Iris Gomez

Combined PET/CT in the follow-up of differentiated thyroid carcinoma: what is the impact of each modality?

Purpose18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a well-established method in the follow-up of patients with differentiated thyroid carcinoma (DTC), elevated thyroglobulin (Tg) and negative 131I scans. This retrospective clinical study was designed to evaluate the impact of computed tomography (CT) and that of FDG-PET in combined FDG-PET/CT examinations on the restaging of DTC patients.MethodsForty-seven FDG-PET/CT scans of 33 patients with a history of DTC, elevated Tg levels and negative 131I uptake or additionally suspected 131I-negative lesions were studied. PET and CT images were analysed independently by an experienced nuclear medicine specialist and a radiologist. Afterwards a final consensus interpretation, the gold standard in our department, was provided for the fused PET/CT images and, if available, for supplementary investigations.ResultsThirty-five investigations (74%) revealed pathological FDG-PET/CT findings. In summary, 25 local recurrences, 62 lymph node metastases and 122 organ metastases (41 lung, 60 bone, 21 other organs) were diagnosed. In 36 out of 47 examinations (77%), the original PET diagnoses were modified in the final consensus interpretation owing to the CT assessments. In 8 of the 35 pathological FDG-PET/CT examinations (23%), the final consensus interpretation of the PET/CT images led to an alteration in the treatment plan.ConclusionPET/CT is a powerful fusion of two pre-existing imaging modalities, which not only improves the diagnostic value in restaging DTC patients with elevated Tg and negative 131I scan, but also provides accurate information regarding subsequent treatment options and may lead to a change in treatment management.

Iodine supplementation in Austria: methods and results.

Until 1963 Austria was an extremely iodine-deficient area with low iodine intake and high goiter prevalence. Therefore, for the first time in 1963, salt iodination with 10 mg of potassium iodide per kilogram of salt was introduced by federal law. Twenty years after this salt iodination, however, investigations in schoolchildren demonstrated iodine deficiency grade I to II according to the World Health Organization (WHO) (urinary iodine excretion, 42-75 microg/g Crea) and goiter prevalence of far more than 10%. In 1990, salt iodination was increased to 20 mg of potassium iodide per kilogram of salt. In 1994, further investigations in schoolchildren demonstrated an increase of urinary iodine excretion (121 microg/g Crea) and a reduction of goiter prevalence below 5%, with the exception of pupils ages 14-19 (12%). In the year 2000, 10 years after the increase of salt iodination in Austria, 430 nonselected adult inhabitants of three communities in Carinthia (a county of Austria) were investigated for iodine excretion, goiter prevalence, and prevalence of thyroid autoantibodies. This study demonstrated that although iodine supply is sufficient now in Austria (males, 163.7 microg of Crea; females, 183.3 microg of iodine per gram of Crea), goiter prevalence is still high in the elderly, who lived for a longer period of iodine deficiency (34.3% in women and 21.3% in men), whereas goiter prevalence in younger people up to age 40 years is below 5%. It could also be shown that the percentage of thyroid autoantibodies is now as high as in other countries with sufficient iodine supply (3.19% in males, 5.17% in females). In addition to the changes of urinary iodine excretion and goiter prevalence because of salt iodination, changes of incidence in hyperthyroidism and histologic types of thyroid cancer are discussed in this paper. In conclusion, the introduction of salt iodination led to an improvement in iodine supply with a marked reduction of goiter prevalence in people who were born after 1963, but also to an increase in hyperthyroidism and autoimmune thyroid diseases as well as changes in histologic types of thyroid cancer.

18F-FDG positron emission tomography in the early diagnosis of enterocolitis: preliminary results

Abstract. Collagenous and eosinophilic colitis are rare diseases characterised by chronic watery diarrhoea. Radiographic evaluation of the gastrointestinal tract and colonoscopy are usually non-diagnostic since as many as one-third of patients will have minor abnormalities. To date a few investigators have reported increased fluorine-18 fluorodeoxyglucose (18F-FDG) uptake on positron emission tomography (PET) in patients with acute enterocolitis, but there have been no reports on the use of 18F-FDG PET for the diagnosis of collagenous or eosinophilic colitis in an early clinical stage. The aim of this preliminary study was to evaluate the usefulness of 18F-FDG PET in the early diagnosis of patients with colitis. We investigated five women (mean age 61.2±12.1 years) who had been diagnosed as having colitis in an early clinical stage. In all but one of the patients, the diagnosis of colitis was based on biopsy. Magnetic resonance colonography, ultrasonography and colonoscopy were performed in all but one of the patients. Two women were identified as having collagenous colitis in an early clinical stage. Another two patients had eosinophilic colitis. The morphological imaging methods, magnetic resonance colonography and ultrasonography, yielded no suspicious findings, and the results of colonoscopy similarly showed no abnormalities. One patient had colitis due to bacterial infection. In all patients 18F-FDG PET showed a pathological increase in tracer uptake in the large bowel, suggestive of colitis. In four of the five patients, colitis was confirmed by histology, and in one, by bacterial analysis. 18F-FDG PET was able to detect colitis in an early clinical stage, when morphological imaging methods and colonoscopy were non-diagnostic. The early performance of 18F-FDG PET imaging in patients with possible colitis is encouraging.

Technetium 99m tetrofosmin parathyroid imaging. Results with double-phase study and SPECT in primary and secondary hyperparathyroidism.

RATIONALE AND OBJECTIVES The aim of our study was to evaluate the sensitivity, specificity, and positive predictive value (PPV) of technetium 99m (99mTc) tetrofosmin double-phase scintigraphy and single-photon emission computer tomography (SPECT) in preoperative localization of parathyroid adenoma in case of primary and secondary hyperparathyroidism (HPT). METHODS Sixty-eight consecutive patients biochemically or sonographically suspected of parathyroid adenoma were included in our study. Apart from biochemical analysis of serum calcium, phosphate, and intact parathyroid hormone, double-phase scintigraphy was performed in each patient 5 and 45 minutes after injection of 370 MBq 99mTc tetrofosmin, followed by SPECT imaging. In consciousness of the scintigraphic results, ultrasound of the neck was performed as well to exclude false-positive results due to thyroid adenomas. RESULTS Depending on the results of the biochemical analysis in combination with the results of the scintigraphic and ultrasound examination, the patients were classified retrospectively into three groups: group A with primary HPT (n = 35), group B with secondary HPT (n = 13), and group C without any biochemical suspicion of primary or secondary HPT (n = 20). In group A, double-phase study localized 25 of 36 (69.2%) parathyroid adenomas (one double adenoma) as against 34 of 36 (94.4%) with SPECT. Nine adenomas could be visualized only by SPECT. The reason for nonvisualization on planar scans was suspected to be an ectopic location in 2 cases (retrotracheal dislocation, retrovascular dislocation), a maximal diameter less than 15 mm (9-13 mm) in 6 cases, and oxyphilic-cell-poor cellularity in 1 case. Four false-positive retention (3 thyroid adenomas and 1 papillary thyroid carcinoma) were observed. SPECT showed a sensitivity of 94.4%, a specificity of 85%, and a PPV of 91.9% in biochemically suspected primary HPT. In group B, planar scintigraphy demonstrated 12 hyperplastic glands in 5 of 13 patients, and SPECT demonstrated 20 hyperplastic parathyroid glands in 8 out of 13 patients, which corresponds to a sensitivity of 38% and 61.5%, respectively. CONCLUSIONS Technetium 99m tetrofosmin seems to be a promising alternative tracer with similar capabilities to 99mTc sestamibi in localization of parathyroid adenoma. SPECT showed clear advantages in terms of sensitivity over planar scintigraphy and should be used at least in cases with poor or no uptake in double-phase study. In endemic goiter areas, ultrasound of the neck should be performed to exclude false positive retention in thyroid adenomas. Technetium 99m tetrofosmin, like 99mTc sestamibi, is not ideal for localization of hyperplastic glands in secondary hyperparathyroidism because of low sensitivity.

Goiter Prevalence and Urinary Iodide Excretion in a Formerly Iodine-Deficient Region After Introduction of Statutory Iodization of Common Salt

The objective of this epidemiologic study was to determine the volume of the thyroid gland as well as urinary iodine excretion in dependence on age and gender in a population from an area of low natural iodine supply now receiving iodine prophylaxis. In 430 persons from three communities in the province of Carinthia, Austria, we determined thyroid volume via sonography as well as urinary iodide excretion. As in numerous other European countries, natural iodine supply is insufficient in Austria. Therefore, to reduce goiter incidence, iodization of common salt with 10 mg potassium iodide (KI) per kilogram of NaCl was made mandatory in Austria in 1963 by federal law. In 1990, the amount of iodine addition was increased to 20 mg KI per kilogram of NaCl. Our results show that mean urinary iodide excretion in the persons investigated was altogether satisfactory (males: 163.7 microg of iodine per gram of creatinine; females: 183.3 microg of iodine per gram of creatinine). Goiter prevalence was 34.3% in women and 21.3% in men. An increase in goiter occurrence with age was noted in both genders. The increase in goiter prevalence was particularly obvious in the age group older than 40, i.e., among those participants who had spent at least a certain span of their lives in an area of iodine deficiency. Thus, the most likely reason for the persistently high goiter prevalence is not current iodine deficit but rather the high number of goiters that had developed previously at the time of iodine deficiency and were unable to undergo regression in spite of todays comparatively good iodine supply situation.

Evaluation of thyroid nodules with technetium-99m tetrofosmin dual-phase scintigraphy

Technetium-99m tetrofosmin, a lipophilic cationic complex molecule, was introduced for myocardial imaging. In some biodistribution studies it has also been reported to accumulate in the thyroid gland. Our objectives were to determine which thyroid nodules retain tetrofosmin and whether preoperative evaluation of malignancy is possible. Tetrofosmin scintigraphy was performed in 57 patients with a cold thyroid nodule on previously performed pertechnetate scintigraphy. All patients had undergone ultrasonography and sonographically guided fine-needle aspiration biopsy. The tetrofosmin scintigrams were obtained 5 min (early image) and 1 h (late image) after intravenous injection of 370 MBq. Only nodules that showed clear tracer retention after 1 h in comparison with retention at 5 min were classified as TETRO positive. Nodules without late retention were classified as TETRO negative. All patients underwent surgery and the histological results were compared with the results of tetrofosmin scintigraphy. Ten out of 11 patients with thyroid carcinoma (two pT1, three pT2, five pT4) were TETRO negative. One patient with papillary carcinoma (pT2) was TETRO positive. The mean nodular to thyroid tissue (N/T) ratio for the late scan was 1.0±0.20. There were 21 patients with thyroid adenomas (seven follicular, seven microfollicular and seven oxyphilic); 15 of these patients were TETRO positive and six TETRO negative. The mean N/T ratio for the late images was 1.34±0.41. All patients with degenerative goitre (24 cases) and the one patient with Hashimotos disease were TETRO negative after 1 h and the N/T ratio was 0.92±0.12 on the late scan. Our results indicate that99mTc-tetrofosmin scanning is of little value preoperatively in distinguishing thyroid carcinoma from other thyroid nodules. Tetrofosmin tends to demonstrate thyroid adenomas but does not have a routine role in the assessment of thyroid nodules.

Technetium-99m-Pertechnetate Scintigraphy in Small Thyroid Nodules

The aim of our study was to compare the scinitgraphic pattern in different tumor stages of thyroid carcinoma. In addition, sonographic and cytologic results are evaluated. In 140 patients 99mTc-pertechnetate scans were evaluated retrospectively by a visual inspection scoring method: Tumor size plays an important role in routinely used planar scintigraphy. Nodules greater 2cm in diameter tend to appear cold but microcarcinomas (≤lcm) are mostly warm on scan. Therefore not all cancers are cold. On ultrasonography, small nodules often have a similar echo structure. The echo structure tends to decrease when the nodules enlarge. Especially for the diagnosis of non palpable carcinomas, ultrasonographically guided FNAB is necessary.