Single photon emission computed tomography

What is SPECT?

Single-photon emission computed tomography (SPECT) is a nuclear based imaging technique that uses radioactive tracers to visualise functional brain activity. SPECT imaging is frequently used in combination with anatomical imaging such as computed tomography (CT) or structural magnetic resonance imaging (MRI). The radioisotope tracers are coupled with a biological molecule such as glucose, which is used during cellular metabolism and can be used to highlight areas with changes in metabolic activity. Functional brain activity has been investigated in people with schizophrenia compared to people without schizophrenia to identify regions of increased or decreased metabolic function or blood flow.

What is the evidence from SPECT studies?

Moderate quality evidence suggests elevated striatal dopamine synthesis and release capacities and increased striatal synaptic dopamine levels in people with schizophrenia compared to controls. The finding for elevated dopamine synthesis was apparent in treatment-responsive and treatment-naive patients, but not in treatment-resistant patients. There were no differences in dopamine D2/3 receptor or transporter availability. Within-group variability was similar for dopamine synthesis and release capacities, but there was greater variability in synaptic dopamine levels, and dopamine D2/3 receptor and transporter availability in the patient groups than in the control groups.

Moderate to low quality evidence finds associations between dopamine receptor occupancy and clinical improvements following treatment with antipsychotic medications. There is greatest dopamine D2 receptor occupancy with haloperidol (91.9%), then risperidone, olanzapine, clozapine, quetiapine, aripiprazole, ziprasidone, and then amisulpride (85%). First-generation antipsychotics in general are associated with higher receptor occupancy in the striatum and temporal cortex than second-generation antipsychotics.

Moderate to high quality evidence suggests significant reductions in functional activity in the whole brain of people with schizophrenia compared to controls. During cognitive tasks and rest periods, there is a medium to large effect of reduced functional activity in bilateral frontal lobes. Moderate quality evidence suggests increased functional activity in the left temporal lobe during cognitive tasks, but no differences between patients and controls during rest periods.

October 2020

Last updated at: 4:44 am, 21st October 2020
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NeuRA Libraries

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