Spatial Frequency Domain Imaging: It is Time to Evolve From the ABI

Jeffrey D. Lehrman, DPM, FASPS, MAPWCA, CPC

Advisor, APMA Coding Committee

Expert Panelist, Codingline

Advisor, APMA MACRA Task Force

Fellow, American Academy of Podiatric Practice Management

Board of Directors, American Society of Podiatric Surgeons

Board of Directors, American Professional Wound Care Association

Editorial Advisory Board, WOUNDS

Twitter: @DrLehrman

Neuropathic Ulcer 5-Year Mortality Rate

3

References: 1. Papanas N, et al. Drug Saf. 2010;33:455-461.

49% of ulcers may fail to heal despite traditional good ulcer care 1

Quality 45%

ACI 25%

Clinical Practice Improvement Activities 15%

Cost 15%

MIPS Score Performance Year 2019

Calculated by:

Medicare Spending per Beneficiary (MSPB)

& Total Per Capita Cost Measures

Cost Category

MSPB

• Sum of standardized, risk-adjusted spending across all eligible episodes divided by number of episodes

• Episode = All Medicare claims between 3 days prior to a hospital admission (“index admission”) and 30 days after hospital discharge.

Total Per Capita Cost

• Total Cost per Beneficiary • Payment standardized • Annualized • Risk adjusted • Specialty adjusted

Source: Agency for Healthcare Research and Quality (AHRQ), Center for Delivery, Organization, and Markets, Healthcare Cost and Utilization Project (HCUP) National Inpatient Sample

(NIS), 2014

Overview of Operating Room Procedures During Inpatient Stays in U.S. Hospitals, 2014 Kimberly W. McDermott, Ph.D., William J. Freeman, M.P.H., and Anne Elixhauser, Ph.D. H-CUP Statistical Brief #233

Inpatient Stay With OR Procedure

Inpatient Stay Without OR Procedure

2 X >>>>>

$$

Overview of Operating Room Procedures During Inpatient Stays in U.S. Hospitals, 2014 Kimberly W. McDermott, Ph.D., William J. Freeman, M.P.H., and Anne Elixhauser, Ph.D. H-CUP Statistical Brief #233

Overview of Operating Room Procedures During Inpatient Stays in U.S. Hospitals, 2014 Kimberly W. McDermott, Ph.D., William J. Freeman, M.P.H., and Anne Elixhauser, Ph.D. H-CUP Statistical Brief #233

What Do We Have Now?

• Physical exam • Hand-held doppler • ABI • TBI • TcO2

Reliability of Current Assessment Methods

• Physical exam • Visual: dry, shiny, taut skin, loss of hair on extremity, nails thickened, edema • Dorsalis pedis: Missing in 10% of normal, calcification • Posterior tibial artery pulse: Requires gentle technique to assess • Capillary refill: Normal refill doesn’t “rule out PAD” • Temperature: Normal temperature doesn’t “rule out PAD”

Per American Heart Association Physical examination is imperfect in diagnosing PAD

Collins TC1, Suarez-Almazor M, Peterson NJ

Reliability of Current Assessment Methods • Hand held laser doppler

• Artificially elevated in diabetes, chronic renal disease, and advanced age • Does not offer detailed description of length, severity or type of diseased

vessel • Time and labor consuming

Reliability of Current Assessment Methods

• ABI • Time consuming: Requires patient rest 15 minutes in supine position • Indirect examination that infers anatomical location of occlusion or stenosis • Relatively low specificity: 45% • False negatives

• Arterial calcinosis in diabetes and renal disease (5 – 15% error) • Subclavian or other UE stenosis

• Lack of standardization • Patient and cuff positioning

Reliability of Current Assessment Methods

• TBI • Room must be warm to avoid vasoconstriction • Digital vessels must be present • Non compressible vessels

Reliability of Current Assessment Methods

• Transcutaneous Oximetry • Has been used to predict healing of wounds, responsiveness to hyperbaric

therapy and amputation level • Time consuming

• Long time required for equilibration • On avg. 25 minutes per site studied • Skin thickening and edema • Pharmacologic agents • Decreased baseline levels with age • Significant overlap with normal • Focal measurements

Diagnostic Options

Region Modality Description Measurement Tissue Assessment

(Integrity)

Type Area Oxygenation

Perfusion

Macrovascular

Physical exam Visual, temperature, pulse, & capillary refill Qualitative Local No No

ABI Blood pressure index Quantitative Leg/foot No No

TBI Blood pressure index Quantitative Toe No No

Microvascular TcPO2 Transcutaneous O2 Quantitative Focal Indirect No

SFDI Oxygenation and perfusion Quantitative Plantar surface

(300 x 225mm) Yes Yes

Spatial Frequency Domain Imaging (SFDI)

• Quantifies concentration and oxygenation of hemoglobin in the papillary and reticular dermis

• Generates anatomically relevant oxygenation and perfusion maps

Spatial Frequency Domain Imaging • 5 Biomarker measurements to characterize distribution, perfusion, and

oxygenation -ctHbO2 – Tissue oxyhemoglobin -ctHbR – Tissue deoxyhemoglobin -ctHb1 – Papillary dermis hemoglobin -ctHb2 – Reticular dermis hemoglobin -StO2 – Tissue hemoglobin oxygen saturation

SFDI – Distribution, Perfusion, and Oxygenation 1. Multiple wavelengths of light

- Visible and near-infrared light interrogate subsurface tissue - Ability to measure transcutaneous Hb in superficial and

deeper skin layers (1–3mm)

2. SFDI / Structured Illumination - Patented and proprietary SFDI algorithms measure

transcutaneous Hb signals in skin - Accurate measurement of tissue hemoglobin and

hemoglobin oxygen saturation 3. Quantitative algorithms

- Visualize and quantify changes in distribution, perfusion, and oxygenation of Hb

With Structured Illumination

Without Structured Illumination

Visible Light Near Infrared Light

Arterio-venous shunting in diabetes

• Vasomotor neuropathy causes issues in the periphery vascular beds

• Loss of sympathetic tone in the vessels

• End result is that the tissue is not getting oxygen due to poor extraction

Arterio-venous shunting

1. SFDI Hb ratio identifies PVD in subjects with diabetes • HbT2/HbT1 ratio higher for clinically-validated PVD • ABI correlation to PVD was poor in diabetes subjects • SFDI correlates with TBI in subjects with diabetes

2. Demonstrated non-invasive measurement of circulatory shunting due to diabetes • Measured elevated StO2 and decrease in HbT1 due to diabetes-related arterio-venous

shunting • Conditions result in under-extraction of oxygen and identifies ulceration risk that ABI cannot

identify

Non-invasive measurement of circulatory shunting identifies DFU risk in diabetes where ABI does not

April Color Image ctHb1 ctHb2

StO2

April Report

ctHbO2 ctHbR

SFDI

30

47 68 25

200 40 60

20 9 2

120 37 32

90 84 98

Local change in ctHb. Pre Ulcer?

April SFDI Map Overlay

Technician generates a report with transcutaneous hemoglobin characterization in multiple areas and

can identify high risk areas

April Report

ctHb1 ctHb2

StO2 ctHbO2 ctHbR

47 68 25

200 40 60

20 9 2

120 37 32

90 84 98

31

June follow-up revealed skin breakdown & ulcer formation

June Report

ctHb1 ctHb2

StO2 ctHbO2 ctHbR

June Color Image

32

47 68 25

200 40 60

20 9 2

120 37 32

90 84 98

Spatial Frequency Domain Imaging: It is Time to Evolve From the ABI

Jeffrey D. Lehrman, DPM, FASPS, MAPWCA, CPC

Advisor, APMA Coding Committee

Expert Panelist, Codingline

Advisor, APMA MACRA Task Force

Fellow, American Academy of Podiatric Practice Management

Board of Directors, American Society of Podiatric Surgeons

Board of Directors, American Professional Wound Care Association

Editorial Advisory Board, WOUNDS

Twitter: @DrLehrman