Targeting murine heart and brain: visualisation conditions for multi-pinhole SPECT with 99mTc- and 123I-labelled probes

The study serves to optimise conditions for multi-pinhole SPECT small animal imaging of (123)I- and (99m)Tc-labelled radiopharmaceuticals with different distributions in murine heart and brain and to investigate detection and dose range thresholds for verification of differences in tracer uptake.A Triad 88/Trionix system with three 6-pinhole collimators was used for investigation of dose requirements for imaging of the dopamine D(2) receptor ligand [(123)I]IBZM and the cerebral perfusion tracer [(99m)Tc]HMPAO (1.2-0.4 MBq/g body weight) in healthy mice. The fatty acid [(123)I]IPPA (0.94 +/- 0.05 MBq/g body weight) and the perfusion tracer [(99m)Tc]sestamibi (3.8 +/- 0.45 MBq/g body weight) were applied to cardiomyopathic mice overexpressing the prostaglandin EP(3) receptor.In vivo imaging and in vitro data revealed 45 kBq total cerebral uptake and 201 kBq cardiac uptake as thresholds for visualisation of striatal [(123)I]IBZM and of cardiac [(99m)Tc]sestamibi using 100 and 150 s acquisition time, respectively. Alterations of maximal cerebral uptake of [(123)I]IBZM by >20% (116 kBq) were verified with the prerequisite of 50% striatal of total uptake. The labelling with [(99m)Tc]sestamibi revealed a 30% lower uptake in cardiomyopathic hearts compared to wild types. [(123)I]IPPA uptake could be visualised at activity doses of 0.8 MBq/g body weight.Multi-pinhole SPECT enables detection of alterations of the cerebral uptake of (123)I- and (99m)Tc-labelled tracers in an appropriate dose range in murine models targeting physiological processes in brain and heart. The thresholds of detection for differences in the tracer uptake determined under the conditions of our experiments well reflect distinctions in molar activity and uptake characteristics of the tracers

Methoden zur Ortsauflösungsverbesserung bei bildgebenden Verfahren in der Nuklearmedizin

Zur dreidimensionalen Darstellung von Stoffwechselvorgängen wurden in den siebziger und achtziger Jahren die tomographischen Verfahren SPECT und PET entwickelt. In dieser Arbeit werden die Entwicklung und Optimierung physikalischer und messtechnischer Methoden zur Verbesserung der Ortsauflösung von PET und SPECT vorgestellt. Im einleitenden Kapitel werden die zugrunde liegenden physikalischen Wechselwirkungen Simulationsprogramme und die verwendete Messtechnik beschrieben. Im zweiten Kapitel wird die Möglichkeit der zweidimensionalen Ortsauflösungsverbesserung bei der PET durch ein externes statisches Magnetfeld untersucht. Im dritten Kapitel werden Optimierungsverfahren bezüglich der Geometrie und Oberflächenbehandlung von Szintillationskristallen vorgestellt. Die Messdaten unterstützen die Validierung einer Monte-Carlo-Simulation für Lichtquanten. Im letzten Teil wird die Kombination von PET-Kamera und einem Kernspintomographen beschrieben. Dies ermöglicht die zeit- und raumgleiche Akquisition funktioneller (PET) und anatomischer (MRT) Information

High resolution SPECT in small animal research

Single Photon Emission Computed Tomography (SPECT) is a technique used to assess physiological and biochemical processes under in vivo conditions. SPECT generates tomographic images from blood flow, glucose metabolism and receptor characteristics using radioactively labelled substances. This paper reviews the state of the art of in vivo imaging of laboratory animals in modified human and dedicated animal SPECT scanners. SPECT cameras with special collimators currently reach spatial resolutions up to 1 min and sensitivities of about 1000 cps/MBq, allowing observation of receptor activity concentration changes in the pico-mole range. The time resolution of such cameras strongly depends on the pharmacological behaviour of the tracer and can range from several minutes to hours. Within these limits the functional characterization of many processes is possible. SPECT also offers the possibility to set up dynamic study protocols and repeated measurements of the same animal. This technique reduces the need for sacrificing animals, as was commonly practiced before the development of animal cameras. Animal SPECT gives the opportunity to monitor physiological and biochemical processes in animals in vivo, without interfering with the system under observation, and may become a valuable adjunct to the instrumentation (autoradiography, in vitro methods) of animal research