Overestimation of grey matter atrophy in glioblastoma patients following radio(chemo)therapy.

OBJECTIVE: Brain atrophy has the potential to become a biomarker for severity of radiation-induced side-effects. Particularly brain tumour patients can show great MRI signal changes over time caused by e.g. oedema, tumour progress or necrosis. The goal of this study was to investigate if such changes affect the segmentation accuracy of normal appearing brain and thus influence longitudinal volumetric measurements. MATERIALS AND METHODS: T1-weighted MR images of 52 glioblastoma patients with unilateral tumours acquired before and three months after the end of radio(chemo)therapy were analysed. GM and WM volumes in the contralateral hemisphere were compared between segmenting the whole brain (full) and the contralateral hemisphere only (cl) with SPM and FSL. Relative GM and WM volumes were compared using paired t tests and correlated with the corresponding mean dose in GM and WM, respectively. RESULTS: Mean GM atrophy was significantly higher for full segmentation compared to cl segmentation when using SPM (mean ± std: ΔVGM,full = - 3.1% ± 3.7%, ΔVGM,cl = - 1.6% ± 2.7%; p < 0.001, d = 0.62). GM atrophy was significantly correlated with the mean GM dose with the SPM cl segmentation (r = - 0.4, p = 0.004), FSL full segmentation (r = - 0.4, p = 0.004) and FSL cl segmentation (r = -0.35, p = 0.012) but not with the SPM full segmentation (r = - 0.23, p = 0.1). CONCLUSIONS: For accurate normal tissue volume measurements in brain tumour patients using SPM, abnormal tissue needs to be masked prior to segmentation, however, this is not necessary when using FSL.

Measurement of relative lung perfusion with electrical impedance and positron emission tomography: an experimental comparative study in pigs.

BACKGROUND: Electrical impedance tomography (EIT) with indicator dilution may be clinically useful to measure relative lung perfusion, but there is limited information on the performance of this technique. METHODS: Thirteen pigs (50-66 kg) were anaesthetised and mechanically ventilated. Sequential changes in ventilation were made: (i) right-lung ventilation with left-lung collapse, (ii) two-lung ventilation with optimised PEEP, (iii) two-lung ventilation with zero PEEP after saline lung lavage, (iv) two-lung ventilation with maximum PEEP (20/25 cm H2O to achieve peak airway pressure 45 cm H2O), and (v) two-lung ventilation under unilateral pulmonary artery occlusion. Relative lung perfusion was assessed with EIT and central venous injection of saline 3%, 5%, and 10% (10 ml) during breath holds. Relative perfusion was determined by positron emission tomography (PET) using 68Gallium-labelled microspheres. EIT and PET were compared in eight regions of equal ventro-dorsal height (right, left, ventral, mid-ventral, mid-dorsal, and dorsal), and directional changes in regional perfusion were determined. RESULTS: Differences between methods were relatively small (95% of values differed by less than 8.7%, 8.9%, and 9.5% for saline 10%, 5%, and 3%, respectively). Compared with PET, EIT underestimated relative perfusion in dependent, and overestimated it in non-dependent, regions. EIT and PET detected the same direction of change in relative lung perfusion in 68.9-95.9% of measurements. CONCLUSIONS: The agreement between EIT and PET for measuring and tracking changes of relative lung perfusion was satisfactory for clinical purposes. Indicator-based EIT may prove useful for measuring pulmonary perfusion at bedside.

Potential of a Cetuximab-based radioimmunotherapy combined with external irradiation manifests in a 3-D cell assay.

Targeting epidermal growth factor receptor (EGFR)-overexpressing tumors with radiolabeled anti-EGFR antibodies is a promising strategy for combination with external radiotherapy. In this study, we evaluated the potential of external plus internal irradiation by [(90) Y]Y-CHX-A″-DTPA-C225 (Y-90-C225) in a 3-D environment using FaDu and SAS head and neck squamous cell carcinoma (HNSCC) spheroid models and clinically relevant endpoints such as spheroid control probability (SCP) and spheroid control dose 50% (SCD50 , external irradiation dose inducing 50% loss of spheroid regrowth). Spheroids were cultured using a standardized platform. Therapy response after treatment with C225, CHX-A"-DTPA-C225 (DTPA-C225), [(90) Y]Y-CHX-A"-DTPA (Y-90-DTPA) and Y-90-C225 alone or in combination with X-ray was evaluated by long-term monitoring (60 days) of spheroid integrity and volume growth. Penetration kinetics into spheroids and EGFR binding capacities on spheroid cells were identical for unconjugated C225 and Y-90-C225. Spheroid-associated radioactivity upon exposure to the antibody-free control conjugate Y-90-DTPA was negligible. Determination of the SCD50 demonstrated higher intrinsic radiosensitivity of FaDu as compared with SAS spheroids. Treatment with unconjugated C225 alone did not affect spheroid growth and cell viability. Also, C225 treatment after external irradiation showed no additive effect. However, the combination of external irradiation with Y-90-C225 (1 µg/ml, 24 hr) resulted in a considerable benefit as reflected by a pronounced reduction of the SCD50 from 16 Gy to 9 Gy for SAS spheroids and a complete loss of regrowth for FaDu spheroids due to the pronounced accumulation of internal dose caused by the continuous exposure to cell-bound radionuclide upon Y-90-C225-EGFR interaction.

[Nuclear medicine procedure guideline for sentinel lymph node localization]. / DGN-Handlungsempfehlung (S1-Leitlinie) ­ Version 3.

The authors present a procedure guideline for scintigraphic detection of sentinel lymph nodes in malignant melanoma, in breast cancer, in penile and vulva tumors, in head and neck cancer, and in prostate carcinoma. Important goals of sentinel lymph node scintigraphy comprise reduction of the extent of surgery, lower postoperative morbidity and optimization of histopathological examination focussing on relevant lymph nodes. Sentinel lymph node scintigraphy itself does not diagnose tumorous lymph node involvement and is not indicated when lymph node or distant metastases have been definitely diagnosed before sentinel lymph node scintigraphy. Procedures are compiled with the aim to reliably localise sentinel lymph nodes with a high detection rate typically in early tumour stages. New aspects in this guideline are new radiopharmaceuticals such as tilmanocept and Tc-99m-PSMA and SPECT/CT allowing an easier anatomical orientation. Initial dynamic lymphoscintigraphy in breast cancer is of little significance nowadays. Radiation exposure is low so that pregnancy is not a contraindication for sentinel lymph node scintigraphy. A one-day protocol should preferentially be used. Even with high volumes of scintigraphic sentinel lymph node procedures surgeons, theatre staff and pathologists receive a radiation exposure < 1 mSv/year so that they do not require occupational radiation surveillance. Aspects of quality control were included (scintigraphy, quality control of gamma probe, 6 h SLN course for surgeons, certified breast centers, medical surveillance center).

Flow cytometric cell-based assay to preselect antibody constructs for radionuclide conjugation.

Radiolabeled antibodies (Abs) are an attractive tool for targeting and delivering particle emitters for therapy or imaging applications. The labeling of Abs with metal radionuclides requires chelating agents and can cause loss of binding to their ligands. The aim of the present approach was to design an easy-handling flow cytometric cell-based assay to evaluate Ab-binding capacity of conjugates of the therapeutic Ab Cetuximab and to verify the most promising candidate in a competitive radioactive binding experiment. The final setup for flow cytometric assessment of cellular binding capacities of epidermal growth factor receptor (EGFR)/ErbB1-directed Ab conjugates is based on (a) the selection of a robust cell line model (b) the definition of nonsaturated staining concentrations for the unconjugated reference Ab Cetuximab plus implementation of a reasonable isotype control, and (c) the calculation of relative Ab affinities based on the flow cytometric data. Two (FaDu, SAS) out of the three cell lines with different total and cell surface expression levels of EGFR turned out to be adequate models but the application of one cell line was sufficient to estimate reduced binding capacities of conjugates relative to Cetuximab. Only 1/11 conjugate Abs exhibited a fluorescence signal comparable to unconjugated Cetuximab and was applied for radiolabeling with Yttrium-90. Unaltered binding affinity of this conjugate was proven in a competitive radioactive Ab-binding study. We conclude that the flow cytometric assay is reliable and that the relative binding capacity of Cetuximab is neither affected by covalent modification with CHX-A"-DTPA (N-[(R)-2-Amino-3-(p-isothiocyanato-phenyl) propyl]-trans-(S,S)-cyclohexane-1,2-diamine-N,N,N',N",N"-pentaacetic acid) with a final chelator-to-Ab ratio of 5 nor by subsequent radiolabeling. [(90)Y]Y-CHX-A"-DTPA-Cetuximab thus qualifies for preclinical treatment testing as a prerequisite for therapeutic application.

Internal radiotherapy of painful bone metastases.

Internal radiotherapy is effective in the treatment of metastatic bone pain and can improve quality of life. A number of controlled studies using various agents have shown a mean response rate in pain relief of 70-80% of treated patients. Some investigators prefer radionuclides which emit low beta particles for the treatment of bone pain, because the assumption of lower bone marrow toxicity of this agents. However, neither dosimetric data for radiation absorbed dose to the bone marrow nor clinical blood count depression have shown any significant differences between these agents. Other researchers suggest enhanced antitumoral effects using high-energy beta emitters and propose aggressive first-line treatment in the early disease stage instead of using these radiopharmaceuticals only in end-stage patients suffering intractable bone pain. Another approach consists of including other treatment modalities such as autologous stem cell rescue or in combination with chemo or bisphosphonate therapy to a radionuclide treatment scheme. Future research should focus more on the curative effects of combination with radiosensitizer, for example, chemotherapy, or repeated treatments with bone seeking agents.

Time- and dose-dependent volume decreases in subcortical grey matter structures of glioma patients after radio(chemo)therapy.

Background and purpose: Radiotherapy (RT) is an adjuvant treatment option for glioma patients. Side effects include tissue atrophy, which might be a contributing factor to neurocognitive decline after treatment. The goal of this study was to determine potential atrophy of the hippocampus, amygdala, thalamus, putamen, pallidum and caudate nucleus in glioma patients having undergone magnetic resonance imaging (MRI) before and after RT. Materials and methods: Subcortical volumes were measured using T1-weighted MRI from patients before RT (N = 91) and from longitudinal follow-ups acquired in three-monthly intervals (N = 349). The volumes were normalized to the baseline values, while excluding structures touching the clinical target volume (CTV) or abnormal tissue seen on FLAIR imaging. A multivariate linear effects model was used to determine if time after RT and mean RT dose delivered to the corresponding structures were significant predictors of tissue atrophy. Results: The hippocampus, amygdala, thalamus, putamen, and pallidum showed significant atrophy after RT as function of both time after RT and mean RT dose delivered to the corresponding structure. Only the caudate showed no dose or time dependant atrophy. Conversely, the hippocampus was the structure with the highest atrophy rate of 5.2 % after one year and assuming a mean dose of 30 Gy. Conclusion: The hippocampus showed the highest atrophy rates followed by the thalamus and the amygdala. The subcortical structures here found to decrease in volume indicative of radiosensitivity should be the focus of future studies investigating the relationship between neurocognitive decline and RT.

[Nuclear Medicine in Germany. Key data from official statistics]. / Nuklearmedizin in Deutschland. Kennzahlen aus offiziellen Statistiken.

AIM: To explain the spectrum and number of in-vivo nuclear medicine examinations and therapies based on official statistics about out-patient and in-patient care. Trends in time of the frequency and spectrum of procedures as well as data on the health care structure for nuclear medicine in Germany should be collected. METHODS: Data from the Gesundheitsberichterstattung des Bundes, from the frequency statistics of the statutory health insurance for out-patients and from the Bundesärztekammer were used. Customized queries were performed to analyse temporal changes. RESULTS: Nuclear medicine physicians are more frequently consulted by out-patients over the last years (2008: 2024498; 2009: 2164664) and the number of colleagues in private practice increased. For in-patients, the frequency of conventional nuclear medicine procedures (mainly for brain, lymphatic system, lung and heart) increased since 2008 after a decline in previous years (2009: 323515; +4.6%) and the number of PET(/CT) examinations continued to rise (2009: 25123; +18%), even if changes in OPS keys may hamper comparisons. Nearly 600 gamma cameras and 76 PET(/CT) scanners were installed in hospitals in 2008. Nuclear medicine procedures are increasingly performed as cross sectional imaging like SPECT(/CT) and PET(/CT). With the supply shortfall with 99Mo, the frequency of thyroid scans with 123I iodine increased as well as the use of 18F PET as a substitute for conventional bone scans. The number of radionuclide therapies, in particular non-thyroid treatments, increased since the mid-nineties and stabilized at nearly 50000 cases per year with shorter lengths of stay. CONCLUSION: The details of the present analysis may help to understand the positive evolution of key numbers for nuclear medicine.

Two or four hour [¹8F]FMISO-PET in HNSCC. When is the contrast best?

UNLABELLED: [¹8F]Fluoromisonidazole positron emission tomography (FMISO-PET) is a non invasive imaging technique that can assist detecting intra tumour regions of hypoxia. FMISO-PET evinces comparatively low signal-to-noise-ratio (SNR) and may be acquired dynamically or after different uptake times post injection (p.i.). The aim of this study was to identify, if static images acquired two hours (MISO2) or four hours (MISO4) p.i. reveal higher contrast. PATIENTS, METHODS: As part of a prospective trial, 23 patients with cancers of the head and neck underwent [¹8F]fluorodeoxyglucose (FDG) PET before and during curative radiochemotherapy. Additionally, FMISO-PET studies 2 h and 4 h p.i. were done before treatment and after a mean dose of 11Gy, 23 Gy and 57 Gy during RCT. After coregistration, a dedicated software was used to define the gross tumour volume (GTV) by FDG PET for the primary tumour. This volume was overlaid to the FMISO images and hypoxia within the GTV was determined. The contrast between hypoxia determined by MISO2 and by MISO4 was investigated and analysed with the Wilcoxon-matched-pairs test. RESULTS: Mean SUVmax in tumours of all examinations was 2.2 (stdev: 0.4, min: 1.3, max: 3.4) after 2 h and 2.4 (stdev: 0.7, min: 1.1, max: 4.4) after 4 h. In the neck musculature the mean SUVmax was 1.5 at both time points and the mean SUVmean decreased from 1.2 after 2 h to 1.1 after 4 h, respectively. These effects resulted in significantly rising contrast ratios from MISO2 to MISO4. The differently defined contrasts revealed significantly higher values for examinations 4 h p.i. (p < 0.002). CONCLUSION: Data acquisition of [¹8F]FMISO should be done 4 h p.i. to gather the optimal contrast, preferably allowing further analysis, e. g. hypoxic sub volume definition for therapy planning.

Reduced diffusion in white matter after radiotherapy with photons and protons.

BACKGROUND AND PURPOSE: Radio(chemo)therapy is standard in the adjuvant treatment of glioblastoma. Inevitably, brain tissue surrounding the target volume is also irradiated, potentially causing acute and late side-effects. Diffusion imaging has been shown to be a sensitive method to detect early changes in the cerebral white matter (WM) after radiation. The aim of this work was to assess possible changes in the mean diffusivity (MD) of WM after radio(chemo)therapy using Diffusion-weighted imaging (DWI) and to compare these effects between patients treated with proton and photon irradiation. MATERIALS AND METHODS: 70 patients with glioblastoma underwent adjuvant radio(chemo)therapy with protons (n = 20) or photons (n = 50) at the University Hospital Dresden. MRI follow-ups were performed at three-monthly intervals and in this study were evaluated until 33 months after the end of therapy. Relative white matter MD changes between baseline and all follow-up visits were calculated in different dose regions. RESULTS: We observed a significant decrease of MD (p < 0.05) in WM regions receiving more than 20 Gy. MD reduction was progressive with dose and time after radio(chemo)therapy (maximum: -7.9 ± 1.2% after 24 months, ≥50 Gy). In patients treated with photons, significant reductions of MD in the entire WM (p < 0.05) were seen at all time points. Conversely, in proton patients, whole brain MD did not change significantly. CONCLUSIONS: Irradiation leads to measurable MD reduction in white matter, progressing with both increasing dose and time. Treatment with protons reduces this effect most likely due to a lower total dose in the surrounding white matter. Further investigations are needed to assess whether those MD changes correlate with known radiation induced side-effects.

TSH receptor antibody (TRAb) assays based on the human monoclonal autoantibody M22 are more sensitive than bovine TSH based assays.

Measurements of TSH receptor autoantibodies (TRAb) using assays based on the human monoclonal TSH receptor autoantibody M22 or bovine TSH have been compared in 136 adult patients. They suffered from Graves' disease (GD, n=62), Hashimoto's thyroiditis (HT, n=26), or non-autoimmune hyperthyroidism (NAH, n=48) and were selected on the basis of undetectable, borderline or low TRAb levels (0.6-3 IU/l) as measured by TSH based TRAb assay (Dynotest TRAKhuman from BRAHMS). The time interval between initial diagnosis of GD and TRAb determination was high and ranged from 1 month to 3.5 years (median: 2.3 years). Using the kit manufacturer's cutoff values, 53/62 (85.5%) of the selected group of GD patients were TRAb positive (>0.4 IU/l) by M22 based TRAb ELISA (Medizym TRAb clone, Medipan) and 45/62 (72.6%) were TRAb positive (>1.5 IU/l) by TSH based TRAb assay. In the HT group, 9/26 (34.6%) sera were positive in the M22 based ELISA and all but one of these 9 were positive or borderline in the TSH based assay. ROC plot analysis of the GD group using the NAH group as reference showed that at 95% specificity, the bovine TSH based TRAb assay had a sensitivity of 62.9% (cutoff for positivity=1.64 IU/l) and the M22 based TRAb ELISA a sensitivity of 90.3% (cutoff for positivity=0.32 IU/l). Overall therefore, the M22 based Medizym TRAb clone assay is more sensitive than the bovine TSH based Dynotest TRAK human assay.

[Biological aspects of radiation in nuclear medicine]. / Strahlenbiologie. Sicht der Nuklearmedizin.

Radiotherapy with unsealed radionuclides differs from external radiotherapy with regard to the radiation quality and energy range, the regional dose uniformity and the time course of irradiation regimen. External radiotherapy is planned precisely and can be applied to a target volume independently from blood flow during a course of irradiation fractions. In contrary, administered radiopharmaceuticals distribute according to their pharmacokinetic properties and generate a continuous irradiation corresponding to the effective halflife. The resulting dose rates are approximately 1Gy/min and 1Gy/h, respectively. The biokinetics of radiopharmaceuticals involves cellular accumulation and retention with highly variable affinity to specific organs that can be modulated as well. A remarkable dose gradient is found at the edge of volumes with enhanced uptake. The biological effect of an irradiation with decreasing intensity can be compared with the radiation effect caused by conventional fractionation with 2 Gy a day in external beam therapy by means of the linear-quadratic model. However, the experimental validation of this translation is still under investigation. Radionuclide therapy is usually performed in several cycles some month apart. This procedure fails to meet external radiotherapy. The vision of a combined external-internal radiotherapy requires efforts for a common dosimetry approach both in vitro and in vivo with a physical and biological verification of the results.

[Positron emission tomography 2008 in Germany - results of the query and current status]. / Positronenemissionstomographie 2008 in Deutschland - Ergebnisse der Erhebung und Standortbestimmung.

AIM: The working group on positron emission tomography (PET) of the DGN (German Society of Nuclear Medicine) initiated this first survey to collect and analyse information on the practise of PET in Germany in the year 2008. METHODS: A questionnaire was sent to PET performing facilities (medical practices, hospitals, university hospitals and others) for retrospective data acquisition. Details regarding the equipment and examination procedures were examined as well as indications and number of studies. In addition, the role of PET within the diagnostic process was evaluated. RESULTS: Responses from 65 sites were analysed. Their technical equipment consisted of 77 PET scanners (40 of them were combined PET/CT devices). About 63500 PET studies had been performed with 86% in the field of oncology, 8% in neurology and 3% in cardiology. The radiotracers were labelled with 18F in 91% of the studies, whereas 68Ga was used in 4% and 11C in 3%. The analyses revealed lung tumours as the most investigated tumour entity, followed by malignant lymphoma, tumours of the gastro-intestinal tract and prostate cancer (about 14000, 6000, 5000 and 2000). Corresponding to the new scanners and software procedures, the number of studies with attenuation correction by CT was high (68%) and nearly all studies were reconstructed iteratively (99%). The PET images were analysed quantitatively in the majority of cases (91%). The clinical reports, which included image documentation for the greater part, were posted regularly within 3 days. However, in 70% of the sites electronic transfer possibilities were used additionally to speed up the diagnostic process. The high standard of quality was demonstrated by the fact, that 40 facilities were engaged in a tumour board. Further on, one third of the physicians had gained a PET certification awarded by the DGN. CONCLUSION: Relative to the high general standard of diagnostic instrumentation in Germany, PET is less established, in particular when compared with other industrialised countries such as USA and Switzerland.

[PET and diagnostic technology evaluation in a global clinical process. DGN's point of view]. / Vorbehalte der DGN zur Nutzenbewertung der PET durch das IQWiG.

The German Society of Nuclear Medicine (DGN) criticizes the methodological approach of the IQWiG for evaluation of PET and the conclusions, which represent the opposite point of view compared to the most other European countries and health companies in the USA: 1.) Real integration of experienced physicians into the interpretation of data and the evaluation of effectiveness should be used for best possible reporting instead of only formal hearing. 2.) Data of the National Oncologic PET Registry (NOPR) from the USA have shown, that PET has changed the therapeutic management in 38% of patients. 3.) The decision of the IQWiG to accept outcome data only for their benefit analyses, is controversial. Medical knowledge is generated by different methods, and an actual analysis of the scientific guidelines has shown that only 15 % out of all guidelines are based on the level of evidence demanded by the IQWiG. Health economics has created different assessment methods for the evaluation of a diagnostic procedure. The strategy chosen by the IQWiG overestimated the perspective of the population and undervalue the benefit for an individual patient. 4.) PET evaluates the effectiveness of a therapeutic procedure, but does not create an effective therapy. When the predictive value of PET is already implemented in a specific study design and the result of PET define a specific management, the trial evaluate the whole algorithm and PET is part of this algorithm only. When PET is implemented as test during chemotherapy or by the end of chemotherapy, the predictive value of PET will depend decisively on the effectiveness of the therapy: The better the therapy, the smaller the differences in survival detected by PET. 5.) The significance of an optimal staging by the integration of PET will increase. Rationale is the actual development of "titration" of chemotherapy intensity and radiation dose towards the lowest possible, just about effective dosage. 6.) The medical therapy of malignancies will be improved continuously. It is the claim of the health insurances to implement innovative therapeutic approaches in controlled clinical trials with tools of quality control. The monitoring committee is responsible for the safety of the patients. PET is part of the health care. Internationally accepted rules for clinical trials stipulate that any interim analyses of those trials are confidential as long as recruitment is active. The delay until evidence is documented by the published final analysis is methodologically accepted and not a characteristic of PET. 7.) Procedures in nuclear medicine without the use of PET-tracers with short half-life will increase the radiation exposure of the patients; the use of non-PET-tracers with longer half-life is in contravention of the German regulation of radiation protection.

[Ventilation-perfusion-lungscintigraphy using PET and 68Ga-labeled radiopharmaceuticals]. / Ventilations-Perfusions-Lungenszintigraphie mit der PET und 68Ga-markierten Radiopharmaka.

AIM: Imaging of lung perfusion with positron emission tomography (PET) is already possible with 68Ga labeled denaturized albumin. The purpose of our study was to produce and test a 68Ga labeled aerosol (Galligas®) for ventilation and 68Ga labeled albumin particles (microspheres) for perfusion imaging with PET. PATIENTS, METHODS: Galligas was produced by simmering and burning generator eluted 68Ga solution (100 MBq/0.1 ml) in an ordinary technegas generator. Fifteen patients with suspicion on pulmonary embolism underwent PET/CT (Biograph 16) after inhalation of Galligas and application of 68Ga labeled microspheres. A low dose CT was acquired for attenuation correction (AC). Images were reconstructed with and without AC. The inhaled activity was calculated compared to the activity injected. RESULTS: Inhaled radioaerosol Galligas demonstrated typical distribution as known from 99mTc-labeled technegas with homogeneous distribution in lung without hilar deposits. Attenuation corrected images resulted in artefacts in the lung base. Therefore, non-corrected images were used for making the results. Three out of fifteen patients showed a deficient perfusion whereas ventilation was normal corresponding to pulmonary embolism. CONCLUSION: Lung scintigraphy with PET is feasible. Galligas is simple to produce (analogously to technegas). 68Ga labeled microspheres are available. The method is applicable to daily routine and rendered clinically relevant informations.

[Chromatographic determination of radiochemical purity - replacement of ITLC SG]. / Chromatographische Bestimmung der radiochemischen Reinheit von Radiopharmaka - Alternativen zu ITLC SG.

UNLABELLED: Thin layer chromatography is well established for quality control of radiopharmaceuticals. A convenient and widely used stationary phase are ITLC SG strips. However, the Pall Corporation stopped manufacturing of the silica gel impregnated glass fibre strips (ITLC SG). Material, Methode: As a replacement we tested silicic acid impregnated glass fibre strips from Varian (ITLC SA) and sufficient mobile phases. RESULTS: The chromatography with these strips takes two to three times longer than with ITLC SG, but it is in an acceptable range. Only three mobile phases are necessary to test most of the common in-house made radiopharmaceuticals. CONCLUSION: The proposed method is suitable for routinely measuring the radiochemical purity of radiophamaceuticals.

[99mTc reduces clonogenic survival after intracellular uptake in NIS-positive cells in vitro more than 131I]. / 99mTc reduziert nach intrazellulärer Aufnahme in NIS-positiven Zellen in vitro das klonogene Uberleben stärker als 131I.

AIM: In addition to gamma radiation of 140 keV 99mTc emits during the transition to 99Tc electrons of low energy and tiny path-lengths. These Auger electrons cannot be utilized in diagnostic procedures. However, they were discussed frequently for therapeutic application. Hitherto proof of effect of the Auger electrons from 99mTc is missing which is supplied now in an in vitro-system in comparison to beta-emitter 131I. METHODS: The thyroid cell line PCCl3 (sodium iodide symporter (NIS)-positive) was incubated with 131I-sodium iodide (131I) or 99mTc-pertechnetate (99mTc) in presence or absence of perchlorate. For comparison the amount of radioactivity was adjusted to obtain the same dose from extracellular irradiation for both radionuclides. The colony forming assay detects the clonogenic cell survival as surviving fraction. In addition, intracellular radionuclide uptake was quantified. RESULTS: Dose effect curves were established for 131I and 99mTc for variable extra- and intracellular distribution of the radioactivity. In presence of perchlorate no cellular uptake of radioactivity was detectable. Survival curves were largely comparable confirming the dosimetric calculations. In absence of perchlorate cellular radiotracer uptake varied from 1.39% (131I) to 1.90% 99mTc). Effects on survival were twice for the beta-emitter and ten-fold higher for 99mTc. CONCLUSIONS: Intracellular uptake of 131I and 99mTc increases DNA-damage compared to strict extracellular radiotracer distribution which was demonstrated by means of colony forming assay. Increasing radiotoxicity from intracellular 99mTc is explained most likely by increased dose deposition in cellular structures due to Auger- and conversion-electrons of low range and high local energy deposition.

[DNA damage in lymphocytes after irradiation with 211At and 188Re]. / DNA-Schäden von Lymphozyten nach Bestrahlung mit 211At und 188Re - Quantifizierung mit dem alkalischen und neutralen Komet-Assay.

AIM: Ionising radiation produces many types of DNA lesions of different complexity. High linear energy transfer (LET) types of radiation are biological more effective than low LET radiation. In the present work we applied the single cell gel electrophoreses (comet assay) to study the induction of initial DNA damage, efficiency of repair and residual DNA damage in lymphocytes after treatment with 211At and 188Re. METHODS: Peripheral blood mononuclear cells (PBMC) were isolated from heparinized blood of healthy donors and irradiated with 211At and 188Re at different doses. The comet assay was performed under alkaline and neutral conditions in order to detect the initial DNA damage and its repair. The measure of damage was % tail DNA (percentage of DNA in the tail). RESULTS: After treatment of cells with 188Re the initial DNA damage (% tail DNA) detected with the alkaline comet assay was higher than the damage measured for 211At. The neutral comet assay estimated higher tail intensities for 211At in contrast to 188Re. Compared with the complete repair (10%) after irradiation with 188Re, the radiotoxicity of alpha particles indicated reduced rejoining of DNA strand breaks (60-80% residual damage). Rejoining of DNA damage measured by the neutral comet method detected about 70% unrepaired strand breaks for 211At and 188Re. CONCLUSIONS: There are major differences between the repair of strand breaks caused by 188Re and 211At detected by the alkaline comet assay. The DNA-damage induced by the high LET Emitter 211At remains nearly unrepaired detected by both alkaline and neutral comet assay. Represented data following irradiation of lymphocytes with alpha and beta particles demonstrated higher biological effectiveness of 211At by factors of 2.0-2.5.

[BeO-OSL detectors for dose measurements in cell cultures]. / Anwendung von BeO-OSL-Detektoren zur Dosismessung in Zellkulturen.

AIM: The absorbed dose is an important parameter in experiments involving irradiation of cells in vitro with unsealed radionuclides. Typically, this is estimated with a model calculation, although the results thus obtained cannot be verified. Generally used real-time measurement methods are not applicable in this setting. A new detector material with in vitro suitability is the subject of this work. METHODS: Optically-stimulated luminescence (OSL) dosimeters based on beryllium oxide (BeO) were used for dose measurement in cell cultures exposed to unsealed radionuclides. Their qualitative properties (e. g. energy-dependent count rate sensitivity, fading, contamination by radioactive liquids) were determined and compared to the results of a Monte Carlo simulation (using AMOS software). OSL dosimeters were tested in common cell culture setups with a known geometry. RESULTS: Dose reproducibility of the OSL dosimeters was +/-1.5%. Fading at room temperature was 0.07% per day. Dose loss (optically-stimulated deletion) under ambient lighting conditions was 0.5% per minute. The Monte Carlo simulation for the relative sensitivity at different beta energies provided corresponding results to those obtained with the OSL dosimeters. Dose profile measurements using a 6 well plate and 14 ml PP tube showed that the geometry of the cell culture vessel has a marked influence on dose distribution with 188Re. CONCLUSION: A new dosimeter system was calibrated with beta-emitters of different energy. It turned out as suitable for measuring dose in liquids. The dose profile measurements obtained are suitably precise to be used as a check against theoretical dose calculations.