Chest X-Ray PDF

CHEST X-RAY Chest x-ray is the most common requested x-ray examination in the radiology department. This stem from the fact that most diseases manifest in the chest as well as the fact that the chest contains important organs like lungs, heart and great vessels. It is therefore, of utmost importan...

CHEST X-RAY Chest x-ray is the most common requested x-ray examination in the radiology department. This stem from the fact that most diseases manifest in the chest as well as the fact that the chest contains important organs like lungs, heart and great vessels. It is therefore, of utmost important that quality chest x-rays are produced for the diagnosis of these illnesses. This can be achieved by strict adherence to the following protocols. RESPIRATION: Chest x-ray is done on arrested deep inspiration which helps in the distension of the lung field for maximum visualization. To assess the adequacy of the inspiration, the number of ribs above the diaphragm should be counted. The posterior ribs should be about 9 or 10 while the anterior ribs should be 6 or7. To achieve maximum deep inspiration, the radiographer should practice breathing techniques with the patients for at least three times before the exposure is made as there is tendency for the patient to raise his shoulders while breathing which may cause the shadow of the clavicle to obscure the apices of the lungs. Also with the patient having taken a deep breath, a few moments should be allowed to elapse to ensure stability before exposure to avoid motion unsharpness. Sub-optimal inspiration has several implications which includes a. The heart will swing up to a more horizontal lie and may thus appear enlarged. b. The lung bases will be less well inflated, which may simulate a variety of pathologies or cause abnormal areas to lie hidden. c. Under-inflation of the lower lobes causes diversion of blood to the upper lobe vessels, mimicking the early signs of heart failure. EXPOSURE PARAMETERS: Choice of exposure parameter depends on the operational protocol of the department although the basic objective is to acquire an image of the chest that will demonstrate the whole structures without interference from the surrounding regions. KILOVOLTAGE PEAK (KVp) Two techniques usually employed in chest x-ray include the low-kVp and high-kVp techniques. Low kVp technique is selected when the exposure is made without the use of grid while in high kVp technique involves the use of grid. Selection of appropriate kVp should be in keeping with the patient thickness, habitus and pathology. Generally, 60-70 kVp provide adequate penetration for PA projection of lung field with minor penetration of the mediastinum and the heart. A high kVp technique (120-150kVp) reduces the dynamic range of information that are to be recorded although, it enable visualization of lung fields and mediastinum with one exposure. Kilovoltages between 80-100 which falls in between the low and high kVp techniques are used to compromise between the advantages and disadvantages of the two techniques. FOCUS FILM DISTANCE (FFD) To obtain quality image with minimal magnification of the intra-thoracic structures, especially the heart and other structures at differing distances from the film, FFDs in the range of 150–180 cm are selected. However, the FFD must be kept constant for any department in order to allow comparison of successive films. At these distances, geometric unsharpness is greatly reduced.An FFD less than those recommended increases the image magnification. However, such a reduction in distance to 120 cm is a satisfactory means of obtaining a short exposure time when using low- output machines such as conventional mobile units. TIME: Due to involuntary movement of the heart and great vessels in the chest, exposure time should be kept as low as possibly achievable which is in the millisecond range. Ideally, exposure times should be less than 20 ms. This can be obtained with high-output units at the higher mA settings, balanced with the speed of the film and screen combination and the kilovoltage selected. The use of rare earth screens and fast film combinations is essential to ensure short exposure times. With high kilovoltage, shorter exposure times are also possible, with the added advantage of selecting a smaller focal spot within the tube rating. IDENTIFICATION: Accurate identification of chest radiographs is essential, with information such as right and left sides, patient’s name, date, hospital number and radiology identification number being distinguished clearly. Congenital transposition of the organs occurs in a small number of people, and without the correct side marker the condition may be misdiagnosed. Additional information relating to orientation of the patient and tube different from the norm should also be recorded. PATIENTS PREPARATION: Patient should undress and put on x-ray gown. Radiopaque materials within the area of interest like necklace should be removed. Long hair should be well parked while dangling ear ring should be removed PROJECTIONS (VIEWS) IN CHEST X-RAY Chest x-ray is taken in an erect or decubitus position. Even though the erect is preferred to the decubitus position, the choice depends on the health condition of the patient and age. Very ill, unconscious and immobile patients are x-rayed in either supine or semi-erect position. The erect position offers the following advantages over other positions which include- a. It is simple to position the patients. b. Control of respiration is easy c. Gravitational force helps to expose maximum area of the lungs d. Air fluid level can easily be identified. Basic positioning for chest x-ray is postero-anterior (PA) view in erect position. The postero- anterior (PA) is preferred because of the following a. It enables the scapula to be thrown off the lung field. b. It also helps in the reduction of the magnification of the heart. c. It compresses the breast tissue with its associated dose reduction. d. The radiation dose to the thyroid gland and the eyes are also reduced. POSTERO-ANTERIOR (PA) ERECT PROJECTION POSITION OF PATIENT: The patient is positioned facing the cassette, with the chin extended and centered to the middle of the top of the cassette. The feet are paced slightly apart so that the patient is able to remain steady. The median sagital plane is adjusted at right-angles to the middle of the cassette. The shoulders are rotated forward and pressed downward in contact with the cassette. This is achieved by placing the dorsal aspect of the hands behind and below the hips, with the elbows brought forward, or by allowing the arms to encircle the cassette.  CASSETTE SIZE: A cassette size of 35 x 43-cm (17"x14’’) or 35 x 35-cm (14"x14’’) should be used depending on the size of the patient. Orientation of the larger cassette will depend on the width of the thorax. CENTERING POINT AND BEAM DIRECTION: ❖ The horizontal beam is centered at right-angles to the cassette at the level of the eighth thoracic vertebrae (i.e. spinous process of T7), which is coincident with the lung midpoint. ❖ The surface marking of T7 spinous process can be assessed by using the inferior angle of the scapula before the shoulders are pushed forward. ❖ Exposure is made in full arrested inspiration. IMAGE COURTESY OF CLARK’S POSITIONING  ALTERNATIVE PROJECTIONS When it is impossible to achieve the desired PA projection, the following alternative projections can be adopted. ANTERO-POSTERIOR ERECT: This is used in patient with kyphosis and also when it is unsafe for patients to stand or sit in the basic position. PATIENT POSITIONING: Patient stands or sits with the back against the cassette which is supported with the upper edge above the apices of the lung. The shoulders are brought backwards and forward with the back of the hands below the hip and the elbows well forward. The mid sagital plane should be at right angle with the middle of the cassette. CASSETTE SIZE: A cassette size of 35x43cm or 35x35cm is used for this exam depending on the size of the patient. CENTERING POINT/ BEAM DIRECTION Horizontal beam which is directed towards the sternal notch, angled until it coincides with the middle of the cassette. Exposure is taken on deep inspiration. ANTERO-POSTERIOR SUPINE: This is usually done on unconscious, immobile patients, and in children. POSITIONING OF PATIENT Patient is carefully lifted and cassette is placed under the patient’s chest with the upper edge above the apices of the lungs. The mid sagittal plane is adjusted to be at right angle to the centre of the cassette. The abdomen and pelvis are well aligned to prevent rotation. The arms are laterally rotated and supported by the side of the trunk with the head placed in a pillow and chin slightly raised. CASSETTE SIZE: A cassette size of 35x43cm or 35x35cm is used for this exam depending on the size of the patient. BEAM DIRECTION AND CENTERING POINT Vertical beam directed at right angled towards the sternal notch. The ray is then angled until it is coincident with the middle of the film to avoid unnecessary exposure to the eyes. FOCUS-FILM DISTANCE (FFD) An FFD of at least 120cm is needed in order to reduce the magnification of the heart. ANTERO-POSTERIOR SEMI-ERECT: This is usually done on immobile patients. PATIENTS POSITIONING: ❖ The patient is supported in a semi-recumbent position, facing the x-ray tube. The degree to which they can sit erect will depend on their medical condition.  ❖ A cassette is supported against the back, using pillows or a large 45-degree foam pad, with its upper edge above the lung fields. ❖ Care should be taken to ensure that the cassette is parallel to the coronal plane. ❖ The median sagittal plane is adjusted at right-angles to, and in the midline of, the cassette. ❖ Rotation of the patient is prevented by the use of foam pads. ❖ The arms are rotated medially, with the shoulders brought forward to bring the scapulae clear of the lung fields. Image courtesy of Clark’s positioning BEAM DIRECTION AND CENTERING POINT Central rays are directed first at right angle to the cassette and towards the sternal notch. It is therefore angled until it is coincident with the middle of the cassette. This is to avoid excessive radiation to the eyes. The use of horizontal central ray is essential to demonstrate fluid level. In such situation, the patient is adjusted with the chest erect as much as possible. If patient is unable to sit erect, fluid levels are demonstrated using a horizontal ray with the patient adopting the lateral decubitus or dorsal decubitus position. SUPPLEMENTARY VIEWS LATERAL PROJECTION: Supplementary lateral view is done when we are interested in the localization of lesion and demonstration of anterior mediastinal masses not seen on the PA projection. POSITION OF PATIENT ❖ The patient is turned to bring the side under investigation in contact with the cassette. ❖ The median sagittal plane is adjusted parallel to the cassette. ❖ The arms are folded over the head or raised above the head to rest on a horizontal bar. Insufficient elevation of the arms will cause the soft tissue of the upper arms to obscure the apices of the lungs ❖ The mid-axillary line is coincident with the middle of the film, and the cassette is adjusted to include the apices and the lower lobes to the level of the first lumbar vertebra. BEAM DIRECTION AND CENTERING: Direct the horizontal central beam at right angle to the middle of the cassette at the mid axillary line. APICAL PROJECTION: Apical projections are done when the lesions in the apical lobes of the lungs are obscured by either the clavicle or the ribs. This projection can be taken either in PA view or in AP view. PATIENT’S POSITIONING In PA apical view, the patient is positioned as for PA chest, the central ray is angled 30º caudad and centered to the 7th cervical spinous process. For AP apical view, the patient bends backwards with the coronal plane at 30º to the cassette so as to rest the nape of the neck against the upper border of the cassette. Horizontal central ray is used and centered to the sternal angle. CASSETTE SIZE: 24x30cm cassette size should be used Apical view in AP position (image courtesy of Clark’s positioning) LORDOTIC PROJECTION Lordotic view is used to demonstrate inter lobar pleural effusion (laminar effusion) or right middle lobe collapse. PATIENT POSITIONING Patient is PA position, holding the sides of the vertical bucky, the patient bends backwards at the waist with the degree of dorsiflexion varying from patient to patient but should be about 30º-40º. BEAM DIRECTION AND CENTERING POINT Horizontal beam at right angle to the cassette and centered to the middle of the film.  LORDOTIC POSITION (image courtesy of Clark’s positioning) POSTERO-ANTERIOR (PA) PROJECTION ON EXPIRATION This is carried out on patient with emphysema detected on normal PA projection done on inspiration. QUALITY OF A GOOD CHEST X-RAY A. A good chest x-ray should be well collimated to include the entire thoracic cage with the apices and costophrenic angles well demonstrated. B. Soft tissue layer of the chest should be well demonstrated. C. The trachea should be equidistant between both clavicular heads. D. The scapula should not obscure the lung field E. Lungs should be well inflated with about 9 posterior ribs seen above the dome of the diaphragm. F. The anatomic marker should be well positioned. G. It should be well penetrated with the vertebrae just visible behind the heart. H. Identification of radiograph should be clear without obscuring the area of interest. I. It should be devoid of artifact which may come from radiographic technique, patient factors or presence of external or internal non anatomic object.  Image courtesey of Clark’s Positioning a. Superior vena cava f. aortic knuckle b. Ascending thoracic aorta g. Main pulmonary artery c. Right atrium h. left ventricle d. Inferior vena cava e. Left subclavian vein MEASUREMENT OF HEART SIZE Heart size is calculated on chest radiograph taken in postero-anterior position using the cardiothoracic ratio (CTR). This is the maximum transverse diameter of the heart and the maximum width of the thorax above the costophrenic angles measured from the inner edge of the ribs. Normal value is ≤ 0.5. (0.5 being the upper limit of normal) CTR = (𝑎 + 𝑏)/𝑐 Where a= right heart border to the midline, b= left border to the midline, c= maximum thoracic diameter above costophrenic angle from inner border of the ribs  CERVICAL VERTEBRAE The cervical spine is part of the vertebral column which starts from the base of the skull and ends at the thoracic vertebrae in the trunk. They are seven in number and are stacked upon each other to form a lordotic curvature. They are numbered C1-C7 starting from the base of the skull although the first cervical vertebra (C1) are called ATLAS because it holds the head while the second vertebra (C2) is called AXIS because it forms the axis upon which the skull and the atlas rotates. Each cervical vertebra consists of a thin ring of bone or vertebral arch which surrounds the vertebral and transverse foramina. The vertebral foramen harbors the spinal cord and its meninges as they pass through the neck. The transverse foramen surrounds the arteries and veins among which are the carotid artery and the jugular vein. They also have spinous processes for the attachment of muscles of the neck. CERVICAL SPINE X-RAY: X-ray of the cervical spine is usually done is cases of trauma, fracture, dislocation, subluxation, arthritis and other degenerative bone diseases, pains in the upper limbs etc. PREPARATION OF PATIENT: Patient should remove his/her cloth and put on the x-ray gown. All radiopaque materials like necklace, ear ring within the area of interest should be removed. Movement of patient with trauma to the neck during examination should be restricted. BASIC PROJECTIONS: Basic projections for cervical x-ray are Lateral projection and Anteroposterior projection.  ANTEROPOSTERIOR PROJECTION: Anteroposterior projections of the cervical vertebrae are grouped into two- Anteroposterior Open mouth for C1 and C2 and Anteroposterior for C3-C7. AP OPEN MOUTH: PATIENT POSITION: Patient lies supine on couch or sits or stands with the posterior aspect of the head and shoulder against an erect bucky. The mid sagital plane of the body is adjusted to coincide with the centre of the cassette. The neck is extended when possible such that the tip of the mastoid process and the inferior border of the upper incisor at right angle to the cassette. The cassette is centered at the level of the mastoid process Rotation should be avoided as small degree of rotation may result in superimposition of the lower molar over the lateral section of the joint space. Images of positioning for open mouth and radiograph demonstrating the odontoid process of the axis courtesy of Clark positioning.  BEAM DIRECTON AND CENTERING POINT For erect position, center the horizontal beam along the midline of the cassette at the midline of open mouth but for supine position, perpendicular central rays are directed to the midline of the cassette which corresponds to the center of the open mouth. For patients who are unable to flex the neck to attain normal position, the tube should be angled 5º-10º cranially or caudally to superimpose the upper incisor to the occiput. In this situation, the cassette should be adjusted to allow the image to be centered on it after angulation. If the front teeth are superimposed on the area of interest, then the view will be repeated with the chin raised or with an increase in cranial angulation of the tube. ANTERO-POSTERIOR FOR C3-C7 VERTEBRAE POSITIONING OF PATIENT Patient lies supine on the bucky table but if erect is preferred, stand or sits with the back of the head and shoulder against the vertical bucky. The mid sagital plane is adjusted to be at right angles to the cassette and coincides with the midline of the table. The neck is extended if possible so that the lower part of the jaw is cleared from the upper cervical vertebra. The cassette is positioned in the bucky to coincide with the central rays Images of position for AP supine and radiograph of cervical spine courtesy of Clark’s Positioning. BEAM DIRECTION/CENTERING POINT A 5º-15º cranial angulation is employed depending on the degree of extension so that the inferior border of the symphysis menti is superimposed over the occipital bone. The x-ray beam is centered to the midline just below the prominence of the thyroid cartilage through the 5th cervical vertebra. LATERAL PROJECTION (ERECT): POSITIONING OF PATIENT Patient stands with the feet slightly apart or sits with either shoulder against the cassette. The median sagittal plane should be adjusted to be parallel to the cassette.  The head should be extended or flexed so the angle of the mandible will not superimposed over the upper anterior cervical vertebra or the occipital bone does not obscure the posterior arch of the atlas. To demonstrate the lower cervical vertebra, the shoulder should be depressed by relaxing it or holding a weight on each hand if possible Due to increased OFD, FFD should be increased to 150cm with no grid used due to air gap technique. Exposure is made on arrested expiration. Image courtesy of Clark’s positioning BEAM DIRECTION AND CENTRING POINT: Horizontal beam is used and centered below the mastoid process at the level of the prominence of the thyroid cartilage. LATERAL PROJECTION SUPINE (LATERAL SHOOT THROUGH) Lateral supine projection is normally done for trauma cases and is done first before the AP projection. PATIENT POSITION AND CASSETTE Patient lying in a supine position on the hospital stretcher with shoulders depressed by caudally applying traction to the arms if there is no injury to the arms. This enable demonstration of C7/T1 junction which is a common site of injury Cassette is either supported vertically on the bed or placed in the erect cassette holder with the top of the cassette at the level with the ear SUPPLEMENTARY PROJECTIONS: Supplementary views for cervical spine includes the following Right and Left Posterior oblique views erect Right and left Posterior oblique views supine Lateral flexion and extension Swimmer’s view. RIGHT AND LEFT POSTERIOR OBLIQUE PROJECTIONS ERECT These projections are recommended in cases of trauma and in degenerative diseases. Its main aim is to examine the intervertebral foramina and the relationship of the facet joints in cases of suspected dislocation or subluxation. PATIENT’S POSITION Patient stands or sit with the posterior aspect of their head and shoulder against the vertical cassette holder The mid sagittal plane of the body is rotated through 45º for right and left side. The head is rotated so that the mid sagittal plane of the head is parallel to the cassette to avoid superimposition of the mandible on the vertebra. The cassette is centered at the prominence of the thyroid cartilage Collimate to avoid irradiation of the eyes. BEAM DIRECTION AND CENTRING POINT Horizontal beam is angled 15º cephalad and the central ray centered to the middle of the neck on the side nearest to the tube. The intervertebral foramina shown are the side nearer to the cassette. N/B: Right and Left anterior oblique can be done to reduce radiation dose to the thyroid gland and in this case, the beam is angled 15º caudad. Right posterior oblique position together with the radiograph courtesy of Clark’s positioning RIGHT AND LEFT POSTERIOR OBLIQUE SUPINE: This is done in cases of severe trauma where it is impossible for the basic views to demonstrate the lower cervical vertebrae. POSITIONING OF PATIENT AND CASSETTE Patient lies supine on the casualty trolley  The cassette is gently slotted under the patient’s neck without moving the patient or inside a cassette tray beneath the trolley. BEAM DIRECTION/ CENTERING POINT The beam is angled 30-45º to the mid sagittal plane and the central ray is directed towards the middle of the neck on the side nearer to the tube at the level of the thyroid cartilage. LATERAL SWIMMER’S PROJECTION This is done when the lateral view cannot show all the vertebrae especially the cervico-thoracic junction which is as a result of superimposition of the vertebrae by the shoulders. POSITION OF PATIENT Patient lies on the casualty trolley, stand or sits with either side of the body against an erect cassette stand with the mid sagital plane parallel to the cassette. The arm nearer to the cassette is folded over the head with the humerus as close to the cassette stand top as possible while the shoulder nearer to the x-ray tube is depressed. The shoulders are now separated vertically and the cassette adjusted so that the vertebrae will be at the middle of the cassette. BEAM DIRECTION /CENTERING POINT The horizontal beam is directed to the middle of the cassette at a level just above the shoulder far away from the cassette. LATERAL FLEXION AND EXTENSION PROJECTIONS: This is usually done in cases of trauma, degenerative bone disease and in theatre to assess the degree of movement of the neck. In cases of trauma, an experience doctor should monitor the degree of flexion or extension. PATIENT POSITION Patient is positioned for basic lateral view. The patient is then asked to flex the neck and tuck in the chin as far as possible or extend the neck and raise the chin as far as possible The patient is advised to hold onto something for immobilization The cassette is centered to the mid cervical region or placed transversely for the lateral in flexion. BEAM DIRECTION AND CENTERING POINT Horizontal central ray is directed towards the middle of the neck.  THORACIC VERTEBRAE The thoracic vertebrae are located between the cervical and lumbar vertebrae. They are stacked upon each other to form a kyphotic curve in lateral view. The thoracic vertebrae are twelve in number and are identified as TI-T12 vertebrae. The region has an extremely high contrast. This is due to the superimposition of the air filled trachea over the upper thoracic vertebrae. This produces a relatively lucent area and a high density on the radiograph. The heart and the liver superimposed over the lower thoracic vertebrae will attenuate more x-ray and yield a much lower film density. To overcome this challenge of high radiographic contrast associated with this region, a number of strategies are employed and this includes a. Use of anode heel effect. This is done by positioning the anode cranially and the cathode caudally. b. Use of graduated screen or wedge filters placed on the light beam diaphragm or attenuators placed over the upper thoracic vertebrae. c. Use of high kVp (80kVp or more). This is necessary for visualization of the intact pedicles which is an important sign in excluding metastatic disease. BASIC PROJECTIONS: The basic projections for thoracic vertebrae are Anteroposterior (AP) and Lateral. ANTEROPOSTERIOR (AP) PROJECTION. PATIENT”S POSITIONING: Patient lies supine on the x-ray couch with the mid sagittal plane perpendicular to the center of the tabletop which corresponds to the midline of the Bucky. The knee and hip are flex so that the plantar aspect of the foot are in contact with the table. Foam pad are placed under the knee for stability and comfort. The arms are placed by the sides. Cassette should be long enough to include C7 and L1 vertebrae (These vertebrae are identified because they don’t have ribs attached to it). Exposure is made on arrested inspiration. This will cause the dome of the diaphragm to move down over the upper lumbar vertebra thereby preventing it from overlapping on the distal thoracic vertebrae. CENTERING POINT AND BEAM DIRECTION: Vertical central rays are directed at right angle to the cassette and towards a point 2.5cm below the sternal angle. LATERAL PROJECTION: PATIENT”S POSITION Patient lies on either sides in lateral decubitus on the x-ray table. The mid sagittal plane should be parallel to the cassette and the mid axillary line coincides with the middle of the table. The arms should be raised well above the head with the head supported with a pillow while pads may be placed between the knees for comfort. The cassette should be long enough to include the lower cervical and upper lumbar vertebrae. The upper edge should be 3-4 cm above the spinous process of C7. Exposure is made on arrested inspiration although in most cases, the ribs may superimpose over the vertebrae and distract the image quality. So use of auto-tomography should be adopted in which a low mA of 10-20 mA and a long exposure time of 3-5s are used with the patient breathing normally during the exposure. CENTERING POINT AND BEAM DIRECTION: The central vertical ray should be at right angles to the long axis of the thoracic vertebrae. Centre at a point which is 5cm anterior to the spinous process of T6/7 which is at the level of inferior angle of the scapula.  LUMBOSACRAL VERTEBRAE The lumbar vertebrae are five and are numbered L1-L5. They form a lordotic curvature in lateral view. BASIC PROJECTIONS: The basic projections for lumbar vertebrae are Anteroposterior (AP) and Lateral. ANTEROPOSTERIOR (AP) PROJECTION: PATIENT’S POSITIONING. Patient lies supine on the x-ray couch with the mid sagittal plane coinciding with, and at right angle to the midline of the table. The anterior superior iliac spine should be equidistant from the tabletop. The hip and knees are raised on a foam pad so that the plantar aspects of the foot are in contact with the table. This will help to reduce the lumbar arch and bring the lumbar vertebrae parallel to the cassette. The exposure should be taken on arrested expiration. The cassette should be large enough to accommodate the lower thoracic vertebrae and the sacro-iliac joints. CENTERING POINT AND BEAM DIRECTION: Vertical central beam is directed towards the midline at the level of the lower costal margin which corresponds to L3 vertebra. N/B: PA projection can be performed when we are interested in the disc spaces of the lumbar vertebrae. This is achieved by the patient lying prone on the Bucky table although due to high OFD, there is mild magnification of the lumbar vertebrae. LATERAL PROJECTION: PATIENT”S POSITIONING Patient should undress and wear the x-ray gown, then lies on either side on the couch although in case of scoliosis, the concave side should face the tube. The coronal plane which runs through the spine should coincides with the centre of the table. The arms are raised and rested on the pillow in front of the patient’s head. The knees and hips are flexed for stability while exposure is made on arrested expiration. CENTERING POINT AND BEAM DIRECTION: Vertical central ray at right angle to the line of spinous processes is centered towards a point 7.5cm anterior to the third lumbar spinous process at the level of the lower costal margin. ALTERNATIVE PROJECTIONS LATERAL WITH HORIZONTAL BEAM (LATERAL SHOOT THROUGH) This is done on patient with suspected fracture of the lumbar vertebrae PATIENT’S POSITIONING Patient lying in a trauma trolley is placed adjacent to the vertical Bucky. The vertical Bucky is adjusted so that the lower costal margin of the patient coincides with the vertical central line of the Bucky and the median sagittal plane is parallel to the cassette. The Bucky should be adjusted so that the patient’s mid coronal plane coincides with the midline of the cassette within the Bucky, along its axis with the arm raised above the head if possible. BEAM DIRECTION AND CENTERING POINT Horizontal central ray is directed parallel to the line joining the anterior superior iliac spines and towards a point 7.5cm anterior to the third spinous process at the level of the lower costal margin. SUPLEMENTARY PROJECTIONS LATERAL FLEXION AND EXTENSION These projections may be requested to demonstrate the mobility and stability of the lumbar vertebrae. PATIENT’S POSITION Patient usually sits on a stool with either side against the vertical Bucky or may be in lateral decubitus on a Bucky table. The dorsal surface of the trunk should be at right angle to the cassette and the vertebral column parallel to the cassette. First, the patient leans forward, flex the lumbar region as far as possible, and grip the front seat to assist in maintaining the position. Exposure is then made. Secondly, the patient lean backwards, extending the lumbar region as far as possible and grip the back of the seat for stability, then another exposure is made. CENTERING POINT AND BEAM DIRECTION Horizontal central beam at right angle to the cassette and centered towards a point 7.5cm anterior to the third lumbar spinous process which corresponds to the lower costal margin. RIGHT OR LEFT POSTERIOR OBLIQUE PROJECTIONS These projections are used to demonstrate the pars interarticularis and the apophyseal joint on the side nearest to the cassette. Both sides should be taken for comparison. POSITIONING OF PATIENT Patient lies supine on the Bucky table with the mid sagittal plane perpendicular to the centre of the table. The patient is then rotated 450 to the right and left in turn with the arms raised and hand resting on the pillow. The hip and knees are flexed and supported with a 450 foam pad placed under the trunk on the raised side. Cassette is centered at the lower costal margin CENTERING POINT AND BEAM DIRECTION Central vertical ray is directed towards the midclavicular line on the raised side at the level of the lower costal margin. LUMBOSACRAL JUNCTION BASIC PROJECTIONS Basic projections for lumbosacral joint are Anteroposterior (AP) and Lateral ANTEROPOSTERIOR PROJECTION: PATIENT POSITIONING. Patient lies supine on the Bucky table with the median sagittal plane corresponding with and perpendicular to the midline of the Bucky. The anterior superior iliac spines should be equidistance from the table top. The knees are flexed over a foam pad for comfort and to reduce the lumbar lordosis. The cassette is placed cranially so that its centre coincides with the central ray. CENTERING POINT AND BEAM DIRECTION Central ray is directed 10-200 cranially from the vertical and towards the midline at the level of the anterior superior iliac spines. This degree of angulation is normally greater for females than for males and will be less for a greater degree of flexion at the hip and knees. LATERAL PROJECTION POSITIONING OF PATIENT Patient lies on either side on the Bucky table with the arms raised or the hand resting on the pillow. The knees and hip are flexed slightly for stability. The dorsal aspect of the trunk should be at right angle to the cassette while the coronal plane should coincide with and perpendicular to the midline of the Bucky. The cassette is centered at the level of 5th lumbar vertebra. SUPLEMENTARY PROJECTIONS RIGHT OR LEFT POSTERIOR OBLIQUE PATIENT POSITIONING Patient is positioned supine on the Bucky table and then rotated to the right and left sides in turn so that the median sagittal plane is at 450 to the table top. The hip and knees are flexed and the patient is supported with 450 foam pad placed under the trunk on the raised side. The cassette is displaced cranially at the level to coincide with the central ray.