*   Antero-posterior and Lateral Views of Thoracic Spine :

The lateral view shows the normal thoracic kyphosis. It may also reveal many systemic disorders, e.g. renal osteodystrophy, ankylosing spondylitis, osteoporosis, osteomalacia and some haemopoietic disorders. Note that the upper few thoracic vertebrae are not visible on the ordinary lateral film and often a special lateral thoracic inlet view has to be taken in order to demonstrate this area. The anteroposterior view shows the prominence of the pedicles, which should be checked thoroughly if secondary deposits are suspected. This projection also shows any paravertebral shadow which may occur in such conditions as tuberculosis, osteomyelitis, Hodgkin's reticulosis or extramedullary haemopoiesis.

*   Antero-posterior View of Lumbosacral Spine :

The interpedicular distance should increase from L1 to L5 in the normal. The distance can decrease in Down's syndrome (trisomy 21). Note the position of the spinous processes of the lumbar vertebrae. Another common congenital variant is sacralization or partial sacralization of L5. Note the position of the psoas major borders.

*   Lateral View of Lumbar Spine :

The normal lumbar lordosis is clearly shown. Note the width of the disc spaces from L1 to L5. Note also that the disc space between L5 and S1 is narrower than those above but, to be considered pathologically narrow, it should be less than one-half of the height of the L4/L5 disc space. In these patients, other signs of degenerative changes are usually present. As in the lateral view of the cervical spine, this view allows the AP sagittal diameter of the lumbar spinal canal to be measured and this should not be less than 15 mm or more than 25 mm.

*   Oblique View of Lumbar Spine :

This view is particularly useful to show the pars interarticularis region and the apophyseal joints. Note that the pars interarticularis is a purely radiological term, its equivalent anatomically being the anterior part of the lamina. The oblique view causes a certain well- known appearance of a Scottie dog: the dog's collar is the pars interarticularis, the eye is the pedicle, the nose is the transverse process and the ear is the superior articular facet. Defects of ossification of the pars may lead to spondylolisthesis. Again, as in the cervical spine, facet articulation disorders can be seen. The sacrum is formed by the fusion of five sacral vertebrae. It has a natural kyphosis. The median sacral crest is seen to bear the spinous tubercles and this crest is the fused spines of the sacral vertebrae. Below the spine of S4 is the sacral hiatus which is due to failure of fusion of the S5 laminae. It is through this hiatus that caudal epidural anaesthesia is performed. Note the four coccygeal segments which, in this case, are existing as separate entities, but are often fused together. The sacral spinal canal contains the cauda equina and the spinal meninges. These are best seen, however, on a lateral lumbosacral myelogram. The filum terminale from the pia mater emerges below the sacral hiatus and passes downwards to insert into the coccyx. Babies of mothers suffering from diabetes mellitus may occasionally have sacral agenesis.

*   Antero-posterior View of Internal Carotid Arteriogram (Arterial Phase with Subtraction) :

These films demonstrate the anatomy of the brain circulation. Carotid angiography with arterial and venous phases is shown first, followed by similar studies of the vertebral circulation. Rapid serial films are obtained in the AP and lateral planes with axial and oblique views if necessary to demontrate any pathology. The films shown are all subtraction views to allow clear demonstration of the normal anatomy. The contrast used is water-soluble with an iodine content of approximately 280 mg/ml. As with all peripheral arteriography, the amount of contrast used must be carefully controlled.

*   Anteroposterior View of Internal Carotid Arteriogram (Venous Phase with Subtraction) :

The carotid angiogram is divided into four phases.The first phase is the arterial phase lasting approximately 2 seconds; the second or capillary phase lasts about 1 second, but is rarely seen clearly on the x-ray because of the length of time of contrast injection; the last two phases are the early and late venograms. The early venograms show the superficial cerebral veins which are variable in position and are less important than the deep cerebral veins which fill on the late venogram. These deep veins are most constant in position, and displacement may help localize a space-occupying lesion such as a tumour. The thalamostriate vein lies in the groove between the caudate nucleus and the thalamus, receiving tributaries from both these structures. It thus lies in the floor and lateral wall of the lateral ventricle and therefore is used to assess the size of the ventricle on this AP view.

*   Lateral View of Internal Carotid Arteriogram (Arterial Phase with Subtraction) :

The carotid artery, which ascends from the neck, is divided into four portions: cervical, petrous, cavernous and intracranial. Note that the cervical portion has no branches. Five main branches come from the intracranial portion: the ophthalmic, anterior cerebral, middle cerebral, posterior communicating and anterior choroidal. The subdivisions of these branches can be seen labelled on the diagram. The posterior communicating artery fills in only about 30% of common carotid arteriograms, but selective catheterization of the internal carotid artery demonstrates a much higher percentage. The anterior choroidal artery is small, but constant; arising near the posterior communicating artery, it passes backwards to cross the optic tract and lies in relation to the crura cerebri. It then turns lateral, again crossing the optic tract, and comes into relationship with the lateral aspect of the lateral geniculate body; it finally enters the inferior horn of the lateral ventricle through the choroidal fissure and terminates in the choroidal plexus. This artery is often of considerable importance when assessing cerebral tumours, and its particular displacement must be noted.

*   Lateral View of Internal Carotid Arteriogram (Venous Phase with Subtraction) :

The veins of the brain are very thin due to the absence of muscle, and they possess no valves. They are divided into two sets: cerebral and cerebellar. Both drain into cranial dural venous sinuses. The cerebral veins are again divided into internal and external groups according to whether they drain the inner or outer surfaces of the hemispheres. The septal vein, the thalamostriate vein, and the internal cerebral vein form the venous angle. This point usually marks the apex of the posterior and superior limits of the interventricular foramen of Monro. This angle appears in approximately 80% of all carotid angiographic studies, but its anatomy is not constant and false venous angles may occur. The internal cerebral vein joins with the basal vein of Rosenthal to form the great cerebral vein of Galen. This in turn drains into the straight sinus, having joined the inferior sagittal sinus.