues is currently experimental. PET/MR imaging is emerging and is likely to become an important tool in the evaluation. It provides metabolic and superior morphological data in one imaging session, expediting the diagnosis and lowering the radiation exposure. Radioactive iodines not only detect residual tissue and metastatic disease but also are used in the treatment of differentiated thyroid cancer. However, these are not well documented in pediatric age group like adult patients. Use of radioactivity in pediatric population is very important and strictly controlled because of the possibility of secondary malignities; therefore, management of oncological cases requires detailed literature knowledge. This article aims to review the literature on the use of radionuclide imaging and therapy in pediatric population with thyroid cancer, sarcomas, lymphoma, and NB.

SPECT-CT imaging of poliostotic fibrous dysplasia.

A 25-year-old healthy woman with no special medical history, complained of persistent back pain after giving birth. Having direct X-ray film of lumbar vertebras suspicious for metastases, she was referred to bone scintigraphy (BS), which revealed increased radiotracer uptake in several ribs and lumbosacral vertebras (fig. 1a). Additional SPECT-CT images verified these findings and showed increased uptake in the lytic lesions with sclerotic rim but no soft tissue component (figs. 1 and 2). The lesions were atypical for metastasis, since they cause lytic lesions without a well defined sclerotic rim and often accompanying soft tissue

Vascular retention of Tc-99m pertechnetate and Tc-99m sestamibi, mimicking thyroid carcinoma metastases.

Follicular thyroid carcinoma is common in regions with insufficient iodine diets and represents approximately 10-20 % of all thyroid malignancies1,2. The treatment of patients suffering from follicular thyroid carcinoma includes surgery and radioiodine therapy3. Although after definitive therapy, the survival of these patients is good, these patients need to be followed for local recurrences and distant metastases. The main radionuclide methods that were used for the follow-up of these patients are; Tc-99m pertechnetate, Tc-99m sestamibi, I-131 scintigraphy and F-18fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET). These methods were found to be helpful in the identification of residual disease, but they have several non-specific uptake sites which may lead to false interpretation. Here we report a patient with false-positive findings in Tc-99m pertechnetate and Tc-99m sestamibi scintigraphy.

Value of technetium scintigraphy and iodine uptake measurement during follow-up of differentiated thyroid cancer

Measurement of serum thyroglobulin (Tg) levels and I-131 whole body scintigraphy (WBS) are used in the follow-up of patients with differentiated thyroid cancer (DTC). This study was designed to evaluate the significance of persistent I-131 uptake in the thyroid bed in patients with DTC following surgery and/or radioactive iodine ablation. Tc-99m thyroid scintigraphy (TS) and I-131 thyroid uptake (IU) were also performed to determine their clinical impact on patient management.Patients and MethodsSixty-two non-metastatic patients (14 men, 48 women) with a mean age of 44 years (range: 16-75) who had undergone surgical thyroidectomy for DTC were evaluated prospectively. All patients had undergone technetium and iodine scintigraphy (IS). Although serum Tg levels were measured in all patients, IU was available in 36.ResultsTg values were in the range of 0.2-24 ng/m/ (median: 0.2 ng/m/) when patients were in the hypothyroid state. 1-131 WBS detected residual tissue in the neck in 30 patients (48%); however TS was positive in only 12 (19%). 1-131 uptake in the thyroid bed ranged from 0 to 14% (median: 0.1%). Twelve of 13 patients with positive IS and negative TS had uptake values ≤ 0.3% (p > 0.00001). When IU values were ≤0.3%, 54% of our patients did not have any uptake in the thyroid bed on TS or IS, whereas when IU was >0.3%, 80% of patients had neck uptake on both TS and IS (p > 0.00001).ConclusionThe results of this study demonstrate that the concordance of IS and TS depends on the IU level after suspension of replacement therapy. Measurements of IU and TS are of considerable value in evaluating patient response to therapy and will substantially reduce the need for repetitive radioiodine scans and unnecessary treatment doses in patients with undetectable Tg values.

Prognosis estimation under the light of metabolic tumor parameters on initial FDG-PET/CT in patients with primary extranodal lymphoma

Abstract Background Non-Hodgkin’s lymphomas arising from the tissues other than primary lymphatic organs are named primary extranodal lymphoma. Most of the studies evaluated metabolic tumor parameters in different organs and histopathologic variants of this disease generally for treatment response. We aimed to evaluate the prognostic value of metabolic tumor parameters derived from initial FDG-PET/CT in patients with a medley of primary extranodal lymphoma in this study. Patients and methods There were 67 patients with primary extranodal lymphoma for whom FDG-PET/CT was requested for primary staging. Quantitative PET/CT parameters: maximum standardized uptake value (SUVmax), average standardized uptake value (SUVmean), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were used to estimate disease-free survival and overall survival. Results SUVmean, MTV and TLG were found statistically significant after multivariate analysis. SUVmean remained significant after ROC curve analysis. Sensitivity and specificity were calculated as 88% and 64%, respectively, when the cut-off value of SUVmean was chosen as 5.15. After the investigation of primary presentation sites and histo-pathological variants according to recurrence, there is no difference amongst the variants. Primary site of extranodal lymphomas however, is statistically important (p = 0.014). Testis and central nervous system lymphomas have higher recurrence rate (62.5%, 73%, respectively). Conclusions High SUVmean, MTV and TLG values obtained from primary staging FDG-PET/CT are potential risk factors for both disease-free survival and overall survival in primary extranodal lymphoma. SUVmean is the most significant one amongst them for estimating recurrence/metastasis.