Three-dimensional quantitation of regional cerebral blood flow in mice using a high-resolution pinhole SPECT system and 123I-iodoamphetamine

Hybrid Imaging of Vascular Cognitive Impairment

Cerebrovascular disease is a significant cause of cognitive impairment leading to a reduction or loss of functioning, including social and occupational. The connection cause-effect between cerebrovascular disease and cerebral infarction was originally theorized by the studies from Newcastle-Upon-Tyne, England, in the 1960s, where vascular dementia (VaD) was defined as a disease originated from several infarctions that overcome a determined threshold. It differs from Alzheimer's disease (AD), although there are various overlaps in risk factors, symptomatology, the similarity of vascular lesions, and treatment benefits. Nevertheless, AD is one-half of all cases of dementia. Cognitive impairment and dementia (VCID) has recently been proposed to include different entities such as VaD, Vascular cognitive impairment, subcortical (ischemic) VaD, and vascular cognitive disorders. VaD is the most common cause of dementia after AD. Neuroimaging is an essential part of the workup of patients with cognitive decline and in those with suspected VCID it should be used to assess the extent, location, and type of vascular lesions. Computed tomography (CT) or structural magnetic resonance imaging (MRI) are usually used for the diagnosis of vascular diseases of the brain. However, images obtained from new hybrid devices could help the neurologist in the differential diagnosis between various neuropathological entities related to VCID. Single-photon emission computed tomography (SPECT) combined with CT or MRI and positron emission tomography (PET) combined with CT or MRI represent the future of neuroimaging tools as morphological and functional data can be provided simultaneously. New prospects have been developed such as hybrid PET/SPECT/CT, a high-performance prototype able to produce high-quality images but for now suitable only for small animals. Nowadays, PET/CT and PET/MRI are good performance and high-quality instruments, even if the magnetic field of MRI represents a limitation that affects the PET electronics and positron detection ability. SPECT/MRI delineates as a potential and tempting device. It could give us both functional and anatomical details, with the advantage of lack of extra ionizing radiation and high soft-tissue contrast, important features, and considerable auxiliary for differential diagnosis in the variegate word of vascular cognitive impairment. The aim of this review is to summarize the newest viewpoints in hybrid imaging in the diagnosis of VaD and to highlight pros and cons of each methodic.

Non-invasive three-dimensional power Doppler imaging for the assessment of acute cerebral blood flow alteration in a mouse model of subarachnoid haemorrhage

We aimed to evaluate the feasibility of a non-invasive method of cerebral blood flow (CBF) measurement using high-frequency power Doppler ultrasound imaging in a mouse model of subarachnoid haemorrhage (SAH). The 3-dimensionally (3D) reconstructed blood flow signals (%vascularity) within the brain volume of the middle cerebral artery territory correlated well with reference parameters, baseline carotid artery blood flow (r²  = 0.52, P < 0.0001) and normalized CBF changes (r²  = 0.74 P < 0.0001). These data suggest that the 3D power Doppler analysis may have the potential for reflecting real-time CBF changes during the acute phase of experimental SAH, which may be applicable to preclinical studies on early brain injury.

The role of preclinical SPECT in oncological and neurological research in combination with either CT or MRI

Preclinical imaging with SPECT combined with CT or MRI is used more and more frequently and has proven to be very useful in translational research. In this article, an overview of current preclinical research applications and trends of SPECT combined with CT or MRI, mainly in tumour imaging and neuroscience imaging, is given and the advantages and disadvantages of the different approaches are described. Today SPECT and CT systems are often integrated into a single device (commonly called a SPECT/CT system), whereas at present combined SPECT and MRI is almost always carried out with separate systems and fiducial markers to combine the separately acquired images. While preclinical SPECT/CT is most widely applied in oncology research, SPECT combined with MRI (SPECT/MRI when integrated in one system) offers the potential for both neuroscience applications and oncological applications. Today CT and MRI are still mainly used to localize radiotracer binding and to improve SPECT quantification, although both CT and MRI have additional potential. Future technology developments may include fast sequential or simultaneous acquisition of (dynamic) multimodality data, spectroscopy, fMRI along with high-resolution anatomic MRI, advanced CT procedures, and combinations of more than two modalities such as combinations of SPECT, PET, MRI and CT all together. This will all strongly depend on new technologies. With further advances in biology and chemistry for imaging molecular targets and (patho)physiological processes in vivo, the introduction of new imaging procedures and promising new radiopharmaceuticals in clinical practice may be accelerated.