[en] Monoclonal antibodies C215, reactive with colorectal carcinomas, and MOv18, reactive with most of the ovarian carcinomas, were radiohalogenated with [²¹¹At]astatine. The radiohalogen was conjugate coupled to antibodies via the intermediate labelling reagent N-succinimidyl-3-(trimethylstannyl)benzoate (m-MeATE) in a two-step, single-pot reaction. Optimisation of the labelling of the reagent was achieved using N-iodosuccinimide, NIS, as the oxidising agent. The yields ranged from 69-95% in the labelling of 0.1-1.0 nmole of the m-MeATE precursor. Subsequent conjugation to antibodies resulted in yields of 58±7%. In vitro binding to tumour cells showed that the immunoreactivity of both antibodies was retained after astatine labelling

[en] A method to extract depth of interaction information for γ-rays in a segmented planar Ge detector is presented. The method is demonstrated on signals from a segmented detector which were stored by a digital oscilloscope event by event and analysed off-line. Event samples were acquired for different interaction points in the detector. A Compton scatter coincidence detection technique ensured that the event samples were highly enriched in single-interaction events. By analysing pulse shapes and the relative timing between anode pulses and the pulses from the irradiated cathode segment, a position sensitivity of 1-2 mm in the depth direction was deduced. A similar transverse position sensitivity was inferred by studying image charge pulses on neighbouring segments

[en] Shell-model calculations using realistic interactions reveal that the ground and low-lying yrast states of the N=Z nucleus ₄₆⁹²Pd are mainly built upon isoscalar neutron-proton pairs, each carrying the maximum angular momentum J=9 allowed by the shell 0g_9/2, which is dominant in this nuclear region. This structure is different from that found in the ground and low-lying yrast states of all other even-even nuclei studied so far. The low-lying spectrum of excited states generated by such correlated neutron-proton pairs has two distinctive features: (i) the levels are almost equidistant at low energies and (ii) the transition probability I→I-2 is approximately constant and strongly selective. This unique mode is shown to replace normal isovector pairing as the dominant coupling scheme in N=Z nuclei approaching the doubly magic nucleus ¹⁰⁰Sn.

[en] A detector system for positron emission tomography with time-of-flight capability has been built to serve as an educational tool for undergraduate students. The set-up consists of 48 BaF₂ scintillator crystals, each coupled to a fast photo-multiplier tube, mounted in a circular geometry. The analogue detector pulses are handled by fast constant fraction discriminators. A dedicated unit reduces the 48 channels to eight channels via delay-line encoding, and the signals are then fed to an eight channel fast time-to-digital converter. A VME processor sorts the events and sends them to a workstation where the coincident events are extracted. The time resolution of the detectors together with fast VME based electronics allows for time-of-flight measurements to improve on the signal-to-noise ratio in the reconstructed images. The system can be used for different types of exercises for the students, varying from the fundamentals of scintillator detectors to advanced image reconstruction. The set-up is described and some results are presented

[en] The biodistribution of the radiolabelled monoclonal antibodies MOv18, OV185 and OV197 in nude mice with subcutaneous tumours of the human ovarian cancer cell line OVCAR3 was investigated. The early uptake of MOv18 (1-24 h) and the uptake in relation to tumour size were also studied. The antibodies were labelled with ¹²⁵I according to the Iodogen method or the m-MeATE method, the latter also being suitable for labelling with ²¹¹Astatine. The tumour/blood ratio and the localization index for MOv18 72 h after antibody injection were 2.21±0.25 and 4.62±1.27, respectively. This is significantly higher than for the other two specific antibodies. The early tumour uptake of MOv18 was low with a tumour/blood ratio of 0.23±0.04 after 6 h, and the uptake was higher in small tumours. The two labelling methods were found to be equivalent. We conclude that MOv18 labelled according to the m-MeATE method should be suitable for further therapeutic studies with ²¹¹Astatine in nude mice. (orig.)

[en] A TOF-PET system has been designed and constructed for educational purposes. The aim of this system is to demonstrate the possibilities of positron emission tomography in general and the time-of-flight method in particular to the students of various courses at the Royal Institute of Technology, Stockholm, Sweden. The set-up consists of 48 small BaF₂ crystals coupled to fast photomultipliers placed in a ring geometry. The signals of the photomultipliers are fed into fast constant fraction discriminators (CFD). The outputs of these are directed to a specially designed logic VME unit, which combines the CFD signals of 6 neighbouring channels to one signal by adding a different delay to each channel. The logic circuitry produces a prompt pulse for each event that serves as the start pulse for the 8-channel fast TDC. The delayed pulses act as the stop pulses for the TDC. In a computer, the measured times are converted into information about which the photomultipliers fired with the difference in the time of flight. The set-up is described and the results are presented

[en] High-spin states in ⁸⁵Nb were studied using the GAMMASPHERE Ge detector array and the MICROBALL charged-particle detector system. Three γ-ray cascades with collective rotational characteristics were observed. One of the bands exhibits a forking at the top, most likely reflecting the termination of one branch into a favoured non-collective, near spherical state. The data are interpreted in terms of cranked Strutinsky-type calculations

[en] The nucleus ¹⁷¹Os has been populated using the reaction ¹¹⁶Sn(⁵⁸Ni,2pn). Four new bands are identified, and the previously known bands are extended in spin, to a maximum of 53/2(ℎ/2π). One- and three-quasiparticle configurations are identified, and β, γ, and octupole configurations are assigned tentatively. The effects of a possible intruder configuration on the negative parity bands are tested using band-mixing calculations

[en] Structure of ¹⁰²In has been investigated applying in-beam γ-spectroscopic methods. The experiment was performed at the Legnaro National Laboratory using the ⁵⁴Fe + ⁵⁸Ni reaction at an energy of 240 MeV to populate nuclei in the vicinity of the double magic ¹⁰⁰Sn nucleus. Proposed level scheme of ¹⁰²In is presented. (R.P.)

[en] A high-spin isomeric beam line has been constructed at RIKEN based on the inverse kinematics of fusion-evaporation reactions. The beam line provides high-spin isomers as secondary beams, whose intensity is more than 10⁵ sec^-1. The characteristics and the present status of the beam line are described