introduction to clinical ultrasound · 2017-04-14 · introduction to clinical ultrasound maj...

Introduction to

Clinical Ultrasound

MAJ Jonathan Monti, DSc, PA-C, RDMS

Director, US Army / Baylor EMPA Residency Program

Madigan Army Medical Center

28th Annual Recertification Review Course and Spring Conference

23 April 2017

Objectives

1. Introduction to clinical ultrasound

2. Basic ultrasound physics

3. Clinical Case Scenarios

4. LCUS for Acute LE DVT

Disclaimer

“The opinions or assertions contained herein are the private views of the author and are not to be construed as official or reflecting the views of the Department of

the Army or the Department of Defense. The author has no relationships to disclose regarding these products.

This presentation is not, and in no way, should be construed as an endorsement of these product by the Department of the Army or Department of Defense.”

History of Ultrasound

1794 - Spallanzani – Echolocation in Bats

1826 - Colladon – Underwater Bell

1880 - Curie Brothers – Piezo-electric effect

1910s - Sonar use during WWI and Titanic

1940s - First use of medical ultrasound

1960s - OB Ultrasound “boom”

History of Ultrasound

in Trauma

1971 - First report of ultrasound dx hemoperitoneum

1976 - American Surgeon dx/grades splenic injury

1990s - Prospectively evaluated by American EM

physicians and surgeons

2000s - FAST incorporated into EM training / ATLS

curriculum

2009 - Ultrasound incorporated into SFMS (18D)

Curriculum

History of Ultrasound

1970 1985

1990

1995

2000

2002

2010

Miniaturization of Ultrasound

1950

2017

Ultrasound Today

• Increasingly portable / used at point of care

• Myriad of providers being trained to utilize • Prehospital

• Multiple specialties

• Rapidly being fully incorporated into medical school curriculum

• Studies increasingly supportive of clinician and non-physician use

Why Ultrasound?

Why Ultrasound?

Extension of physical exam?

Clinical vs Consultative US

Clinical Ultrasound

• Clinician-performed

• At bedside / Point-of-Care

• Timely clinical information

• Focused

• Limited Exam

• Rapid

• Repeatable

Consultative Ultrasound

• Sonographer-performed

• Radiology interpreted

• Comprehensive anatomy

• Time/resource-intensive

Why Not Ultrasound?

• Prohibitive cost of machines

• Lack of adequate training by potential users

• Operator-Dependent

Physics

• Diagnostic ultrasound uses sound waves in the frequency range 2-20 MHz

• Key properties of sound waves: – Frequency is number of

times per second the sound wave is repeated

– Wavelength is the distance traveled in 1 cycle

– Amplitude is distance between peak and trough

Transducer

• Energy created by electric current -> sent to the crystals -> excites the crystals which vibrate -> creating the resulting wave in the tissue – Piezoelectric Effect

• Beam is ~ 1mm

Physics

Principles

• The density of tissues determine the intensity of the returning echo

• The intensity of the returning echo determines the brightness of the image

• Strong signals = white (hyperechoic) images

• Weak signals or lack of signal all together = black (hypoechoic) images

Attenuation

• As ultrasound travels through the body, it loses strength & returns less signal

• Different tissues cause this effect to different degrees:

• Bone, Diaphragm, Pericardium & air = Bright (Hyperechoic) images

• Muscle, Liver, Kidney = gray (Isoechoic) images

• Blood, Ascites, Urine = Darker (Hypoechoic) images

Attenuation - Terminology

Anechoic

Isoechoic

Hyperechoic

Hypoechoic

Attenuation - Terminology

Isoechoic

Anechoic

Hyperechoic

Hypoechoic

Artifacts Edge Artifact

Posterior Enhancement Reverberation

Mirror Artifact

Enemies of Ultrasound

Bone Air

“Clean” Shadow “Dirty” Shadow

Shadowing

Clean vs Dirty

Clean Dirty

Why different transducers? • Lower frequencies image deep

structures, but sacrifice resolution.

• Higher frequencies provide better

resolution, but sacrifice depth.

HIGHER FREQUENCY Shorter wavelength

LOWER FREQUENCY Longer wavelength

Transducer Choices

Freq – 5-2 MHz

eFAST, abdomen, AAA

More penetration (30cm), Lower Resolution

Freq- 10-5MHz

Superficial, PTX, Nerve Blocks

Less penetration (9cm), greater resolution

Freq – 5-1 Mhz

Cardiac/eFAST/AAA

More penetration (35cm), less resolution

Transducer Use

• Hold the probe lightly in your hand

• Like a pencil

• Small movements equal big changes

Transducer Use

• Probe marker facing the patient’s right or head

• Exceptions: cardiac & procedures

Probe indicator

Leading edge Generally to the patient’s head or right side.

Manipulating the

Transducer

Scanning Planes

Screen Orientation

Far Field

Near Field

Image Quality – The 4 P’s

• Plenty of Gel

• Perpendicular to structure

• Pressure (right amount)

• Scan in multiple Planes

Gel & Water Stand-offs

Is Ultrasound Safe?

• YES

• Ultrasound does alter tissue

– Heat

– Cavitation

• Harmful effects at energy levels far higher than medical ultrasound

• No literature to suggest ultrasound is dangerous when used appropriately

• ALARA Principle

Clinical Applications

Basic • eFAST

• Skin/Soft Tissue

• DVT

• Renal

• MSK / Ortho

• Aorta

• Limited OB

• Ocular

• Procedural

• Focused Cardiac

Advanced • Testicular

• Appendix

• Biliary

• GYN / Pelvic

• Echo

Focused Assessment with

Sonography for Trauma

Abdomen Chest

Skin / Soft Tissue

Infections

Cellulitis Abscess

Biliary

Stones Cholecystitis

Deep Vein Thrombosis

Long Bone Fractures

Tendon / MSK

Ocular

Intracranial Pressure Retinal Detachment Foreign Body

Regional Anesthesia

23y/o male with complaint of “spider bite”

• Presented to PCM earlier in the day, dx with cellulitis - given clindamycin.

• Didn’t trust his PCM’s evaluation

• Goes to ER later that day

Case #1

Case #1

Case #1 Outcome

• Pt underwent incision/drainage and packing

• Was continued on clindamycin

• Wound healed without sequelae

• Costly / unnecessary ED visit

Case #2

42y/o male CC: “my heartburn is acting up” x 3 days

• History of intermittent epigastric pain – typical for him

• History of same for which you have been treating him with PPI

• Nausea and anorexia

• Because ongoing and didn’t feel like you were “doing anything about it”, he decides to go to the ED….

Case #2 Outcome

Pt admitted to Surgery Service – underwent cholecystectomy for symptomatic cholelithiasis

Case #3

• 33y/o G6P2 female, currently 18wks pregnant presents to sick call with upper abd after vomiting from her typical morning sickness

– Pulse 122, BP 100/70

– Mild diffuse abdominal tenderness

“ I don’t know….send her to OB”

Case #3

OB Transabdominal Ultrasound

“I don’t know…send her to the ER”

Case #3

ED Ultrasound

RUQ LUQ

Case #3 Outcome

• Pt taken directly OR

• Massive transfusion protocol initiated

• Ruptured Splenic Artery Aneurysm

• Emergent Splenectomy

• Mother / fetus survived

• Mom gave birth to term baby boy

Case #4

• Improvised Explosive Device

• Multiple casualties

• 23y/o male with multiple seemingly superficial penetrating wounds

• Triaged as delayed

Case #4

Case #4 Outcome

• Pt taken directly to OR

• Small piece shrapnel embedded in RV

• Pericardial window / drain placed

• Pt recovered without sequelae

Case #5

• 35y/o male 1 wk s/p knee surgery

• Saw your colleague two days ago for leg swelling – attributed to surgery

• Returns with increasing swelling

Case #5

Ultrasound Evaluation of Lower Extremity for Deep Vein Thrombosis

Objectives

• Determine when & how to perform compression ultrasound

• Understanding of relevant lower extremity vascular anatomy

• Scanning Technique

• Pearls and Pitfalls

Pertinent Studies Pomero et al - Accuracy of emergency physician-performed ultrasonography in the diagnosis of deep-vein thrombosis – Thromb Haemos 2014 Blaivas, et al. Lower-extremity Doppler for deep vein thrombosis - can emergency physicians be accurate and fast? Acad Emerg Med 2000 Kline JA, et al. Emergency-clinician performed compression ultrasonography for deep venous thrombosis of the lower extremity. Ann Emerg Med 2008 Palareti G, Schellong S. Isolated distal deep vein thrombosis: what we know and what we are doing. J Thromb Haemost. 2012 Jan;10(1):11-9 Adhikari S, Zeger W, Thom C, Fields JM. Isolated Deep Venous Thrombosis: Implications for 2-Point Compression Ultrasonography of the Lower Extremity. Ann Emerg Med. 2014 Nov 20

Indications

• Leg pain, leg swelling, shortness of breath with concern for pulmonary embolism

• Risk factors:

– Immobility

• Generally regarded as > 6-8 hrs

• Splinting/casting of an extremity

– Trauma/injury

• Polytrauma AND isolated extremity trauma

– Hypercoagulability (medications, genetic factors)

Differentials to Consider

• Cellulitis / Skin or Soft Tissue Infection

• Abscess

• Local soft tissue reaction

• Hematoma

• Calf Strain

Simplified Anatomy

Deep Veins

• Iliac

• Common Femoral

• (Superficial) Femoral

• Deep Femoral

• Popliteal

• Anterior Tibial

• Posterior Tibial

• Peroneal Veins

Superficial Veins

• Greater Saphenous

• Short Saphenous

• Perforating Veins

Deep vs Superficial

Anatomy – Pearl

• Deep Femoral Vein is not our primary vessel of concern – isolated DFV clot is very rare (<1%)

• Superficial Femoral Vein (AKA Femoral Vein) IS part of the deep venous system, and is a more common location for DVT

Clot Location

• Majority of patients (~80%) have clot present in multiple vessels

– Isolated to CFV – 2-10%

– Isolated to FV – ~5%

– Isolated to DFV – <1%

– Isolated to Popliteal – 10-14%

Adhikari S, Zeger W, Thom C, Fields JM. Isolated Deep Venous Thrombosis: Implications for 2-Point Compression Ultrasonography of the Lower Extremity. Ann Emerg Med. 2014 Nov 20

Three Points

1) CFV and GSV

2) Bifurcation of CFV 3) Popliteal vein

GSV CFV

DFV

SFV/FV

Three Points

1 – 3 cm

PV

Trifurcation (calf)

8 cm

1

2

3

Anatomic Pearls

Proximal to Distal

1) Remember “NAVEL”

2) 1st branch – Greater Saph – branches medially (10 o’clock or 2 o’clock)

3) Visualize fem artery bifurcation

4) Following fem art bifurcation, CFV will bifurcate, with DVF typically coursing laterally between sup and deep fem arts

5) Find Pop – “Pop on Top”

Sonographic Anatomy

Proximal Thigh

Sapheno-Femoral Junction

CFA CFV

GSV

Right Leg

Medial Lateral

Left Leg GSV + CFV

CFA CFV

GSV

Left Leg

Medial Lateral

SFV

SFA

DFA

DFV

Left Leg

Bifurcation:

CFV SFV and DFV

Left leg: 1 – 3 cm distal to GSV junction

Medial Lateral

Popliteal Fossa

PV

PA

Orientation

Skin

PV

PA

Orientation

Popliteal Vein

Technique

• High Frequency Linear Transducer

• Probe orientation

• Start High – Inguinal crease

• Compress every 1cm

• May augment with

– Color

– Augmentation

• Semi-upright to upright

• Reverse trendelenberg to maximize vein size

• Distal probe control

• External hip rotation

• Partially flex knee

Patient Positioning

Popliteal Imaging

• Pt supine – Knee bent

– Leg hanging over the side of the gurney

• Prone position is easier to scan

• Compression at two anatomical regions

– Follow the SFV aka “femoral vein” to the distal 1/3 of the thigh where it disappears at the adductor hiatus

– Follow the PV from the calf trifurcation until it disappears proximal (about 8 cm above popliteal fossa)

Technique

• Pay close attention to branch points which are high risk

– CFV – GSV branch

– CFV bifurcation into SFV and DFV

– Popliteal vein trifurcation in calf

• +/- Contralateral leg

– Not required if suspect DVT in one leg

Technique

• Optimal plane is transverse • Optimal probe position is perpendicular to skin

– Easiest to compress vein

Compression Ultrasound

Left Leg

• Enough pressure to completely collapse the vein

• Not too much pressure that the artery is collapsed

Compression Ultrasound

Methods to Capture Images

Dual Screen Image Capture

• One side shows the non-compressed view

• Second screen shows the compression view

• Only use if there is no way to save clips

Video clip method

• Capture area of interest without and then with compression

• Typically use 6 second clips

• Provides best images for documentation & review

Imaging Pitfalls and

Anatomic Variants • Acute clot can be anechoic – don’t rely on 2D

appearance

• Ensure appropriate amount of compression • Lymph nodes

• Baker’s cyst

• Duplicate venous system – up to 30%

Pitfalls

Three-point compression ultrasound DOES NOT rule out isolated calf vein DVT

Pitfalls

Strategies for distal deep calf vein rule-out?

• Get consultative study which evaluates distal veins (check local radiology protocol)

OR

• Repeat exam in 3-7 days to evaluate for propagation into proximal vessels

Palareti G, Schellong S. Isolated distal deep vein thrombosis: what we know

and what we are doing. J Thromb Haemost. 2012 Jan;10(1):11-9

Lymph Nodes

Pitfall: Lymph Nodes

Pitfall: Baker’s Cyst

Duplicate Femoral Vein

Duplicate femoral and popliteal veins occur in 20-30%

DVT: Popliteal Vein

Noncompressible vein

DVT: Popliteal Vein

DVT: Common Femoral Vein

Medial Lateral

Noncompressible vein

FV DVT

DVT Example – Video

DVT Example

CFV DVT Non compressible common femoral vein

Summary

• Start high – inguinal crease

• Compress hard… but not too hard

• Focus on the simplified anatomy

• Watch out for lymph nodes and baker’s cysts

• ACEP policy = no augmentation; no duplex required

How can I become

proficient?

• ACEP Recommendations

– 16-24hr Introductory Course

– 150-300 proctored exams total

– 25-50 per application

– Trial period

• Most other specialties creating similar guidelines

Resources

• Society of PAs in Clinical Ultrasound (SPACUS)

• AAPA Clinical Policy Letter – HOD May 2017

• Find local ultrasound fellowship program

• Conference workshops

• Ultrasound Leadership Academy

• Gulfcoast Ultrasound Institute

Online Educational Resources

• Sonoguide.com

• ultrasoundpodcast.com

• ACE4CUS.com

• ultrasoundgel.org

• Sonospot.com

• YouTube

• SonoSim

• Vimeo SAEM Ultrasound Lecture Series

Resources

Resources - Apps

$$$

• 1 Minute Ultrasound

• SonoAccess

• POC Ultrasound eBook

• Trauma Ultrasound eBook

Free

• SonoSupport - $9.99

• Emergency Medicine Ultrasound – $4.99

• Pocket Atlas of Emergency Ultrasound - $69.99

• Ultrasound Exam Protocols and Images - $5.99

• Intro to Bedside Ultrasound vols 1/2 – iTunes

• Trauma Ultrasound eBook - Free

Resources - eBooks

Resources - Texts

Key Points

• Ultrasound is coming to a bedside near you

• Ideal bedside diagnostic adjunct due to portability

• Quick & timely answer for a specific question

• Numerous applications

• Doesn’t require extensive training

Get out there and scan!

References

• Crisp et al. Compression ultrasonography of the lower extremity with portable vascular ultrasonography can accurately detect deep venous thrombosis in the emergency department. Ann Emerg Med. 2010 Dec;56(6):601-10.

• Kory et al. Accuracy of ultrasonography performed by critical care physicians for the diagnosis of DVT. Chest. 2011

Mar;139(3):538-42. • Blaivas et al. Lower-extremity Doppler for deep venous thrombosis--can emergency physicians be accurate and

fast? Acad Emerg Med. 2000 Feb;7(2):120-6.

• Theodoro et al. Real-time B-mode ultrasound in the ED saves time in the diagnosis of deep vein thrombosis (DVT). Am J Emerg Med. 2004 May;22(3):197-200.

• Adhikari et al. Isolated Deep Venous Thrombosis: Implications for 2 Point Compression Ultrasonography of the

Lower Extremity. Ann Emerg Med. 2014 Nov 20. • Palareti et al. Evolution of untreated calf deep-vein thrombosis in high risk symptomatic outpatients: the blind,

prospective CALTHRO study. Thromb Haemost. 2010 Nov;104(5):1063-70. • Gualtiero Palareti. How I treat isolated distal deep vein thrombosis (IDDVT). Blood: 2014 Mar; 123 (12). • Singh et al. Early follow-up and treatment recommendations for isolated calf deep venous thrombosis. J Vasc

Surg. 2012 Jan;55(1):136-40. • Schwarz et al. Therapy of isolated calf muscle vein thrombosis: a randomized, controlled study. J Vasc Surg. 2010

Nov;52(5):1246-50. doi: 10.1016/j.jvs.2010.05.094. Epub 2010 Jul 13.

Questions