Thumb

Question 1

Standard Thumb projections

Answer 1

AP/PA

PA Oblique

Lateral

Question 2

AP Thumb

Positioning

CR

Angle

kVp

mAs

Answer 2

Patient sitting at end of table parallel to end so legs
not under the table
• Flex elbow at 90o or arm extended
• Hand resting on table
• Rotate hand internally so palm of hand is facing
away from imaging plate
• Move other fingers away
• Long axis of thumb should be parallel to edge of
imaging plate
• Central ray perpendicular to imaging plate
• Center to the MCP joint
• Collimate on four sides to outer margins of thumb
• FFD 110cm
• kVp 42
• mAs 2
• Fine focus, no grid
• You can also put imaging plate at 45o angle

Question 3

PA thumb

Positioning

CR

Angle

kVp

mAs

Answer 3

Patient sitting at end of table parallel to end so
legs not under the table
• Flex elbow at 90o
• Hand and forearm resting on table
• Hand on side so radial aspect is elevated
• Make sure thumb is straight and flat
• Move other fingers away
• Long axis of thumb should be parallel to edge of
imaging plate
• Use some form of immobilisation
• Central ray perpendicular to imaging plate
• Center to the MCP joint
• Collimate on four sides to outer margins of thumb
• FFD 110cm
• kVp 42
• mAs 2
• Fine focus, no grid

Question 4

PA Oblique Thumb

Answer 4

Patient sitting at end of table parallel to end so
legs not under the table
• Flex elbow at 90o
• Hand and forearm resting on table
• Place hand flat on cassette palm surface down as
in a PA hand position
• Long axis of thumb should be parallel to edge of
imaging plate
• Central ray perpendicular to imaging plate
• Center to the MCP joint
• Collimate on four sides to outer margins of thumb
• FFD 110cm
• kVp 42
• mAs 2
• Fine focus, no grid

Question 5

Lateral Thumb

Positioning

CR

Angle

kVp

mAs

Answer 5

Patient sitting at end of table parallel to end so
legs not under the table
• Flex elbow at 90o
• Hand and forearm resting on table
• From the PA oblique position slightly raise the
fingers rolling hand onto the radial side
• Long axis of thumb should be parallel to edge of
imaging plate
• Central ray perpendicular to imaging plate
• Center to the MCP joint
• Collimate on four sides to outer margins of thumb
• FFD 110cm
• kVp 42
• mAs 2
• Fine focus, no grid