Anticardiolipin Antibodies Are Elevated in HIV-1 Infected Haemophiliacs but Do Not Predict for Disease Progression

Levels of anticardiolipin antibodies (ACA) were measured in 55 patients with haemophilia A in serum samples obtained in 1983 and in 1987. Twenty-one patients were negative for anti HIV-1 antibodies in 1983 and remained negative in 1987; 34 patients had anti HIV-1 antibodies in 1983; 17 of these latter patients remained asymptomatic, whereas 17 patients developed ARC or AIDS during the 4 years follow-up. Thirteen anti HIV-1 negative patients had elevated ACA levels in 1983; subsequently, a significant decrease was observed in all these subjects (p <0.001). All anti HIV-1 positive patients had elevated ACA levels in 1983; normal values were found in 9 patients in 1987. Yet, these changes were not significant (p >0.05). ACA levels were significantly higher in HIV-1 infected patients than in those without anti HIV-1 antibodies (p <0.05). There was no difference of ACA levels between the two anti HIV-1 positive patient groups, be it in 1983 or be it in 1987 (p >0.05). There was no correlation of ACA levels with serum IgG concentrations, CD4+ lymphocytes, or the consumption of factor VIII concentrates.

Platelet Deposition at Angioplasty Sites and Platelet Survival Time After PTA in lliac and Femoral Arteries: Investigations with Indium-111-Oxine Labelled Platelets in Patients with ASA (1.0 g/Day)-Therapy

In this study we have assessed the deposition of 111-In-oxine-labelled platelets - using a dual radiotracer method - at angioplasty sites of the lower extremities in 20 patients (14 male, 6 female; median age: 60 years) with ASA (1.0 g/day)-therapy. The platelet survival time (PST) - using the multiple hit model -was evaluated before and after percutaneous transluminal angio-plasry, and we also measured the plasma levels of β-thrombo-globulin (β TG) and platelet fuetui 4 (PF 4) before and after PTA.

Before PTA, scintigraphy was positive in only one patient, while 24 hours after PTA a positive scintigraphic result was observed in 16/20 patients. The median target/non target-ratio was 1.0 (0.66-1.3) before PTA, and this ratio increased significantly (p <0.0005) to 1.53 (1.0-3.3) after PTA.

The median PST decreased significantly (185.0 hours before PTA → 145.2 hours after PTA; p <0.001), while the median platelet turnover increased from 34,000/μl/day to 47,900/μl/day(p<0.01).

The median plasma levels of the platelet specific proteins increased significantly immediately after PTA (p <0.001), but one day later they were not significantly different from the pretreatment values.

The quantitative methods used in this study seem a valuable tool to evaluate the effects of different therapeutical - especially antiplatelet - interventions after PTA in humans, thus helping to find the best antithrombotic regimen for this widely used therapeutical procedure.

[18F]FDG-PET/CT and MRI for initial pelvic lymph node staging in patients with cervical carcinoma: The potential usefulness of [18F]FDG-PET/MRI

The current study aimed to determine the optimum diagnostic imaging technique out of magnetic resonance imaging (MRI), ¹⁸F-fludeoxyglucose positron emission tomography/computed tomography ([¹⁸F]FDG-PET/CT, otherwise known as PET/CT) and [¹⁸F]FDG-PET/MRI (otherwise known as PET/MRI) for the pelvic lymph node staging (N-staging) of untreated cervical carcinoma (CC). A total of 27 patients were included in the present study. All patients had undergone pre-treatment with PET/CT and MRI ≤45 days prior to undergoing a lymphadenectomy. The results from PET (separated from PET/CT), MRI and the statistically combined results of (virtual) PET/MRI were compared to those from histological analyses (the gold standard). A per-patient-based analysis of the detection of pelvic lymph node metastases indicated that PET/MRI had a sensitivity of 64%. The specificity of PET/CT and MRI were 69 and 62%, respectively. The positive predictive value (PPV) was 69 and 64% for PET/CT and MRI, respectively. The negative predictive value (NPV) was 64 and 62% for PET/CT and MRI, respectively. The sensitivity of the PET-guided PET/MRI and the MRI-guided PET/MRI was 64% for both. The specificity of the PET-guided PET/MRI and the MRI-guided PET/MRI was 77 and 62%, respectively. The PPV was 75% for PET-guided PET/MRI and 64% for MRI-guided PET/MRI, and the NPV was 67 and 62%, respectively. PET/CT and the virtual PET/MRI exhibited the same low sensitivity (64%). PET/MRI exhibited slightly better results than PET/CT regarding specificity (77 vs. 69%, respectively), PPV (75 vs. 69%, respectively) and NPV (67 vs. 64%, respectively). The results of the present study suggested that PET/CT and MRI are not optimal diagnostic modalities, and that PET/MRI does not necessarily lead to better results than PET/CT, in the pelvic N-staging of CC.

Myokardszintigraphie mit kationischen 99mTc-Komplexen

This report summarizes the results which have been achieved by the use of 99mTc-labeled cationic complexes for myocardial scintigraphy. Radiopharma-cological aspects of 99mTc(lll)-CI2 (D.MPE)2 and 99mTc(l)-TBI as well as their scintigraphic behaviour in patients with coronary artery disease are described. In contrast to 99mTc-CI2 (DMPE)2, 99mTc-TBI could be used successfully for the assessment of ischemic and infarcted myocardial tissue. Yet in general, 201TI scintigraphic findings remained superior. However, from the considerable improvements achieved it is likely that soon a 99mTc-labeled tracer will be available to serve as clinical useful myocardial imaging agent

Combined transmission and 99mTc-sestamibi emission tomography for localization of mediastinal parathyroid glands

Aim: Although parathyroid scintigraphy using 99mTc-sestamibi is considered the best preoperative localization method for hyperfunctioning parathyroid tissue it lacks the anatomical details required for successful, minimal invasive surgery of ectopic parathyroid lesions. This study presents the role of combined SPECT/X-ray-CT imaging in a single device for localization of mediastinal parathyroid glands. Methods: 99mTc-sestamibi SPECT/ X-ray-CT was performed by gamma camera-mounted anatomical X-ray tomography (GMAXT; GE Medical systems, Millenium VG with Hawkeye) in four patients with ectopic parathyroid glands (two patients with primary, two with persistent secondary hyperparathyroidism). The device contains an X-ray tube and a set of detectors that rotate around the patient combined with a gamma camera. For comparison with GMAXT additionally high resolution computed tomography images of the neck and mediastinum were performed. Results: Correct preoperative localization was achieved. The parathyroid glands were located in the anterior mediastinum. High resolution computed tomography could not provide further details. Three patients were operated by a minimal invasive open and one patient by a transsternal approach because of concomitant aortic valve replacement. Conclusion: 99mTc-sestamibi/X-ray-CT fusion imaging in a single device can accurately localise ectopic or supernumerary mediastinal parathyroid tumours in primary and secondary hyperparathyroidism. Morbidity, radiation exposure, time, and costs are reduced by avoiding multiple diagnostic examinations and minimal invasive parathyroid surgery becomes possible.

Attenuation correction for myocardial perfusion imaging

Aim: We investigated the impact of photon attenuation in myocardial perfusion imaging with SPECT and PET in patients with coronary artery disease. In fact, the regional tracer distribution can be quantitatively assessed by polar map analysis if the effects of photon attenuation are accounted for. PET imaging permits accurate measurement of and correction for photon attenuation, whereas results of attenuation correction in SPECT imaging have been inconsistent. Patients, methods: We compared photon attenuation in resting perfusion imaging studies with SPECT (99mTc-sestamibi) and PET (13N-ammonia) from 21 patients. Transaxial images were reconstructed with and without attenuation correction and reoriented into short axis images. Polar map analysis was utilized to generate regional tracer uptake in six anatomical segments. Results: Average segmental photon attenuation calculated as the ratio of counts in corrected and uncorrected images was 7.2 ± 1.4 in SPECT and 14.0 ± 3.1 in PET imaging (p <0.01). This attenuation factor was significantly related to body mass index for both methods (p <0.001). While attenuation correction for SPECT imaging did compensate for attenuation effects in the inferior wall (from –15% to +6% vs. PET), relative tracer uptake in the anterior wall in SPECT images was significantly reduced after attenuation correction (from –2% to –18% vs. PET, p <0.01). Conclusion: Differential effects of attenuation correction for myocardial SPECT perfusion imaging need to be considered when algorithms designed to compensate effects of photon attenuation in SPECT imaging are employed in clinical practice.

Influence of PET reconstruction para meters on the TrueX algorithm

With the increasing use of functional imaging in modern radiotherapy (RT) and the envisaged automated integration of PET into target definition, the need for reliable quantification of PET is growing. Reconstruction algorithms in new PET scanners employ pointspread-function (PSF) based resolution recovery, however, their impact on PET quantification still requires thorough investigation. Patients, material, methods: Measurements were performed on a Siemens PET/CT using an IEC phantom filled with varying activity. Data were reconstructed using the OSEM (Gauss filter) and the PSF TrueX (Gauss and Allpass filter) algorithm with all available products of iterations (i) and subsets (ss). The recovery coeffcient (RC) and threshold defining the real sphere volume were determined for all settings and compared to the clinical standard (4i21ss). PET acquisitions of eight lung patients were reconstructed using all algorithms with 4i21ss. Volume size and tracer uptake were determined with different segmentation methods. Results: The threshold for the TrueX was lower (up to 40%) than for the OSEM. The RC for the different algorithms and filters varied. TrueX was more sensitive to permutations of i and ss and only the RC of the OSEM stabilised with increasing number. For patient scans the difference of the volume and activity between TrueX and OSEM could be reduced by applying an adapted threshold and activity correction. Conclusion: The TrueX algorithm results in excellent diagnostic image quality, however, guidelines for native algorithms have to be extended for PSF based reconstruction methods. For appropriate tumour delineation, for the TrueX a lower threshold than the 42% recommended for the OSEM is necessary. These filter dependent thresholds have to be verified for different scanners prior to using them in multicenter trials.

Uptake of 18F-FLT and 18F-FDG in primary head and neck cancer correlates with survival

The aim of the study was to determine the practicability of 18F-FLT in tumours of the head and neck area in terms of visualization, a possible correlation between FLT uptake and proliferation fraction as determined by Ki-67 immunostaining, and if tumoural FLT-uptake has a prognostic meaning, as determined by a correlation to patient survival time. Results were compared to 18F-FDG. Patients, methods: 20 patients with previously untreated lesions of the head and neck area, which were clinically highly suspicious to be malignant, underwent PET scans with 18F-FLT and 18F-FDG, a CT of the head and neck area, and a biopsy. Tumour tracer uptake was determined by standardized uptake value (SUV) normalized to body weight and /non-tumor ratios (T/N). 18F-FDG and 18F-FLT uptake were compared with histopathologic and immunohistochemical results. Results: 19 patients had malignant tumours; one patient had a benign cystadenoma (so called Warthin's tumour) of the parotid gland. One negative lesion turned out to be a malignant T1 stage squamous cell carcinoma in both PET scans, the Warthin's tumour was false positive with 18F-FDG but showed only faint uptake with 18F-FLT, resulting in a sensitivity of 95 % for both tracers. Of all lesions, maximum SUVs of 18F-FLT ranged from 1.53 to 11.70 (mean ± SD 5.81 ± 2.28) those of FDG from 2.63 to 16.50 (mean ± SD 8.91 ± 3.58), p < 0.001. 18F-FLT-T/N ranged from 0.94 to 5.85 (mean ± SD, 3.18 ± 1.21), 18F-FDG-T/N was from 0.92 to 7.50 (mean ± SD, 3.6 ± 1.74), n.s. The mean survival time was 18 months in a maximum follow up time of 36 months. A significant correlation between both PET tracers and survival was detected, but no correlation between the amount of Ki-67 positive cells and FLT. Conclusion: In head and neck cancer in the primary setting 18F-FLT does not provide additional visual information in comparison to 18F-FDG.18F-FLT uptake is inversely correlated with patient survival, as well as 18F-FDG.

Clinical Value of 18F-fluorodihydroxyphenylalanine Positron Emission Tomography/Contrast-enhanced Computed Tomography (18F-DOPA PET/CT) in Patients with Suspected Paraganglioma

AIM

To evaluate (18)F-fluorodihydroxyphenylalanine-positron emission tomography/ contrast-enhanced computed tomography ((18)F-DOPA PET/CT) for the detection of paragangliomas (PARA) without any patient selection, such as genetic predisposition for the development of these tumors, history of metastatic PARA or hormonal status.

PATIENTS AND METHODS

In this retrospective study, 28 consecutive patients (15 women, 13 men; mean age=46.4 years; age range=19-73 years), who were referred to our PET/CT center for the detection of clinically suspected PARA, were included. Final diagnosis was confirmed by histological reports of surgically proven lesions and/or clinical follow-up (including laboratory results and/or PET/CT follow-up).

RESULTS

On a per-lesion basis (45 lesions) analysis, there was a sensitivity of 64.3% for CT, 73.8% for PET, 100% for PET/CT and a positive predictive value (PPV) of 93.1% for CT, 96.9% for PET and 100% for PET/CT. On a per-patient basis analysis, the sensitivity, specificity and accuracy for CT was 86.7%, 84.6% and 85.7%, respectively, and, for PET 80%, 100% and 89.3%, respectively, and, for PET/CT 100%.

CONCLUSION

Based on our data, (18)F-DOPA PET/CT is a "one-stop diagnostic modality" for the assessment of patients with suspected PARA.

Relevance of calcitonin cut-off in the follow-up of medullary thyroid carcinoma for conventional imaging and 18-fluorine-fluorodihydroxyphenylalanine PET

AIM

The American thyroid association (ATA) recommends that additional imaging procedures supplement cervical ultrasonography (US) in any patient with a basal calcitonin value above 150 pg/ml in the follow-up of medullary thyroid carcinoma (MTC). The aim of the present study was to reaffirm or challenge this cut-off for 18-Fluorine-Fluorodihydroxyphenylalanine positron emission tomography (18F-DOPA PET) and conventional imaging ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI)).

MATERIALS AND METHODS

Thirty-nine patients (18 females, 21 males), mean age 62 years, range from 35 to 86, followed-up for MTC were included in the present retrospective study. In our patients 64 18F-DOPA scans, 28 neck US, 28 CT and 8 MRI were performed. For all cases basal calcitonin values were available. Sensitivity and specificity of 18F-DOPA PET and conventional imaging (US, CT, MRI) related to calcitonin values were calculated.

RESULTS

According to the calcitonin cut-off of 150 pg/ml, we found the following sensitivities and specificities: 79% and 80% for 18F-DOPA PET, 75% and 92% for US, 80% and 25% for CT, 50% and 75% for MRI. Taking the level of detectable calcitonin, we calculated the following sensitivities: 52% for 18F-DOPA PET, 46% for US, 79% for CT and 38% for MRI.

CONCLUSION

We cannot confirm the calcitonin cut-off proposed by the ATA for the detection of MTC recurrences and contemporaneously we cannot state that 18F-DOPA PET has a very high sensitivity. For the neck region 18F-DOPA PET and US showed similar results. 18F-DOPA PET/CT seems to be the best imaging modality for whole-body tumor detection. Bone metastases are best detected by MRI.

(18)F-DOPA PET/CT and MRI: description of 12 histologically-verified pheochromocytomas

AIM

To describe the (18)F-fluorodihydro-xyphenylalanine ((18)F-DOPA), positron emission tomography (PET) and magnetic resonance imaging (MRI) appearance of pheochromocytomas, with a focus on the presence or absence of typical MRI features.

MATERIALS AND METHODS

Eleven patients with histologically-verified pheochromocytoma [sporadic (n=9), multiple endocrine neoplasia (MEN) 2A syndrome (n=2)] were enrolled retrospectively. All patients underwent an MRI examination of the upper abdomen. Nine out of 11 patients underwent (18)F-DOPA PET/CT, and the remaining two patients underwent independent PET and computed tomography (CT) examinations. (18)F-DOPA-PET/CT examinations were considered positive when an increased tracer accumulation in the adrenal region, as shown on CT images, was observed. When an adrenal mass was detected on MRI, the T1 and T2 signal intensity and contrast enhancement pattern were recorded. Based on MR characteristics, the lesions were divided into typical and atypical.

RESULTS

Ten out of 11 patients had one lesion, while one patient had two lesions. All pheochromocytomas were detected by both PET/CT and MRI. On (18)F-DOPA scans, all lesions showed an increased tracer accumulation, with a mean maximum standardized uptake value (SUVmax) of 13.7±5.75. Eight out of 12 pheochromocytomas exhibited typical MRI features, with intermediate signal intensity on T1-weighted images in-phase, absence of signal drop on T1-weighted images out-of-phase, high signal intensity on T2-weighted images, and clear contrast enhancement in the arterial phase. The remaining four lesions exhibited atypical MRI features, namely absence of one of the listed criteria.

CONCLUSION

In the assessment of pheochromocytoma, the combination of (18)F-DOPA PET with MRI is superior to MRI-alone. (18)F-DOPA PET/MRI may yield a higher diagnostic confidence for the detection of pheochromocytoma than (18)F-DOPA PET/CT.

Improved quality of life in patients treated with Peptide radionuclides

Peptide receptor radionuclide therapy (PRRT) has recently been established as an important treatment modality for somatostatin receptor (SSTR)-positive tumors. The purpose of this study was to evaluate the clinical response, side-effects as well as the quality of life following ⁹⁰Y-DOTA-lanreotide (DOTALAN) and/or ⁹⁰Y-DOTA-Tyr ³-DPhe¹-octreotide (DOTATOC) therapy in patients with progressive metastatic disease during a 6-year follow-up period. Following dosimetric evaluation with ¹¹¹In-DOTALAN and ¹¹¹In-DOTATOC, 13 patients with estimated absorbed tumor doses of >5 Gy/GBq (carcinoid, n = 5; radioiodine-negative thyroid cancer, n = 4; gastrinoma, n = 1; insulinoma, n = 1; glucagonoma, n = 1; glomus jugularis tumor, n = 1) were assigned for PRRT. A dose of 925 MBq of ⁹⁰Y-DOTALAN (four patients) or 1.85–3.7 GBq of ⁹⁰Y-DOTATOC (10 patients) was administered intravenously and repeated every 4–8 weeks. Tumor dosimetry was performed prior to and under therapy, re-staging every 2–3 months. Pain intensity, Karnofsky score and general symptoms were evaluated in order to determine quality of life. Patients were followed until death. Altogether, 53 infusions of PRRT (1.85–14.1 GBq) were administered. After the first follow-up of 3 months of ⁹⁰Y-DOTALAN therapy, stable disease (SD) was observed in one patient and progressive disease (PD) in three patients. With ⁹⁰Y-DOTATOC therapy, SD was found in all 10 patients. During the re-evaluation period (4–27 months), one patient had to be shifted from ⁹⁰Y-DOTALAN to ⁹⁰Y-DOTATOC therapy due to reduced ¹¹¹In-DOTALAN uptake after 5.5 GBq. In the first 6 months after PRRT with DOTATOC, SD was found in nine of 10 patients and PD in one patient. Thereafter, SD was observed in two patients and PD in eight patients. Nine of 13 patients after PRRT with either DOTALAN or DOTATOC died. None of the patients had experienced severe acute hematological side-effects. Transient thrombocytopenia or lymphocytopenia was seen in 10 patients after 3.7 GBq, and a skin reaction in one patient. Total accumulated kidney dose ranged between 4 and 64 Gy, with reduced creatinine clearance in two patients. Pain relief was achieved in three of three patients after ~3.7 GBq ERT within 4–6 months. Appetite, weight, Karnofsky score and general well-being had improved in patients with SD during and after therapy. Based on the results of this study conducted on a small group of patients, we conclude that PRRT may offer an alternative treatment option for SSTR-positive tumors, with only mild transient side-effects and a marked improvement in the quality of life.

Optimization of [11C]DASB-synthesis: vessel-based and flow-through microreactor methods

The intention for the present study was to implement a microfluidic set-up for N-(11)C-methylations in a flow-through microreactor device with [(11)C]DASB as model-compound and [(11)C]CH(3)I and [(11)C]CH(3)OTf, respectively, as (11)C-methylation agents. Due to an observed "aging" effect of the (11)C-methylation agents' solution, this goal was not achieved. Nevertheless, based on these observations, the time consumption for the vessel-based routine production of [(11)C]DASB was reduced (34±1 min) and RCY was increased to 45.1±4.6% (EOB; 5.2±0.95 GBq EOS).

Imaging of highly malignant osteosarcoma with iodine-123-vascular endothelial growth factor

OBJECTIVE

Vascular endothelial growth factor (VEGF) is an important angiogenic factor, and its receptors have been shown to be overexpressed in various human carcinomas. In this study, we investigated the role of scanning with iodine-123 ((123)I)-labelled VEGF(165) in patients with highly malignant osteosarcoma.

METHODS

Two patients (a 15-year-old female and a 14-year-old male) with osteosarcoma were injected with 140 MBq [<130 pmol (<5 µg) VEGF(165) per patient] of (123)I-VEGF(165). Dynamic acquisition was initiated immediately after administration and carried out until 30 min after injection. Whole-body images were done in anterior and posterior views at various time points. All patients underwent single-photon emission tomography imaging.

RESULTS

(123)I-VEGF(165) scans were positive in these patients. Sequential images clearly showed increased (123)I-VEGF(165) activity in osteosarcoma lesions. The tumour lesions were still visualized in whole-body images and single-photon emission tomography examinations 2 h after injection. Intravenous injection of (123)I-VEGF(165) did not cause any side effects.

CONCLUSION

Our results suggest that (123)I-VEGF(165) receptor scintigraphy may be useful for the visualization of highly malignant osteosarcoma and/or metastasis and the angiogenic activity of the tumour.

Radiolabeling of [18F]altanserin - a microfluidic approach

INTRODUCTION

Our aim was the optimization of radiochemical parameters for the microfluidic preparation of [(18)F]altanserin. The four main parameters evaluated were (1) precursor concentration, (2) reaction temperature, (3) bolus flow rate through the microreactor and (4) bolus volume.

METHODS

For the determination of optimal reaction conditions within a flow-through microreactor synthesizer, 5-400 μL of precursor and dried [(18)F]fluoride solution were simultaneously pushed through the temperature-controlled reactor (180-220°C) with defined bolus flow rates of 10-60 μL/min. Radiochemical incorporation yields (RCIYs) were examined using a thin layer chromatography (TLC) set-up and radio- high-performance liquid chromatography (HPLC).

RESULTS

Optimum reaction parameters for the microfluidic set-up were determined as following: 220°C, 5-10 μL/min pump rate per reactant (10-20 μL/min reaction overall flow rate) and 2mg/mL precursor concentration in the reaction mixture. Applying these optimized conditions, RCIYs of 53.7 ± 7.9 were observed for scaled-up preparations. A positive "bolus effect" was observed: applying higher reaction volume resulted in increased RCIYs.

CONCLUSION

This study proved that the reaction bolus volume is an essential parameter influencing the RCIY of [(18)F]altanserin. A possible explanation is the inhomogeneous distribution within the reaction volume probably caused by diffusion at the bolus interface. This important finding should be considered an important variable for the evaluation of all novel radiotracers labeled using a flow-through reactor device.

Coronary vasoreactivity in subjects with thyroid autoimmunity and subclinical hypothyroidism before and after supplementation with thyroxine

BACKGROUND

The association of subclinical hypothyroidism (SCH) with increased risk for cardiovascular disease is still controversial. This study aimed to examine coronary vascular reactivity by positron emission tomography (PET) in asymptomatic patients with SCH before and after levothyroxine (LT4) supplementation.

METHODS

Ten patients (7 women and 3 men; mean age 43±15 years) with untreated autoimmune SCH, defined by elevated levels of thyroid-stimulating hormone (mean TSH: 16.9±11.3 μU/mL), normal levels of free thyroxine (0.9±0.1 μg/mL), free triiodothyronine (3.2±0.4 pg/mL), and positive thyroid peroxidase antibodies were studied. Eight euthyroid subjects with similar low-risk cardiovascular risk profile served as controls. Myocardial blood flow (MBF) and coronary flow reserve (CFR) were quantitatively assessed with rest/stress N-13 ammonia PET at baseline and after 6 months of LT4 replacement therapy (given only to patients).

RESULTS

At baseline, stress MBF and CFR corrected (c) for rate pressure product (RPP) and myocardial vascular resistance (MVR) during stress were significantly reduced in SCH compared with controls (stress MBF: 2.87±0.93 vs. 4.79±1.16 mL/g/min, p=0.003; CFR: 2.6±0.73 vs. 4.66±1.38, p=0.004; MVR: 40.14±18.76 vs. 20.47±6.24 mmHg/mL/min, p=0.02). Supplementation therapy with LT4 normalized TSH in all subjects and was associated with an increase in CFR (2.6±0.73 vs. 3.81±1.19, p=0.003) and with a tendency toward a decrease in MVR. Differences in CFR between SCH and controls were also seen after correction of resting MBF for RPP.

CONCLUSIONS

In asymptomatic subjects with SCH due to thyroid autoimmunity, coronary microvascular function is impaired and improves after supplementation with LT4. This may partially explain the increased cardiovascular risk attributed to SCH.

Optimization of the radiosynthesis of the Alzheimer tracer 2-(4-N-[11C]methylaminophenyl)-6-hydroxybenzothiazole ([11C]PIB)

[(11)C]PIB is still the standard PET compound for Alzheimer imaging targeting beta-amyloid plaques. We aimed to establish a fully-automated procedure for the synthesis and purification of [(11)C]PIB with a high degree of reliability and improved specific activity as well as a suitable and fast quality control assay. The optimum reaction conditions were 75°C, 4 mg/mL precursor yielding at 48.0±2.7% (EOS, based on [(11)C]CH(3)OTf, corrected for decay), 183±14 GBq/μmol specific activity and >99% radiochemical purity. Time consumption was kept to a minimum (40 min from EOB) and overall yields were enough to serve 2 consecutive patients with a single preparation.

Assessment of left ventricular volumes, ejection fraction and mass

Aim: We compared and delineated possible differences of model-based analysis of ECGgated SPECT using 99mTc-sestamibi (Tc- SPECT) with ECG-gated 18F-fluorodeoxyglucose- PET (FDG-PET) for determination of enddiastolic (EDV) and end-systolic (ESV) cardiac volumes, left ventricular ejection fraction (LVEF), and myocardial mass (LVMM). Patients, methods: 24 patients (21 men; age: 54 ± 12years) with coronary artery disease underwent Tc-SPECT and FDG-PET imaging for evaluation of myocardial perfusion and viability. By using model-based analysis EDV, ESV, LVEF and LVMM were calculated from short axis images of both Tc-SPECT and FDGPET. Results: Left ventricular volumes by Tc- SPECT and FDG-PET were 176 ± 60 ml and 181 ± 59 ml for EDV, and 97 ± 44 ml and 103 ± 45 ml for ESV respectively, LVEF was 47 ± 8% by Tc-SPECT and 45 ± 9% by FDG-PET. The LVMM was 214 ± 40 g (Tc-SPECT) and 202 ± 43 g (FDG-PET) (all p = NS, paired t-test). A significant correlation was observed between Tc-SPECT and FDG-PET imaging for calculation of EDV (r = 0.93), ESV (r = 0.93), LVEF (r = 0.83) and LVMM (r = 0.72). Conclusion: ECG-gated Tc-SPECT and FDG-PET using two tracers with different characteristics (perfusion versus metabolism) showed close agreement concerning measurements of left ventricular volumes, contractile function and myocardial mass by using a model-based analysis.

Evaluating repetitive 18F-fluoroazomycin-arabinoside (18FAZA) PET in the setting of MRI guided adaptive radiotherapy in cervical cancer

BACKGROUND

The aim of this pilot study was to assess tumour hypoxia in patients with cervical cancer before, during and after combined radio-chemotherapy and Magnetic Resonance Imaging (MRI) guided brachytherapy (BT) by use of the hypoxia Positron Emission Tomography (PET) tracer (18)F-fluoroazomycin-arabinoside ((18)FAZA ).

MATERIAL AND METHODS

Fifteen consecutive patients with locally advanced cervical cancer referred for definitive radiotherapy (RT) were included in an approved clinical protocol. Stage distribution was 3 IB1, 1 IB2, 10 IIB, 1 IIIB, tumour volume was 55 cm(3) (+/- 67, SD). Dynamic and static (18)FAZA -PET scans were performed before, during and after external beam therapy (EBRT) and image guided BT +/- concomitant cisplatin. Dose was prescribed to the individual High Risk Clinical Target Volume (HR CTV) taking into account the dose volume constraints for adjacent organs at risk.

RESULTS

Five patients had visually identifiable tumours on (18)FAZA -PET scans performed prior to radio-chemotherapy and four patients before brachytherapy. One of five (18)FAZA PET positive patients had incomplete remission three months after RT, one had regional recurrence. Four of ten (18)FAZA-PET negative patients developed distant metastases. The one patient with incomplete remission received 69 Gy (D90) in the HR CTV, whereas all other patients received mean 99 Gy (+/-12, SD).

CONCLUSION

PET imaging with (18)FAZA is feasible in patients with cancer of the uterine cervix. However, its predictive and prognostic value remains to be clarified. This applies in particular for the additional value of (18)FAZA-PET compared to morphologic repetitive MRI within the setting of image guided high dose radiotherapy which may contribute to overcome hypoxia related radioresistance.

[18F]FE@SUPPY and [18F]FE@SUPPY:2--metabolic considerations

INTRODUCTION

Recently, [(18)F]FE@SUPPY and [(18)F]FE@SUPPY:2 were introduced as the first positron emission tomography (PET) tracers for the adenosine A(3) receptor. Thus, aim of the present study was the metabolic characterization of the two adenosine A(3) receptor PET tracers.

METHODS

In vitro carboxylesterase (CES) experiments were conducted using incubation mixtures containing different concentrations of the two substrates, porcine CES and phosphate-buffered saline. Enzymatic reactions were stopped by adding acetonitrile/methanol (10:1) after various time points and analyzed by a high-performance liquid chromatography (HPLC) standard protocol. In vivo experiments were conducted in male wild-type rats; tracers were injected through a tail vein. Rats were sacrificed after various time points (n=3), and blood and brain samples were collected. Sample cleanup was performed by an HPLC standard protocol.

RESULTS

The rate of enzymatic hydrolysis by CES demonstrated Michaelis-Menten constants in a micromolar range (FE@SUPPY, 20.15 microM, and FE@SUPPY:2, 13.11 microM) and limiting velocities of 0.035 and 0.015 microM/min for FE@SUPPY and FE@SUPPY:2, respectively. Degree of metabolism in blood showed the following: 15 min pi 47.7% of [(18)F]FE@SUPPY was intact compared to 33.1% of [(18)F]FE@SUPPY:2; 30 min pi 30.3% intact [(18)F]FE@SUPPY was found compared to 15.6% [(18)F]FE@SUPPY:2. In brain, [(18)F]FE@SUPPY:2 formed an early hydrophilic metabolite, whereas metabolism of [(18)F]FE@SUPPY was not observed before 30 min pi

CONCLUSION

Knowing that metabolism in rats is several times faster than in human, we conclude that [(18)F]FE@SUPPY should be stable for the typical time span of a clinical investigation. As a consequence, from a metabolic point of view, one would tend to decide in favor of [(18)F]FE@SUPPY.

PET and PET/CT in endocrine tumours

Functional information provided by PET tracers together with the superior image quality and the better data quantification by PET technology had a changing effect on the significance of nuclear medicine in medical issues. Recently introduced hybrid PET/CT systems together with the introduction of novel PET radiopharmaceuticals have contributed to the fact that nuclear medicine has become a growing diagnostic impact on endocrinology. In this review imaging strategies, different radiopharmaceuticals including the basic mechanism of their cell uptake, and the diagnostic value of PET and PET/CT in endocrine tumours except differentiated thyroid carcinomas will be discussed.

Radiosynthesis of a novel potential adenosine A3 receptor ligand, 5-ethyl 2,4-diethyl-3-((2-[18F]fluoroethyl)sulfanylcarbonyl)-6-phenylpyridine-5-carboxylate ([18F]FE@SUPPY:2)

Since, to date very limited information on the distribution and function of the adenosine A3 receptor is available, the development of suitable radioligands is needed. Recently, we introduced [ 18F]FE@SUPPY (5-(2-[ 18F]fluoroethyl) 2,4-diethyl-3-(ethylsulfanylcarbonyl)-6-phenylpyridine-5-carboxylate) as the first PET-ligand for the A3R. Regarding the metabolic profile – this class of dialkylpyridines comprises two ester functions within one molecule, one carboxylic and one thiocarboxylic – one could expect carboxylesterases significantly contributing to cleavage and degradation. Therefore, our aim was the development of [ 18F]FE@SUPPY:2 (5-ethyl 2,4-diethyl-3-((2-[ 18F]fluoroethyl)sulfanylcarbonyl)-6-phenylpyridine-5-carboxylate), the functional isomer containing the label at the thiocarboxylic moiety.

For satisfactory yields in high scale radiosyntheses, a reaction temperature of 75 °C has to be applied for at least 20 min using 20 mg/mL of precursor. So far, 6 complete high-scale radiosyntheses were performed. Starting from an average of 51.2±21.8 GBq (mean±SD) [ 18F]fluoride, 5.8±4.1 GBq of formulated [ 18F]FE@SUPPY:2 (12.0±5.4%, based on [ 18F]fluoride, not corrected for decay) were prepared in 75±8 min.

Preparation and radiosynthesis of [18F]FE@CFN (2-[18F]fluoroethyl 4-[N-(1-oxopropyl)-N-phenylamino]-1-(2-phenylethyl)-4-piperidinecarboxylate): a potential μ-opioid receptor imaging agent

PET imaging of the μ-opioid receptor (OR) is still restricted to [11C]carfentanil ([11C]CFN) but its use is limited due to its short half-life and high agonistic potency. Recently, the radiosynthesis of [18F]fluoroalkyl esters of CFN was proposed, unfortunately yielding products not suitable for human PET due to their low specific activities. Therefore, our rationale was to develop a reliable radiosynthesis of a [18F]fluoroethylated CFN derivative overcoming these drawbacks.

The [18F]fluoroethyl ester of carfentanil, [18F]FE@CFN (2-[18F]fluoroethyl 4-[N-(1-oxopropyl)-N-phenylamino]-1-(2-phenylethyl)-4-piperidinecarboxylate), and its corresponding inactive standard compound were prepared. Purification of [18F]FE@CFN was achieved via a simple solid phase extraction method. [18F]FE@CFN was prepared with excellent purity (> 98%) and sufficient yields. Specific activity surpassed the level required for safe administration. We therefore conclude that our simplified synthesis of [18F]FE@CFN, for the first time, overcomes the shortcomings of [11C]CFN and the previously suggested alternatives, namely, (1) longer half-life; (2) easy production and (3) adequate specific activity, should make a wider application possible. Hence, [18F]FE@CFN may become a valuable PET tracer for the imaging of the μ-OR in human brain and heart.

Diagnostic imaging in Merkel cell carcinoma: lessons to learn from 16 cases with correlation of sonography, CT, MRI and PET

OBJECTIVE

The authors report imaging findings in a series of 16 patients with MCC, a rare tumour which is often managed primarily by a dermatologist. To our knowledge, no equivalent series of MCC has been described in the nuclear medicine literature.

MATERIAL AND METHODS

In this IRB-approved retrospective noncomparative case series 16 patients with biopsy-proven Merkel cell carcinoma were included between January 1999 and October 2007. Twenty-nine whole body PET scans (18F-FDG n=24, 18F-FDOPA n=5) in 16 patients were retrospectively reviewed with regard to tracer uptake in six anatomical sites per patient. For 127/144 of FDG-PET evaluated regions and 68/144 of regions depicted by conventional imaging methods, a valid standard of reference could be obtained. A combined standard of reference was applied, which consisted of histopathology (lymphadenectomy or biopsy) or clinical or radiological follow-up for at least 12 months.

RESULTS

the mean FDG uptake over the clinicopatholigical verified FDG avid areas was 4.7 SUV (1.5-9.9 SUV). The region based assessment of diagnostic value, in consideration of the standard of reference, resulted in a sensitivity of 85.7% and a specificity of 96.2% of FDG-PET (n=127) and in a combined sensitivity of 95.5% and a specificity of 89.1% for morphological imaging methods (n=68). Differences between methods did not reach statistical significance (p=1.00, p=0.18).

CONCLUSIONS

FDG-PET is a highly useful whole body staging method of comparable value compared to conventional imaging methods with restricted field of view. The lessons learned from case series are discussed.

Uptake of (18)F-FLT and (18)F-FDG in primary head and neck cancer correlates with survival

The aim of the study was to determine the practicability of (18)F-FLT in tumours of the head and neck area in terms of visualization, a possible correlation between FLT uptake and proliferation fraction as determined by Ki-67 immunostaining, and if tumoural FLT-uptake has a prognostic meaning, as determined by a correlation to patient survival time. Results were compared to (18)F-FDG.

PATIENTS, METHODS

20 patients with previously untreated lesions of the head and neck area, which were clinically highly suspicious to be malignant, underwent PET scans with (18)F-FLT and (18)F-FDG, a CT of the head and neck area, and a biopsy. Tumour tracer uptake was determined by standardized uptake value (SUV) normalized to body weight and /non-tumor ratios (T/N). (18)F-FDG and (18)F-FLT uptake were compared with histopathologic and immunohistochemical results.

RESULTS

19 patients had malignant tumours; one patient had a benign cystadenoma (so called Warthin's tumour) of the parotid gland. One negative lesion turned out to be a malignant T1 stage squamous cell carcinoma in both PET scans, the Warthin's tumour was false positive with (18)F-FDG but showed only faint uptake with (18)F-FLT, resulting in a sensitivity of 95 % for both tracers. Of all lesions, maximum SUVs of (18)F-FLT ranged from 1.53 to 11.70 (mean +/- SD 5.81 +/- 2.28) those of FDG from 2.63 to 16.50 (mean +/- SD 8.91 +/- 3.58), p < 0.001. (18)F-FLT-T/N ranged from 0.94 to 5.85 (mean +/- SD, 3.18 +/- 1.21), (18)F-FDG-T/N was from 0.92 to 7.50 (mean +/- SD, 3.6 +/- 1.74), n.s. The mean survival time was 18 months in a maximum follow up time of 36 months. A significant correlation between both PET tracers and survival was detected, but no correlation between the amount of Ki-67 positive cells and FLT.

CONCLUSION

In head and neck cancer in the primary setting (18)F-FLT does not provide additional visual information in comparison to (18)F-FDG.(18)F-FLT uptake is inversely correlated with patient survival, as well as (18)F-FDG.

Preparation and first evaluation of [(18)F]FE@SUPPY: a new PET tracer for the adenosine A(3) receptor

INTRODUCTION

Changes of the adenosine A(3) receptor subtype (A3AR) expression have been shown in a variety of pathologies, especially neurological and affective disorders, cardiac diseases and oncological and inflammation processes. Recently, 5-(2-fluoroethyl) 2,4-diethyl-3-(ethylsulfanylcarbonyl)-6-phenylpyridine-5-carboxylate (FE@SUPPY) was presented as a high-affinity ligand for the A3AR with good selectivity. Our aims were the development of a suitable labeling precursor, the establishment of a reliable radiosynthesis for the fluorine-18-labeled analogue [(18)F]FE@SUPPY and a first evaluation of [(18)F]FE@SUPPY in rats.

METHODS

[(18)F]FE@SUPPY was prepared in a feasible and reliable manner by radiofluorination of the corresponding tosylated precursor. Biodistribution was carried out in rats, and organs were removed and counted. Autoradiography was performed on rat brain slices in the presence or absence of 2-Cl-IB-MECA.

RESULTS

Overall yields and radiochemical purity were sufficient for further preclinical and clinical applications. The uptake pattern of [(18)F]FE@SUPPY found in rats mainly followed the described mRNA distribution pattern of the A3AR. Specific uptake in brain was demonstrated by blocking with a selective A3AR agonist.

CONCLUSION

We conclude that [(18)F]FE@SUPPY has the potential to serve as the first positron emission tomography tracer for the A3AR.

No immunological benefit of selenium in consecutive patients with autoimmune thyroiditis

BACKGROUND

Recently it has been demonstrated that after selenium (Se) supplementation in autoimmune thyroiditis (AIT) patients, there was a significant decrease of thyroid peroxidase (TPO) autoantibody (TPOAb) levels. The aim of our study was to evaluate the immunological benefit of Se administration in unselected AIT patients and thus address the question whether Se administration should generally be recommended for AIT patients.

METHODS

Thirty-six consecutive AIT patients (aged 19-85 years) were included in the present study. In addition to their levothyroxine (LT(4)) treatment, 18 patients received 200 microg (2.53 micromol) sodium selenite per day orally for the time span of 3 months, whereas 18 patients received placebo. All patients had measurement of thyroid hormones, thyrotropin (TSH), autoantibodies (thyroglobulin antibodies [TgAb] and TPOAb), Se levels, and intracellular cytokine detection in CD4(+) and CD8(+) T cells of peripheral blood mononuclear cells (PBMC) by flow cytometry before and after Se or placebo administration.

RESULTS

No significant difference in the TPOAb levels was found after Se administration (524 +/- 452 vs. 505 +/- 464 IU/mL; p > 0.05). Furthermore, we found no significant differences in the CD4(+) or CD8(+) cytokine pattern (IFN-gamma, IL-2, IL-4, IL-5, IL-6, IL-10, IL-13, TNF-alpha, TNF-beta) in patients before and after Se administration, in patients before and after placebo administration and between Se group and placebo group before and after Se vs. placebo administration.

CONCLUSION

We demonstrate that Se administration in our AIT patient's cohort does not induce significant immunological changes, either in terms of cytokine production patterns of peripheral T lymphocytes or of TPOAb levels. Our data suggest that AIT patients with moderate disease activity (in terms of TPOAb and cytokine production patterns) may not (equally) benefit as patients with high disease activity.

Preparation and pre-vivo evaluation of no-carrier-added, carrier-added and cross-complexed [(68)Ga]-EDTMP formulations

PURPOSE

The present study aimed to develop convenient preparation and quality control protocols for [(68)Ga]-EDTMP, a potential radiotracer for skeletal PET imaging. Furthermore, bone binding characteristics with special focus on the influence of carrier addition were evaluated.

METHODS

No-carrier-added (nca), carrier-added and novel cross-complexed [(68)Ga]-EDTMP formulations were prepared using [(68)Ga]-gallium chloride and a commercial EDTMP kit. Respective bone binding characteristics were determined on the basis of an established in-vitro method using hydroxyapatite and human bone powders as binding matrices.

RESULTS

Pre-vivo evaluation of nca [(68)Ga]-EDTMP yielded irreversible binding on the mineral bone phase characterised by fast binding kinetics. Generally, nca [(68)Ga]-EDTMP showed low uptake values comparable to nca [(99m)Tc]-EDTMP. Interestingly, the bone binding affinity of [(68)Ga]-EDTMP could be increased by the addition of carriers, presumably by changing the complex structure.

CONCLUSIONS

This fast and reliable preparation protocol could enable small PET facilities without onsite cyclotron to perform PET bone scans. A comparison of all cross-complexed [(68)Ga]-EDTMP preparations further strengthens the recently presented "foreign carrier theory", which highlights carrier addition as a factor strongly affecting bone uptake of radiolabelled polyphosphonates. The clinical applicability of [(68)Ga]-EDTMP - particularly with respect to lesion specificity and sensitivity - should be clarified in forthcoming in-vivo studies.

[11C] methionine and [18F] fluorodeoxyglucose PET in the follow-up of glioblastoma multiforme

BACKGROUND

The aim of this study was to evaluate the value of [11C] methionine (MET) and [18F] fluorodeoxyglucose (FDG) PET in the follow-up of glioblastoma multiforme (GBM).

PATIENTS AND METHODS

After surgical and/or conservative treatment, 28 patients (pts) with GBM underwent FDG and MET PET on average 12.7 months after the diagnosis had been established. Scans were evaluated visually and by calculating the maximal tumor SUV as well as the ratio of tumor vs. contralateral region (RTu). The degree of tracer uptake was compared with survival time, disease duration and MRI findings.

RESULTS

The mean overall duration of survival was 12.7 months. The patients were divided into two groups: those that survived less than 12 months and those that survived longer than 12 months. Focally increased uptake was revealed by MET PET in 24 patients and by FDG PET in 2 patients. On MRI scans, viable tumor tissue was suspected in 18 patients. No correlations were registered between FDG/MET uptake and survival time or disease duration respectively; Kaplan-Meier calculations were negative in this regard. Similarly, negative results were obtained in subgroups of patients who had undergone microsurgical resection and whose disease was at least of 6 months' duration, and additionally in a subgroup who had undergone their last treatment longer than 6 months ago. With respect to survival groups, a positive MET PET was associated with a sensitivity of 86% and a specificity of 8%. SUV and RTu values did not differ between patients with positive or negative MRI results.

CONCLUSIONS

In this study FDG PET seems to be of limited value in the work-up of recurrent GBM because of its lower sensitivity than MET PET and the fact that it allows no prediction of the outcome. MET PET visualizes viable tumor tissue without adding any prognostic information and appears to be in no way superior to conventional imaging.

Vascular endothelial growth factor in thyroid cyst fluids

BACKGROUND

The pathogenesis of cystic thyroid nodules is incompletely understood. Based on the assumption that vascular endothelial growth factor (VEGF) may play an important role in the pathogenesis of thyroid cyst fluid, we investigated the VEGF concentration in cyst fluids of thyroid lesions.

DESIGN

Cyst fluids from 24 patients (age 31-84 years) were obtained using ultrasound-guided fine-needle aspiration. The patients' cystic thyroid nodules were of different origins.

METHODS

Thyroid and cyst volumes were determined using high-resolution ultrasonography. VEGF concentrations were determined using a solid-phase enzyme-linked immunosorbent assay (ELISA).

RESULTS

Differing elevated VEGF concentrations were demonstrated in cyst fluids of thyroid nodules of varied origins. The VEGF concentration in cyst fluid of patients with adenomatous goiter was significantly higher (P < 0.05) than that in thyroid nodules with cystic degeneration. The highest level of VEGF was found in bloody cyst fluid when compared with levels in other cyst fluids (P < 0.05). Interestingly, there was significant correlation (P < 0.01) between thyroid volume and VEGF concentration in cyst fluid, but no significant correlation (P = 0.20) between cyst volume and VEGF concentration.

CONCLUSION

Significantly increased VEGF concentrations were found in bloody cyst fluid and in cyst fluid of thyroid adenomatous goiter, compared with VEGF concentrations in degenerative thyroid cysts. Our results suggest that VEGF may play an important role in the pathogenesis of thyroid cyst fluid.

Pre vivo, ex vivo and in vivo evaluations of [68Ga]-EDTMP

INTRODUCTION

The objectives of this study were to develop a simple preparation method for [68Ga]-EDTMP and to evaluate the applicability of [68Ga]-EDTMP as a potential positron emission tomography (PET) bone imaging agent using pre vivo, ex vivo and in vivo models.

METHODS

[68Ga]-EDTMP was prepared using 68Ga]-gallium chloride eluted from the 68Ge/68Ga generator and commercially available Multibone kits. Binding affinity to bone compartments was evaluated using a recently established pre vivo model. In vivo (microPET) and ex vivo experiments were performed in mice, and the results of which were compared with those obtained with [18F]-fluoride.

RESULTS

[68Ga]-EDTMP was accessible via simple kit preparation and predominantly accumulated in bone tissue in vivo, ex vivo and pre vivo. Binding to mineral bone was irreversible, and low binding was observed in organic bone. In vivo microPET evaluation revealed predominant uptake in bone with renal excretion. Compared with [18F]-fluoride, the uptake was lower and the PET image quality was reduced.

CONCLUSIONS

From the present evaluation, apart from the autonomy for PET centers without an onsite cyclotron, the advantage of [68Ga]-EDTMP over [18F]-fluoride is not apparent and the future clinical prospect of [68Ga]-EDTMP remains speculative.

Pharmacoresistance in epilepsy: a pilot PET study with the P-glycoprotein substrate R-[(11)C]verapamil

PURPOSE AND METHODS

Regional overexpression of the multidrug transporter P-glycoprotein (P-gp) in epileptic brain tissue may lower target site concentrations of antiepileptic drugs and thus contribute to pharmacoresistance in epilepsy. We used the P-gp substrate R-[(11)C]verapamil and positron emission tomography (PET) to test for differences in P-gp activity between epileptogenic and nonepileptogenic brain regions of patients with drug-resistant unilateral temporal lobe epilepsy (n = 7). We compared R-[(11)C]verapamil kinetics in homologous brain volumes of interest (VOIs) located ipsilateral and contralateral to the seizure focus.

RESULTS

Among different VOIs, radioactivity was highest in the choroid plexus. The hippocampal VOI could not be used for data analysis because it was contaminated by spill-in of radioactivity from the adjacent choroid plexus. In several other temporal lobe regions that are known to be involved in seizure generation and propagation ipsilateral influx rate constants K(1) and efflux rate constants k(2) of R-[(11)C]verapamil were descriptively increased as compared to the contralateral side. Parameter asymmetries were most prominent in parahippocampal and ambient gyrus (K(1), range: -3.8% to +22.3%; k(2), range: -2.3% to +43.9%), amygdala (K(1), range: -20.6% to +31.3%; k(2), range: -18.0% to +38.9%), medial anterior temporal lobe (K(1), range: -8.3% to +14.5%; k(2), range: -14.5% to +31.0%) and lateral anterior temporal lobe (K(1), range: -20.7% to +16.8%; k(2), range: -24.4% to +22.6%). In contrast to temporal lobe VOIs, asymmetries were minimal in a region presumably not involved in epileptogenesis located outside the temporal lobe (superior parietal gyrus, K(1), range: -3.7% to +4.5%; k(2), range: -4.2% to +5.8%). In 5 of 7 patients, ipsilateral efflux (k(2)) increases were more pronounced than ipsilateral influx (K(1)) increases, which resulted in ipsilateral reductions (10%-26%) of R-[(11)C]verapamil distribution volumes (DV). However, for none of the examined brain regions, any of the differences in K(1), k(2) and DV between the epileptogenic and the nonepileptogenic hemisphere reached statistical significance (p > 0.05, Wilcoxon matched pairs test).

CONCLUSIONS

Even though we failed to detect statistically significant differences in R-[(11)C]verapamil model parameters between epileptogenic and nonepileptogenic brain regions, it cannot be excluded from our pilot data in a small sample size of patients that regionally enhanced P-gp activity might contribute to drug resistance in some patients with temporal lobe epilepsy.

Binding kinetics of 123I[ADAM] in healthy controls: a selective SERT radioligand

[123I]ADAM (2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine) is a promising radioligand for in-vivo quantification of serotonin transporters (SERT) using single photon emission computed tomography (SPECT) in man. We performed tracer kinetic analysis in various brain regions to determine the optimum equilibrium time for SERT quantification with [123I]ADAM and SPECT. Radiosyntheses of [123I]ADAM were performed at MAP Medical Technologies Oy, Tikkakoski, Finland. Thirty healthy male volunteers (21-41 yr) received between 104 and 163 MBq [123I]ADAM intravenously as a bolus. Consecutively, multiple SPECT scans were performed between 14 and 420 min post-injection (p.i.) using a Siemens Multispect 3 camera. Reconstruction was performed applying filtered back projection with a Butterworth filter (cut-off 0.7, order 7) in 128x128 matrices. Regions of interest (ROI) were drawn manually on the individual T1-weighted magnetic resonance image (MRI) comprising midbrain/hypothalamus for specific binding to SERT, and the cerebellum as reference region. After re-orientation to the MRI, the ROI template was applied to SPECT studies. We generated time-activity curves for the ROI and calculated the ratio countstarget/countscerebellum minus 1 (=V3'') as a measure for specific SERT binding. Counts were corrected for applied activity, acquisition time and body-weight. Peak uptakes were observed between 14 and 50 min after bolus injection. Counts per voxel were highest in the midbrain/hypothalamus, 798 (max. 872, min. 728), whereas 462 counts per voxel (max. 599, min. 412) were measured in the cerebellum at a mean time of 31 min p.i. Stable values for V3'' reached 205-320 min p.i. Mean peak V3'' value was 1.43 (95% CI 171-230) for the midbrain/hypothalamus at 205 min p.i. [123I]ADAM is a useful ligand for in-vivo quantification of human SERT by means of SPECT, with a comparatively better signal-to-noise ratio compared to beta-CIT. Our data suggest that the acquisition time for the SPECT scan is optimally, under pseudo-equilibrium conditions, between 205-320 min post-bolus injection of the tracer.

Higher serotonin transporter occupancy after multiple dose administration of escitalopram compared to citalopram: an [123I]ADAM SPECT study

OBJECTIVES

Previous studies have investigated the occupancy of the serotonin reuptake transporter (SERT) after clinical doses of citalopram and other selective serotonin reuptake inhibitors. In the present study, the occupancies of SERT after multiple doses of escitalopram and citalopram were compared using the radioligand [(123)I]ADAM and single photon emission computed tomography (SPECT).

METHODS

Fifteen healthy subjects received escitalopram 10 mg/day (n = 6) or citalopram 20 mg/day (n = 9) for a total of 10 days. SERT occupancies in midbrain were determined with SPECT and [(123)I]ADAM at three different time points: at baseline (no medication) and at 6 and 54 h after last drug intake.

RESULTS

At 6 h after the last dose, mean SERT occupancies were 81.5 +/- 5.4% (mean+/-SD) for escitalopram and 64.0 +/- 12.7% for citalopram (p < 0.01). At 54 h after the last dose, mean SERT occupancies were 63.3 +/- 12.1% for escitalopram and 49.0 +/- 11.7% for citalopram (p < 0.05). The plasma concentrations of the S-enantiomer were of the same magnitude in both substances. For both drugs, the elimination rate of the S-enantiomer in plasma was markedly higher than the occupancy decline rate in the midbrain.

CONCLUSION

The significantly higher occupancy of SERT after multiple doses of escitalopram compared to citalopram indicates an increased inhibition of SERT by escitalopram. The results can also be explained by an attenuating effect of R-citalopram on the occupancy of S-citalopram at the SERT.

Striatal D(2) receptor occupancy in bipolar patients treated with olanzapine

We explored the relationship between striatal dopamine-2 (D(2)) receptor occupancy and extra-pyramidal symptoms (EPS) in bipolar patients receiving olanzapine. Seventeen patients with a DSM-IV diagnosis of bipolar disorder were treated with 5-45 mg/day olanzapine for at least 14 days. After that period, D(2) receptor occupancy was determined using Iodobenzamide (IBZM) and SPECT. EPS were assessed by the Simpson-Angus Scale (SAS) and Barnes-Akathisia Scale (BAS). We found a dose-dependent increase in occupancy: 5 mg led to 28-50%, 10 mg to 40-68%, 15 mg to 69%, 20 mg to 57-66%, 30 mg to 66% and 45 mg to 80% D(2) receptor occupancy; and a significant correlation between plasma levels and occupancy (R(2)=.55, P=.001). Similar to schizophrenic patients, bipolar patients did not exhibit EPS at D(2) occupancy levels of 28 to 80%. Although we did not find an increased vulnerability for acute EPS in bipolar patients receiving olanzapine at clinical relevant doses, this needs to be replicated with larger sample sizes.

Measurement of calcitonin by immunoassay analyzers

BACKGROUND

Since Nichols Institute Diagnostics (NID) ended production of their automated calcitonin immunoassay, evaluation of an alternative calcitonin assay was necessary.

METHODS

Calcitonin measured by the NID procedure was compared with a test from Diagnostic Products Corporation (DPC). Calcitonin was also measured by assays from DiaSorin (DS) and Scantibodies (SC).

RESULTS

In 187 samples, detection failed either by NID (39%) or DPC (96%) assay; in 35% of samples, the tests agreed for non-measurable calcitonin. The regression line DPC=0.78 x NID-0.3 (r=0.998) fitted results from 236 samples with detectable calcitonin. A linear relationship, albeit with scattering at low concentrations, was observed. Importantly, stimulation by pentagastrin above basal calcitonin concentrations yielded similar results with both assays. Comparisons (DPC=0.80 x DS-3.4 and DPC=0.81 x SC-1.1) confirmed an aberrant calibration of the DPC test. To overcome the method bias, we propose a multiplication factor of 0.8 to convert NID to DPC results.

CONCLUSIONS

Apparently due to non-specific effects, the DS and SC assays produced calcitonin results in samples from completely thyroidectomized patients, while the DPC assay correctly failed to detect calcitonin. Thus, the DPC assay on an Immulite 2000 analyzer may be used as a more accurate substitute for NID if the different calibration is noted.

T lymphocyte cytokine production patterns in hashimoto patients with elevated calcitonin levels and their relationship to tumor initiation

The aim of the study was to evaluate the possible changes in CD4+ and CD8+ T-cell cytokine production patterns in Hashimoto's thyroiditis (HT) with elevated calcitonin (CT). Fourteen consecutive patients with verified HT were included in the present study. Patients were divided into two groups. Group I: 7 HT patients with elevated CT levels (>10 pg/ml); Group II: 7 HT patients with CT levels <10 pg/ml). All patients underwent intracellular cytokine detection in CD4+ and CD8+ T-cells of peripheral blood mononuclear cells (PBMC) by flow cytometry. Patients with elevated CT levels (group I) had significantly higher percentages of CD8+ cells producing IFN-gamma compared to healthy donors. A detailed analysis of cytokine production patterns revealed that this was accompanied by an increased frequency of single IFN-gamma positive cells, i.e., cells not expressing most of the other cytokines tested. Similarly, patients in group I also showed higher percentages of CD8+ TNF-alpha positive cells than healthy donors. In this case, cells co-expressing TNF-alpha and IFN-gamma were found at significantly higher frequencies. No increase in Th1 type cytokines, such as IFN-gamma or TNF-alpha, was detectable in CD4+ T-cells. In contrast, CD4+ T-cells from group I patients showed significantly higher percentages of cells producing Th2 cytokines, such as IL-4 or IL-13. The lack of increased Th1 cytokine production accompanied by an increased Th2 cytokine production seems to be a special feature of HT patients with elevated CT levels that may reflect a pathogenetic mechanism for tumor initiation.

Comparison of iodine uptake in tumour and nontumour tissue under thyroid hormone deprivation and with recombinant human thyrotropin in thyroid cancer patients

AIM

Recombinant human thyrotropin (rhTSH) is a new option for diagnostic follow-up in patients with differentiated thyroid cancer (DTC). Iodine kinetics after administration of rhTSH is controversially discussed. The aim of our study was to compare the time course of radioiodine in tumour and normal tissue during periods of TSH elevation in patients in a hypothyroid state (HS) following hormone withdrawal, with those under euthyroidism (ES) after the administration of rhTSH.

PATIENTS AND METHODS

We investigated four patients who had undergone near-total thyroidectomy and were suffering from metastatic disease. Dosimetric calculations were performed using tumour and whole-body uptake, and background measurements from 123-iodine scans performed 0, 4, 24 and 48 h after the application of (123)I.

RESULTS

All patients had lesser uptake of (123)I under rhTSH stimulation than after hormone withdrawal. The median maximum TG (thyroglobulin) levels were 733.1 ng/ml with HS and 548.0 ng/ml with ES. The median half-life in tumour tissue was 39.8 h (mean 65.9, range 11.5-194.0) with HS and 21.9 h (mean 38.7, range. 8.7-113.9) with ES. The median uptake dose in per cent in tumour tissue was 0.08 (mean 0.15, range 0.04-0.6) with HS and 0.05 (mean 0.08, range 0.03-0.2) with ES. Furthermore, the cumulative activity in metastatic tissue was lower after rhTSH than during hypothyroidism, with considerable variations between individual lesions.

CONCLUSION

In our small group of DTC patients with metastatic disease, the effectiveness of radioiodine therapy following rhTSH was anticipated to be less than that in individuals who were hypothyroid after levothyroxine (L-T(4)) withdrawal. Endogenous TSH stimulation of metastatic thyroid cancer with radioiodine should not be performed without prior target tumour lesion dosimetry with (123)I.

In vivo imaging of serotonin transporter occupancy by means of SPECT and [123I]ADAM in healthy subjects administered different doses of escitalopram or citalopram

BACKGROUND

Escitalopram is a dual serotonin reuptake inhibitor (SSRI) approved for the treatment of depression and anxiety disorders. It is the S-enantiomer of citalopram, and is responsible for the serotonin reuptake activity, and thus for its pharmacological effects. Previous studies pointed out that clinically efficacious doses of other SSRIs produce an occupancy of the serotonin reuptake transporter (SERT) of about 80% or more. The novel radioligand [123I]ADAM and single photon emission computer tomography (SPECT) were used to measure midbrain SERT occupancies for different doses of escitalopram and citalopram.

METHODS

Twenty-five healthy subjects received a single dose of escitalopram [5 mg (n=5), 10 mg (n=5), and 20 mg (n=5)] or citalopram [(10 mg (n=5) and 20 mg (n=5)]. Midbrain SERT binding was measured with [(123)I]ADAM and SPECT on two study days, once without study drug and once 6 h after single dose administration of the study drug. The ratio of midbrain-cerebellum/cerebellum was the outcome measure (V3") for specific binding to SERT in midbrain. Subsequently, SERT occupancy levels were calculated using the untreated baseline level for each subject. An Emax model was used to describe the relationship between S-citalopram concentrations and SERT occupancy values. Additionally, four subjects received placebo to determine test-retest variability.

RESULTS

Single doses of 5, 10, or 20 mg escitalopram led to a mean SERT occupancy of 60+/-6, 64+/-6, and 75+/-5%, respectively. SERT occupancies for subjects treated with single doses of 10 and 20 mg citalopram were 65+/-10 and 70+/-6%, respectively. A statistically significant difference was found between SERT occupancies after application of 10 and 20 mg escitalopram, but not for 10 and 20 mg citalopram. There was no statistically significant difference between the SERT occupancies of either 10 mg citalopram or 10 mg escitalopram, or between 20 mg citalopram and 20 mg escitalopram. Emax was slightly higher after administration of citalopram (84%) than escitalopram (79%). In the test-retest study, a mean SERT "occupancy" of 4% was found after administration of placebo, the intraclass correlation coefficient was 0.92, and the repeatability coefficient was 0.25.

CONCLUSION

SPECT and [123I]ADAM were used to investigate SERT occupancies after single doses of escitalopram or citalopram. The test-retest study revealed good reproducibility of SERT quantification. Similar SERT occupancies were found after administration of equal doses (in respect to mg) of escitalopram and citalopram, giving indirect evidence for a fractional blockade of SERT by the inactive R-citalopram.

Comparison of (11)C-acetate positron emission tomography and (67)Gallium citrate scintigraphy in patients with hepatocellular carcinoma

AIMS

Nuclear imaging may have an increasing role in the diagnosis of hepatocellular carcinoma (HCC). The aim of this study was to compare prospectively the Gallium-67 citrate ((67)Ga) scintigraphy results with those obtained by positron emission tomography (PET) using (11)C-acetate in patients with HCC.

METHODS

We prospectively analysed 21 patients (mean age, 64+/-11 years) with histopathologically verified HCC undergoing (11)C-acetate PET and (67)Ga scintigraphy. (67)Ga scans were not performed in three of these 21 patients due to the exacerbation of the disease. Whole-body (11)C-acetate PET were performed following intravenous injection of 850 MBq of (11)C-acetate. For (67)Ga scintigraphy, whole-body, planar and single photon emission computed tomography imaging acquisitions were performed after intravenous application of a mean dose of 189 MBq (67)Ga.

RESULTS

(67)Ga scintigraphy found abnormalities only in 10 of 18 patients (56%) and detected 22 of 46 clinically involved sites (48%); it was false-positive in two patients. (11)C-acetate PET found abnormalities in 14 of 18 patients (78%) and detected 36 of 46 clinical lesions (78%); it was false-positive in one patients. In one patient with left supraclavicular lymph node metastases, neither the (67)Ga scintigraphy nor the conventional computed tomography have shown the lesions, which were clearly demonstrated by the (11)C-acetate PET.

CONCLUSION

Our results indicate significantly higher sensitivity and specificity of (11)C-acetate PET than (67)Ga scan in detection of HCC lesions. This study suggests that imaging with (11)C-acetate PET might play a potential role in the diagnostic workup of patients with HCC.

A positron emission tomography microdosing study with a potential antiamyloid drug in healthy volunteers and patients with Alzheimer’s disease

This work describes a microdosing study with an investigational, carbon 11-labeled antiamyloid drug, 1,1'-methylene-di-(2-naphthol) (ST1859), and positron emission tomography (PET) in healthy volunteers (n = 3) and patients with Alzheimer's disease (n = 6). The study aimed to assess the distribution and local tissue pharmacokinetics of the study drug in its target organ, the human brain. Before PET studies were performed in humans, the toxicologic characteristics of ST1859 were investigated by an extended single-dose toxicity study according to guidelines of the Food and Drug Administration and European Medicines Agency, which are relevant for clinical trials with a single microdose. After intravenous bolus injection of 341 +/- 21 MBq [(11)C]ST1859 (containing <11.4 nmol of unlabeled ST1859), peripheral metabolism was rapid, with less than 20% of total plasma radioactivity being in the form of unchanged parent drug at 10 minutes after administration. In both the control and patient groups, uptake of radioactivity into the brain was relatively fast (time to reach maximum concentration, 9-17 minutes) and pronounced (maximum concentration [standardized uptake value], 1.3-2.2). In both healthy volunteers and patients, there was a rather uniform distribution of radioactivity in the brain, including both amyloid-beta-rich and -poor regions, with slow washout of radioactivity (half-life, 82-185 minutes). In conclusion, these data provide important information on the blood-brain barrier penetration and metabolism of an investigational antiamyloid drug and suggest that the PET microdosing approach is a useful method to describe the target-organ pharmacokinetics of radiolabeled drugs in humans.