[Incorporation monitoring of employees of a radioiodine therapy ward. Is incorporation monitoring required for routine?]. / Überwachung der Mitarbeiter einer Radioiodtherapiestation mittels Ausscheidungsmessungen. Ist im Routinebetrieb eine Inkorporationsüberwachung erforderlich?

UNLABELLED: Aim of the study was to determine the annual incorporation of staff on a radioiodine therapy ward and the resulting annual effective dose (aed). Following the German incorporation guideline (gig), incorporation monitoring is not necessary for potential aed below 0.5 mSv/a. For aed > 0.5 mSv/a adherence to the 1 mSv dose limit must be verified. For doses > 1 mSv/a incorporation has to be monitored by the authority. Furthermore, the (131)I incorporation factor from the gig should be verified. METHODS: To determine the actual work related incorporation, the (131)I activity concentration in urine samples (collection over 24 h) of 14 employees of different professions were examined over a period of 27 months. RESULTS: Measured activity concentrations were related to the individual time of exposure. A constant activity supply for at least three days was assumed. The mean annual effective doses were 2.4 · 10⁻¹ mSv/a (nursing staff; n = 3), 5.6 · 10⁻² mSv/a (cleaning staff; n = 2), 2.8 · 10⁻³ mSv/a (technical staff; n = 2) and 5.2 · 10⁻³ mSv/a (physicians; n = 7). All aed were below the dose limits of the gig. The calculated mean incorporation factors ranged from 3.0 · 10⁻8 for the nursing staff to 3.6 · 10⁻¹° for the technical staff (cleaning staff: 7 · 10⁻9; physicians: 6.5 · 10⁻¹°) and were therefore well below the (131)I incorporation factor defined by the gig. CONCLUSIONS: To estimate the aed caused by incorporation of (131)I it has to be subdivided for the different requirements in the diverse fields of activity of the employees. Regarding those who spend most of their time nearby the patient an incorporation monitoring by the authority might be required. The (131)I incorporation factor from the guideline (10⁻6) can be reduced by a factor of 10. For (99m)Tc and (18)F an incorporation factor of 10⁻7 is accepted.

Risk of malignancy in follicular thyroid neoplasm: predictive value of thyrotropin.

UNLABELLED: The cytological diagnosis of follicular neoplasm is a common finding in fine needle aspiration cytology (FNAC) of thyroid nodules and includes benign disease as well as differentiated thyroid cancer. The aim of the study is to determine if thyrotropin is a predictive factor for a malignant nature of follicular neoplasm. PATIENTS, METHODS: The records of 119 patients with follicular neoplasm on FNAC, who underwent surgery for final diagnosis, were reviewed retrospectively. The predictive value of serum parameters including thyrotropin, thyroglobulin, and anti-thyroid antibodies, ultrasonographic criteria and clinical variables was evaluated by univariate analysis and logistic regression analysis. RESULTS, DISCUSSION: Patients with malignant nodules showed a higher thyrotropin concentration compared to patients with benign nodules (median 1.6 mU/l, interquartile range 1.4-3.0 mU/l vs. median 1.2 mU/l, interquartile range 0.8-1.6 mU/l, p < 0.01). ROC-analysis of thyrotropin revealed an optimal cut off value to differentiate benign and malignant nodules of 1.34 mU/l. The incidence of malignancy was 30.3% for a thyrotropin concentration higher than 1.34 mU/l compared to 6.4% for a thyrotropin concentration lower than or equal to 1.34 mU/l. On univariate analysis thyroglobulin higher than 300 ng/ml, positive anti-thyroid antibodies, hypoechogenicity, and ill-defined margins, respectively, were also significantly associated with malignancy. On logistic regression analysis higher thyrotropin concentrations, ill-defined margins, and thyroglobulin higher than 300 ng/ml, respectively, were independent predictive factors for malignancy (OR 20.0, 10.7, and 22.7, respectively). CONCLUSION: Higher thyrotropin concentrations are predictive for a malignant nature of follicular neoplasm.

Comparison of positron emission tomography with [(18)F]FDG and [(68)Ga]DOTATOC in recurrent differentiated thyroid cancer: preliminary data.

AIM: The aim of this study was to retrospectively analyse the value of positron emission tomography (PET) with a radiolabelled somatostatin analogue, [(68)Ga]DOTATOC, in recurrent radioiodine positive and negative differentiated thyroid cancer (DTC) compared to [(18)F]FDG PET. METHODS: Seventeen patients with known or suspected recurrent DTC were enrolled in this study. All patients underwent PET with [(68)Ga]DOTATOC and [(18)F]FDG under TSH suppressive therapy and whole-body scintigraphy (WBS) after administration of [(131)I] following TSH stimulation. The total number of tumour lesions was defined as the sum of the lesions detected by at least one of these three imaging techniques. Pathologic findings were confirmed histopathologically or by follow-up and conventional radiological imaging. RESULTS: Both PET tracers consistently detected metastases in 12 patients. In two cases, only [(131)I] WBS and computed tomography revealed metastatic disease; in the remaining three patients with an increased thyroglobulin no correlate could be found. From a total of 104 tumour lesions, [(18)F]FDG PET showed only slightly higher detection rate than [(68)Ga]DOTATOC PET in radioiodine positive patients (28/31 versus 25/31), whereas significant differences were seen in the group with negative [(131)I] WBS (70/73 versus 26/73, P<0.01). Three out of 104 lesions were only visible using [(68)Ga]DOTATOC PET. CONCLUSIONS: [(68)Ga]DOTATOC and [(18)F]FDG PET showed comparable diagnostic performance in recurrent, radioiodine positive DTC. Due to much higher lesion detection rates, [(18)F]FDG PET should be preferred to [(68)Ga]DOTATOC PET in the work-up of radioiodine negative DTC relapse. These preliminary results have to be confirmed by more extensive data in further studies.