Properties of a good chest X-ray and all views John-Henry Corbett 02/2012

PA chest Technical Central ray Exposure at full inspiration 110-125 kV, 3 mAs Hand on hips, palms out Shoulder rotated forward against IR (scapula out of lung fields) Shoulder pressed downward to remove clavicles from apices Central ray Central ray perpendicular to IR in midsagittal plane at level of T7 18-20cm below vertebral prominence or inferior angle of scapula Source image distance of 180cm Exposure at full inspiration 10-11 posterior ribs visible Alternative if patient cannot stand Sit with feet over edgde of bed / trolley – ‘hugging’ IR

AP Chest Technical Central ray Supine or semi-erect (if patient cannot stand/sit) Raise head of trolley/bed where possible Roll shoulder forward by rotating arms medially or internally IR behind patient Central ray Central ray angled caudally (± 5˚) to be perpendicular to long axis of sternum 3 posterior ribs should be seen above clavilces Central ray to T7 : 8-10cm below jugular notch Source image distance of 100cm (vs 180cm) The heart will appear larger because of decreases source-image distance and increase object image distance Pleural effusion will obscure vascular markings Inspiration will not be as full – 8-9 posterior ribs Lungs will appear more dense because of decreased aeration

Lateral chest (left) Left side against IR with arms crossed above head or holding arm support Technical 110-125kV , 6mAs Central ray Perdendicular on level of T7 Source image distance of 180cm If patient cannot stand, he/she can sit on trolley/wheelchair against IR

AP lordotic projection Lateral decubitus Demonstrates small pleural fluid or air collections For air the affected side most be up For fluid the affected side must be down AP lordotic projection Performed primarily to rule out masses and calcifications beneath the clavivles Patient stands 30cm away from IR, leaning back, with shoulders, back and neck against IR Central ray perpendicular to IR 9cm below jugular notch If patient is too weak/ unable to take this position AP semi-axial projection Patient supine AP with central ray angled 15-20 degrees cephelad Clavicles appear nearly horizontal with medial ends superimposed over 1st ribs

Anterior oblique positions (RAO/ LAO) Ribs, pathology in lung fields or mediastinum Left or right shoulder against IR with angle of 45 degrees Arm nearest IR flexed on hip with palm out Other arm above head Rest as normal chest XR For anterior obliques, the side furthest from the IR is usually the side of interest RAO will best show the left lung Inspiratory and expiratory CXR Easier detection of pneomothorax Doubles cost and radiation dose ; not routinely recommended Children with suspected foreign body inhilation

Properties of a good chest x-ray Structures shown Both lung fields included from lung apices to costophrenic angles Hilum region markings, heart, great vessels Bony thorax Postion Chin sufficiently elevated to prevent superimposition over lung apices Sufficient forward shoulder rotation to prevent scapulae superimposition over lung fields Large breast shadows, primarily lateral to lung fields No rotation Sternoclavicular joints same distance from centre line of spine Distance from lateral rib margins to vertebral comlumn the same on each side for upper and lower rib cage Scoliosis and kyphosis may lead to differences without rotation

Properties of a good chest x-ray Collimation and central ray Collimation margins near equal on bottom and top Center of collimation field (CR) at T7 Full inspiration with no motion 10-11 posterior ribs above diaphragm No motion evident by Sharp outlines of rib margins, diaphragm and heart borders Sharp lung markings in hilar regions and throughout lungs Exposure criteria Outline of at least upper and mid thoracic vertebra through the cardiac shadow and mediastinal structures Visualization of fine vascular markings in the lungs

Reference list Bontrager, KL. Textbook of radiographic positioning and related anatomy, 7th Edition. Mosby Elsevier; 2011. Chapter 3 : Chest.