equine radiography: positioning techniques & tips for acquiring good images

TITLE

Equine Radiography:

Positioning, Techniques & Tips for Acquiring Good Images

Shalyn J. Crawford, DVM

Images

Unless otherwise indicated, all positioning photographs included in this lecture have been reproduced with permission from Christine Garloff's presentation Large Animal Radiology Digital X-ray of the Front and Hind Limb

All anatomical model and unlabeled radiographic views drawn from Iowa State University College of Veterinary Medicine Horse Limb Anatomy free resource website. Accessed web 9 Aug 2015

Restraint & Safety

Horse holder preferred to cross tie

Opposite front limb held up, or ipsilateral front limb held up

Twitch

Sedation:

Xylazine 150mg

Detomidine 3mg

ALL individuals wearing lead aprons and monitoring badges, plate holder lead gloves

Make sure to provide owner with lead apron

Use an inanimate plate holder and tripod whenever possible

Radiation Safety Aids

X100S Tripod Stand. Digital Image. Pacific Northwest X-ray. Pacific Northwest X-ray. Web. 9 Aug 2015.

TOMAHAWK Portable Cassette/CR-Plate Holder/Positioner. Digital Image. MinXray. MinXray. Web. 9 Aug 2015.

Positioning

Standing square

Level solid ground surface

Stand horse on blocks L and R to level

Stand out of direct or bright light to see collimator guide light

Position horse so cords can reach both L and R sides

Adequate power supply

Positioning Aids

Redden Offset Lateral & D.P. X-Ray Positioning Block. Digital Image. Nanric. Nanric. Web. 9 Aug 2015.

Redden navicular xray block. Digital Image. Nanric. Nanric. Web. 9 Aug 2015.

EZ BLOX strap-on xray blocks. Digital Image. EDSS Hoof Care Products. Equine Digital Support Systems. Web. 9 Aug 2015.

Technique

Varying plain film, CR, DR

Contact generator manufacturer for technique chart

Know focal distance for your generator

Use the retractable tape measure!!

Collimate, collimate, collimate...collimate

Tip always place the plate as close to the anatomy of interest as possible

Tip (80kVp/15mA generators) shorten focal distance to improve penetration

Tip if images are dark enough but grainy, cut kVp 15% and increase mAs ~20%.

Adjusting Image Technique

Too dark? Decrease mAS by half

Too bright? Increase mAS by 2

Too much contrast? Increase kVp

Too little contrast? Decrease kVp

Too noisy (grainy)? Increase kVp

Technique Cont.

Use positioning markers

Custom LF, RF, LH, RH markers

Can use coin or paper clip in a pinch

Dorsal hoof wall markers: barium, horse shoe nail, wire

Patient preparation

Clean visible dirt/mud from limbs

Foot prep:Remove shoes

Clean dirt/mud from bottom and outside of hoof

Lightly pare sole if necessary

Pack frog sulci with play-doh

Markers

Markers always to be placed dorsal or lateral to the anatomy

Affix to plate with velcro tabs or duct tape

Tip to only move the marker once take film series in order of DP, DLPMO, DMPLO, then LM

Tip if taking a two foot series, stand horse one foot on block and one on tunnel. Take the tunnel series of one foot and the DP and LM of the other foot then switch blocks only once

Know Thy Anatomy

Sample resources:Iowa State University interactive horse limb anatomy (free!)http://vetmed.iastate.edu/limbanatomy/horse.html

Virtual Radiography of the Horse (free)http://www.3d-it.vet.ed.ac.uk/xrayhandbook/webpages/horse.html

Clayton, Flood & Rosenstein, Clinical Anatomy of the Horse ~$120

The Glass Horse, Elements of the Equine Distal Limb ~$50http://www.3dglasshorse.com/default.asp

Horse Anatomy: Equine 3D, app for iOS & Android ~$10

P3 Lateromedial (LM)

Position: weight bearing on blocks

Casette: against medial aspect of limb on ground, perpendicular to limb

Beam: centered at mid coronary band with heel bulbs visually superimposed, generator on the ground

Use dorsal hoof wall markers for rotation/sinking eval

P3 Dorsopalmar (DP)

Position: weight bearing on blocks

Casette: on ground palmar/plantar aspect of limb, perpendicular to limb

Beam: parallel to ground, centered at coronary band

Make sure to radiograph in reference to the hoof, if horse toes out place on block accordingly and direct beam straight at toe

P3 Dorsolateral-Palmaromedial Oblique (DLPMO), Dorsomedial-Palmarolateral Oblique (DMPLO)

Position: weight bearing on tunnel

Casette: in tunnel

Beam: 60PrDi, 45 off DP (either lateral or medial), just distal to coronary band

P3 Dorso-Proximal Palmaro-Distal Oblique Views (D65Pr-PaDiO, Solar Margin and Dorsal Navicular)

Position: weight bearing on tunnel

Casette: inside tunnel

Beam: centered 2cm above dorsal coronary band 60-65 angle

This view can also be taken with foot on Redden block and beam parallel to ground

Increase mAs to view navicular bone, decrease mAs to not burn through solar margin

P3 Palmaroproximal-Dorsodistal Oblique
(PaPr-DDiO, Navicular skyline)

Position: weight bearing on tunnel with limb placed caudally

Casette: in tunnel

Beam: 50-55PaPr centered just above heel bulbs

50-55

Fetlock Lateromedial (LM)

Position: weight bearing

Casette: medial to limb, perpendicular to ground

Beam: parallel to floor, centered on PIP joint

Distal condyles of cannon bone should be superimposed in a true lateral

Fetlock Dorsopalmar/plantar (DP)


Casette: palmar/plantar aspect of limb, on ground parallel to pastern

Beam: 20 proximally angled

Proximal sesamoids should be offset proximally from joint when viewing radiograph

Ergot is clearly visible in this view

Oblique Views

Oblique Views and Large Animal Distal Limb Normal Anatomy, Anderson K L, 2011

D-L-P-M

D-M-P-L

Lateral structures will be viewed/highlighted on the palmar/plantar aspect of the radiograph

Medial structures will be viewed/highlighted on the palmar/plantar aspect of the radiograph

Markers always placed laterally

Fetlock Dorsolateral-Palmaromedial Oblique (DLPMO), Dorsomedial-Palmarolateral Oblique (DMPLO)


Casette: palmaro/plantaro-medial or lateral to limb, parallel to pastern

Beam: 45 off DP (medial or lateral) centered at fetlock joint

Proximal sesamoid of interest should be clearly offset

Fetlock Flexed Lateromedial

Position: held in flexionTip hold toe of foot with one gloved hand and the plate with the opposite hand

Casette: medial and parallel to limb

Beam: parallel to ground/perpendicular to limb, centered at PIP joint

Make sure to have generator and computer settings set before having plate/limb holder get in position

MC/MT II & IV (Splint bones)
Dorsolateral-Palmaromedial Oblique (DLPMO),
Dorsomedial-Palmarolateral Oblique (DMPLO)


Casette: palmaro/plantarolateral or medial to limb

Beam: 45 off DP (medial or lateral) centered at area of interest on splint bone

Decrease mAs to not overexpose the delicate splint bones

To offset MC/MT IV DLPMO/PMDLO

To offset MC/MT II DMPLO/PLDMO

Carpus Lateromedial (LM)



Beam: parallel to floor, centered on mid-carpus

Carpus Dorsopalmar (DP)


Casette: palmar aspect of limb, perpendicular to ground

Beam: parallel to floor, centered mid-carpus

Carpus Dorsolateral-Palmaromedial Oblique (DLPMO), Dorsomedial-Palmarolateral Oblique (DMPLO)


Casette: palmaromedial/lateral to limb

Beam: parallel to floor, 30 off LM or ML, centered mid-carpus

Carpus Flexed Lateromedial

Position: held in flexion 60Tip hold toe of foot with one gloved hand and the plate with the opposite hand

Casette: medial and parallel to limb

Beam: parallel to ground/perpendicular to limb, centered between proximal and distal row of carpal bones

Make sure to have generator and computer settings set before having plate/limb holder get in position

Carpus Skyline Views (proximal and distal rows)

Position: held in flexionHold limb in flexion and push forward to expose distal row of carpal bones

Casette: plate held against dorsal aspect of cannon with carpus centered

Beam: steep dorsoproximal-palmarodistal angle downward standing in front of the horse, adjust angle to focus on proximal vs distal row of carpal bones

Distal ulnar, 4th, 3rd, 2nd

Proximal ulnar, intermediate, radial

Tarsus Lateromedial (LM)



Beam: parallel to floor, centered proximal intertarsal joint

Tarsus Dorsoplantar (DP)


Casette: plantar aspect of limb, perpendicular to ground

Beam: slightly proximodistal angle, centered proximal intertarsal joint

Tarsus Dorsolateral-Plantaromedial Oblique (DLPMO), Dorsomedial-Plantarolateral Oblique (DMPLO)


Casette: plantaromedial/lateral to limb

Beam: parallel to floor, 45 off DP, centered proximal intertarsal joint

DMPLO

DLPMO

Anything wrong here?

JL Werner, http://www.sfredhead.com/cartoons/cartoonarchive

Stifle Lateromedial (LM)


Casette: medial to limb, as dorsal as possibleMove slowly and carefully as horse's can be very sensitive to the plate in this area!!

Beam: parallel to floor, centered stifle joint

Femoral condyles should be superimposed

Make sure to get the entire patella and proximal tibia in the image; if your plate is too small/horse too large you may have to take two views to image all of the anatomy

Stifle Lateromedial (LM)


Casette: medial to limb, as dorsal as possibleMove slowly and carefully as horse's can be very sensitive to the plate in this area!!

Beam: parallel to floor, centered stifle joint

Femoral condyles should be superimposed

Make sure to get the entire patella and proximal tibia in the image; if your plate is too small/horse too large you may have to take two views to image all of the anatomy

Stifle Caudolateral-Craniomedial Oblique (CdLCrMO)


Casette: held against dorsomedial aspect of stifle

Beam: centered at stifle 30 caudolateral (from true lateral)

Medial femoral condyle should be clearly visible

Stifle Caudocranial (CdCr)


Casette: held against dorsal aspect of limb centered at patella

Beam: stand directly behind the horse (CAUTION) with generator held close to hindquarters, angle proximodistally (downward) aiming for middle of joint

Humeroradial Joint (Elbow)

Medial-lateral (ML):Position: weight bearing or limb held extended forward (more motion)

Casette: against lateral aspect elbow

Beam: directed medial-lateral

Love, N. Equine Appendicular Radiology [SlideShare slides]. Retrieved from ://radfileshare.cvm.ncsu.edu/VMB976/setup/eqpositioning.pdf

Humeroradial Joint (Elbow)

Craniocaudal (CrCd):Position: weight bearing or limb held up with radius parallel to floor

Casette: against caudal aspect elbow

Beam: centered elbow joint, for standing view may need to direct beam slightly caudodistally


Selected Dental Radiographs

Tip helps to have horse markedly sedate and resting head on a stand, tall trash can, hay bales, etc. to minimize motion

Tip use a rope halter, no metal fittings

Remember! plate MUST be closest to the anatomy of interest

Incisor block can be used for oblique views

Can use malleable metal probe to mark draining facial tracts or contrast material

Dental Radiographs Cont.

LM plate L or R of head depending on anatomy of interest, beam centered near rostral aspect facial crest

DV plate against mandible, beam perpendicular centered near rostral facial crest

DV oblique (for viewing maxillary tooth roots) beam centered rostral facial crest, angled 30-45 (from lat) dorsal-ventral

VD oblique (for viewing mandibular tooth roots) beam centered ventral edge mandible, angled 45-60 (from lat) ventral-dorsal

Maxillary cheek teeth are highlighted which view was taken?

Scapulohumeral Joint (Shoulder)

Requires higher output machine due to large soft tissue mass

Medial-lateral view:Position: holder extends front limb of interest as far out in front of the horse's body as possible

Casette: held against lateral aspect shoulder

Beam: directed medial-lateral

Try to superimpose shoulder joint over trachea to reduce soft tissue overlap


Temporomandibular Joint (TMJ) - R45V30L-CdDO

Position: Standing with head extended on head stand

Casette: Dorsal aspect of poll/occipital protuberance, 15 angle centered on TMJ of interest

Beam: Directed 30 lateral to DV, 45 rostroventral-caudodorsal angle

Positioning of the head on the post and the placement of the cassette holder, From: Ebling, A.McKnight, A., Seiler, G., & Kircher, P. (2009). A Complementary Projection of the Equine Temporomandibular Joint. Veterinary Radiology and Ultrasound 50 (4) 388.

References

Butler, Janet A. Clinical Radiology of the Horse. Oxford, UK: Wiley-Blackwell Pub., 2008. Print.Ebling, Alessia J., Alexia L. Mcknight, Gabriela Seiler, and Patrick R. Kircher. "A Complementary Radiographic Projection Of The Equine Temporomandibular Joint." Veterinary Radiology & Ultrasound 50.4 (2009): 385-91. Print.Griffin, Cleet. "EQ8 Dental Imaging." Proc. of Western Veterinary Conference, Las Vegas. Web.O'Brien, Timothy R. O'Brien's Radiology for the Equine Ambulatory Practitioner. Jackson, WY: Teton NewMedia, 2005. Print.Redden, R. F. "The Equine Foot In-Depth: Clinical and Radiographic Examination of the Equine Foot." 49th Annual Convention of the American Association of Equine Practitioners, 2003. New Orleans. 21 Nov. 2003. Web. 1 Aug. 2015.Thrall, Donald E. Textbook of Veterinary Diagnostic Radiology. St. Louis, MO: Saunders Elsevier, 2007. Print.

Thank you! Questions?

equine radiography: positioning techniques & tips for acquiring good images

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