CT brain imaging

Lovelock CE, Anslow P, Molyneux AJ, Byrne JV, Kuker W, Pretorius PM, CouU A, Rothwell PM Substantial observer variability in the differentiation between primary intracerebral hemorrhage and hemorrhagic transformation of infarction on ct brain imaging. Stroke 2009 40 pp. 3763-3767. 

An early report from our group indicated that, in the absence of early recanalization, CTA-Sl typically defines minimal final infarct size and, hence, like DWI and thresholded CBF maps (Fig.5.5, 5.6), can be used to identify infarct core in the acute setting [34] (Figs. 5.5, 5.6). Coregistration and subtraction of the conventional, unenhanced CT brain images from the axial, post contrast CTA source images should result in quantitative blood volume maps of the entire brain [15, 27, 70]. CTA-SI subtraction maps, obtained by coregistration and subtraction of the unenhanced head CT... 

DaTscan ([ Ijloflupane Injection DaTscan is the approved name in the USA and DaTSCAN is the approved name in the European Union) is a radiopharmaceutical approved in Europe and the USA, used for single-photon emission CT brain imaging. DaTscan binds to the dopamine transporter membrane (as opposed to vesicular) located on presynaptic terminals of dopaminergic neurons, and thereby, identifies loss of functional dopaminergic neuron terminals. DaTscan was performed in 135 patients. One patient had an adverse event (headache) with suspected relationship to DaTscan administration [62 j. 

Fig. 1 CT brain image of early infarct (a) Image before windowing process and (b) grayscale image after undergoing convorsion process...

Fig. 2 CT brain image of early infarct case, (a) Early infarct area indicated by a circle, (b) Early infarct area is represented by ted color...

In 1ST and CAST not all patients underwent brain imaging with CT before randomization. It was estimated that about 800 of the 40,000 included subjects in fact had ICH on subsequent imaging. The investigators found no indication in either trial that aspirin treatment led to a deterioration in clinical condition, leading the CAST group to suggest that the hazard of aspirin use in these patients cannot be large (Fig. 7.3). 

Brain imaging (preferably MRI) to look for evidence of structural damage is essential after TBI. MRI, while more expensive and time-consuming, can sometimes detect small brain lesions that are missed by CT, especially in the frontal and temporal lobes that are common sources of psychiatric complications after TBI. In addition, an electroencephalogram (EEG) can detect seizure activity or other signs of abnormal brain function. Although they are not yet part of the routine post-TBI evaluation, the so-called functional brain imaging techniques such as positron emis-... 

A CT scan or MRI of the brain following a strokelike episode reveals a lucency (an area of luminosity) that is consistent with infarction. Later, cerebral atrophy and calcifications may be observed on brain imaging studies. The vascular territories of focal brain lesions and the prior medical history of these patients differ substantially from those of typical patients with stroke. Serial MRI studies often demonstrate lesion resolution, differentiating these lesions from typical ischemic strokes. An electroencephalogram is often performed when seizures are a concern. This is especially necessary in MELAS since patients occasionally have intractable status epilepticus as a terminal condition. Mental deterioration usually progresses after repeated episodic attacks. Psychiatric abnormalities (e.g., altered mental status, schizophrenia) may accompany the strokelike episodes. The encephalopathy may progress to... 

Vascular dementia Brain imaging (CT or MRI) reveals brain lesions, examination reveals neurological signs, usually there is a long history of hypertension... 

Stroke localization using clinical data is not infallible in about one-quarter of cases where a recent lesion is visible on brain imaging, it is not in the expected place (Mead et al. 1999). For example, although most pure motor strokes are caused by a lacunar infarct as a result of small vessel disease, in a few cases the CT or MR scan shows striatocapsular infarction caused by middle cerebral artery occlusion with good cortical collaterals... 

Over a five year period, 1438 patients were referred either to the hospital or to the study cUnic with a suspected TIA or minor stroke (defined on assessment as a score of < 3 on the National Institutes of Health Stroke Scale [NIHSS]) (Wityk et at 1994) (Fig. 10.1). Of these, a pre-scan diagnosis of definite or possible TIA was made in 405 patients (46% male, mean age 74 years), and definite or possible minor stroke in 414 patients (54% male, mean age 76 years). Overall, 97% underwent brain imaging for definite or possible events (699 CT, 93 MRI). 

Brain imaging is required to distinguish between primary intracerebral hemorrhage and cerebral infarction since this distinction cannot be made reliably on clinical criteria alone (Hawkins et al. 1995). Recent developments in brain imaging, in particular new MRI sequences, and to a lesser extent CT techniques, have enabled visualization of the pathophysiological processes involved in brain infarction. These new techniques are being developed to select patients suitable for thrombolytic treatment beyond the three-hour time window (Ch. 21) and may in the future enable targeting of treatments such as neuroprotection. 

The use of brain imaging to select patients for thrombolysis is discussed in detail in Ch. 11. Assuming equal access to diffusion-weighted/perfusion-weighted imaging and CT perfusion, decisions regarding optimum imaging use can be dictated by time elapsed since stroke onset and symptom severity. 

Muldple parameters can be calculated with CT perfusion imaging of the brain and include cerebral blood flow, cerebral blood volume, dme-to-peak, and mean dansit time (Wintermark etal., 2006). 

Prior to the introduction of PET/CT, multimodahty images were fused by the algorithm technique that was limited mainly to the brain. In 1999, GE Healthcare introduced the first PET/CT, called the Hawkeye, using a dualhead Nal(Tl) camera and a low-energy CT scanner, followed later in 2001 by the Discovery LS (GE Healthcare). Since then, manufacturers such as Siemens, GE, and Philips have brought a variety of much improved PET/CT units into the market. The physical features of a few PET/CT scanners are listed in Table 2.3 and a typical PET/CT scanner is shown in Fig.2.9. 

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