Common indications<br />• Diagnosis and evaluation of a lesion specifically in the temporal lobes (tumours, vascular malformations, leucodystrophies and atrophic processes).<br />• Temporal lobe epilepsy.<br />• Evaluation of signal change in the hippocampus and the temporal lobe.<br />• Measurement of the hippocampal volume (hippocampal atrophy is presently considered the most sensitive indicator of hippocampal disease especially in Alzheimer’s disease and schizophrenia).<br />Equipment<br />• Head coil (quadrature or multi-coil array(.<br />• Immobilization pads and straps.<br />• Earplugs or headphones.<br />Patient positioning<br /> The patient lies supine on the examination couch with their head within the head coil. The head is adjusted so that the inter-pupillary line is parallel to the couch and the head is straight. The patient is positioned so that the longitudinal alignment light lies in the midline, and the horizontal alignment light passes through the nasion. Straps and foam pads are used for immobilization.<br /><br />Suggested protocol<br />Sagittal SE T1<br />Medium slices/gaps are prescribed on either side of the longitudinal alignment light through the whole head. The area from the foramen magnum to the top of the head is included in the image.<br />Axial/oblique SE/FSE T2<br />Thin slices/gap or interleaved slices are angled parallel to the temporal lobe that can be seen on a lateral slice on the sagittal images (Figure 8.22). Prescribe the slices from the inferior aspect of the temporal lobes to the superior border of the body of the corpus callosum.<br />Coronal/oblique SE/FSE T1<br />As for the axial/oblique T2, except thin slices interleaved are angled perpendicular to the axials (Figure 8.23). Slices are prescribed from the posterior portion of the cerebellum to<br />the anterior border of the genu of the corpus callosum.<br />Coronal 3D incoherent (spoiled) GRE T1 (Figure 8.24)<br />Thin slices are either prescribed through the temporal lobes only<br />(medium number of slice locations), or the whole head (large number of slice locations). For hippocampal measurements, slices are prescribed from the posterior portion of the cerebellum to the anterior border of the genu of the corpus callosum. Hippocampal volumes are measured by using system software to calculate the area of the hippocampus on each slice and multiplying this by the depth of the slice slab. If reformatting of slices is desired, then an isotropic data set should be acquired (see Volume imaging under Parameters and trade-offs in Part 1).<br />Axial/oblique/coronal/oblique IR-FSE T2 (Figures 8.25 and 8.26)<br />Slice prescription as for axial/oblique/coronal/oblique FSE T2.<br />This sequence often provides images with high contrast between grey matter and white matter. A TI selected to null the signal from the white matter (about 300 ms) can be used to increase the grey/white (G/W) contrast in the hippocampal region. Images may be video inverted so that the white matter appears white and the grey matter appears grey.<br />This is sometimes useful to increase the conspicuity of white matter lesions, which have a low signal intensity when using this technique and to improve visualization of the basil ganglia.<br />Image optimization<br />Technical issues<br />The SNR and contrast characteristics of the temporal lobes are usually excellent as the quadrature head coil and phased array coil yield high and uniform signal. Good spatial resolution is therefore achievable in relatively short scan times. Surface coils placed directly on the patient’s head increase local SNR and resolution, especially in children. However, using this method, other areas of the brain cannot be imaged due to signal falloff.<br />As lesions within the temporal lobes are often quite small, volume acquisitions are useful as they allow for very thin slices and no gap. As they are mainly utilized to demonstrate anatomy or contrast enhancement, an incoherent (spoiled) GRE that produces PD and T1 contrast is desirable. Alternatively, angling the slices perpendicular to the sylvian fissure in 2D acquisitions often improves visualization of the temporal lobes. FSE is a useful pulse sequence especially for T2-weighted images, as FSE in conjunction with fine matrices acquires high-resolution images of the temporal lobes in a relatively short scan time. However, IR sequences can also be utilized to great effect. FLAIR sequences usually demonstrate subtle areas of increased T2 signal intensity better than T2-weighted SE or FSE sequences. As the brain contains no fat (only small amounts occur in the scalp), reducing the receive bandwidth significantly improves the SNR without significantly increasing chemical shift artefact, although there may be increased blurring (see Flow phenomena and artefacts in Part 1). A rectangular/asymmetric FOV can be effectively used to reduce scan times in axial and coronal imaging with the phase axis R to L.<br />Patient considerations<br />Claustrophobia is often troublesome because of the enclosing nature of the head coil. Careful explanation of the procedure and reassurance is necessary. As many of these patients have drug-resistant epilepsy, careful observation of the patient throughout the examination is important.<br />The gradient noise and bore and alignment lights are potential sources of epileptic stimuli. If the patient fits during the examination, stop scanning immediately, withdraw the patient from the magnet, call a physician, and instigate first-aid measures. Owing to excessively loud gradient noise associated with some sequences, earplugs or headphones must always be<br />provided to prevent hearing impairment.<br /><br />