The effect of hypoxia on the induction of strand breaks in plasmid DNA by alpha-, beta- and Auger electron-emitters 223Ra, 188Re, 99mTc and DNA-binding 99mTc-labeled pyrene.

INTRODUCTION: Radiation-induced DNA damage occurs from direct and indirect effects. The induction is influenced by the physical characteristics of the radionuclide, especially its linear energy transfer. Hypoxia reduces the effect of irradiation treatment in tumor cells and leads to poor patient outcomes. High linear energy transfer emitters can overcome this obstacle. Our aim is to demonstrate the influence of hypoxia on the interaction of different radiation qualities with isolated DNA. METHODS: PuC19 Plasmid DNA was irradiated with 223Ra, 188Re, 99mTc and 99mTc-labeled pyrene with and without DMSO under hypoxia or normoxic conditions. DNA damages in form of single-(SSB) and double-strand breaks (DSB) were analyzed by gel electrophoresis. RESULTS: Radiation doses up to 200 Gy of 223Ra, 188Re and 99mTc led to maximal yields of 80% SSB and 30%, 28% and 32% DSB, respectively. Hypoxia had minor effects on damages from 223Ra, but caused a small enhancement in DSB for 188Re and 99mTc. DMSO prevented DSB completely and reduced SSB from the "free" radionuclides to comparable levels. DNA-binding 99mTc-labeled pyrene induced less SSB and DSB compared to [99mTc]TcO4-. However, the incubation with DMSO could prevent the SSB and DSB induction only to a minor extent. CONCLUSIONS: Hypoxia does not limit DNA damage induced by 223Ra, 188Re, 99mTc and 99mTc-labeled pyrene. Dose-dependent radiation effects were comparable for alpha-emitters and both high- and low-energy electron emitters. The radioprotection by DMSO was not influenced by hypoxia. The results indicate the contribution of mainly indirect radiation effects for 99mTc, 188Re and 223Ra. 99mTc-labeled pyrene caused direct DNA damages and Auger-electrons from 99mTc-labeled pyrene are more effective than high-energy electrons or alpha particles. ADVANCES IN KNOWLEDGE: Without the consideration of DNA repair mechanisms, oxygen has no direct influence in radiation-induced DNA damages by different radiation qualities. IMPLICATIONS FOR PATIENT CARE: The short-time stimulation with oxygen during patient radiation could have minor influence compared to constant oxygen flooding to overcome hypoxic barriers.

[Radiation Exposition of preparations of radiopharmaceuticals in routinely use, measured with optical-stimulated luminescence (OSL) dosimeters]. / Strahlenexposition bei der Herstellung von Radiopharmaka im nuklearmedizinischen Routinelabor, gemessen mit optisch stimulierten Lumineszenzdetektoren (OSL).

AIM: Because of the new regulation of the radiation protection in Germany in 2018 (Strahlenschutzverordnung) it was meaningful to calculate an overview of the radiation exposition of the personal in the radiopharmaceutical "Hotlab". The regulation demands that the radiation exposition must be minimized, documented and reduced to an optimized level. In the Klinik und Poliklinik für Nuklearmedizin at the University Hospital of Dresden measurements were done with optical-stimulated luminescence (OSL) dosimeters. MATERIALS AND METHODS: Light protected OSL dosimeters were positioned on the fingertips (thumb, forefinger and middle finger) of both hands and on the forehead. Before use the OSL dosimeters were calibrated. The exposition of the hands was measured at three different days in the preparation lab: 99mTc preparation in the daily routine, syringes application for radiosynoviorthesis (RSO) and 90Y Sirtex particles and for preparation of 177Lu and 68Ga radiopharmaceuticals. RESULTS: A relatively high exposition was seen after 99mTc preparations because of the quantity of preparations and syringes. Handling of syringes for RSO lead to an likewise raised exposition. The radiation exposition at preparation of 177Lu and 68Ga radiopharma-ceuticals depends on handling and use of modules. The exposition of the eye lenses was 0.02 mGy or lower and therefore not critical. But an appropriate radiation protection is necessary and a requirement for the most slightly radiation exposition. CONCLUSION: An optimized number of personal is necessary for preparation of radiopharmaceuticals in a "Hotlab" in nuclear medical facility. Therefore, the individual radiation exposition will be limited.

A theranostic PSMA ligand for PET imaging and retargeting of T cells expressing the universal chimeric antigen receptor UniCAR.

Chimeric antigen receptor (CAR) T cells have shown impressive therapeutic potential. Due to the lack of direct control mechanisms, therapy-related adverse reactions including cytokine release- and tumor lysis syndrome can even become life-threatening. In case of target antigen expression on non-malignant cells, CAR T cells can also attack healthy tissues. To overcome such side effects, we have established a modular CAR platform termed UniCAR: UniCAR T cells per se are inert as they recognize a peptide epitope (UniCAR epitope) that is not accessible on the surface of living cells. Bifunctional adapter molecules termed target modules (TM) can cross-link UniCAR T cells with target cells. In the absence of TMs, UniCAR T cells automatically turn off. Until now, all UniCAR TMs were constructed by fusion of the UniCAR epitope to an antibody domain. To open up the wide field of low-molecular-weight compounds for retargeting of UniCAR T cells to tumor cells, and to follow in parallel the progress of UniCAR T cell therapy by PET imaging we challenged the idea to convert a PET tracer into a UniCAR-TM. For proof of concept, we selected the clinically used PET tracer PSMA-11, which binds to the prostate-specific membrane antigen overexpressed in prostate carcinoma. Here we show that fusion of the UniCAR epitope to PSMA-11 results in a low-molecular-weight theranostic compound that can be used for both retargeting of UniCAR T cells to tumor cells, and for non-invasive PET imaging and thus represents a member of a novel class of theranostics.

68Ga-RM2 PET in PSMA- positive and -negative prostate cancer patients.

AIM: 68Ga-PSMA-11 is the gold standard for molecular imaging of prostate cancer. However, recurrent tumor manifestations or metastases cannot be detected in every case. Therefore, we investigated if there is an additive value of the gastrin-releasing peptide receptor (GRP-R) ligand 68Ga-RM2 compared to the well-established 68Ga-PSMA-11 in patients with (Group 1) and without (Group 2) pathologic PSMA-expression in different tumor stages. PATIENTS AND METHODS: Sixteen men (median age: 74 years, range 50-80 years) with prostate cancer in different stages who had a recent negative (n = 8) or pathologic (n = 8) PSMA PET underwent a subsequent 68Ga-RM2 PET. Both examinations were analyzed qualitatively and quantitatively and compared in terms of pathologic and physiologic tracer distribution. RESULTS: None of the PSMA-negative patients showed any pathological RM2-accumulation. Pathologic PSMA-uptake was observed in 8 patients of whom 5 had pathologic RM2-uptake. The number of patients with a local recurrence was equal in both scans (n = 3). Bone metastases and lymph node metastases were detected in less patients in RM2 PET compared to PSMA PET (n = 4 vs. 7 and n = 2 vs. 5, respectively). In one patient, PSMA-positive liver metastases were not detected in RM2. RM2 PET revealed two additional lesions indicative for bone metastases in two patients with multiple PSMA-positive bone metastases, which had no therapeutic consequence. CONCLUSION: At least in our small and heterogeneous patient population, 68Ga-RM2 showed no clinically relevant, additional benefit compared to 68Ga-PSMA-11 PET.

[Radio- and photosensitization of plasmid DNA by DNA binding ligand propidium iodide: Investigation of Auger electron induction and detection of Cherenkov-emission]. / Radio- und Photosensitivierung von Plasmid-DNA durch den DNA-bindenden Liganden Propidiumiodid: Untersuchungen zur Auger-Elektronen-Induktion und zum Nachweis von Cherenkov-Strahlung.

PURPOSE: We investigated whether propidium iodide (PI) enhances DNA damaging effects of ionizing and non-ionizing radiation species (X-rays, alpha-, beta-, auger electron emission and light of various wavelengths, respectively). This biophysical experimental setting allowed us, furthermore, to investigate whether Cherenkov emission can be detected by photodynamic effects and increased DNA damage. MATERIAL AND METHODS: Conformation changes of plasmid DNA were detected and quantified by gelelectrophoresis and fluorescence imaging. Hydrogen peroxide, stannous dichloride, and dimethylsulfoxide were used as chemical modulators, Tc-99m, Re-188, Ra-223, and x-ray (32 kV and 200 kV) reflected radiotoxicity and light (λ = 254 nm, 366 nm and 530-575 nm) induced phototoxicity. RESULTS: Radiotracers and x-rays induced dose dependent DNA damage. PI did not serve as radiosensitizer in radioisotopes, while a low effect was detected in X-rays. The phototoxicity was dependent on the wavelengths of light. Light with a wavelength range of 530-575 nm in combination with PI resulted in direct DNA damage. The yield of Cherenkov emission was far below the photon emission of light irradiation and not distinguishable from general radiotoxicity. CONCLUSIONS: PI binds to plasmid DNA, is not chemotoxic, and increases radiotoxicity only to minor extent. Phototoxicity and its stimulation by PI is dependent on the wavelength of the light. No kind of energy deposition was capable of inducing an Auger electron cascade. Furthermore, no increase in DNA damage induced by photodynamic effects from Cherenkov emission was detectable.

Dual-time-point 64 Cu-PSMA-617-PET/CT in patients suffering from prostate cancer.

Regardless of its high positron energy, 68 Ga-labeled PSMA ligands have become standard of care in metabolic prostate cancer imaging. 64 Cu, a radionuclide with a much longer half-life (12.7 h), is available for PSMA labeling allowing imaging much later than 68 Ga. In this study, the diagnostic performance of 64 Cu-labeled PSMA was compared between early and late scans. Sixteen men (median age: 70 y) with prostate cancer in different stages underwent 64 Cu-PSMA-617-PET/CT 2 and 22 hours post tracer injection. Pathologic and physiologic uptakes were analyzed for both points of time. Pathologic tracer accumulations occurred in 12 patients. Five patients presented with pathologic uptake in 17 different lymph nodes, two patients showed pathologic bone uptake in nine lesions, and seven patients had pathologic PSMA uptake in eight prostatic lesions. Physiologic uptake of the renal parenchyma, urine bladder, and salivary glands decreased over time, while the physiologic uptake of liver and bowel increased. In the present study, 64 Cu-PSMA-617-PET demonstrated to be feasible for imaging prostate cancer for both the primary tumor site and metastases. Later imaging showed no additional, clinically relevant benefit compared with the early scans. At least the investigated time points we chose did not vindicate the additional expenditure.

Feasibility of CXCR4-Directed Radioligand Therapy in Advanced Diffuse Large B-Cell Lymphoma.

We have recently reported on our experience with C-X-C-motif chemokine receptor 4 (CXCR4)-directed radioligand therapy (RLT) in multiple myeloma and acute leukemia. Methods: Six patients with heavily pretreated relapsed diffuse large B-cell lymphoma (3 men, 3 women; aged, 54 ± 8 y) underwent CXCR4-directed RLT in combination with conditioning chemotherapy and allogeneic stem cell transplantation. In 2 patients, radioimmunotherapy targeting CD20 or CD66 was added to enhance antilymphoma activity. Endpoints were incidence and severity of adverse events, progression-free survival, and overall survival. Results: RLT and additional radioimmunotherapy were well tolerated, without any acute adverse events or changes in vital signs. Successful engraftment was recorded after a median of 11 d (range, 9-13 d). Of the 4 patients who were available for follow-up (one patient died of CNS aspergillosis 29 d after RLT and another of sepsis in aplasia 34 d after RLT), CXCR4-directed RLT resulted in a partial response in two (both treated with additional radioimmunotherapy) and a mixed response in the remaining two. The response duration was rather short-lived, with a median progression-free survival of 62 d (range, 29-110 d) and a median overall survival of 76 d (range, 29-334 d). Conclusion: CXCR4-directed RLT (in combination with additional radioimmunotherapy) is feasible as a conditioning regimen before allogeneic stem cell transplantation in diffuse large B-cell lymphoma.

[Combined internal-external radiotherapy (CIERT) in a cell model]. / Untersuchungen zur kombinierten internen-externen Radiotherapie (CIERT) am Zellmodell.

AIM: Combined internal-external radiotherapy (CIERT) requires a unified assessment of biologic radiation effects in addition to the total dose. The concept of biological effective dose (BED) was evaluated in a cell model. METHODS: The thyroid NIS-positive cell line FRTL-5 was irradiated with X-ray and the radiotracer Tc-99m pertechnetate either alone or in combination. The cellular uptake of the radionuclide during the incubation time of 24 h was controlled by the presence or absence of perchlorate. Dose calculation was performed based on measured uptake values. Cell specific radiobiologic parameters were derived from dose effect curves using the colony forming assay as biological endpoint. For the combination of the radiation qualities the sequence and time difference were varied. Cell survival was compared with the prediction of the BED model. RESULTS: The radiobiologic parameters from X-ray dose response were α = (0.22 ± 0.02) Gy-1 and ß = (0.021 ± 0.001) Gy-2. The half life for repair was (1.51 ± 0.21) h. These values could also explain the dose response curves for Tc-99m-irradiation with exponential decreasing dose rate. CIERT experiments showed no significant differences in cell survival regarding sequence and irradiation break. When the radionuclide uptake was not prevented the cell survival for the combination of X-ray and Tc-99m was lower than the prediction by BED calculations. CONCLUSIONS: The validity of the BED formalism for different dose rates and radiation qualities was verified. Supraaddive effects measured in the combination of X-ray and intracellular Tc-99m might be caused by Auger and conversion electrons, however further experiments are necessary.

A novel third-generation TSH receptor antibody (TRAb) enzyme-linked immunosorbent assay based on a murine monoclonal TSH receptor-binding antibody.

TSH receptor (TSHR) autoantibody (TRAb) is the serological hallmark of Graves' disease (GD). Third-generation enzyme-linked immunosorbent assays (ELISAs) using monoclonal TRAbs instead of TSH have been found useful for TRAb analysis recently. For the first time, a mouse monoclonal antibody (mAb) against TSHR was analyzed for TRAb detection and compared with human mAb M22 and TSH by the same competitive binding assay technique. A mouse monoclonal antibody (T7) binding to the TSH receptor and inhibiting TSH binding was generated and used for TRAb analysis in a third-generation ELISA. Obtained TRAb levels were compared with a second-generation TRAb assay employing bovine TSH and a third-generation assay with human mAb M22 as TSHR-binding reagents by investigating 89 patients with GD, 56 with Hashimoto's thyroiditis (HT), 73 with non-autoimmune thyroid diseases, 17 with rheumatoid arthritis, and 100 healthy subjects. The T7-based TRAb ELISA did not reveal a significantly different assay performance (area under the curve [AUC]) in contrast to the TSH and M22-based TRAb ELISAs by receiver operating characteristic (ROC) curve analysis (AUC-T7 0.967, AUC-TSH 0.972, AUC-M22 0.958, p > 0.05, respectively). After adjustment of cutoffs by ROC, all three TRAb ELISAs demonstrated sensitivities and specificities above 89.9% and 96.0%, respectively. Both third-generation TRAb ELISAs showed a tendency for a higher prevalence of TRAb positives in HT in contrast to the second-generation ELISA. Mouse mAbs against the TSHR may be used for the reliable detection of TRAb by third-generation TRAb ELISA. The earlier reported higher sensitivity of third-generation TRAb ELISA in GD needs to be considered in the context of a slightly lower specificity regarding HT.

Twins in spirit part IV - [177Lu] high affinity DOTATATE. A promising new tracer for peptide receptor radiotherapy?

AIM: Besides the use of somatostatin analogues, small molecules like sunitinib and everolimus as well as conventional chemotherapy, peptide receptor radiotherapy (PRRT) using radiolabelled somatostatin analogues has gained an important role in the treatment of inoperable, metastasized neuroendocrine tumours (NET). There are various radiotracers in use. Based on our experience with the PET tracer [68Ga]DOTA-3-iodo-Tyr3-octreotate ([68Ga]HA-DOTATATE), a DOTATATE derivative with an increased binding affinity to hsst5, the current retrospective analysis is exploring the therapeutic potential of [177Lu]HA-DOTATATE. METHODS: Eighteen patients with metastatic NET (G1/G2) were treated using [177Lu]DOTATATE and/or [177Lu]HA-DOTATATE, and dosimetric results of both tracers were compared. RESULTS: Using [177Lu]HA-DOTATATE, a mean tumour dose of 5.34 Gy/GBq (median 2.53 Gy/GBq; range 0.89-33.3 Gy/GBq) was achieved, while [177Lu]DOTATATE delivered a tumour dose of 5.53 Gy/GBq (median 2.70 Gy/GBq; range 0.44-15.3 Gy/GBq). Organ doses for [177Lu]HA-DOTATATE vs. [177Lu]DOTATATE were as follows: kidney 2.31 ± 0.85 vs. 2.03 ± 0.96 Gy/GBq, liver 1.06 ± 0.79 vs. 1.67 ± 1.73 Gy/GBq, spleen 3.89 ± 4.04 vs. 4.50 ± 3.69 Gy/GBq and whole body 0.16 ± 0.10 Gy/GBq vs. 0.15 ± 0.08 Gy/GBq. Tumour-to-kidney dose ratio was slightly higher for [177Lu]DOTATATE (2.4 ± 5.6) compared to [177Lu]HA-DOTATATE (1.5 ± 3.6). CONCLUSION: Both tracers showed marked inter-patient variation in their dosimetry, and no significant differences in dosimetry of [177Lu]HA-DOTATATE and [177Lu]DOTATATE were observed when taking all patients into account. Thus, [177Lu]HA-DOTATATE appears viable for PRRT, although it was marginally inferior regarding kidney dose and tumour-to-kidney dose ratio compared to the established [177Lu]DOTATATE.

Comparison of the radiotoxicity of the 99mTc-labeled compounds 99mTc-pertechnetate, 99mTc-HMPAO and 99mTc-MIBI.

PURPOSE: In addition to gamma radiation, 99mTc emits low-energy Auger electrons with path-lengths of nanometers to micrometers that cannot be utilized for diagnostic procedures; however, they have frequently been discussed for therapeutic applications. We compared radiotoxicity of three 99mTc-labeled radiopharmaceuticals with differences in the subcellular distribution. MATERIALS AND METHODS: The intracellular radionuclide uptake and subcellular distribution of [99mTc]-pertechnetate (99mTc-pertechnetate), [99mTc]Tc-hexamethyl-propylene-aminoxime (99mTc-HMPAO) and [99mTc]Tc-hexakis-2-methoxyisobutylisonitrile (99mTc-MIBI) were quantified in rat thyroid FRTL-5 cells. Radiotoxicity was compared using late phosphorylated histone H2AX (γH2AX) foci as a marker for unrepaired DNA double-strand breaks (DNA-DSB) and clonogenic cell survival. RESULTS: 99mTc-HMPAO showed a substantially higher uptake into the nucleus and the membrane/organelles than 99mTc-pertechnetate or 99mTc-MIBI. The colony-forming assay showed that 99mTc-pertechnetate and 99mTc-HMPAO caused a similar reduction in cell survival. 99mTc-MIBI is less radiotoxic in terms of the estimated nucleus dose and induced the fewest number of γH2AX foci compared with the other 99mTc-tracers, and 99mTc-HMPAO induced a fewer number of γH2AX foci than 99mTc-pertechnetate. CONCLUSIONS: Our findings reveal that clonogenic cellular survival is not solely determined by the DNA-DSB response. This finding may suggest the involvement of extra-nuclear radiosensitive targets in cell inactivation. For example, the mitochondria or the cell membrane could be affected by 99mTc-HMPAO.

Reduced-Intensity Conditioning Combined with (188)Rhenium Radioimmunotherapy before Allogeneic Hematopoietic Stem Cell Transplantation in Elderly Patients with Acute Myeloid Leukemia: The Role of In Vivo T Cell Depletion.

The combination of reduced-intensity conditioning, (188)rhenium anti-CD66 radioimmunotherapy, and in vivo T cell depletion was successfully applied in elderly patients with acute myeloid leukemia or myelodysplastic syndrome. Within a prospective phase II protocol, we investigated whether a dose reduction of alemtuzumab (from 75 mg to 50 mg MabCampath) would improve leukemia-free survival by reducing the incidence of relapse. Fifty-eight patients (median age, 67 years; range, 54 to 76) received radioimmunotherapy followed by fludarabine 150 mg/m(2) and busulfan 8 mg/kg combined with either 75 mg (n = 26) or 50 mg (n = 32) alemtuzumab. Although we observed a trend towards a shorter duration of neutropenia in the 50 mg group (median, 19 versus 21 days; P = .07), the time from transplantation to neutrophil and platelet engraftment as well as the overall incidence of engraftment did not differ. The incidence of severe acute graft-versus-host disease tended to be higher after the lower alemtuzumab dose (17% versus 4%; P = .15). No significant differences in the cumulative incidences of relapse (38% versus 35%; P = .81) or nonrelapse mortality (46% versus 27%; P = .31) were observed. Accordingly, disease-free and overall survival were not significantly different between groups. Although the feasibility of radioimmunotherapy plus reduced-intensity conditioning could be demonstrated in elderly patients, the dose reduction of alemtuzumab had no positive impact on overall outcome.

Theranostic mercury: (197(m))Hg with high specific activity for imaging and therapy.

The no carrier added (NCA) radionuclide (197(m))Hg is accessible through proton induced nuclear reactions on gold. The decay properties of both simultaneous produced nuclear isomers (197m)Hg and (197)Hg like convenient half life, low energy gamma radiations for imaging, Auger and conversion electrons for therapy are combined with unique chemical and physical properties of mercury and its compounds. Gold as a monoisotopic element has a natural abundance of 100% (197)Au superseding expensive enrichment for the target material. Additionally, the high thermal conductivity of gold enables high beam current irradiations. For separation of target material a liquid-liquid extraction method was applied.

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 Ga-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.

Dose-dependent histological alterations in the rat lung following intravenous application of Re-188-labeled microspheres.

PURPOSE: The objective of this study was to determine the dose-effect correlation of pneumopathy after application of Rhenium-188 microspheres (Re-188 MS) in an animal model using histological changes as an end-point. METHODS AND MATERIALS: Wistar rats received an intravenous injection of Re-188 MS yielding doses that ranged from ˜ 2 to ˜ 55 Gy. Lungs were removed after ˜ 25 weeks and prepared for histology. Sections were evaluated using a semi-quantitative 5-tiered score. Dose groups of 10 Gy intervals were statistically analyzed using the Chi-square test with respect to grade and extent of connective tissue accumulation, thickness of vessel walls and accumulation of alveolar macrophages (AM). RESULTS: There was a statistically significant increase in connective tissue content and extent in all dose groups compared to control lungs and at least between each other dose group. The steepest increase in connective tissue was at doses higher than 40 Gy. Starting from that dose, a statistically significant increase of AM accumulation and vessel wall thickness occurred. CONCLUSIONS: There was a clear dose-effect correlation between radiation dose and histological changes. These findings allow an estimation of potential normal tissue damage especially during tumor treatments of liver lesions with radioactive particles in patients with significant liver-to-lung shunts.

Comparison between F-18 fluorodeoxyglucose and Ga-68 DOTATOC in metastasized melanoma.

PURPOSE: Somatostatin binding to somatostatin receptors (SSTRs) is known to have an antiproliferative effect in neuroendocrine tumours. Melanoma cells are derived from the neural crest and thus express SSTR. Treatment options in metastasized melanomas are limited. Therefore, we aimed to investigate whether there is a relevant uptake of the SSTR analogue DOTATOC in metastasized melanoma patients, which could be used for therapy with radiolabelled SSTR analogues. MATERIALS AND METHODS: We investigated 18 patients (nine men and nine women; mean age 61 years) with metastasized melanoma using PET/CT, first with F-18 fluorodeoxyglucose ((18)F-FDG) and then with Ga-68 DOTATOC. The number of (18)F-FDG-positive or DOTATOC-positive lesions and the maximum standardized uptake value (SUV(max)) for an index lesion were determined for each patient. RESULTS: DOTATOC could reveal metastatic lesions in 11 of 18 patients (61%). However, on a lesion-by-lesion basis only 59 of 263 (22%) (18)F-FDG-avid metastases were seen with DOTATOC. Further, DOTATOC uptake was only faint. The mean SUV(max) was 3.1 (range, 1.2-4.2) for DOTATOC, in contrast to 28.2 (range, 2.3-115) for (18)F-FDG. CONCLUSION: Radiolabelled DOTATOC does not seem to be a promising agent for treatment of metastasized melanoma.

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 (188)Re. 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 R(2) = 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.

Radiation pneumopathy in the rat after intravenous application of (188)Re-labeled microspheres.

PURPOSE: To determine the dose dependence and kinetics of pneumopathy after systemic administration of rhenium-188 ((188)Re)-labeled microspheres in a rat model. METHODS AND MATERIALS: (188)Re-microspheres were injected intravenously into adult Wistar rats (n = 54, age, 8 ± 2 months). The rats were divided into 6 groups according to the intended absorbed dose in the lung (maximum 60 Gy). Gamma camera scans were used to estimate the individual whole lung doses. One control group (n = 5) received nonlabeled microspheres. The breathing rate was measured before and weekly after the treatment using whole body plethysmography until 24 weeks. An increase in the breathing rate by 20% compared with the individual pretreatment control value was defined as the quantal endpoint for dose-effect analyses. RESULTS: A biphasic increase in the breathing rate was observed. The first impairment of lung function occurred in Weeks 3-6. For late changes, the interval to onset was clearly dose dependent and was 17 weeks (10-30 Gy) and 10 weeks (50-60 Gy), respectively. The incidence of the response was highly dependent on the estimated lung dose. The median effective dose for an early and late response was virtually identical (19.9 ± 0.6 Gy and 20.4 ± 3.1 Gy, respectively). A significant correlation was found between the occurrence of an early and a late effect in the same rat, suggesting a strong consequential component. CONCLUSIONS: The effects of radiolabeled microspheres can be studied longitudinally in a rat model, using changes in the breathing rate as the functional, clinically relevant response. The isoeffective doses from the present study using radionuclide administration and those from published investigations of homogeneous external beam radiotherapy are almost similar.