Radiographic Techniques Lecture Notes PDF

Radiographic Techniques Lec 9 Thoracic vertebrae BY AHMED JASEM ABASS MSC of Medical Imaging 1  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...

Radiographic Techniques Lec 9 Thoracic vertebrae BY AHMED JASEM ABASS MSC of Medical Imaging 1  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. 2 3 4  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). 5 6  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. 7  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. 8  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. 9  Localised projections(Figs 6.19c, 6.19d)  Localised projections are requested occasionally, e.g. when The following anterior surface markings can be used as a guide to the appropriate centring point:  Cricoid cartilage: sixth cervical vertebra.  Sternal notch: 2nd to 3rd thoracic vertebra.  Sternal angle: lower border of 4th thoracic vertebra.  Xiphisternal joint: 9th thoracic vertebra.  Posterior surface markings are more convenient for lateral projections. The level of the upper and middle thoracic vertebrae may be found by first palpating the prominent spinous process of the 7th cervical vertebrae and then counting the spinous processes downwards. The lower vertebrae can be identified by palpating the spinous process of the 3d lumbar vertebrae at the level of the lower costal margin and then counting the spinous processes upwards. 10  Position of patient and image receptor  The patient lies supine on the Bucky table, with the median sagittal plane coincident with, and at right-angles to, the midline of the table and Bucky.  The anterior superior iliac spines should be equidistant from the tabletop.  The hips and knees are flexed and the feet are placed with their plantar aspect on the tabletop to reduce the lumbar arch and bring the lumbar region of the vertebral column parallel with the image receptor.  CR cassette should be large enough to include the lower thoracic vertebrae and the sacro-iliac joints and is centred at the level of the lower costal margin.  The exposure should be made on arrested expiration, as expiration will cause the diaphragm to move superiorly. The air within the lungs would otherwise cause a large difference in density and poor contrast between the upper and lower lumbar vertebrae. 11  Essential image characteristics (Figs 6.21c, 6.21d)  The image should include from T12 down, and sacro-iliac joints.  Rotation can be assessed by ensuring that the sacro-iliac joints are equidistant from the spine.  The exposure used should produce a density such that bony detail can be discerned throughout the region of interest.  Common faults and solutions  The most common fault is to miss some or all of the sacroiliac joint. An  additional projection of the sacro-iliac joints should be performed. 12 13  Position of patient and image receptor  The patient lies on either side on the Bucky table.  The arms should be raised and resting on the pillow in front of the patient’s head.  The knees and hips are flexed for stability.  The coronal plane running through the centre of the spine should coincide with, and be perpendicular to, the midline of the Bucky.  Non-opaque pads may be placed under the waist and knees, as necessary, to bring the vertebral column parallel to the image receptor.  The image receptor is centred at the level of the lower costal margin.  The exposure should be made on arrested expiration.  This projection can also be undertaken erect with the patient standing or sitting. 14  Direction and location of the X-ray beam  The collimated vertical beam is centred at right-angles to the line of spinous processes anterior to the 3rd lumbar spinous process at the level of the lower costal margin  Essential image characteristics (Fig. 6.22c)  The image should include T12 downwards, to include the lumbar sacral junction.  The posterior and anterior margins of the vertebral body should also be superimposed.  The imaging factors selected must produce an image density sufficient for diagnosis from T12 to L5/S1, including the spinous processes. 15  Common faults and solutions(Figs 6.23c, 6.23d)  High-contrast images will result in an insufficient or high image density over areas, software application is recommended.  The spinous processes can easily be excluded from the image as a result of collimation.  Poor superimposition of the anterior and posterior margins of the vertebral bodies is an indication that the patient was rolled too far forward or backward during the initial positioning (i.e. mean sagittal plane not parallel to receptor).  Failure to demonstrate a clear intervertebral disc space usually results as a consequence of the spine not being perfectly parallel with the receptor or is due to scoliosis or other patient pathology. 16 17  Lateral projections in flexion and extension may be requested to demonstrate mobility and stability of the lumbar vertebrae.  Position of patient and image receptor  This projection may be performed supine, but it is most commonly performed erect with the patient seated on a stool with either side against the vertical Bucky.  For the first exposure the patient leans forward, flexing the lumbar region as far as possible, and grips the front of the seat to assist in maintaining the position.  For the second exposure the patient then leans backward, extending the lumbar region as far as possible, and grips the back of the seat or another support placed behind the patient.  The Bucky is centred at the level of the lower costal margin, 18 and the exposure is made on arrested expiration.  Direction and location of the X-ray beam  The collimated horizontal beam is directed at right- angles to the image receptor and centred anterior to the 3rd lumbar spinous process at the level of the lower costal margin. 19  Essential image characteristics (Figs 6.25c, 6.25d)  All of the area of interest must be included on both projections.  A short exposure time is desirable, as it is difficult for the patient to remain stable. 20  AP Axial  Position of patient and image receptor  The patient lies supine on the Bucky table, with the median sagittal plane coincident with, and at right-angles to, the midline of the Bucky.  No rotation of pelvis (ASIS the same distance from tabletop)  Direction and location of the X-ray beam  The collimated vertical beam is directed cephalad (5cm) below level of ASIS 21 22