Radiographic Techniques Lecture Notes PDF

Radiographic Techniques Lec 5 Thoracic vertebrae BY AHMED JASEM ABASS MSC of Medical Imaging 1  Useful landmarks  The inferior angle of the scapula indicates the level of T7 when the arms are placed by the side.  The sternal notch lies at the junction between T2 and...

Radiographic Techniques Lec 5 Thoracic vertebrae BY AHMED JASEM ABASS MSC of Medical Imaging 1  Useful landmarks  The inferior angle of the scapula indicates the level of T7 when the arms are placed by the side.  The sternal notch lies at the junction between T2 and T3.  T4 is indicated by the sternal angle with T9 corresponding to the xiphisternal joint, although the size of this structure is variable.  The lower costal margin indicates L3 and is located easily. This is a very useful aid to positioning in spinal radiography.  A line joining the most superior parts of the iliac crests indicates the level of L4, whilst the tubercle of the iliac crest discloses the location of L5.  The anterior and posterior iliac spines lie at the level of the second sacral vertebra. 2 3 4 5 6 7 8  Position of patient and image receptor  The patient is positioned supine on the X-ray table, with the median sagittal plane perpendicular to the tabletop and coincident with the midline of the Bucky.  The upper edge of the CR cassette should be at a level just below the prominence of the thyroid cartilage to ensure that the upper thoracic vertebrae are included.  Direction and location of the X-ray beam  The vertical collimated beam is centred at right-angles to the image receptor and towards a point 2.5 cm below the sternal angle.The beam is collimated tightly to the spine. 9 10 11  Essential image characteristics  The image should include the vertebrae from C7 to L1.  The image density should be sufficient to demonstrate bony detail for the upper as well as the thoracic lower vertebrae.  Common faults and solutions  The image receptor and beam are often centred too low, there by excluding the upper thoracic vertebrae from the image.  The lower vertebrae are also often not included. L1 can be identified easily by the fact that it usually will not have a rib attached to it.  High radiographic contrast (see below) causes high density over vertebrae (Fig. 6.17c). 12 13  Position of patient and image receptor  The examination is usually undertaken with the patient in the lateral decubitus position on the X- ray table, although this projection can also be performed erect.  The median sagittal plane should be parallel to the image receptor and the midline of the axilla coincident with the midline of the table or Bucky.  The arms should be raised well above the head.  The head can be supported with a pillow  The upper edge of the cassette should be positioned 3–4 cm above the spinous process of C7. 14  Direction and location of the X-ray beam  The collimated vertical beam should be at right-angles to the long axis of the thoracic vertebrae. This may require a caudal angulation.  Centre usually just below the inferior angle of the scapula (assuming the arms are raised), which is easily palpable. 15  Essential image characteristics  The upper two or three vertebrae may not be demonstrated due to the superimposition of the shoulders.  Look for the absence of a rib on L1 at the lower border of the image. This will ensure that T12 has been included within the field.  The posterior ribs should be superimposed, thus indicating that the patient was not rotated too far forwards or backwards.  The image density should be adequate for diagnosis. 16 17