Scintigraphy with 99mTc-pertechnetate in the evaluation of functional thyroidal autonomy.

Iodine deficiency and iodine deficiency disorders are still present in several parts of Europe. Sonography is neither specific in the diagnosis nor sensitive in the evaluation of the amount of autonomous thyroid tissue. Thyroidal autonomy is defined as a functional state of the thyroid and therefore only functional scintigraphic imaging, preferably performed with 99mTc-pertechnetate (99mTcO4-), will offer both high sensitivity and specificity in its diagnosis. Recently the cloning and characterisation of the Na+/I- symporter (NIS) offered a deeper understanding of iodine and pertechnetate uptake in the thyroid gland. Overexpression of the Na+/I- symporter following activation of the adenylate-cyclase-cAMP-cascade has been demonstrated in hot nodules, which gives for the first time an explanation for the enhanced iodine clearance of autonomous thyroidal tissue on a molecular level. The scintigraphic evaluation of thyroidal autonomy is performed both as a quantitative and qualitative thyroid scintigraphy, using a gamma camera fitted with an on-line computer system. A strong and linear correlation between the global 99mTc-pertechnetate thyroid uptake (TCTU) and 123I clearance has been recognised. Therefore TCTU-values can be used as a reliable equivalent of the iodine clearance in the evaluation of actual thyroid function. The clinical value of the TCTU in the diagnosis of thyroidal autonomy is limited because it represents iodine clearance of both normal and autonomous tissue. As a consequence scintigraphic diagnosis and quantification of autonomy can only be established if the global 99mTc-pertechnetate thyroid uptake under suppression (TCTUs) is determined. This method is sensitive in risk stratification of spontaneous or iodine induced hyperthyroidism, in the estimation of the target volume prior to radioiodine therapy independently of its distribution and in the evaluation of therapeutic success after definitive therapy.     

Clinical significance of endogenously labelled thyroid hormones in the diagnosis of thyroidal autonomy

The clinical value of the determination of 123I concentration in serum 48 hrs after tracer administration (123I)48 is investigated with special regard to thyroidal autonomy. Serum radioiodine concentration, thyroid radioiodide uptake at 4 and at 48 hrs were measured in 74 healthy subjects and patients with simple goiter, in 36 patients with thyroidal autonomy (diagnosis by thyroid suppression test), and in 20 hyperthyroid patients. 83% of the patients with elevated radioiodine concentration belonged to the group of thyroidal autonomy. The product of radioiodine concentration and thyroid radioiodide uptake is a much better parameter. 95% of the patients in which this product was elevated, belonged to the autonomy group (5% diagnostic error). Also in the control group the diagnostic error was 5%. The combination of (123I)48 with the result of the TRH-test is very useful in excluding thyroidal autonomy, if (123I)48 is normal and the TRH-test is positive (100% of the patients have regulated thyroid glands). 94% of the patients having elevated (123I)48 and a negative TRH-test belonged to the group of thyroidal autonomy. A very useful combination for the diagnosis of borderline hyperthyroidism is the determination of the product of (123I)48 and the uptake48 together with the pulse rate or fine tremor of the fingers (or TRH-test). The results suggest that the determination of (123I)48 is a very good parameter of thyroidal autonomy beside the thyroid suppression test. It may be used alone for the diagnosis of thyroidal autonomy if the suppression test is contraindicated. In the diagnosis of borderline hyperthyroidism its determination makes the suppression test unnecessary in many instances.     

A case study in developing a radiology information technology (RIT) specialist position for supporting digital imaging

Support services in providing PACS to healthcare facilities are becoming more complex. Imaginative staffing models are imperative to provide a successful PACS program to customers. Choosing the right staffing grid of support staff can be assisted by locations with like volumes or geographic areas. The RIT (radiology information technology) specialist is an excellent asset in a growing PACS environment. RITs can be the crucial liaison between the radiology department and the customer. RITs with different backgrounds can be recruited based on what type of support services your customers need. RITs are a great resource for one-on-one training from physicians to nursing staff. This mobile PACS spokesperson can take the concerns of the customers to the PACS administrator to open dialogue and communication that will win customer loyalty in this ever changing world of technology.     

Imaging findings of thyroidal sarcoma

From 1997 to 2013, 8849 patients with several disorders of the thyroid were treated in our surgical department. In nine patients (0.1%), primary thyroid sarcoma (PTS) was diagnosed. In eight patients, PTS manifested as a thyroid mass (range, 25–90 mm). In one case, a global enlargement of the thyroid was seen. Clinically, all patients presented with neck swelling. On ultrasound, PTS was predominantly hypoechoic. On computed tomography, the sarcomas were hypodense. On magnetic resonance imaging, PTS had inhomogeneous signal increase on T2-weighted images and signal decrease on T1-weighted images with inhomogeneous enhancement.     

In vitro characterization of the thyroidal uptake of O-(2-[(18)F]fluoroethyl)-L-tyrosine

OBJECTIVES: Positron emission tomography (PET) using O-(2-[(18)F]fluoroethyl)-l-tyrosine (FET) has been successfully employed in the diagnostic workup of brain tumors. Knowledge on the mechanisms of the uptake of radiolabeled amino acids into thyroidal tissues and well-differentiated thyroid carcinomas is limited. We therefore studied several factors potentially governing the uptake of FET in the rat thyroid cell line FRTL-5 in comparison with thyroid tumor cell lines of human origin. METHODS: FET uptake was determined in thyroid-stimulating hormone (TSH)-stimulated and TSH-deprived FRTL-5 cells, as well as in the cell lines U-138 MG (human glioblastoma), Onco DG-1 (human papillary thyroid carcinoma) and ML-1 (human follicular thyroid carcinoma). The TSH responsiveness of cells was measured by the incubation of TSH-treated and untreated control cells with 2-[(18)F]fluoro-2-deoxyglucose (FDG). All cellular tracer uptake values were related to total protein mass and expressed as percentage per milligram. For countertransport studies, FRTL-5 cells were exposed to 10-300 microM tyrosine methyl ester. TSH-stimulated and TSH-deprived FRTL-5 cells were incubated with 100 kBq/ml FET for 20 min. 2-Aminobicyclo-[2,2,1]heptane-2-carboxylic acid (BCH), alpha-(methylamino)-isobutyric acid, L-serine and tryptophan were used as competitive inhibitors of FET uptake. All inhibition experiments were repeated with the human thyroid carcinoma cell lines to obtain comparative FET uptake values. RESULTS: The FET uptake was 155+/-30%/mg in FRTL-5 cells (n=6), 108+/-14%/mg in U-138 MG cells (n=6), 194+/-60%/mg in ML-1 cells (n=9) and 64+/-23%/mg in Onco DG-1 cells (n=6) under identical incubation conditions. Preloading with tyrosine methyl ester increased cellular FET uptake dose dependently in FRTL-5 cells (165+/-25%, n=6). While TSH increased the uptake of FDG in FRTL-5 cells by sixfold, there was no TSH effect on FET accumulation. FET uptake by TSH-treated FRTL-5 cells was sodium independent and significantly inhibited by BCH (91.4+/-3.0%, n=9), tryptophan (94.8+/-1.6%, n=8) and serine (83.2+/-10.8%, n=12). TSH-starved FRTL-5 cells had a sodium-dependent component with a similar inhibition pattern. Onco DG-1 mainly confirmed the inhibition pattern of FET uptake in FRTL-5 cells, reflecting System-L-mediated FET uptake that was blocked by BCH and serine (72-85%, n=9). ML-1 cells revealed a pronounced sodium-dependent FET uptake that was inhibited by tryptophan (70+/-10%, n=9, P<.05) in the presence and in the absence of sodium, suggesting a contribution of alternative amino acid carriers. CONCLUSION: FET uptake by FRTL-5 cells is not TSH dependent. FET uptake by FRTL-5 cells seems to be mainly mediated by a carrier exhibiting the characteristics of the System L amino acid transporter. FET uptake in thyroid cells and thyroid carcinoma cells was in the same range as that in a glioblastoma cell line. This encourages further research efforts towards the clinical evaluation of FET for the diagnostic workup of well-differentiated thyroid carcinomas.     

Influence of dose rate on therapeutic success of radioiodine therapy of functional thyroid autonomy

OBJECTIVE: To evaluate the effect of dose rate on the therapeutic success of radioiodine therapy (RIT) by retrospective analysis of two groups of patients with different dose rates during RIT. METHODS: The average dose rate until deposition of 50% of the total radiation dose achieved (the DL50 value) was calculated. Ninety patients with autonomy of the thyroid receiving radiation doses between 300 and 400 Gy were separated in groups with high DL50 values (the DL50 H group) and low DL50 values (the DL50L group). Before and 4 months after RIT free triiodothyronine (FT3), free thyroxine (FT4), basal thyroid stimulating hormone (TSHB), stimulated TSH (TSHS), thyroidal technetium uptake (TcTU), and the existence of focal abnormalities in thyroid scintigraphy were evaluated. RESULTS: The DL50 H and DL50L groups showed no differences before RIT in the parameters assessed as well as in total achieved dose and autonomous thyroid volume. After therapy a significant difference was found in TSHB with higher values in DL50 H (1.89+/-1.49 vs. 1.31+/-1.48 mU . l, P<0.05), FT4 showed a trend to lower values (13.8+/-4.0 vs. 16.1+/-6.2 pmol . l, P=0.09). CONCLUSION: The DL50 value has an influence on therapeutic success of RIT. This influence is only discrete and not likely to produce clinically relevant effects in the practical use of RIT.     

Iterative reconstruction of thyroidal SPECT images

First SPECT results using a multiplicative iterative reconstruction algorithm are presented. The superiority of the iterative technique over filtered backprojection is demonstrated in two thyroid SPECT studies. Obvious benefits of the new reconstruction technique are better defined outlines of the imaged organ and patient body as well as negligible artificial image amplitudes outside the patient.     

Iterative reconstruction of thyroidal SPECT images

First SPECT results using a multiplicative iterative reconstruction algorithm are presented. The superiority of the iterative technique over filtered backprojection is demonstrated in two thyroid SPECT studies. Obvious benefits of the new reconstruction technique are better defined outlines of the imaged organ and patient body as well as negligible artificial image amplitudes outside the patient.     

Euthanasia--he illusion of autonomy

The paper deals with some of the more common arguments used for the legalisation of voluntary euthanasia. It looks at these arguments from an ethical and philosophical point of view. First, the argument that to offer a person the possibility of euthanasia is to respect that person's autonomy is questionable. Can a person's decision on euthanasia be really autonomous? If euthanasia were legal everybody would be conscious of this option: the patient, the doctor, the family and the nursing staff. Thus, there could be indirect pressure on the patient to make a decision. The choice is meant to be free but the patient is not free not to make the choice. Secondly, a choice that seeks to alleviate suffering and thus improve life by annihilating it is irrational. Thirdly, autonomy as to one's own death is hardly exercised freely. Even an otherwise competent person may not be competent in deciding on his own death on account of despair, hopelessness, fear or maybe a feeling of being weak, superfluous and unwanted. This is a very uncertain base for decision-making, especially in the irrevocable decision of euthanasia. Finally, a competent person usually makes any choice in a responsible way and after due consideration; a 'good' decision should consider and respect the wishes and feelings of others. This will be no less the case in making a decision on the so-called free choice of euthanasia. Thus 'normal' behaviour in decision making will only add to the tendency of the already depressed person to feel a burden on his family, the staff and even on society.     

Morphologic (CT) and functional (rCBF-SPECT) correlates in Alzheimer's disease.

Thirty-five patients with a clinical diagnosis of probable Alzheimer's disease underwent computed tomography (CT) and regional cerebral blood flow (rCBF) studies using single photon emission computed tomography (SPECT). Two sets of images in each subject were scored for the extent of structure and function changes. Thirty-four of 35 patients had various degrees of atrophy on CT, 33 of whom also had perfusion deficits of varying severity. One patient with normal CT had perfusion deficits, and another patient with a normal perfusion pattern had changes on CT. Regional perfusion deficits on SPECT were seen with and without associated changes on CT. Correlations were studied between CT and SPECT scores using Spearman's rank correlation coefficients. While regional scores on CT and SPECT did not significantly correlate, the total and left hemisphere scores on two sets of images showed fair correlations (r = 0.425 and r = 0.535, respectively, P less than 0.01). The correlations between cognitive performance in patients as assessed on Mini-Mental State Examination (MMSE) and CAM-COG and perfusion scores were highly significant while CT scores showed lower correlations. These findings suggest that the relationship between structural and functional changes in Alzheimer's disease is not straightforward and that the extent of changes in function as assessed by regional cerebral blood flow studies is a reliable measure of deficits in cognitive function.     

Selenium and thyroidal function; the role of immunoassays

It is well known that selenium plays a fundamental role in regulating thyroid and other functions of the human body like reproduction, autoimmunity, glucose metabolism or bone metabolism. While for thyroid function investigation, radioimmunoassays and radioimmunometric assays both key techniques of nuclear medicine are used, for selenium measurements atomic absorption spectrometry is the method of choice. Normal thyroid gland retains high selenium concentrations even under conditions of inadequate selenium supply and expresses many of the known selenocysteine-containing proteins. Adequate selenium nutrition supports efficient thyroid hormone synthesis and metabolism and protects the thyroid gland damage by excessive iodide exposure. In regions where a combined severe iodine and selenium deficiency exist, normalization of iodine supply is mandatory before initiation of selenium supplementation in order to prevent hypothyroidism. Selenium deficiency and disturbed thyroid function may develop under conditions of special dietary regimens, such as long-term total parenteral nutrition or after inadequate nutrition in children. Some investigators suggest that selenium may be a useful adjunctive treatment for autoimmune thyroid diseases, such as Hashimoto and Graves' disease. Low serum selenium levels have been associated with higher incidence of thyroid cancer, as well as with chronic illness or lomicronw triiodothyronine syndrome. These biological actions are mediated through the expression of selenoproteins, the most important being the glutathione peroxidases, the iodothyronine deiodinases, the thioredoxine reductase and the selenoprotein P. Selenium is also associated with animal proteins. Subsequently meats and seafood are dietary sources of selenium. The ingestion of large quantities of selenium may have adverse effects. It has been shown that dietary intake of about 300 micro g of selenium daily may have a toxic effect on growth hormone and insulin like growth factor-1 metabolism, as well as in the synthesis of thyroid hormones. Main adverse effects may be anorexia, diarrhea, depression, hemorrhage, liver and kidney necrosis, blindness, ataxia and respiratory disturbances. Dermatitis and CNS deficiency have also been described. It is concluded that selenium plays an important role in regulating thyroid function, as well as in the homeostasis of thyroid hormones through the action of selenoproteins, in which it incorporates as selenocystein.     

Radioiodine therapy of thyroid autonomy

Over half a century, treatment of thyroid autonomy with an oral dose of iodine-131 has proven to be effective. The optimum management strategy for the patient is, however, still a matter of debate. The article provides an overview of the pathogenesis of functional autonomy and its clinical relevance. According to the guidelines on both sides of the Atlantic, radioiodine treatment is considered the most comfortable and economical approach to the treatment of the toxic nodular goitre. Some differences in the preparation procedures in the guidelines of the American and the German Society of Nuclear Medicine are discussed with respect to therapy results and the subtypes of thyroid autonomy. The results of studies are summarised concerning changes in thyroid function and thyroid volume after a course of radioiodine treatment. Therapy-related risks, such as immunogenic hypothyroidism or thyroid cancer, are discussed. (131)I treatment of functional autonomy and hyperthyroidism is considered an effective and safe procedure.     

Unexpected differences in early thyroidal trapping of iodide and pertechnetate

Compartmental analysis was applied to simultaneously acquired ¹³²I-iodide and ^99mTc-pertechnetate thyroid uptake data. The method allowed for arterio/venous differences in plasma tracer level and for an instantaneous phase of thyroid uptake.Observations in four thyrotoxic patients, before and during antithyroid drug therapy, revealed greater instantaneous uptake of TcO ₄ ^- . The results also revealed that instantaneous uptake of both I^– and TcO ₄ ^– may increase over the first six months of drug therapy. These findings could not be explained by the estimates of unidirectional clearance which were greater for I^- and varied little during the early stages of drug therapy.     

Improved echo volumar imaging (EVI) for functional MRI

Echo volumar imaging (EVI) is a 3D modification of echo‐planar imaging (EPI) that allows data from an entire volume to be acquired following a single RF excitation. EVI provides a high rate of volumar data acquisition, which is advantageous for functional MRI (fMRI). However, few studies to date have applied EVI to fMRI, since because of gradient hardware limitations EVI generally has to be used with long sampling times, resulting in high sensitivity to susceptibility‐induced distortions. In this study we modified the EVI sequence to improve its suitability for fMRI. The sampling time is reduced by the use of a high gradient‐switching frequency, a small number of echoes, and outer volume suppression (OVS); rewind gradients ameliorate Nyquist ghosting; and phase correction via a calibration scan reduces ghosting and distortion. It is shown that the modified EVI sequence allows fMRI data to be acquired with a temporal resolution of 167 ms. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.