Chapter 18 Foot Radiography

• Fractures are characterized by involvement of the subtalar joint (75%) and not involving the subtalar joint.

• Stress fractures are common in runners but typically not seen on radiographs.

• Stress fractures , plantar fascitis or heel spurs are common repetitive use conditions.

Foot or Heel Radiography

• Views of the foot and calcaneus are totally different.

• If a heel injury is suspected, take heel views and not foot views.

• A 30 degree medial oblique view can be useful. The oblique and lateral will demonstrate the subtalar joint.

Foot Radiography

• Foot view must include the tarsal bones, metatarsals and phalanges.

• A tube angle is used to open the tarsal bone articulations on the A-P view.

• If the patient is flat footed, no tube angle would be needed.

Foot Radiography

• The medial oblique view is particularly useful. It provides:

• A clear view of the tarsal bone including the calcaneus.

• The 4th & 5th metatarsals

• Intertarsal joints

• Detail of the 5th metatarsal

Foot Radiography

• The “basketball foot” is a traumatic medial subtalar dislocation resulting from landing on an inverted foot.

• The “Jones fracture is an avulsion fracture off the base of the 5th metatarsal.

• Stress fractures of the metatarsals are generally transverse resulting from marching or jumping.

Toe Radiography

• Toe radiography can be particularly challenging.

• The natural curve of the toes toward the plantar surface of the foot results in foreshortening and closure of the interphalangeal joint spaces.

• Besides the A-P, an angled axial view is used to open the joint spaces.

18.4 Foot A-P

• Measure: A-P at base of third metatarsal

• Protection: Apron• SID: 40” Table Top• Tube Angle: 10°

cephalad• Film: 1/2 of 10” x 12

Extremity Cassette I.D. up

Foot A-P• Patient seated or lying on

table with the long axis of the affected foot centered to table.

• Place cassette on table.• Have patient place foot

flat on cassette.• Horizontal CR: base of

third metatarsal

Foot A-P• Vertical CR: long axis of

foot.• Collimation Top to

Bottom: distal tibia to tips of toes.

• Collimation Side to Side: soft tissue of foot

• Instructions: Remain still• Make exposure and let

patient relax

Foot A-P Film

• Should demonstrate toes , metatarsals and most of the tarsal bones. The talus and calcaneus will not be seen.

• The tube angle will help open the tarsal joint spaces.

18.5Foot Oblique

• Measure: A-P at base of third metatarsal

• Protection: Apron• SID: 40” Table Top• No Tube Angle• Film: 1/2 of 10” x 12

Extremity Cassette I.D. up

Foot Oblique• Patient seated or lying

on table with the long axis of the affected foot centered to table.

• Place cassette on table.• Have patient place foot

flat on cassette.• The foot is medially

rotated 30 to 40°• A sponge may be used

under the plantar surface of the foot.

Foot Oblique• Horizontal CR: base of

third metatarsal• Vertical CR: long axis

of foot.• Collimation Top to

Bottom: distal tibia to tips of toes.

• Collimation Side to Side: soft tissue of foot

• Instructions: Remain still

• Make exposure and let patient relax

Foot Oblique Film

• Should demonstrate toes , metatarsals and most of the tarsal bones. The talus and calcaneus will not be seen.

• The calcaneus will be well visualized

• Tarsal joint spaces should be open.

18.6 Foot Lateral

• Measure: Lateral at base of first metatarsal

• Protection: Lead Apron• SID: 40” Table Top• No Tube Angle• Film: 8” x 10” or 10” x 12”

Extremity depending on foot size.

Foot Lateral

• Patient lies on the affected side with lower leg in lateral position.

• The foot should be dorsiflexed until the plantar surface is perpendicular to ankle.

• The plantar surface of foot is perpendicular to film.

Foot Lateral

• The film may be turned diagonally or the foot placed diagonally on film to fit the entire foot on the film.

• Horizontal CR: base of 1st metatarsal

• Vertical CR: base of first metatarsal

Foot Lateral

• Collimation Top to Bottom: to include ankle to plantar surface soft tissue

• Collimation Side to Side: to include from heel to tips of toes.

• Instructions: Remain still• Make exposure and let

patient relax.

Foot Lateral Film

• The foot and ankle should be in a lateral position.

• The metatarsals and toes will be superimposed.

• The distal fibula should overlie the distal tibia.

• The talotibial joint space should be open.

18.7 Toes A-P & Axial A-P

• Measure: A-P at 3rd metatarsal phalangeal joint or affected toe

• Protection: Lead Apron• SID: 40” Table Top• Tube Angle A-P: none• Tube Angle Axial A-P:

15° cephalad• Film: 1/4 of 10 x 12

Extremity

Toes A-P & Axial A-P

• A-P : patient places foot flat on film.

• Horizontal & Vertical CR: 3rd M-P joint for all toes or M-P joint of the affected toe for individual toe series.

• A-P Axial tube angle: same as above but with 15° cephalad angle.

Toes A-P & Axial A-P

• A-P Axial with Sponge: a 15° sponge is placed under toes instead of angling the tube. Or

• The Sponge is placed under the cassette

• Horizontal & Vertical CR: 3rd M-P joint for all toes or M-P joint of affected toe.

Toes A-P & Axial A-P

• Collimation top to bottom: to include all M-P joints to tips of toes or M-P joint to tip of affected toe.

• Collimation Side to Side: soft tissue of foot or individual toe.

• Instructions: Remain Still

• Expose and let patient relax

Toes A-P & Axial A-P Film

• A-P is upper right image.

• A-P Axial is upper left image. The phalangeal joints will be open on the axial view.

• Views must include all of the affected toe or toes.

• Note that collimation was too tight top to bottom.

18.8 Toes Medial Oblique

• Measure: A-P at metatarsal-phalangeal joints

• Protection: Apron• SID: 40” Table Top• No tube angle• Film: 1/4 of 10” x 12”

or 8” x 10” Extremity Cassette

Toes Medial Oblique

• Patient places distal foot on unexposed portion of cassette.

• Patient medially rotates lower leg until the plantar surface forms a 30 to 45° angle.

• Horizontal CR: 3rd MTP joint or the affected toe.

Toes Medial Oblique

• Vertical CR: centered to long axis of foot or the affected toe

• Collimation top to bottom: Distal metatarsal to tips of toes or affected toe

• Collimation side to side: soft tissue of foot or affected toe.

Toes Medial Oblique

• Patient instructions: Remain Still

• Make exposure and let patient relax.

• Note that a sponge may be placed under plantar surface of foot to control angle of view . It will also make it more comfortable for the patient.

Toes Medial Oblique

• The joint spaces should be open.

• The distal metatarsal and tips of the toes should be visualized.

18.8 Toes Lateral

• Measure: Lateral across the metatarsal-phalangeal joints For individual toe use A-P measurement.

• Protection: Apron• SID: 40” Table Top• No tube angle• Film: 1/4 of 10” x 12” or

8” x 10” Extremity Cassette

1st Toe Lateral • Patient places distal foot

on unexposed portion of cassette.

• For 1st through 3rd toes

• Patient medially rotates lower leg until the plantar surface forms a 90° angle.

• For 4th and 5th toes

• Patient laterally rotates foot until the plantar surface is perpendicular to film.

2nd Toe Lateral

• For individual toes, tape and tongue depressors are used to clear the other toes out of the view.

• Without the use of tape and tongue depressors, there will be too much superimposition

3rd Toe Lateral• Horizontal CR: 3rd MTP joint or the affected toe.

• Vertical CR: centered to long axis of foot or the affected toe

• Collimation top to bottom: Distal metatarsal to tips of toes or affected toe

• Collimation side to side: soft tissue of foot or affected toe.

4th Toe Lateral

• Patient instructions: Remain Still

• Make exposure and let patient relax.

• Note that the lateral surface of the foot is next to the film.

5th Toe Lateral

• Note that the lateral surface of the foot is next to the film.

• The toe need to remain parallel to the film.

• The 5th toe is the most challenging lateral toe view.

Toes Lateral Film

• The joint spaces should be open.

• The distal metatarsal and tips of the toes should be visualized.

• The affected toe should be free of superimposition.

Accessory Testing

• Accessories include the cassettes, grids outside the Bucky, Lead Aprons and gonadal protection.

• The cassettes and screens are the primary concern.

• Screens should be cleaned monthly with screen cleaner. Keeping the darkroom clean is also important for screen cleanliness.

23.4 Screen Contact Testing

• Procedure:• Clean screens and let

them dry. Use screen cleaner design for the screen used.

• With a felt tip pen, write an identification number on the screen next to the I.D. and on the back of the cassette.

• Load cassettes.

Screen Contact Testing

• Procedure:• Set SID to 40” Table Top• Place cassette on table.• Place wire mesh tool on

cassette.• Set collimation to film

size.• Make exposure and

process film.

Screen Contact Testing

• Procedure:• Hang film on view box.• Step back 72” from view

box and view film.• Areas of increased

density or loss of resolution indicates poor contact or stained screens.

Screen Contact Testing

• Procedure:• The I.D. # will help you

find a cassette that needs to be cleaned or taken from service.

• Frequency of tests: semiannual

Poor Screen Contact

• There is a loss of detail in the thoracic and lumbar spine due to poor screen contact.

• This was a new cassette.

Poor Screen Contact

• Note the blurry image in the spine but sharp image of the ribs.

• The screens were not in proper contact in the middle of the cassette due to a bow in the cassette back.

Screen Cleaning

• Materials needed:• Screen Cleaner

designed for type of screens used.

• 4 x 4 gauze or cotton balls

• Tape & Pen

Screen Cleaning

• Procedure:• Unload cassette if

contact is not being tested.

• Apply cleaner with gauze.

• Wipe excess off with dry gauze.

Screen Cleaning

• Leave open to air dry.• Make sure cassette #

is still legible.• After dry, reload

cassette.

Screen Cleaning

• Record date on tape and place on back of cassette.

• By having each cassette identified, selected cassette can be cleaned as needed.

Screen Cleaning

• California Department of Radiologic Health recommends cleaning screens monthly.

• Should definitely be done quarterly and sooner as needed when artifacts are identified on films.

• Never use alcohol or detergents not designed for cleaning screens.

Cassette Care

• Methods to get the maximum life from cassettes:– Avoid dropping the cassettes– Open only far enough the change films– Keep outside of cassette clean and dry.– Keep screens clean– Store on end.

Dirty or Damaged Screens

• Dirty or damaged screen will cause white spots on the image.

Dirty & Damaged Screens

• The white spots on this film are the result of damaged or worn out screens.

• Never use alcohol or detergents to clean screens.

Speed Matching

• After looking for screen contact problems:• Measure speed of cassettes by reading density

with the Densitometer. The density of the exposed area should not vary more than ± 0.05 OD.

• As screen age, they loose speed. • Always make sure the light spectrum of the

screens and film are matched.

23.5 Apron and Gonad Shield Testing

• Lead aprons and shields should be tested semiannually for defects

• Aprons with defective lead provide little protection for the patient.

Apron and Gonad Shield Testing

• Tools needed:– 14” x 17” cassette– View Box

• Coat Apron Procedure:• Drape apron over Bucky• Place cassette in Bucky

make exposures in upper and lower Bucky slots.

Apron and Gonad Shield Testing

• Coat Apron Procedure:• Note that this is the same

test as used for grid alignment.

• Process films• View films on view box:

Apron and Gonad Shield Testing

• Half Apron and Small Shield Procedure:

• Place cassette on table• Set SID at 40”• Place apron or shields

on cassette.• Make exposure and

process the film.

Apron and Gonad Shield Testing

• Viewing the test films:– Note creases in the

lead.– Full holes will produce

a black area on the film.

– If cracks or defects are in the area that should cover the gonads, replace apron.

Care of Aprons

• Never fold aprons

• Store flat or hung on apron rack

• Use only aprons with the lead equivalency of 0.5mm for patient and staff protection.

• Do not use as lead blockers for extremity films.

• Protect from heat and direct sun light.

Grid Uniformity Testing

• Procedure is the same as testing the Bucky Grid.

• Place homogenous phantom or lead apron over grid that is taped to the top of the cassette.

• Make exposure and look for density changes and grid damage.