The role of nuclear medicine in differentiated thyroid cancer.

In differentiated thyroid cancer (DTC) nuclear medicine is able to cover the spectrum from diagnosis and treatment to follow up keeping patient's management in one institution. Nowadays, DTC is often diagnosed per chance, presenting as small indolent nodule diagnosed on routinely performed ultrasound. Ultrasound and ultrasonography-guided fine-needle aspiration biopsy together with scintigraphy are probably the most adequate tools for diagnosis. After thyroidectomy, treatment with iodine-131 is routinely performed in a nuclear medicine therapy institution as a standard procedure in most of the cases with regard to histology. In case of iodine positive metastases, repeated therapies can be performed in order to reduce tumour burden. In the follow up of DTC thyroglobulin (tumour marker), ultrasound and diagnostic whole body scan are established procedures. With the development of SPECT/CT and PET/CT ((18)F-FDG, (68)Ga-somatostatin receptor) combining functional and anatomic imaging the nuclear medicine spectrum has further increased.

[Thyroid and pregnancy]. / Schilddrüse und Schwangerschaft.

Screening for thyroid dysfunction is recommended among certain groups of women, who plan a pregnancy, for example women with history of hyperthyroid or hypothyroid disease, with type 1 diabetes or other autoimmune disorders or women with previous therapeutic head or neck irradiation, in the case of infertility. Management of thyroid disease during pregnancy requires special consideration because pregnancy induces major changes in thyroid function, and maternal thyroid disease can have adverse affects on the pregnancy and the foetus. Under ideal conditions there is a cooperation among several healthcare professionals, such as endocrinologists, nuclear medicine physicians, gynaecologists, neonatologists and if necessary surgeons. This article surveys the physiological and pathological changes of thyroid, their diagnosis and therapy in the case of women in childbearing age, women with unfulfilled desire to have children, pregnant women, as well as women after delivery.

The value of 18F-DOPA PET-CT in patients with medullary thyroid carcinoma: comparison with 18F-FDG PET-CT.

The purpose of this prospective study was to compare the value of DOPA PET-CT with FDG PET-CT in the detection of malignant lesions in patients with medullary thyroid carcinoma (MTC). Twenty-six consecutive patients (10 men, 16 women, mean age 59 +/- 14 years) with elevated calcitonin levels were evaluated in this prospective study. DOPA and FDG PET-CT modalities were performed within a maximum of 4 weeks (median 7 days) in all patients. The data were evaluated on a patient- and lesion-based analysis. The final diagnosis of positive PET lesions was based on histopathological findings and/or imaging follow-up studies (i.e., DOPA and/or FDG PET-CT) for at least 6 months (range 6-24 months). In 21 (21/26) patients at least one malignant lesion was detected by DOPA PET, while only 15 (15/26) patients showed abnormal FDG uptake. DOPA PET provided important additional information in the follow-up assessment in seven (27%) patients which changed the therapeutic management. The patient-based analysis of our data demonstrated a sensitivity of 81% for DOPA PET versus 58% for FDG PET, respectively. In four (4/26) postoperative patients DOPA and FDG PET-CT studies were negative in spite of elevated serum calcitonin and CEA levels as well as abnormal pentagastrin tests. Overall 59 pathological lesions with abnormal tracer uptake were seen on DOPA and/or FDG PET studies. In the final diagnosis 53 lesions proved to be malignant. DOPA PET correctly detected 94% (50/53) of malignant lesions, whereas only 62% (33/53) of malignant lesions were detected with FDG PET. DOPA PET-CT showed superior results to FDG PET-CT in the preoperative and follow-up assessment of MTC patients. Therefore, we recommend DOPA PET-CT as a one-stop diagnostic procedure to provide both functional and morphological data in order to select those patients who may benefit from (re-)operation with curative intent as well as guiding further surgical procedures.

Respective roles of thyroglobulin, radioiodine imaging, and positron emission tomography in the assessment of thyroid cancer.

Depending on the iodine supply of an area, the incidence of thyroid cancer ranges between 4 and 12/100,000 per year. To detect thyroid cancer in an early stage, the assessment of thyroid nodules includes ultrasonography, ultrasonography-guided fine-needle aspiration biopsy, and conventional scintigraphic methods using (99m)Tc-pertechnetate, (99m)Tc-sestamibi or -tetrofosmin, and (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in selected cases. After treatment of thyroid cancer, a consequent follow-up is necessary over a period of several years. For following up low-risk patients, recombinant thyroid-stimulating hormone-stimulated thyroglobulin and ultrasonography is sufficient in most cases. After total thyroidectomy and radioiodine ablation therapy, thyroid-stimulating hormone-stimulated thyroglobulin should be below the detection limit (eg, <0.5 ng/mL, R: 70-130). An increase of thyroglobulin over time is suspicious for recurrent or metastatic disease. Especially in high-risk patients, aside from the use of ultrasonography for the detection of local recurrence and cervial lymph node metastases, nuclear medicine methods such as radioiodine imaging and FDG-PET are the methods of choice for localizing metastatic disease. Radioiodine imaging detects well-differentiated recurrences and metastases with a high specificity but only moderate sensitivity. The sensitivity of radioiodine imaging depends on the activity administered. Therefore a low activity diagnostic (131)I whole-body scan (74-185 MBq) has a lower detection rate than a high activity post-therapy scan (3700-7400 MBq). In patients with low or dedifferentiated thyroid cancer and after several courses of radioiodine therapy caused by metastatic disease, iodine negative metastases may develop. In these cases, despite clearly elevated levels of thyroglobulin, radioiodine imaging is negative or demonstrates only faint iodine uptake. The method of choice to image these iodine negative metastases is FDG-PET. In recent years the combination of PET and computed tomography has been introduced. The fusion of the metabolic and morphologic information was able to increase the diagnostic accuracy, reduces pitfalls and changes therapeutic strategies in a reasonable number of patients.

Role of Fluorodeoxyglucose PET in Inflammatory Bowel Disease: A Review.

Inflammatory bowel disease (IBD) requires a complex diagnostic workup. In contrast to endoscopy and cross-sectional imaging methods, scintigraphy enables a complete survey of the whole small and large bowel intestinal tract with a single noninvasive examination. For detection of IBD, 80% to 90% sensitivity and 92% to 100% specificity can be found for conventional scintigraphy. A new imaging method like fluorine-18 (F-18) fluorodeoxyglucose PET has been shown to be useful in tumor diagnostics. A major problem in PET is the limited anatomic information and nonspecific tracer uptake within the colon, however, which may lead to false-positive results. New imaging methods like combined PET/CT can help to solve the problem, because physiologic tracer uptake can be easily distinguished from pathologic lesions as a result of the anatomic detail provided by CT.

[Diagnosis, treatment and follow-up in the case of differentiated thyroid cancer]. / Diagnose, Therapie und Nachsorge des differenzierten Schilddrüsenkarzinoms.

For early diagnosis of thyroid cancer, ultrasonography (US) and US-guided fine-needle aspiration biopsy are the methods of choice. Thyroid scintigraphy using Tc-99m pertechnetate can underline the necessity of surgery in case of hypofunctioning nodules. Treatment of thyroid cancer includes total thyroidectomy and staging lymphadenectomy, in the case of lymph node metastases, radical neck dissection of the ipsilateral side. Four weeks after surgery, if TSH exceeds a value of 50 mU/l, with the exception of papillary thyroid cancer pT1a (TNM 1997), radioiodine remnant ablation using activities between 2960 and 3700 MBq I-131 is performed in all other cases. As growth of benign and malignant thyroid cells depends on TSH stimulation, thyroid hormone therapy using TSH suppressive doses (TSH, <0.03 mU/l) follows radioiodine remnant ablation. Additional fractionated external radiation therapy (50 Gy) may be administered in advanced cases (e.g., pT4 N1M0; TNM 1997). Standard follow-up of differentiated thyroid cancer includes measurement of serum thyroglobulin, US of the neck and I-131 whole-body scintigraphy (I-131 WBS). With about 98% the sensitivity of thyroglobulin is very high under TSH stimulation. In case of elevated thyroglobulin, US is the method of choice to detect local recurrences and lymph node metastases of the neck. At defined intervals of follow-up or in case of increasing thyroglobulin, I-131 WBS will be performed under TSH stimulation. With the availability of recombinant TSH (exogenous TSH stimulation) the need to withdraw thyroid hormone over a period of 3-4 weeks (endogenous TSH stimulation) is no longer necessary to perform I-131 WBS. However, in about 20-40% of cases or in the course of disease after several radioiodine therapies, recurrences or metastases may be or become iodine negative. In this case, cationic complexes such as Tc-99m Sestamibi or Tc-99m Tetrofosmin are available to detect less differentiated metastases. In the course of dedifferentiation of malignant thyroid cells, the ability of iodine uptake decreases and uptake of glucose increases. This elevated glucose metabolism can be imaged using FDG PET. Today the combination of PET (metabolic imaging) and CT (morphologic imaging) using PET/CT fusion imaging is the method of choice to image iodine-negative metastases.