Gerd Wunderlich

Serum Thyroglobulin Measurements with a High Sensitivity Enzyme-Linked Immunosorbent Assay: Is There a Clinical Benefit in Patients with Differentiated Thyroid Carcinoma?

Serial serum thyroglobulin (Tg) measurements with a highly sensitive enzyme-linked immunosorbent assay (ELISA; functional sensitivity 0.03 ng/mL) in 126 patients (Tg autoantibody negative) with treated differentiated thyroid cancer (DTC) are described. At the beginning of the retrospective study, all 126 patients were in remission and Tg was detectable by ELISA in 92 (73%; range, 0.03-0.8 ng/mL). Over the following 4-year period, Tg levels remained essentially unchanged (i.e., any increases were less than 2 times the Tg level at the start of the study) in 121 of 126 (96%) and all 121 patients remained well. In 5 patients, Tg levels increased to more than 2 times the starting Tg level over the study period and in 4 of these 5, there was recurrence of DTC. The fifth patient in this group remains well as evidenced by extensive diagnostic imaging, although his serum Tg level continues to increase and can be stimulated by thyrotropin (TSH). Our results suggest that serial measurements of low levels of Tg by ELISA in treated patients with DTC enable detection of recurrence (without using TSH stimulation) 6-12 months earlier than would have been possible using a conventional Tg immuno-radiometric assay (IRMA). A prospective study is now needed to confirm these observations.

Fully automated interpretation of ionizing radiation-induced γH2AX foci by the novel pattern recognition system AKLIDES®

Purpose: Assessment of phosphorylated histone H2AX (γH2AX) foci as a measure for double-strand breaks (DSB) is a common technique. Since visual interpretation is time-consuming and influenced by subjective factors, we adapted the pattern recognition algorithms of autoantibodies to automated reading of γH2AX foci. Materials and methods: DSB formation was assessed by detection of γH2AX foci after exposition of thyreocyte rat cell line to 188Re. We used pattern recognition algorithms of the automated fluorescence interpretation system AKLIDES® for evaluation of γH2AX foci. Manual investigation was performed by three laboratories involving five observers. The results were compared by determining correlation and inter-laboratory variability. Results: The study confirmed the adaptation of automated interpretation system AKLIDES® to automated assessment of γH2AX foci in irradiated cells. Both manual and automated quantification resulted in increasing focus numbers depending on dose. Comparison of automated reading with visual assessment for five manual observers resulted in a determination coefficient of R2 = 0.889. The inter-laboratory variability for five manual investigators of three laboratories was 38.4 %. Conclusion: The interpretation system AKLIDES® demonstrated a high correlation with visually observed results. High inter-laboratory variability found for manual investigations revealed the usefulness for a standardized technique for evaluation of γH2AX foci.

Preparation and biodistribution of rhenium-188 labeled albumin microspheres B 20: a promising new agent for radiotherapy

Intra-arterial infusion of labeled particles is an effective method for endoradiotherapy of tumors. In this study, we radiolabeled biodegradable HSA microspheres (mean diameter = 25 microm) with the short-lived beta-emitter 188Re available from the aluminia-based 188W/188Re generator system. After 1 h 35-40% of the relative large amount of Sn(II) chloride required for effective reduction of Re(VII) for efficient attachment to the particles is precipitated as an amorphous coat of tin hydroxid colloid on the particle surface. The final 188Re bound to the particles was found to be stable in vitro. The radiolabelling yield was > 90%. The biological half-life was > 250 h and demonstrated sufficient in vivo stability after i.v. injection in Wistar rats. Because of the attractive properties of 188Re and the uniform particle size and stability, in vivo, this new agent is an attractive candidate for endoradiotherapy of tumors after selective catheterization.

Radiation exposure of patients during 68Ga-DOTATOC PET/CT examinations

AIM Investigation of the biodistribution and calculation of dosimetry of Ga-68-DOTATOC- for patients imaged in the routine clinical setting for diagnosis or exclusion of neuroendocrine tumours. PATIENTS, METHODS Dynamic PET/CT-imaging (Biograph 16) was performed over 20 min in 14 patients (8 men, 6 women) after injection of (112+/-22) MBq 68Ga-DOTATOC followed by whole body 3D-acquisition (8 bed positions, 3 or 4 min each) 30 min p.i. and 120 min p.i.. Urinary tracer elimination was measured and blood activity was derived non-invasively from the blood pool of the heart. The relevant organs for dosimetry were spleen, kidneys, liver, adrenals, urinary bladder and pituitary gland. Dosimetry was performed using OLINDA/EXM 1.0 software and specific organ uptake was expressed as standardized uptake values (SUVs). RESULTS Rapid physiological uptake of the radiotracer could be demonstrated in liver, spleen and kidneys, adrenals and pituitary gland (mean SUVs were 6, 20, 16, 10, and 4, respectively). Radiotracer elimination was exclusively via urine (16% of injected dose within 2h); no redistribution could be observed. The spleen and the kidneys received the highest radiation exposure (0.24 mSv/MBq, 0.22 mSv/MBq resp.), mean effective dose yielded 0.023 mSv/MBq. CONCLUSION 68Ga-DOTATOC is used extensively for diagnosis of somatostatin receptor positive tumours because it has several advantages over the 111In-labelled ligand. The derived dosimetric values are lower than first approximations from the biological data of OctreoScan. The use of CT for transmission correction of the PET data delivers radiation exposure up to 1 mSv (low dose).

Higher levels of spontaneous breathing induce lung recruitment and reduce global stress/strain in experimental lung injury.

Background:Spontaneous breathing (SB) in the early phase of the acute respiratory distress syndrome is controversial. Biphasic positive airway pressure/airway pressure release ventilation (BIPAP/APRV) is commonly used, but the level of SB necessary to maximize potential beneficial effects is unknown. Methods:Experimental acute respiratory distress syndrome was induced by saline lung lavage in anesthetized and mechanically ventilated pigs (n = 12). By using a Latin square and crossover design, animals were ventilated with BIPAP/APRV at four different levels of SB in total minute ventilation (60 min each): (1) 0% (BIPAP/APRV0%); (2) greater than 0 to 30% (BIPAP/APRV>0–30%); (3) greater than 30 to 60% (BIPAP/APRV>30–60%); and (4) greater than 60% (BIPAP/APRV>60%). Gas exchange, hemodynamics, and respiratory variables were measured. Lung aeration was assessed by high-resolution computed tomography. The distribution of perfusion was marked with 68Ga-labeled microspheres and evaluated by positron emission tomography. Results:The authors found that higher levels of SB during BIPAP/APRV (1) improved oxygenation; (2) decreased mean transpulmonary pressure (stress) despite increased inspiratory effort; (3) reduced nonaerated lung tissue, with minimal changes in the distribution of perfusion, resulting in decreased low aeration/perfusion zones; and (4) decreased global strain (mean ± SD) (BIPAP/APRV0%: 1.39 ± 0.08; BIPAP/APRV0–30%: 1.33 ± 0.03; BIPAP/APRV30–60%: 1.27 ± 0.06; BIPAP/APRV>60%: 1.25 ± 0.04, P < 0.05 all vs. BIPAP/APRV0%, and BIPAP/APRV>60% vs. BIPAP/APRV0–30%). Conclusions:In a saline lung lavage model of experimental acute respiratory distress syndrome in pigs, levels of SB during BIPAP/APRV higher than currently recommended for clinical practice, that is, 10 to 30%, improve oxygenation by increasing aeration in dependent lung zones without relevant redistribution of perfusion. In presence of lung recruitment, higher levels of SB reduce global stress and strain despite an increase in inspiratory effort.

A high-sensitivity enzyme-linked immunosorbent assay for serum thyroglobulin.

A sensitive enzyme-linked immunosorbent assay (ELISA) for measuring serum thyroglobulin (Tg) is described. The assay has a functional sensitivity of 0.03 ng/mL and values obtained in sera from patients with treated differentiated thyroid cancer (DTC; n = 24, 17 of whom showed some evidence of recurrence) and from healthy blood donors (n = 48) were in agreement with those obtained by Tg immunoradiometric assay (IRMA) (functional sensitivity = 0.6 ng/ml) (r = 0.99 and 0.98 for the two groups, respectively). The Tg levels measured by ELISA in 47 of the healthy blood donor sera ranged from 2.3 to 139 ng/ml with 1 serum giving a value of 0.03 ng/mL. The mean +/- standard deviation (SD) Tg concentration for the healthy blood donors was 20.3+/-23 ng/mL. Studies with a recovery test suggest that Tg measurements by ELISA were not always reliable when Tg autoantibodies were present. Analysis of samples from 167 patients treated successfully for DTC (papillary carcinoma, 94; follicular carcinoma, 73) showed that 139 were negative for Tg autoantibodies and of these 106 (76%) had Tg levels measurable by ELISA (0.03 ng/mL or greater). In contrast, only 7 (5%) of these 139 sera had Tg levels measurable by IRMA (0.6 ng/mL or greater). It is possible that this ability to measure Tg simply and easily in most treated DTC patients will have significant advantages for patient care. In particular, the Tg level after initial ablative treatment will usually be measurable rather than undetectable. Furthermore, any increases in serum Tg levels which may herald relapse will be detectable earlier.

PET aerosol lung scintigraphy using Galligas

Dear Sir, The trend in imaging—no matter if in radiology or nuclear medicine—goes towards smaller voxels acquired in less time with less radiation dose. Thus, it is merely a matter of time or costs when conventional methods like bone, sentinel lymph node (SLN), octreotide or lung ventilation/ perfusion scans are replaced by PET/CT. The costs of PET/ CT can be dramatically reduced when using the generatorproduced positron emitter Ga instead of F, which requires a cyclotron. Regarding perfusion imaging, binding Ga to macroaggregated albumin or microspheres had already been proposed in 1979 [1] and is possibly experiencing its renaissance in the molybdenum—and consequently Tc—crisis [2] and/ or with the increasing use and spread of PET/CT scanners and Ga generators [3, 4]. However, for PET lung ventilation/perfusion imaging an analogue to Technegas [5, 6] is still missing. Therefore, we used Ga instead of Tc to produce a radioaerosol feasible for PET imaging. Ga (1,110 MBq) was eluted from a commercially available generator (1,110 MBq) (Eckert & Ziegler AG, Berlin, Germany) based on a titanium oxide phase adsorbing Ge(IV) equipped with a labelling module (ModularLab) providing an elution and cleaning programme. About 0.15 ml (150–200 MBq) of this solution was loaded into a graphite crucible (AlmediS Altmann GmbH, Salzgitter, Germany) and simmered in an atmosphere of pure argon using a commercially available Technegas generator (Tetley Manufacturing Ltd., Sydney, Australia). Following vaporization inhalation was performed in a common manner according to the manufacturer’s instructions. Two healthy male volunteers (age: 46 and 50 years) inhaled the radioaerosol, one in the prone position and the other in the supine position, and underwent PET/CT in an early and late phase (15 min and 3.5 h, respectively) after inhalation. PET imaging was performed on a 16-slice PET/CT (HIREZ biograph Sensation 16, Siemens/CTI, Knoxville, TN, USA) providing an axial field of view of 15.5 cm and an image resolution 4.5 mm in all three dimensions. The CT acquisition protocol included a low-dose CT (10 mAs, 120 kV, 0.5 s per rotation, 5-mm slice thickness) from the neck to mid-thigh for attenuation correction. PET scans were acquired in 3-D mode with an acquisition time of 3 min per bed position. Images were reconstructed by an iterative algorithm with attenuation and scatter correction (6 iterations, 4 subsets) followed by a post-reconstruction smoothing Gaussian filter (5 mm full-width at halfmaximum). The PET/CT system is calibrated with a Ge/Ga phantom (1.94 cps/kBq true coincidence). PET imaging demonstrated intense radiotracer uptake in the lungs without bronchial deposits (Fig. 1). Late images demonstrated persistent tracer distribution with only trace activity in the urinary bladder and a lack of radioactivity in the blood pool or abdomen (Fig. 2). Early PET imaging revealed 12 million ECAT counts in the 3-min bed position corresponding to an activity of 35 MBq. Late PET imaging J. Kotzerke (*) :M. Andreeff :G. Wunderlich Klinik und Poliklinik für Nuklearmedizin, Technische Universität Dresden, Dresden, Germany e-mail: joerg.kotzerke@mailbox.tu-dresden.de

Comparison of the stability of Y-90-, Lu-177- and Ga-68- labeled human serum albumin microspheres (DOTA-HSAM)

INTRODUCTION Microparticles derived from denatured human serum albumin (DOTA-derivatized human serum albumin microspheres, or DOTA-HSAM) are attractive carriers of radionuclides for both therapeutic and diagnostic purposes. In this article, we describe a labeling procedure for diagnostic (Ga-68) and therapeutic (Y-90, Lu-177) radionuclides and report on the results of stability studies of these products. METHODS DOTA-HSAM was labeled in 0.5 M ammonium acetate buffer, pH 5.0, containing 0.02 mg/ml detergent. After adding the radionuclide, the mixture was shaken for 15 min at 90°C. Labeling yields and in vitro stability were determined by thin-layer chromatography. For determination of the in vivo stability of Ga-68 and Y-90 DOTA-HSAM, the particles were injected intravenously in Wistar rats. RESULTS Labeling yields up to 95% in the case of Ga-68 and Lu-177 were achieved. Ga-68-labeled DOTA-HSAM showed high in vitro and in vivo stability. The amount of particle-bound radioactivity of Lu-177 DOTA-HSAM declines slowly in a linear manner to approximately 72% after 13 days. For Y-90, the labeling yield decreased with increasing radioactivity level. We presume radiolysis as the reason for these findings. CONCLUSION The labeling of DOTA-HSAM with different radionuclides is easy to perform. The radiation-induced cleavage of the labeled chelator together with the rather short half-life of radioactivity fixation in vivo (3.7 days) is, in our opinion, opposed to therapeutic applications of DOTA-HSAM. On the other hand, the high stability of Ga-68 DOTA-HSAM makes them an attractive candidate for the measurement of regional perfusion by PET.

188Re anti‐CD66 radioimmunotherapy combined with reduced‐intensity conditioning and in‐vivo T cell depletion in elderly patients undergoing allogeneic haematopoietic cell transplantation

The addition of radioimmunotherapy to conventional and reduced‐intensity conditioning has been shown to be feasible and effective. Within an ongoing prospective phase II trial, 22 patients with advanced myeloid malignancies and a median age of 65 years (range 54–76) received anti‐CD66 Rhenium radioimmunotherapy followed by fludarabine (150 mg/m2), busulfan (8 mg/kg) and alemtuzumab (75 mg) before allogeneic haematopoietic stem cell transplantation from matched sibling (n = 7) and unrelated donors (n = 15). The extramedullary toxicity in the first 100 d post‐transplantation was limited and all patients engrafted with complete donor chimaerism. The incidence of non‐relapse mortality at day 100 and after 2 years was 4·5% and 23%, respectively. The probability of overall survival at 2 years was 40%. A comparison with a younger historical cohort (median age 57 years) having received the same dose of fludarabine and busulfan but neither radioimmunotherapy nor alemtuzumab showed no difference in outcome. Although the use of alemtuzumab reduced the incidence of acute graft‐versus‐host‐disease, it was associated with a relapse incidence of 40% despite the incorporation of radioimmmunotherapy. In summary, we confirmed the feasibility of combined radioimmunotherapy and reduced‐intensity conditioning in elderly patients. Further optimisation, probably involving less T cell depletion, is necessary before a randomized comparison with standard conditioning can be planned.

Myocardial uptake and biodistribution of newly designed technetium-labelled fatty acid analogues.

PurposeIn an effort to develop 99mTc-labelled fatty acids (FAs) for myocardial metabolism and flow imaging, several 99mTc analogues according to the ‘3+1’ and the ‘4+1’ mixed-ligand approach were synthesized and myocardial extraction was evaluated in non-working isolated guinea pig hearts. An example of biodistribution patterns in guinea pigs was determined by using one FA analogue. MethodsThe coordination moieties contain a +5, respectively +3, oxidation state metal core attached to the end position of a FA chain. FA complexes of the ‘3+1’ and the ‘4+1’ mixed-ligand type were prepared and investigated using the isolated heart model. To estimate the diagnostic value of the analogue 99mTc-FAs, the biodistribution of one well-extracted FA was evaluated. ResultsThe ‘4+1’ FA compounds achieved the highest uptake rates of all the technetium FAs investigated. In particular, the ‘4+1’ 99mTc-C11-FA achieved at least a 2-fold higher ventricular extraction of the applied activity than the established control tracers including ω-(p-[123I]iodophenyl)pentadecanoic FAs (BMIPP and IPPA) and 99mTc-MIBI. Furthermore, the ‘4+1’ dodecanoic FA derivative and the thiadodecanoic FA derivative showed an extraction comparable to established 123I-labelled tracers. Biodistribution experiments performed for the thiadodecanoic FA derivative indicated a good heart/blood and heart/lung ratio and also a high uptake in the liver. In contrast, ‘3+1’ 99mTc complexes showed a low myocardial extraction rate. Nevertheless, the differentiation in the extraction profile, which depends on the FA chain length and structure, indicates a specific heart uptake of these 99mTc-labelled FA derivatives as well. ConclusionsThe excellent extraction rates found for ‘4+1’ 99mTc-FAs indicate possibly promising structures for innovative myocardial tracers.