TIRADS for sonographic assessment of hypofunctioning and indifferent thyroid nodules.

AIM: To test the feasibility of the Thyroid Imaging Reporting And Data System (TIRADS) according to Horvath and Kwak for the assessment of thyroid nodules. PATIENTS, METHOD: Retrospective analysis of patients with thyroid nodules applying the following inclusion criteria: B-mode-ultrasound, surgery and histological results. Thyroid nodules were classified as TIRADS 2, 3, 4A, 4B, 4C, 5 and 6. RESULTS: A total of 172 patients were included (133 women, 48 ± 13 years, 39 men, 49 ± 11 years) with 222 thyroid nodules (24.9 ± 11.5 mm). Final histological diagnosis revealed 203 benign nodules (91%) and 19 malignant nodules (9%; 18 papillary thyroid carcinoma, PTC, and one medullary thyroid carcinoma, MTC). One hundred and sixty thyroid nodules were hypofunctioning in 99mTc-pertechnetate-scintigraphy, 14 nodules were hyperfunctioning and 46 nodules were classified as indifferent. In two cases with small carcinoma < 1 cm 99mTc-pertechnetate-scintigraphy was not performed. According to Horvath, the prevalence of malignancy was 6.7% in TIRADS 2, 0% in 3, 1.9% in 4A, 33% in 4B, 12.5% in 5 and 100% in 6; 73 nodules (39%) were not clearly classifiable, including 3 carcinoma (4.1%). According to Kwak, the prevalence of malignancy was 6.9% in TIRADS 2, 0% in 3, 2% in 4A, 4.1% in 4B, 23.1% in 4C, and 100% in 5 and 6, respectively. Notably, in the subgroup of hot nodules, 11 (79%) were graded as TIRADS 4A or higher, and thus advisable for fine-needle aspiration biopsy in both TIRADS. CONCLUSION: The TIRADS described by Horvath is not practicable due to numerous unclassifiable nodules. The revised TIRADS published by Kwak is feasible and suitable to assess the prevalence of malignancy, but it cannot replace scintigraphic imaging. Fine-needle-biopsy is not necessary in nodules categorized as (K)TIRADS 3, 4A and 5.

[99mTc-MIBI scintigraphy of hypofunctional thyroid nodules. Comparison of planar and SPECT imaging]. / 99mTc-MIBI-Szintigraphie hypofunktioneller Schilddrüsenknoten. Vergleich von planarer und tomographischer Technik.

UNLABELLED: 99mTc-MIBI-scintigraphy allows to assess the dignity of hypofunctional thyroid nodules. A concordant pattern in MIBI- and pertechnetate-scintigraphy excludes malignancy with high accuracy. For increased MIBI-uptake histological evaluation is advised. The assessment of MIBI-isointense nodules is discussed controversially. Objective of our study was to analyse the prevalence of malignancy for isointense nodules and the diagnostic accuracy of image acquisition in SPECT-technique. PATIENTS, METHODS: MIBI-scintigraphies were analysed retrospectively. Imaging was performed 60 min after intravenous injection of 510 MBq 99mTc-MIBI. Thyroid nodules were assessed as hypo-, iso- or hyperintense compared to the paranodular tissue. RESULTS: 83 of 225 patients underwent thyroid surgery (age 48.6 ± 12.6 years, 72% women). In 12 (14.5%) cases a papillary carcinoma was diagnosed. In planar imaging 12, 34 and 37, in tomographical imaging 16, 21 and 46 nodules, respectively, were classified as hypo-, iso- oder hyperintense. Among hypo-, iso- and hyperintense nodules in planar imaging 1, 5 and 6 carcinomas were found, resp. In tomographical imaging no, 4 and 8 carcinomas were found, respectively. Classification of iso- and hyperintense nodules as "suspicious for malignancy" showed for planar imaging a sensitivity, specificity, NPV and PPV of 91.7, 15.5, 91.7 and 15.6%, for tomographical imaging of 100, 22.5, 100 and 17.9%, respectively. CONCLUSION: Hypofunctional thyroid nodules with iso- and hyperintense MIBI-Uptake have a comparable prevalence of malignancy. Image acquisition in SPECT-technique results in improved diagnostic sensitivity and negative predictive value.

Thyroiditis de Quervain. Are there predictive factors for long-term hormone-replacement?

BACKGROUND: Subacute thyroiditis is a usually self-limiting disease of the thyroid. However, approximately 0.5-15% of the patients require permanent thyroxine substitution. Aim was to determine predictive factors for the necessity of long-term hormone-replacement (LTH). PATIENTS, METHODS: We retrospectively reviewed the records of 72 patients with subacute thyroiditis. Morphological and serological parameters as well as type of therapy were tested as predictive factors of consecutive hypothyroidism. RESULTS: Mean age was 49 ± 11 years, f/m-ratio was 4.5 : 1. Thyroid pain and signs of hyperthyroidism were leading symptoms. Initial subclinical or overt hyperthyroidism was found in 20% and 37%, respectively. Within six months after onset 15% and 1.3% of the patients developed subclinical or overt hypothyroidism, respectively. At latest follow-up 26% were classified as liable to LTH. At onset the thyroid was enlarged in 64%, and at latest follow-up in 8.3%, with a significant reduction of the thyroid volume after three months. At the endpoint the thyroid volume was less in patients in the LTH group compared with the non-LTH group (41.7% vs. 57.2% of sex-adjusted upper norm, p = 0.041). Characteristic ultrasonographic features occurred in 74% of the patients in both lobes. Serological and morphological parameters as well as type of therapy were not related with the need of LTH. CONCLUSIONS: In this study the proportion of patients who received LTH was 26%. At the endpoint these patients had a lower thyroid volume compared with euthyroid patients. No predictive factors for LTH were found.

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.

[Scintigraphically "hot" thyroid nodules mainly go hand in hand with a normal TSH]. / Szintigraphisch mehranreichernde Schilddrüsenknoten gehen überwiegend mit normwertigem TSH einher.

AIM: In recent years, various professional societies published guidelines for diagnostic evaluation of thyroid nodules, in which the indication for scintigraphy is restricted to patients with subnormal TSH values. It is seen controversial whether such recommendations should be transferred to Germany, partly because of lower iodine intake in this country and the consequent higher percentage of autonomous thyroid nodules, which are not accompanied by a measurable dysfunction. Since reliable data to this topic are scarce, we analyzed multicentrically the spectrum of scintigraphically "hot" and "warm" nodules under the current epidemiological conditions. PATIENTS, METHODS: In 10 German nuclear medicine out-patient institutions we evaluated the diagnostic data from a total of 514 patients, in whom unequivocally hyperfunctional nodules (focal increased uptake in comparison to perinodular tissue with a sonographically nodular correlative ≥1 cm) could be detected by (99m)Tc-pertechnetate scintigraphy. To minimize selection bias, the surveys were not carried out in hospitals.The recorded parameters included the thyroid hormone levels, the global (99m)Tc-uptake (TcTU), the size of each nodule and the total autonomous nodular volume (V(aut)). RESULTS: Only 20% of the patients with "hot" nodules had subnormal TSH levels (<0.1 to 0.33 mU / l), the remaining patients had TSH levels from 0.34 to 3.5 mU /l (in one third of the patients TSH levels even exceeded 1.0 mU/l). Moreover, we found no relevant correlation between TSH and TcTU or V(aut). CONCLUSIONS: In Germany, in at far the largest proportion of patients with autonomous thyroid nodules objectified by means of scintigraphy, TSH levels are within the normal range. Since such nodules with maximum safety can be classified as benign, a corresponding scintigraphic finding has a high priority for the patient. These current data support that it is not reasonable to restrict scintigraphy to patients with subnormal TSH values in this country.

[3D volume and SUV analysis of oncological PET studies: a voxel-based image processing tool with NSCLC as example]. / Dreidimensionale Uptake- und Volumenanalyse von onkologischen PET-Studien: Voxel-basiertes Bildverarbeitungstool am Beispiel von NSCLC.

AIM: The standardized uptake value (SUV) of 18FDG-PET is an important parameter for therapy monitoring and prognosis of malignant lesions. SUV determination requires delineating the respective volume of interest against surrounding tissue. The present study proposes an automatic image segmentation algorithm for lesion volume and FDG uptake quantitation. METHODS: A region growing-based algorithm was developed, which goes through the following steps: 1. Definition of a starting point by the user. 2. Automatic determination of maximum uptake within the lesion. 3. Calculating a threshold value as percentage of maximum. 4. Automatic 3D lesion segmentation. 5. Quantitation of lesion volume and SUV. The procedure was developed using CTI CAPP and ECAT 7.2 software. Validation was done by phatom studies (Jaszczak phantom, various "lesion" sizes and contrasts) and on studies of NSCLC patients, who underwent clinical CT and FDG-PET scanning. RESULTS: Phantom studies demonstrated a mean error of 3.5% for volume quantification using a threshold of 41% for contrast ratios >or=5 : 1 and sphere volumes >5 ml. Comparison between CT- and PET-based volumetry showed a high correlation of both methods (r = 0.98) for lesions with homogeneous FDG uptake. Radioactivity concentrations were underestimated by on average -41%. Employing an empirical threshold of 50% for SUV determination, the underestimation decreased to on average -34%. CONCLUSIONS: The algorithm facilitates an easy and reproducible SUV quantification and volume assessment of PET lesions in clinical practice. It was validated using NSCLC patient data and should also be applicable to other tumour entities.

[Spectrometric assessment of thyroid depth within the radioiodine test]. / Spektrometrisches Verfahren zur Tiefenbestimmung der Schilddrüse im Rahmen des Radioiodtests.

UNLABELLED: Aim of this study is the validation of a simple method for evaluating the depth of the target volume within the radioiodine test by analyzing the emitted iodine-131 energy spectrum. PATIENTS, METHODS: In a total of 250 patients (102 with a solitary autonomous nodule, 66 with multifocal autonomy, 29 with disseminated autonomy, 46 with Graves' disease, 6 for reducing goiter volume and 1 with only partly resectable papillary thyroid carcinoma), simultaneous uptake measurements in the Compton scatter (210 +/- 110 keV) and photopeak (364-45/+55 keV) windows were performed over one minute 24 hours after application of the 3 MBq test dose, with subsequent calculation of the respective count ratios. Measurements with a water-filled plastic neck phantom were carried out to perceive the relationship between these quotients and the average source depth and to get a calibration curve for calculating the depth of the target volume in the 250 patients for comparison with the sonographic reference data. Another calibration curve was obtained by evaluating the results of 125 randomly selected patient measurements to calculate the source depth in the other half of the group. RESULTS: The phantom measurements revealed a highly significant correlation (r = 0,99) between the count ratios and the source depth. Using these calibration data, a good relationship (r = 0,81, average deviation 6 mm corresponding to 22%) between the spectrometric and the sonographic depths was obtained. When using the calibration curve resulting from the 125 patient measurements, the overage deviation in the other half of the group was only 3 mm (12%). There was no difference between the disease groups. CONCLUSION: The described method allows on easy to use depth correction of the uptake measurements providing good results.

[Concept and validation of a simple model of the intrathyroidal iodine kinetics]. / Prinzip und Validierung eines einfachen Modells der intrathyroidalen Iodkinetik.

UNLABELLED: AIM of this study is the introduction and validation of a simple model of the intrathyroidal iodine kinetics, designed for optimizing radioiodine therapy planning and dose measurement in a routine clinical setting. METHODS: The new model defines the intrathyroidal iodine kinetics as balance of the thyroidal iodine intake and -excretion, characterized by the two exponential equations A(t) = A(0) * (1-exp(-lambda(1) t)) and A(t) = A(0) * (exp(-lambda(2) t) -1), respectively. A(0) describes the theoretically maximum iodine uptake when the thyroidal iodine excretion is ignored, lambda(1) and lambda(2) represent the constants characterizing the iodine intake and excretion, respectively. The thyroidal iodine content at the time t equals the sum of both functions, which is A(t) = A(0) * (exp(-lambda(2) t)-exp(-lambda(1) t)). In 25 patients with autonomous goiter / nodules (n = 18), Graves' disease (n = 5), or endemic euthyroid goiter (n = 2), the iodine uptake in the thyroid during the radioiodine therapy as fraction of the applied activity was determined daily, with the remaining body covered by a lead shield. On average, 7.2 measurements were performed per patient (minimum 4, maximum 13). With these uptake values, individual regression curves were fitted using the above equation, and the difference between the actual measurements and the corresponding values of the regression curves was determined. RESULTS: The average deviation of the 179 uptake values from the calculated points of the respective regression curves was only 1.4%. There was no significant difference between the three disease groups. The distribution of the relative deviations during the individual courses was constant, systematic errors were not detected. CONCLUSION: Our results suggest that the intrathyroidal iodine kinetics can be precisely described with the model A(t) = A(0) * (exp(-lambda(2) t)-exp(-lambda(1) t)). With only three measurements, the trend of the curve can be calculated, which allows to determine the total radioiodine storage in the thyroid.

Radioiodine therapy in patients with hyperthyroid disorder: standard versus dosimetric activity application.

Due to its high success rate and non-invasive character, an increasing demand for radioiodine therapy can be seen. This study was conducted to determine whether standardized 131I activities can be used to facilitate management of patients with hyperthyroid disorder or whether a pre-therapeutic radioiodine test is advisable to determine an adequate therapeutic activity. The therapeutic uptake of 218 patients with benign thyroid disorders were determined and compared with 24 h and 48 h test uptake measurements as well as with calculated standard uptake values. Since there is a linear relationship between iodine uptake and delivered radiation dose, the effect of the different therapeutic approaches on the latter parameter was analysed. Special care was taken to assess possible differences between the various thyroid disorders. A mean deviation between pre-therapeutic test uptake and actual therapeutic uptake of 14.7% was observed in contrast to one of 29.1% when using disease specific standard values per millilitre of thyroid tissue. Furthermore, the proportion of patients with large deviations of more than 40% increased drastically when using standard uptake values (with radioiodine test, 4.1%; with standard values, 18.8%). In conclusion, the dosimetric approach with a pre-therapeutic radioiodine test proved to be the most accurate therapeutic procedure. Both the 24 h and 48 h test uptake measurements gave analogous results and yielded a correlation coefficient of 0.91 when compared with the therapeutic uptake. While it may be tempting to use standard activities to facilitate patient management, the findings of this study confirm that, for precise therapy planning, a pre-therapeutic radioiodine test is advised. Since no significant difference could be found between the 24 h and 48 h test uptake values, an early measurement 24 h after administration of the test activity is recommended.

[Relevance of colour-duplex echography for detection and therapy of recurrences in the follow-up of head and neck cancer]. / Relevanz farbduplexsonographischer Untersuchungen für Rezidivdetektion und -behandlung in der Tumornachsorge von Kopf-Hals-Karzinomen.

BACKGROUND: Head and neck malignancies have a high rate of recurrences. Since the prognosis is often limited an early detection and therapy onset is essential for survival. This study surveys the relevance of regular colour-duplex echography examinations in the follow-up for detection and therapy of recurrent head and neck carcinomas. PATIENTS AND METHODS: In a prospective non-randomized study 43 patients were surveyed over a mean observation period of 28 (8-44) months. In addition to clinical and colour-duplex echography (CDS) examinations, computed tomography (CT) and positron-emission-tomography using 18fluorodeoxyglucose (PET) were performed. RESULTS: A recurrence was detected in 17/43 (39.5 %) patients. The median survival was 42 months. CDS was the most reliable procedure for the diagnosis of regional recurrences with an accuracy of 94.2 %. Sensitivity and specificity of CDS for the diagnosis of all recurrences was found to be 80 % and 78,6 % respectively. CT yielded identical results. In PET sensitivity was 82.4 % and specificity was found to be 88.4 %. In clinical examinations including panendoscopy sensitivity was 64.7 % only. In 7/17 recurrences a therapy was performed with curative intention. In 4 cases an early diagnosis by CDS contributed to a successful therapy. CONCLUSION: CDS is the imaging procedure of choice for the routine follow-up of head and neck cancer patients. In order to perform a comprehensive assessment of the head and neck region, for re-staging and to exclude second primary tumours additional (pan)endoscopy is necessary. CDS supports due to a high resolution and reliability an early therapy onset and a minimal invasive therapy. Thus, this procedure can significantly contribute to the successful treatment of recurrences in head and neck cancer.

Pre-transplant positron emission tomography (PET) using fluorine-18-fluoro-deoxyglucose (FDG) predicts outcome in patients treated with high-dose chemotherapy and autologous stem cell transplantation for non-Hodgkin's lymphoma.

We investigated the predictive value of sequential FDG PET before and after high-dose chemotherapy (HDT) and autologous stem cell transplantation (ASCT) in 24 patients suffering from non-Hodgkin's lymphoma (NHL). FDG PET was performed at baseline, after three cycles of induction therapy, before and after HDT with ASCT. Response assessment from sequential PET scans using standardized uptake values (SUV) was available in 22 patients at the time of transplantation. Partial metabolic response (PMR) was defined as a >25% decrease of SUV between successive PET scans [corrected]. Six of seven patients who did not achieve a PMR after complete induction therapy developed lymphoma progression, while 10 of 15 patients with complete metabolic response (CMR) or PMR remained in continuous remission. Four of seven patients with less than PMR after induction therapy died vs two of 15 patients with CMR/PMR. Median progression-free and overall survival of patients with less than PMR after HDT and ASCT was 9 and 29 months, respectively. In contrast, neither conventional re-staging nor the International Prognostic Index were predictive. These data suggest that sequential quantitative PET imaging does enlarge the concept of chemosensitivity used to select patients with high-risk NHL for HDT and ASCT or to route them to alternative treatments.

Uptake of cis-4-[18 F]fluoro-L-proline in scar formation: a marker of collagen synthesis?

Excessive scar formation is accompanied by abnormal collagen synthesis. The feasibility of monitoring collagen synthesis in vivo with no-carrier-added cis-4[18F]fluoro-L-proline (cis-FPro) was evaluated in an animal model with scar formation induced by implanted meshes. The abdominal wall of rats was replaced by alloplastic meshes. At days 3, 7, 14, 21 and 90 after implantation, the uptake of cis-FPro at 4 h post-injection was determined for resected samples of the mesh and normal tissues. The highest uptake was found in the kidneys (1.73+/-0.47%ID/g) followed by the liver (0.59+/-0.19%ID/g). The meshes showed the maximum uptake at day 3 (0.20+/-0.07%ID/g) with a decrease to 0.10+/-0.03%ID/g at day 90 (P<0.001). After 3 days no connective tissue was shown by histopathological morphometric analysis. The maximum partial volume (PV%) of connective tissue was 43+/-14 PV% 90 days after implantation. The maximum levels of granulocytes and inflammatory infiltrate were found at day 3 with minimal levels at day 90, paralleling the course of cis-FPro uptake. In conclusion, the uptake of cis-FPro at 4 h post-injection is not related to the content of connective tissue. Cis-FPro radiolabelled with 18F appears not to be a suitable radiopharmaceutical for in vivo monitoring of collagen synthesis in scar formation.

Combined image interpretation of computed tomography and hybrid PET in head and neck cancer.

AIM: Evaluation of potential synergistic effects of combined image interpretation of FDG PET using a gamma camera modified for coincidence detection (hybrid PET) and computed tomography (CT) and comparison of the diagnostic accuracy of hybrid PET and dedicated PET in patients with head and neck cancer. METHODS: Forty-two patients with suspected primary or recurrent cancer were included. Twenty-four patients underwent dedicated PET in addition to attenuation-corrected hybrid PET using a one-day protocol. RESULTS: Sensitivity, specificity and accuracy for detection of primary or recurrent head and neck cancer were 74, 73, and 74% for hybrid PET, 52, 82, and 60% for CT and 77, 82, and 79% for combined reading. With the combination of CT and hybrid PET all cases of recurrent disease were detected. The largest tumour not detected was 1.7 cm in diameter. Sensitivity, specificity and accuracy for the detection of neck sides with lymph node metastases were 69, 88, and 85% for hybrid PET, 62, 88, and 84% for CT, 69, 99, and 94% for combined image interpretation. With combined interpretation four involved neck sides were missed including two cases of microscopic metastases. Hybrid PET revealed concordant results to dedicated PET in all patients with respect to the detection of primary or recurrent tumour and in 45 of 48 neck sides (94%) with the same number of false negative findings. CONCLUSION: The combination of functional information of hybrid PET and morphological information of CT by the simple approach of combined image interpretation improves the sensitivity for the detection of primary/recurrent head and neck cancer and increases the specificity of lymph node staging compared to CT alone. The accuracy of hybrid PET and dedicated PET was almost identical.

Localisation of motor areas in brain tumour patients: a comparison of preoperative [18F]FDG-PET and intraoperative cortical electrostimulation.

Assessment of the exact spatial relation between tumour and adjacent functionally relevant brain areas is a primary tool in the presurgical planning in brain tumour patients. The purpose of this study was to compare a preoperative fluorine-18 fluorodeoxyglucose positron emission tomography ([18F]FDG PET) activation protocol in patients with tumours near the central area with the results of intraoperative direct cortical electrostimulation, and to determine whether non-invasive preoperative PET imaging can provide results equivalent to those achieved with the invasive neurosurgical "gold standard". In this prospective study, we examined 20 patients with various tumours of the central area, performing two PET scans (each 30 min after i.v. injection of 134-341 MBq [18F]FDG) in each patient: (1) a resting baseline scan and (2) an activation scan using a standardised motor task (finger tapping, foot stretching). Following PET/MRI realignment and normalisation to the whole brain counts, parametric images of the activation versus the rest study were calculated and pixels above categorical threshold values were projected to the individual MRI for bimodal assessment of morphology and function (PET/MRI overlay). Intraoperative direct cortical electrostimulation was performed using a Viking IV probe (5 pulses, each of 100 micros) and documented using a dedicated neuro navigation system. Results were compared with the preoperative PET findings. PET revealed significant activation of the contralateral primary motor cortex in 95% (19/20) of the brain tumour patients (hand activation 13/13, foot activation 6/7), showing a mean increase in normalised [18F]FDG uptake of 20.5% +/- 5.2% (hand activation task) and 17.2% +/- 2.5% (foot activation task). Additionally detected activation of the ipsilateral primary motor cortex was interpreted as a metabolic indication for interhemispheric compensational processes. Evaluation of the PET findings by cortical stimulation yielded a 94% sensitivity and a 95% specificity for identification of motor-associated brain areas. In conclusion, the findings indicate that a relatively simple and clinically available [18F]FDG PET activation protocol enables a sufficiently precise assessment of the local relation between the intracranial tumour and the adjacent motor cortex areas and may facilitate the presurgical planning of tumour resection.

[Fluorodeoxyglucose positron emission tomography (FDG-PET) in the differential diagnosis of pancreatic lesions]. / Fluordeoxyglucose Positronenemissionstomographie (FDG-PET) zur Dignitätsbeurteilung von Läsionen des Pankreas.

Various diagnostic modalities have been introduced for the diagnostic work-up of suspected pancreatic cancer. However, the differentiation of pancreatic cancer and chronic pancreatitis is still a challenge. Positron emission tomography (PET) with radiolabeled fluorodeoxyglucose (FDG) is an imaging modality that is based on the increased glucose metabolism of malignant cells. In contrast to conventional imaging, which provides morphological information, FDG-PET demonstrates functional alterations of malignant tumours. The value of FDG-PET in differentiating pancreatic lesions has been validated by numerous studies with variable patient selection criteria. In these studies a sensitivity between 71% and 100% and a specificity between 64% and 100% was reported. The median sensitivity was 92% and the median specificity 82%. The diagnostic accuracy was limited in hyperglycemic patients and in patients with active inflammation of the pancreas, as is found in acute pancreatitis or active chronic pancreatitis. These limitations have to be taken into account for the indication of FDG-PET as well as the interpretation of PET findings.

2-[Fluorine-18]-fluoro-2-deoxy-d-glucose positron emission tomography in the diagnosis of recurrent ovarian cancer.

OBJECTIVE: The aim of the study was to investigate the role of 2-[fluorine-18]-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) in the diagnosis of recurrent ovarian cancer. METHODS: One hundred six FDG PET scans performed in 54 patients in the follow-up after cytoreductive surgery and chemotherapy of ovarian cancer were reevaluated. Fifty-eight scans were performed in patients with suspected recurrence and 48 scans in patients who were clinically disease free. Thirty-seven PET scans were validated by histology and 66 studies by a median follow-up of 22 months in disease-free patients or 12 months in patients with recurrent disease. Three scans were validated by concordant positive findings of tumor marker CA125, computed tomography, and FDG PET. RESULTS: FDG PET correctly identified recurrent disease in 73/88 cases. PET ruled out recurrent disease in 15/18 cases. The sensitivity and specificity for PET were 83 and 83%, respectively. In patients with suspected disease, sensitivity was 94% compared to 65% in patients judged clinically disease free. The sensitivity of PET was 96% if suspicion of recurrence was based on a rise of CA125 alone. PET preceded the conventional diagnosis by a median of 6 months in patients judged clinically free of disease. The median relapse-free interval after a negative PET scan was 20 months. CONCLUSION: FDG PET provides the chance to detect recurrent ovarian cancer at an earlier stage during follow-up. Patients with a negative PET scan have a longer relapse-free interval than patients with a positive PET scan.

Analysis of FDG uptake with hybrid PET using standardised uptake values.

The standardised uptake value (SUV) has been used as an index of glucose metabolism to classify malignant tumours. To date, calculation of SUVs has been restricted to dedicated PET. The aim of this study was to investigate the feasibility of SUV calculation with attenuation-corrected hybrid PET, applying a singles count rate-related calibration method. Calibration factors for hybrid PET at different singles count rates were determined by phantom studies. SUVs were determined for hot spheres in a phantom study as well as for 68 malignant lesions in 56 patients. Recovery coefficients calculated for hot spheres were applied to SUVs of malignant lesions to correct for partial volume and recovery effects. At a sphere-to-background ratio of 10:1, SUVs of spheres with diameters from 34 to 16 mm varied from 5.0 to 1.5 for hybrid PET, and from 8.0 to 4.3 for dedicated PET. SUVs of malignant lesions calculated by hybrid and dedicated PET showed a strong correlation (r=0.95, P<0.001), with a mean percentage difference of 36%. SUVs calculated by hybrid PET were significantly lower than SUVs calculated by dedicated PET (6.2+/-4.3 vs 8.5+/-5.3, P<0.001). Application of recovery coefficients revealed an SUV of 12.2+/-7.3 for hybrid PET versus 10.8+/-6.3 for dedicated PET, with a significant reduction in the mean percentage difference (22%, P<0.01). In conclusion, singles count rate-related calibration factors allow calculation of SUVs with hybrid PET for lesions with a diameter larger than 15 mm. Correction for partial volume and recovery effects is needed to improve the agreement of SUVs of lesions determined by hybrid PET and dedicated PET.

Optimizing ventilation-perfusion lung scintigraphy: parting with planar imaging.

AIM: Of the study was to introduce and verify a ventilation-perfusion (V/Q) acquisition protocol that incorporates new developments in scintigraphy in order to allow for a more balanced comparison with other diagnostic procedures. METHODS: In 103 patients suspect of having pulmonary embolism, V/Q scans were acquired exclusively with SPECT technique. Ventilation was done with ultrafine aerosol. Planar images in eight directions were reconstructed through addition of three consecutive SPECT projections. Three referees examined the scans in regard to type, localization, and extent of V/Q defects. RESULTS: Using this protocol, significantly more defects, especially of subsegmental size, were detected (p < 0.01). Sensitivity, and diagnostic accuracy were also significantly improved (p < 0.01) to 0.96, and 0.99, respectively. Furthermore, kappa values were increased up to 0.82--a relevant enhancement in the ability to precisely localize V/Q defects. CONCLUSION: In conclusion this protocol provides high-resolution tomographic scans as well as high-quality planar images within a short acquisition time. Due to the significant increase in lesion detection, sensitivity, diagnostic accuracy, and anatomical localization of defects, it is a substantial improvement in the diagnosis of pulmonary embolism that will put V/Q scintigraphy on a par with other tomographic methods.

[Characterization of therapy failures in radioiodine therapy of Graves' disease without simultaneous antithyroid agents]. / Charakterisierung von Therapieversagern bei der Radioiodtherapie des Morbus Basedow ohne simultane Thyreostase.

UNLABELLED: Aim of this study was a characterization of radioiodine therapy (RIT) failures in Graves' disease without simultaneous carbimazole. METHOD: 226 patients with a confirmed diagnosis of Graves' disease received 686.8 +/- 376.4 MBq of iodine-131 orally for thyroid ablation. Target dose was 250 Gy. All patients were followed up for 6 months. Therapy failures were compared with successes regarding possible influencing variables initial thyroid volume, thyroid function, immune activity (TRAb), I-131 uptake, effective half-life, absorbed energy dose, age and gender. RESULTS: 212 of 226 patients (93.8%) were treated successfully, 14 (6.2%) showed a hyperthyroidism relapse within 6 months which required a second radioiodine therapy. A success rate of 92.5% (62/67) could also be achieved with 67 patients who were hyperthyroid at the time of RIT. Compared to the therapy successes, the 14 failures achieved significantly lower absorbed doses (223.8 +/- 76.6 Gy vs. 285.2 +/- 82.1 Gy, p < 0.005), but with no significant differences regarding age, thyroid volume, function or TRAb (all p > 0.2). Of the 14 failures, n = 8 reached an absorbed dose < 200 Gy and n = 1 a dose < 250 Gy, although 5 of the failures reached an absorbed dose of > 250 Gy. Stepwise logistic regression revealed only absorbed energy dose as a variable significantly influencing therapy success (p < 0.005), but no influence of initial thyroid volume, function, TRAb value, age (all p > 0.2) or gender (p = 0.13). Two-tailed Fisher's exact test showed no significant influence of gender on success rates (failures/successes: male 1/36, female 13/176, p = 0.48). CONCLUSIONS: Except for the absorbed energy dose, no other significant variable influencing the outcome of radioiodine therapy in Graves' disease without simultaneous carbimazole could be found. It should be noted, though, that 5 therapy failures (2.2%) reached an absorbed energy dose of > 250 Gy.