131I Imaging Research Articles

Accuracy of patient-specific I-131 dosimetry using hybrid whole-body planar-SPECT/CT I-123 and I-131 imaging

PurposeThis study aimed to assess the accuracy of patient-specific absorbed dose calculations for tumours and organs at risk in radiopharmaceutical therapy planning, utilizing hybrid planar-SPECT/CT imaging.MethodsThree Monte Carlo (MC) simulated digital patient phantoms were created, with time-activity data for mIBG labelled to I-123 (LEHR and ME collimators) and I-131 (HE collimator). The study assessed the accuracy of the mean absorbed doses for I-131-mIBG therapy treatment planning. Multiple planar whole-body (WB) images were simulated (between 1 to 72 h post-injection (p.i)). The geometric-mean image of the anterior and posterior WB images was calculated, with scatter and attenuation corrections applied. Time-activity curves were created for regions of interest over the liver and two tumours (diameters: 3.0 cm and 5.0 cm) in the WB images. A corresponding SPECT study was simulated at 24 h p.i and reconstructed using the OS-EM algorithm, incorporating scatter, attenuation, collimator-detector response, septal scatter and penetration corrections. MC voxel-based absorbed dose rate calculations used two image sets, (i) the activity distribution represented by the SPECT images and (ii) the activity distribution from the SPECT images distributed uniformly within the volume of interest. Mean absorbed doses were calculated considering photon and charged particle emissions, and beta emissions only. True absorbed doses were calculated by MC voxel-based dosimetry of the known activity distributions for reference.ResultsConsidering photon and charged particle emissions, mean absorbed dose accuracies across all three radionuclide-collimator combinations of 3.8 ± 5.5% and 0.1 ± 0.9% (liver), 5.2 ± 10.0% and 4.3 ± 1.7% (3.0 cm tumour) and 15.0 ± 5.8% and 2.6 ± 0.6% (5.0 cm tumour) were obtained for image set (i) and (ii) respectively. Considering charged particle emissions, accuracies of 2.7 ± 4.1% and 5.7 ± 0.7% (liver), 3.2 ± 10.2% and 9.1 ± 1.7% (3.0 cm tumour) and 13.6 ± 5.7% and 7.0 ± 0.6% (5.0 cm tumour) were obtained for image set (i) and (ii) respectively.ConclusionThe hybrid WB planar-SPECT/CT method proved accurate for I-131-mIBG dosimetry, suggesting its potential for personalized treatment planning.

Pre-Treatment and Post-Treatment I-131 Imaging in Differentiated Thyroid Carcinoma.

Radioiodine imaging in initial perioperative settings, after the total thyroidectomy, includes pre-treatment and post-treatment radioiodine imaging. While the benefit of post-treatment whole-body imaging (PT-WBI) is well established, the role of diagnostic whole-body imaging (dx WBI), prior to radioiodine (I-131) ablative or therapeutic doses, is controversial. Dx WBI has been abandoned in most nuclear medicine centers long ago. Planar low-dose dxWBI provides the volume of postoperative thyroid remnants, but it cannot detect occult metastatic foci in the neck. The modern integrated multimodality, i.e., SPECT/CT imaging, provides three dimensional images and accurate anatomic/metabolic data. This hybrid technology offers better spatial resolution but not better sensitivity. Dx WBI has low theranostic power because of the radioiodine indifference and low detection sensitivity for small-volume nodal disease in the neck. Since dx WBI cannot clarify the paratracheal cervical uptake, thyroid remnants may be easily misinterpreted as nodal disease, leading to a false N upstaging (from N0 stage to N1 stage) in DTC patients. Post-ablation I-131 imaging has a significant role in the initial staging of radioiodine-avid DTC and in the identification of non-radioiodine avid tumors. Additionally, SPECT/CT in the post-treatment setting provides more accurate initial TNM staging and better risk stratification of DTC patients. Post-treatment I-131 imaging is obligatory and must be performed in all DTC patients who receive radioiodine treatment.

Implementation of Review Technique and Critical Path Method on Academic Programs am<!-- ============== --> <journal_article publication_type='full_text'> <titles> <title>“Comparison of Thyroid Uptake by Tc – 99m Pertechnetate and Iodine – 131 for Euthyroid & Hypothyroid Patients”

Euthyroidism is defined as normal functioning thyroid gland that occurs with normal serum levels of TSH and T4. Lower than normal T4 levels usually mean its hypothyroidism. This thyroid condition can be treated with radioactive therapy using uptake studies by Iodine-131 and Tc-99m. Oral administration of I-131 has been a commonly accepted procedure for treatment of benign and malignant conditions of the thyroid since the 1940s. However, thyroid uptake using Tc-99m has proven to be more advantageous than with I-131, since the procedure is faster, short half-life (only 6 hours), short retention in the gland, no beta (-) radiation thus providing low dose to the thyroid gland (10000 times less than that of I-131) and the images have better quality for its gamma photon of 140keV. So the aim of this study was to make a comparison between I-131 and Tc-99m for performing thyroid uptake and to correlate them for both euthyroid and hypothyroid patients and hence to standardize a simple and fast method for performing thyroid uptake. This study was made for 87 patients (58 females and 29 males) with ages ranging from 14 to 75 years (mean of 39.2 years) were done with both I-131 and Tc-99m. The type of patients was euthyroid, hyperthyroid and hypothyroid. The correlation and comparison between I-131 and Tc-99m was studied for euthyroid and hypothyroid patients. From this study out of 87 patients 32 were found euthyroid, 12 were hypothyroid and others were hyperthyroid. Out of 32 euthyroid patients 26 patients were positive with both Tc-99m and I-131. 6 patients had negative results with Tc-99m and positive results with I-131. Out of 12 hypothyroid patients 10 patients were positive with both Tc-99m and I-131. 2 patients had negative results with Tc-99m and positive results with I-131. A statistically significant correlation was found between I-131 and Tc-99m data for euthyroid patients (r = 0.49, p-value = 0.005). But for hypothyroid patients (r = 0.56, p value = 0.058) which indicates statistically not significant correlation. Considering I-131 imaging as the gold-standard procedure, Tc-99m had a good correlation with I-131 for the detection of euthyroidism but not for the hypothyroidism. So, the consideration of thyroid structure and function using Tc-99m is a simple, fast, better and efficient method for euthyroid patients according to its advantages over I-131 and also for the good quality correlation of this study. To show better correlation for hypothyroidism; further study should be needed with more patients.

On the use of solid 133Ba sources as surrogate for liquid 131I in SPECT/CT calibration: a European multi-centre evaluation

IntroductionCommissioning, calibration, and quality control procedures for nuclear medicine imaging systems are typically performed using hollow containers filled with radionuclide solutions. This leads to multiple sources of uncertainty, many of which can be overcome by using traceable, sealed, long-lived surrogate sources containing a radionuclide of comparable energies and emission probabilities. This study presents the results of a quantitative SPECT/CT imaging comparison exercise performed within the MRTDosimetry consortium to assess the feasibility of using 133Ba as a surrogate for 131I imaging.Materials and methodsTwo sets of four traceable 133Ba sources were produced at two National Metrology Institutes and encapsulated in 3D-printed cylinders (volume range 1.68–107.4 mL). Corresponding hollow cylinders to be filled with liquid 131I and a mounting baseplate for repeatable positioning within a Jaszczak phantom were also produced. A quantitative SPECT/CT imaging comparison exercise was conducted between seven members of the consortium (eight SPECT/CT systems from two major vendors) based on a standardised protocol. Each site had to perform three measurements with the two sets of 133Ba sources and liquid 131I.ResultsAs anticipated, the 131I pseudo-image calibration factors (cps/MBq) were higher than those for 133Ba for all reconstructions and systems. A site-specific cross-calibration reduced the performance differences between both radionuclides with respect to a cross-calibration based on the ratio of emission probabilities from a median of 12–1.5%. The site-specific cross-calibration method also showed agreement between 133Ba and 131I for all cylinder volumes, which highlights the potential use of 133Ba sources to calculate recovery coefficients for partial volume correction.ConclusionThis comparison exercise demonstrated that traceable solid 133Ba sources can be used as surrogate for liquid 131I imaging. The use of solid surrogate sources could solve the radiation protection problem inherent in the preparation of phantoms with 131I liquid activity solutions as well as reduce the measurement uncertainties in the activity. This is particularly relevant for stability measurements, which have to be carried out at regular intervals.

A study on energy window-based scatter correction methods in 99mTc and 123I imaging

Tc-99m and I-123 are radionuclides commonly used for diagnostic examination in nuclear medicine. Detection of the scattered photons by the Compton interactions in the photopeak energy window is a factor affecting the image quality. DEW and TEW scatter correction methods are used to improve the image quality degrade by Compton scattered photons. In the study, planar and SPECT images of sphere, rod and cardiac phantom containing different activities were acquired with a gamma camera system. DEW/TEW corrected and uncorrected images for Tc-99m/I-123 were evaluated qualitatively and quantitatively. Both for planar and SPECT images, the DEW and TEW scatter correction methods were found to improve the image quality at varying rates.

Unusual spread of the follicular thyroid carcinoma, metastases to liver and pancreas

We report a multimetastatic follicular thyroid carcinoma(FTC) with match lesions between 18F-FDG PET/CT and post-treatment 131I imaging. The patient had a history of thoracic vertebra corpectomy surgery and liver tru-cut biopsy; both resulted in metastases of FTC. After total thyroidectomy surgery, the patient was referred to the 18F-FDG PET/CT to investigate other possible metastatic foci. 18F-FDG PET/CT showed increased FDG uptakes on a cervical lymph node, bones, lung, liver, and pancreas. After treatment of 131I, post-treatment iodine scintigraphy demonstrated iodine uptakes in the same areas as the 18F-FDG PET/CT scan and at the thyroid bed. All the matched lesions were concluded as a spread of the FTC. Here we describe an infrequent differentiated thyroid carcinoma case with metastases to the liver and pancreas. This case report also highlights the importance of 18F-FDG PET/CT in determining the extent of thyroid cancer.

Dual-tracer 99mTc-sestamibi/ 123I imaging in primary hyperparathyroidism.

Surgery is the only curative treatment for primary hyperparathyroidism (PHPT). Preoperative imaging is always recommended. 99mTc-sestamibi scintigraphy is often used in combination with neck ultrasonography as first-line imaging. 99mTc-sestamibi scintigraphy plays a major role in depicting ectopic parathyroid lesions, as well as in guiding a targeted, minimally invasive parathyroidectomy (MIP). Detecting multiple gland disease (MGD) is important to reduce the risks of surgical failure or unplanned conversion to bilateral surgery. However, the ability to recognize MGD varies greatly depending on the 99mTc-sestamibi imaging protocol that is used. Dual-tracer 99mTc-sestamibi/123I highly improves MGD detection compared to single-tracer "dual-phase" 99mTc-sestamibi imaging. It can thus improve patient selection for MIP. The main requirements for successful dual-tracer imaging are: 1) to acquire 99mTc-sestamibi and 123-iodine images simultaneously, thus avoiding motion artifacts on subtraction images; to use neck pinhole imaging, in addition to planar imaging, to improve resolution and MGD detection; to follow with dual-tracer SPECT/CT imaging to better define anatomic position of detected parathyroid lesions. If dual-tracer 99mTc-sestamibi/123I and neck ultrasonography are negative or inconclusive, the second-line imaging in our practice is 18F-fluorocholine PET/CT. The CT component of 18F-fluorocholine PET/CT is performed as non-enhanced acquisition plus a contrast-enhanced arterial phase acquisition, to minimize the risk from false-positives due to choline uptake in inflammatory lymph nodes. We use the same strategy of first-line dual-tracer 99mTc-sestamibi/123I plus neck ultrasonography, followed if necessary by second-line contrast-enhanced 18F-fluorocholine PET/CT, in patients requiring reoperation for persistent or recurrent PHPT. Additional localization techniques are now rarely necessary.

Validity of Anti-PSMA ScFvD2B as a Theranostic Tool: A Narrative-Focused Review

Prostate cancer (PCa) is the second leading cause of cancer among men, and its diagnosis and adequate staging are fundamental. Among the biomarkers identified in recent years for PCa management, prostate-specific-membrane-antigen (PSMA), physiologically expressed at a low level on healthy prostate and in other normal tissues and highly overexpressed in PCa, represents a reliable marker ideal for imaging and therapy. The development of anti-PSMA antibodies, such as D2B, demonstrated slow clearance of intact antibodies compared with fragments resulting in low tumor-to-blood ratios; however, the modular structural and functional nature of antibodies allowed the generation of smaller fragments, such as scFvs. In this review of the anti-PSMA antibody fragment scFvD2B, we combined further characterization of its biomolecular and tissue cross-reactivity characteristics with a comprehensive summary of what has already been performed in preclinical models to evaluate imaging and therapeutic activities. A molecular dynamics study was performed, and ScFvD2B occupied a limited conformational space, characterized by low-energy conformational basins, confirming the high stability of the protein structure. In the cross-reactivity study, the weak/absent immunoreactivity in non-tumor tissues was comparable to the PSMA expression reported in the literature. Biodistribution studies and therapeutic treatments were conducted in different animal models obtained by subcutaneous or locoregional injection of PSMA-positive-versus-negative xenografts. The maximum tumor uptake was observed for 123I(SPECT), 124I(PET), and optical imaging, which avoids kidney accumulation (compared with radiometals) and leads to an optimal tumor-to-kidney and tumor-to-background ratios. Regarding its possible use in therapy, experimental data suggested a strong and specific antitumor activity, in vitro and in vivo, obtained using CAR-T or NK-92/CAR cells expressing scFvD2B. Based on presented/reviewed data, we consider that scFvD2B, due to its versatility and robustness, seems to: (i) overcome some problems observed in other studied scFvs, very often relatively unstable and prone to form aggregates; (ii) have sufficient tumor-to-background ratios for targeting and imaging PSMA-expressing cancer; (iii) significantly redirect immune killing cells to PSMA-positive tumors when inserted in second-generation CAR-T or NK-92/CAR cells. These data suggest that our product can be considered the right reagent to fill the gap that still exists in PCa diagnosis and treatment.

PET/CT in the management of differentiated thyroid cancer

The standard treatment of differentiated thyroid cancer (DTC) consists of surgery followed by iodine-131 (131I) administration. Although the majority of DTC has a very good prognosis, more aggressive histologic subtypes convey a worse prognosis. Follow-up consists of periodically measurements of serum thyroglobulin, thyroglobulin antibodies and neck ultrasound and 123I/131I whole-body scan. However, undifferentiated thyroid tumors have a lower avidity for radioiodine and the ability of DTC to concentrate 131I may be lost in metastatic disease. Positron emission tomography (PET)/computed tomography (CT) has been introduced in the evaluation of patients with thyroid tumors and the 2-[18F]-fluoro-2-deoxyd-glucose (18F-FDG) has been largely validated as marker of cell's metabolism. According to the 2015 American Thyroid Association guidelines, 18F-FDG PET/CT is recommended in the follow-up of high-risk patients with elevated serum thyroglobulin and negative 131I imaging, in the assessment of metastatic patients, for lesion detection and risk stratification and in predicting the response to therapy. It should be considered that well-differentiated iodine avid lesions could not concentrate 18F-FDG, and a reciprocal pattern of iodine and 18F-FDG uptake has been observed. Beyond 18F-FDG, other tracers are available for PET imaging of thyroid tumors, such as Iodine-124 (124I), 18F-tetrafluoroborate and Gallium-68 prostate-specific membrane antigen. Moreover, the recent introduction of PET/MRI, offers now several opportunities in the field of patients with DTC. This review summarizes the evidences on the role of PET/CT in management of patients with DTC, focusing on potential applications and on elucidating some still debating points.

18F]-FDG-PET/CT and [18F]-FAZA-PET/CT Hypoxia Imaging of Metastatic Thyroid Cancer: Association with Short-Term Progression After Radioiodine Therapy.

To examine the relationships between 2-deoxy-2-[18F]fluoro-D-glucose ([18F]-FDG) and hypoxia tracer [18F]fluoro-azomycinarabinofuranoside ([18F]-FAZA) and between 131I and [18F]-FAZA uptake in patients with metastatic thyroid cancer and to evaluate imaging features associated with short-term progression after 131I therapy. The study population was 20 patients (17 women and 3 men; mean age, 67years) with metastatic thyroid cancer who underwent both [18F]-FDG- and [18F]-FAZA-positron emission tomography (PET)/X-ray computed tomography (CT) examinations before 131I therapy. Short-term response to radioiodine was assessed (mean follow-up, 19months ± 9). PET parameters including [18F]-FDG-SUVmax, [18F]-FAZA-SUVmax, and [18F]-FAZA-tumor-to-muscle [T/M] were obtained. Mann-Whitney U, Wilcoxon signed-rank, or χ2 tests were used to assess differences between two quantitative variables or compare categorical data. Predictive factors for short-term progression were investigated with logistic regression analysis. Eleven lymph node metastatic lesions were identified in 9 patients and 46 distant metastatic lesions (lung, 19; bone, 17; and liver, 10) in 14 patients. A total of 24 131I-positive and 33 131I-negative lesions were detected. SUVmax was significantly lower with [18F]-FAZA-PET/CT (1.3 ± 0.6) than with [18F]-FDG-PET/CT (6.4 ± 5.9, p < 0.001). No significant correlation was observed between [18F]-FAZA-PET/CT and 131I imaging concerning visibility (p = 0.36). After 131I therapy, 31 of 57 metastatic lesions displayed short-term progression. Multivariate logistic regression revealed that [18F]-FDG-SUVmax (p = 0.022) and [18F]-FAZA-T/M (p = 0.002) showed significant associations with short-term progression. Although [18F]-FAZA uptake was low in metastatic thyroid cancers, not only glucose metabolism but also hypoxic conditions may be associated with progression after 131I therapy in patients with metastatic thyroid cancer.

SUN-120 Regional Hyperthermia Enhances Selective Mesenchymal Stem Cell Migration Towards the Tumor Stroma

The tumor homing characteristics of mesenchymal stem cells (MSCs) make them attractive vehicles for the tumor-specific delivery of therapeutic agents, such as the sodium iodide symporter (NIS). NIS is a theranostic protein that allows non-invasive monitoring of the in vivo biodistribution of functional NIS expression by radioiodine imaging as well as the therapeutic application of 131I. To enhance the actively recruitment of MSCs to growing tumor stroma and thereby trigger targeted delivery of the NIS gene to the tumor, we examined the combination with regional hyperthermia, as heat induces the secretion of immunomodulatory chemokines, cytokines and growth factors, well-known attractants of MSCs.Human hepatocellular carcinoma cells (HuH7) were heat-treated in a water bath at 41 °C for 1h, followed by incubation at 37 °C for 0-48h. mRNA and protein levels of chemokines involved in MSC migration was analyzed by RT-PCR and ELISA. Chemotaxis of MSCs in relation to a gradient of supernatants was tested in a 3D live cell tracking migration assay. In a subcutaneous HuH7 mouse xenograft tumor model, a single systemic injection of CMV-NIS-MSCs was applied 6h, 24h, 48h after or 24h, 48h before hyperthermia treatment and tumoral 123I accumulation was assessed by 123I-scintigraphy. Ex vivo NIS analysis of tumor sections was performed by RT-PCR and immunohistochemistry. The optimal imaging regime was then used for a 131I therapy study.Chemokine mRNA and protein analysis indicated a substantial increase in expression levels of chemokines and growth factors, involved in MSC tumor homing, after heat exposure. In addition, MSCs showed directed migration towards the supernatant of thermo-stimulated cancer cells. In vivo, with the optimal regime, we observed a significantly increased uptake of 123I in tumors of heat-treated animals (41 °C) when thermostimulated 24h after CMV-NIS-MSC injection compared to control animals (37 °C). Immunohistochemical staining of tumor sections showed strong tumoral NIS-specific immunoreactivity and RT-PCR an increased NIS mRNA expression in heat-treated tumors, thereby confirming tumor-selective, temperature-dependent MSC migration. CMV-NIS-MSC-mediated 131I therapy combined with regional hyperthermia resulted in a reduced tumor growth that was associated with prolonged survival of regional heat-treated animals compared to normothermic mice and to the saline control group.In summary, we have demonstrated a significantly increased, selective MSC migration towards the tumor stroma after regional hyperthermia in the 123I imaging study. The combination of MSC-mediated NIS gene therapy with mild regional hyperthermia resulting in stimulated therapeutic efficacy of NIS-mediated 131I therapy.

Primary, scatter, and penetration characterizations of parallel-hole and pinhole collimators for I-123 SPECT

Multi-pinhole (MPH) collimators are known to provide better trade-off between sensitivity and resolution for preclinical, as well as for smaller regions in clinical SPECT imaging compared to conventional collimators. In addition to this geometric advantage, MPH plates typically offer better stopping power for penetration than the conventional collimators, which is especially relevant for I-123 imaging. The I-123 emits a series of high-energy (>300 keV, ~2.5% abundance) gamma photons in addition to the primary emission (159 keV, 83% abundance). Despite their low abundance, high-energy photons penetrate through a low-energy parallel-hole (LEHR) collimator much more readily than the 159 keV photons, resulting in large downscatter in the photopeak window. In this work, we investigate the primary, scatter, and penetration characteristics of a single pinhole collimator that is commonly used for I-123 thyroid imaging and our two MPH collimators designed for I-123 DaTscan imaging for Parkinson’s Disease, in comparison to three different parallel-hole collimators through a series of experiments and Monte Carlo simulations. The simulations of a point source and a digital human phantom with DaTscan activity distribution showed that our MPH collimators provide superior count performance in terms of high primary counts, low penetration, and low scatter counts compared to the parallel-hole and single pinhole collimators. For example, total scatter, multiple scatter, and collimator penetration events for the LEHR were 2.5, 7.6 and 14 times more than that of MPH within the 15% photopeak window. The total scatter fraction for LEHR was 56% where the largest contribution came from the high-energy scatter from the back compartments (31%). For the same energy window, the total scatter for MPH was 21% with only 1% scatter from the back compartments. We therefore anticipate that using MPH collimators, higher quality reconstructions can be obtained in a substantially shorter acquisition time for I-123 DaTscan and thyroid imaging.

Improving individualised dosimetry in radioiodine therapy for hyperthyroidism using population biokinetic modelling

The application of an individualised dosimetric procedure for radioiodine therapy requires the intensive use of resources in nuclear medicine facilities. In practice, the amount of data taken per patient is too limited to obtain an accurate estimate of the absorbed dose in the thyroid. The individualised absorbed dose estimates can be enhanced using statistical tools for population-based approaches. The aim of this work was to build a population biokinetic model of thyroid uptake and elimination of radioiodine using a nonlinear mixed-effects approach in patients with Graves’ disease. Input data for the model development were taken from a dosimetric method based on 123I imaging data. 123I decay-corrected uptake values were estimated at 4, 24, and 96 h post-administration and for 58 patients. The root mean squared error (RMSE) for predicted 123I uptake values by the fitted model was 4%. The root mean squared error of prediction (RMSEP) for out-of-sample 123I uptake values, computed by a leave-one-out cross-validation, was 12%. We calculated 131I activity to administer from out-of-sample predicted 123I uptake values and compared the result with that calculated from observed 123I uptake values. RMSEP values for therapeutic activity revealed that there were measuring points with higher weight than others in the model. The mixed-effects approach can be used to enhance the accuracy of dosimetric calculations in therapies using 131I. Assessing the accuracy of the predictive model enables choosing among different time-sampling schedules of the radioiodine thyroid uptake curve. This methodology can also be applied in other areas of radiation dosimetry.

SAT-611 Abdominal Goiter

A 79 year old woman with hyperlipidemia, hypertension, congestive heart failure was referred for evaluation of ectopic thyroid tissue found on a liver biopsy. The patient originally presented with abdominal pain and was noted to have a liver mass measuring 5.7 x 3.2 x 5 cm on computed tomography (CT) that appeared contiguous with the medial segment of the left hepatic lobe. A subsequent ultrasound (US) showed the same 3.1 x 4.7 x 4.7 cm ovoid mass with a central focus of increased echogenicity and a well-circumscribed margin; a fine needle aspiration (FNA) of the hepatic lesion showed thyroid follicular cells and abundant colloid. Magnetic resonance imaging of the abdomen was done 6 months later, which showed a soft tissue abnormality in the porta hepatis extending centrally into the liver of decreased T2 signal intensity relative to the liver and containing iron deposition. The size of the lesion by MRI was unchanged in comparison with the CT. Eight years later, she presented to the Emergency Room with suprapubic abdominal pain. On CT, she had a large mass (8.3 x 5.5 x 7.1 cm) in the porta hepatis with mass effect upon the gallbladder and pancreas without biliary dilatation or evidence of frank invasion. An FNA was repeated, again showing benign appearing thyroid tissue (bland follicular cells without features of papillary thyroid cancer and abundant colloid). Immunohistochemical staining for TTF-1 was positive, supporting thyroid origin. Thyroid function tests were normal ( TSH-0.85 uIU/mL; free T4 direct- 1.1 ng/dL; and total T3 - 125 ng/dL) There are only three prior case reports detailing ectopic thyroid tissue in the porta hepatis (1). Benign ectopic thyroid tissue in the liver is generally explained as a metaplastic phenomenon, as the thyroid shares a common embryologic origin with the liver and proximal segment of the gastrointestinal tract (2). Workup typically includes CT or US imaging, followed by I-123 imaging to determine the presence of functional thyroid tissue, followed by a biopsy. The prevalence of all ectopic thyroid tissue is 1 per 100,000-300,000 persons, with less than 1% being malignant. The majority (85%) of malignant ectopic thyroid tissue is papillary thyroid cancer. Excision of ectopic thyroid mass in the liver has generally been favored, due to their minor malignant potential. The patient has been referred to Surgical Oncology/Endocrine Surgery for possible resection.

Study on High Density Scintillators and Multi-energy Windows for Improving I-131 Gamma Image Quality: Monte Carlo Simulation Approach

An energy window with a gamma peak centered at 364 keV (86%) is usually used for I-131 imaging. However, the image performance indexes such as image count, scatter fraction (SF), spatial resolution (SR) obtained using a conventional gamma camera, which uses a 3/8-in sodium iodide scintillator, are poor mainly due to its low detection efficiency. In this study, we investigated the feasibility of using a higher energy peak (637 and 723 keV) for the energy window to obtain a better imaging performance compared with the conventional I-131 imaging method. GATE (v7.0), which is based on Monte Carlo method, was used for performing simulations. A clinical gamma camera, SYMBIA-T2 (Siemens), was mounted on a NaI scintillator in the simulation. A GAGG scintillator was also realized for effective detection of high energy gamma, in addition to using high energy (HE) and ultrahigh energy (UHE) collimators. We obtained I-131 planar images through the conventionally used window method (364 keV ± 10%). The high-energy gamma ray of I 131 (637 and 723 keV) have been additionally used for improving image performance. The scatter correction method was applied to images for suppressing scatter due to high-energy gamma rays. Various indexes are used for validating image performance such as SR, SF, and contrast-to-noise ratio. High-energy gamma rays could be used to increase the image counts, but the other image performances were degraded compared to the scatter-corrected 364 keV images (SF of 6.33 - 27.73%; SR of 0.93 - 6.02%). The UHE collimator was useful in obtaining a better spatial resolution and suppressing scatter components compared with the HE collimator. However, it did not exhibit a sufficient image performance to be considered as a replacement for the HE collimator. In order to use the high-energy gamma rays of I-131 (637 and 723 keV), it is necessary to design a new collimator to control penetration and improve resolution, instead of using a UHE collimator. Furthermore, scatter correction methods also need to be optimized.

P099] Comparative assessment of three scatter correction techniques in 99M-TC and 131-I planar imaging

Purpose The purpose of this study is to evaluate and compare single (SEW), dual (DEW) and triple energy window (TEW) scatter correction techniques, on 99mTc and 131I planar images, based on signal-to-noise ratio (SNR) criterion. Methods Four reference sources filled with known activities of 99mTc and 131I were prepared. Voxel size for 256x256 matrix during planar acquisition was defined. Serial planar acquisitions of the reference sources were performed on a SOPHA DST-Xli, dual head γ -camera and single head γ -camera. Furthermore, planar images of patient’s sample that have been administered with 99mTc and 131I were analyzed. During acquisition of 99mTc images, to perform TEW scatter correction, main window was centered 140 keV, whereas the windows used to estimate the scatter contribution were placed at 93 keV (67Ga) and 173 keV (111In) with a width of 20%. In the case of 131I images DEW scatter correction was performed after setting the main window centered 364 keV, whereas adjacent window was placed at 280 keV (75Se). TEW and DEW scatter correction and background subtraction was applied to all planar images and this energy-window removal processing was performed through ImageJ software. Moreover, a study about SNR was performed to achieve quantification of the obtained images. For this processing counts for a specific irradiated volume of interest and background were obtained, both for each window image. Results Planar images for both radioisotopes were acquired to enhance the comparison of energy windows. The analysis of 99mTc images for a specific activity indicated the SNR for SEW was equal 35,55, while for DEW 39,25 and for TEW 43,40. In the case of 131I image the SNR of SEW corresponded to 39,15 while for DEW 54,30. The increase of SNR was proportional to the growth of energy windows indicating that as the number of energy-windows increases, the more noise is reduced. Conclusions The analysis indicates that TEW method was more precise than DEW one for both radioisotopes. This method produces significant improvement of scatter correction leading to development nuclear medicine images with high quality.

Septal penetration correction in I-131 imaging following thyroid cancer treatment

Whole body gamma camera images acquired after I-131 treatment for thyroid cancer can suffer from collimator septal penetration artefacts because of the high energy of the gamma photons. This results in the appearance of ‘spoke’ artefacts, emanating from regions of high activity concentration, caused by the non-isotropic attenuation of the collimator. Deconvolution has the potential to reduce such artefacts, by taking into account the non-Gaussian point-spread-function (PSF) of the system. A Richardson–Lucy deconvolution algorithm, with and without prior scatter-correction was tested as a method of reducing septal penetration in planar gamma camera images. Phantom images (hot spheres within a warm background) were acquired and deconvolution using a measured PSF was applied. The results were evaluated through region-of-interest and line profile analysis to determine the success of artefact reduction and the optimal number of deconvolution iterations and damping parameter (λ). Without scatter-correction, the optimal results were obtained with 15 iterations and λ = 0.01, with the counts in the spokes reduced to 20% of the original value, indicating a substantial decrease in their prominence. When a triple-energy-window scatter-correction was applied prior to deconvolution, the optimal results were obtained with six iterations and λ = 0.02, which reduced the spoke counts to 3% of the original value. The prior application of scatter-correction therefore produced the best results, with a marked change in the appearance of the images. The optimal settings were then applied to six patient datasets, to demonstrate its utility in the clinical setting. In all datasets, spoke artefacts were substantially reduced after the application of scatter-correction and deconvolution, with the mean spoke count being reduced to 10% of the original value. This indicates that deconvolution is a promising technique for septal penetration artefact reduction that could potentially improve the diagnostic accuracy of I-131 imaging.Novelty and significanceThis work has demonstrated that scatter correction combined with deconvolution can be used to substantially reduce the appearance of septal penetration artefacts in I-131 phantom and patient gamma camera planar images, enable improved visualisation of the I-131 distribution. Deconvolution with symmetric PSF has previously been used to reduce artefacts in gamma camera images however this work details the novel use of an asymmetric PSF to remove the angularly dependent septal penetration artefacts.

Imaging of the thyroid and parathyroid using a cardiac cadmium zinc telluride camera: Phantom studies.

Purpose: Cadmium zinc telluride (CZT) detectors have recently been introduced to the field of clinical nuclear cardiology. However, the feasibility of using them for organs other than the heart remains unclear. The aim of this study was to evaluate the potential of a cardiac CZT camera to acquire thyroid and parathyroid images. We used custom-made phantoms and the currently available standard protocols for CZT, instead of a sodium-iodine scintillation (NaI) camera. Materials and Methods: Thyroid phantoms with or without parathyroid adenomas were made from agar using radiopharmaceuticals (99mTc or 123I) and imaged using CZT and NaI cameras. Using the CZT camera data, we prepared maximum intensity projection (MIP) images and planar equivalent (PE) images. Image counts were compared to those from the NaI camera, and the radioactivity of the phantoms was measured. For parathyroid imaging, three different protocols with the NaI camera were tested using MIP images. Results: For thyroid imaging, MIP could provide images as clear as those obtained from the NaI camera. The radioactivity and image counts correlated better for the PE images than the MIP images, especially for 123I images. We succeeded in obtaining clear parathyroid adenoma images from MIP images using all three protocols. Conclusion: A cardiac CZT camera can effectively perform qualitative and quantitative assessments of the thyroid and parathyroid organs.

Values of (99m)Tc-methoxyisobutylisonitrile imaging after first-time large-dose (131)I therapy in treating differentiated thyroid cancer.

ObjectiveThe aim of this study is to investigate the use of 99mTc-methoxyisobutylisonitrile (MIBI) imaging for evaluating the treatment response of differentiated thyroid cancer (DTC) after the first administration of a high dose of 131I.MethodsPatients with DTC who received 131I therapy underwent 99mTc-MIBI imaging after successive increases in the therapeutic dose of 131I, and the serum levels of thyroglobulin (Tg) were measured.ResultsA total of 191 patients were enrolled in the final analysis, including 65 metastases and/or thyroid remnant-positive patients (22 patients with metastases and 43 patients with thyroid remnants). The sensitivity of 99mTc-MIBI imaging for detecting positive cases and thyroid remnants was 56.9% and 39.5%, respectively, which was significantly lower than that of 131I imaging (92.3% and 100%, respectively, P<0.01 for both). The sensitivity of 99mTc-MIBI imaging for detecting metastases was 90.9%, which was slightly higher than that of 131I imaging (77.3%, P>0.05). The Tg levels in the positive group were significantly higher than that in the negative group (P<0.01). In addition, the Tg levels in the 99mTc-MIBI+/131I− group were significantly higher than that in the 131I+/99mTc-MIBI group (P<0.05).ConclusionAfter the first 131I therapy, although 99mTc-MIBI imaging was able to detect the existence of metastatic lesions in patients with DTC better, its assessment for the removal efficiency of thyroid remnants was unsatisfactory. The results of 99mTc-MIBI imaging showed good correlations with the Tg level.

Clinical value of 99Tcm-MIBI scintigraphy in patients with differentiated thyroid carcinoma after surgery and first 131I therapy

Objective To evaluate the clinical value of 99Tcm-MIBI scintigraphy for diagnosis of residual thyroid tissue and metastasis in patients with DTC after their first 131I therapy. Methods From February 2010 to March 2014, 192 DTC patients (38 males, 154 females, average age (43.2±8.6) years) who received total or near-total thyroidectomy and were pathologically diagnosed as DTC (171 papillary and 21 follicular carcinomas) underwent 99Tcm-MIBI scan (average dosage: 740-925 MBq) 6 months after their first 131I therapy. 131I scans was performed 4 d after oral administration of 131I of therapeutic dose (average dosage: 5 550-8 140 MBq). Pre- and post-therapeutic images and the serum Tg level (detected before the imagings) were compared and analyzed. Any abnormal uptake of agent found inside or outside the thyroid was regarded as positive result. Patient-based and lesion-based data analysis were performed by χ2 test and two-sample t test. Results A total of 191 patients were finally included, of which 65 positive cases were found. The sensitivity of 99Tcm-MIBI imaging was significantly lower than that of 131I imaging(56.9% (37/65) vs 92.3%(60/65); χ2=14.7, P 0.05). The serum Tg level of positive groups (99Tcm-MIBI positive + 131I positive or 131I negative) were significantly higher than that of 99Tcm-MIBI negative + 131I negative group (t=-20.7 and -6.0, both P<0.01), and that of 99Tcm-MIBI positive + 131I negative group was higher than that of 131I positive + 99Tcm-MIBI negative group(t=-2.7, P<0.05). Conclusion 99Tcm-MIBI imaging could detect metastasis of DTC patient after first radioiodine therapy, but the value in detecting thyroid remnants is limited. Key words: Thyroid neoplasms; Radiotherapy; Iodine radioisotopes; Radionuclide imaging; MIBI