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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