Noncontact Warming Therapy, Ultrasound Therapy, and Fluorescence Imaging for Wounds

Coverage Summary

UnitedHealthcare policy CS132.Q (effective February 1, 2026) addresses noncontact normothermic wound therapy (NNWT), low-frequency ultrasound therapy (including MIST/UltraMIST and other noncontact low-frequency ultrasound modalities), and handheld noncontact real-time fluorescence wound imaging (e.g., MolecuLight i:X).

The policy concludes these technologies are unproven and not medically necessary for treatment or routine clinical use because the current evidence is insufficient to demonstrate safety and/or efficacy.

This coverage position applies despite device 510(k) clearances or procedure code listings, which are provided for reference and do not by themselves determine coverage.

Key Policy Facts

Policy identifierCS132.Q

Effective date2026-02-01

Modalities addressed3 (Noncontact warming/NNWT, Low-frequency ultrasound, Real-time fluorescence imaging)

Clinical evidence assessment statusECRI clinical evidence assessment 2021 (updated 2024)

Devices with 510(k) referencedFDA 510(k) clearances referenced (e.g., Warm-Up Active Wound Therapy, MIST/UltraMIST, MolecuLight i:X)

Medical‑Necessity Criteria

Coverage Determination

Covered when ALL of the following are met:

ALL of the following

Warming therapy (NNWT): Warming therapy (noncontact normothermic wound therapy, NNWT) is considered unproven and not medically necessary for treating wounds due to insufficient evidence of efficacy.
Not covered for treatment of chronic wounds per policy rationale.
Low frequency ultrasound therapy (including non-contact low-frequency ultrasound and MIST Therapy®) is considered unproven and not medically necessary for treating wounds due to insufficient evidence of efficacy.
Not covered as treatment; evidence mixed and limited by small sample sizes and risk of bias.
Noncontact real-time fluorescence wound imaging for bacterial presence (e.g., MolecuLight i:X) is considered unproven and not medically necessary due to insufficient evidence of safety and/or efficacy.

Provider Actions & Billing Notes

Prior Authorization

Prior authorization or medical necessity review may be required

As the policy states these therapies are considered unproven and not medically necessary, providers should expect denials or need for preauthorization and should submit supporting evidence if seeking coverage.

0598T
0599T
97610
A6000
E0231
E0232

Documentation Required

Do not interpret code listing as coverage guarantee

The applicable codes are provided for reference only; listing does not imply that the service is covered. Benefit coverage is determined by federal, state, or contractual requirements and applicable laws.

Coding

Procedure codes referenced (for imaging and ultrasound)CPT

0598T	Real-time fluorescence wound imaging with clinical darkness, to identify location of bacterial wound pathogens and measure wound size, per session; first anatomic site (e.g., lower extremity, right leg).
0599T	Real-time fluorescence wound imaging with clinical darkness, to identify location of bacterial wound pathogens and measure wound size, per session; each additional anatomic site (e.g., upper extremity, left leg) (List separately in addition to code for primary procedure).
97610	Low frequency, non-contact, non-thermal ultrasound, including topical application(s), when performed, wound assessment, and instruction(s) for ongoing care, per day.

HCPCS / Device codes referenced (noncontact warming devices)HCPCS

A6000	Noncontact wound-warming wound cover for use with the noncontact wound-warming device and warming card.
E0231	Noncontact wound-warming device (temperature control unit, AC adapter and power cord) for use with warming card and wound cover.
E0232	Warming card for use with the noncontact wound-warming device and noncontact wound warming- wound cover.

Applicable CPT codes (annual edits noted)CPT

No codes listed

FDA device product codes referencedmixed

MSA	Warm-Up Active Wound Therapy product code (FDA)
NRB	Additional device product code reference (FDA)

Background and Evidence Summary

The policy describes NNWT as a system using a noncontact wound cover and warming unit to apply radiant heat and maintain high humidity to raise wound temperature, with the intent to increase blood flow and oxygen to the wound. Low-frequency ultrasound (including the MIST/UltraMIST systems) delivers ultrasound energy (commonly ~40 kHz) via a saline mist or contact ultrasound to cleanse/debride wounds and potentially stimulate healing. Handheld fluorescence devices (e.g., MolecuLight i:X) use violet light to visualize bacterial autofluorescence and to measure wound area in real time.

Across modalities, the policy found the evidence base limited by small sample sizes, heterogeneous study designs, short follow-up, lack of adequate control groups or randomization in many studies, and risk of bias. While diagnostic accuracy and some efficacy signals are reported for fluorescence imaging and certain ultrasound analyses, the clinical utility and proven impact on patient-centered outcomes remain unestablished.

Evidence / Study	Key finding
Systematic review finding (Yue et al. 2018)
No RCTs found comparing local warming therapy to standard care for chronic wounds; lack of robust evidence for warming therapy
Randomized pilot studies (Thomas et al. 2005; Karr 2003; Ellis et al. 2003)
Small RCTs/pilot trials reported non‑significant differences or limited findings (e.g., 13% difference not statistically significant; small samples) limiting conclusions
Meta-analysis (Chen et al. 2023)
Low‑frequency ultrasound as an adjunct showed lower non‑healed wounds at ≥3 months and greater wound area reduction in some comparisons, but limited by small study numbers and heterogeneity
Systematic review/meta-analyses (Flores‑Escobar 2022; Cullum & Liu 2017)
Some analyses show higher healing rates or favorable ORs for ultrasound but overall evidence is mixed, with many studies small, heterogeneous, and risk of bias high
Diagnostic accuracy (Mayer et al. 2024; Armstrong et al. 2023; Le et al. 2020)
Fluorescence imaging demonstrated higher sensitivity (e.g., 84% sensitivity, 63% accuracy vs SEM/microbiology; increased detection of bacterial loads vs clinical signs), but clinical utility for improving patient‑centered outcomes is unproven and RCT evidence is limited
Prospective cohort and observational studies (Oropallo 2025; Derwin 2023; Rahma et al. 2022 pilot RCT)
Studies report fluorescence signals correlate with bacterial burden and may guide targeted debridement with signals of reduced pain or improved wound area reduction, but sample sizes are small and larger RCTs are needed
ECRI assessment (2021, updated 2024)
Concluded evidence is inconclusive to determine improvement in patient outcomes with MolecuLight i:X; additional RCTs needed

Noncontact Normothermic Wound Therapy (NNWT): Use of a noncontact wound cover and warming unit to apply radiant heat and maintain high humidity to raise wound temperature, intended to increase blood flow and oxygen to the wound.

Low-Frequency Ultrasound (NLFU/MIST): Ultrasound therapy delivered at low frequency (commonly ~40 kHz) noncontact via a saline mist or contact ultrasound for wound cleansing/debridement and proposed stimulation of healing.

Real-time Fluorescence Wound Imaging: Handheld devices using violet light to visualize bacterial fluorescence and measure wound area in real time to assist diagnostic and treatment decisions.

MolecuLight i:X: A handheld noncontact fluorescence imaging device intended to detect bacterial autofluorescence in wounds (FDA 510(k) cleared).

MIST Therapy / UltraMIST: Low-frequency ultrasound-generated mist systems intended to promote wound healing through wound cleansing and maintenance debridement (FDA cleared).

Not Medically Necessary / Experimental

ALL of the following

Not Medically Necessary: Warming therapy (NNWT): Warming therapy (noncontact normothermic wound therapy, NNWT) is considered unproven and not medically necessary for treating wounds due to insufficient evidence of efficacy.
Not covered for treatment of chronic wounds per policy rationale.
Not Medically Necessary: Low frequency ultrasound therapy: Low frequency ultrasound therapy (including non-contact low-frequency ultrasound and MIST Therapy®) is considered unproven and not medically necessary for treating wounds due to insufficient evidence of efficacy.
Not covered as treatment; evidence mixed and limited by small sample sizes and risk of bias.
Not Medically Necessary: Noncontact real-time fluorescence wound imaging:

Revision History

2026-04-01non-material update

Template update removed content/language pertaining to the state of Louisiana.

2026-02-01material updateLatest

Annual edits to applicable CPT codes; updated list of applicable CPT codes and revised descriptions for 0598T and 0599T; previous policy CS132.P archived.

2026-02-01material updateLatest

Coverage/Clinical Positioning (evidence summary)

Summarized findings and guideline positions informing coverage considerations:

ALL of the following

Fluorescence imaging evidence summary: Evidence for MolecuLight i:X fluorescence imaging is inconclusive for improving patient-centered outcomes; studies suggest higher sensitivity for detecting bacterial burden but lack RCTs demonstrating improved healing or antibiotic stewardship (ECRI 2021; updated 2024).
Observational diagnostic accuracy: Multiple small observational and pilot studies report improved diagnostic accuracy/sensitivity for detecting moderate-to-heavy bacterial loads when fluorescence imaging is used alongside clinical signs and symptoms (Le et al. 2020; Serena et al. 2019; Hurley et al. 2019; others).
Ultrasound evidence summary: Randomized and meta-analytic evidence for noncontact low-frequency ultrasound (USSD, MIST/UltraMIST, other devices) shows mixed results; some meta-analyses and RCTs report higher healing rates or benefit as adjunctive therapy, but many studies are small, heterogeneous, and have methodological limitations requiring further RCTs.
Guideline positions: Guideline recommendations: AAWC (2015) suggests low-frequency ultrasound may support healing and improve QOL for non-healing venous/mixed ulcers as an adjunct with compression and dressings; warming therapy has insufficient evidence. AAWC (2010) included noncontact ultrasound as potential second-line treatment but evidence strength low (Level C).
NICE and Medtech: NICE Medtech briefing (2020) concluded limited evidence for MolecuLight i:X to reduce closure time or improve antibiotic stewardship; NICE (2011, reaffirmed 2025) noted MIST Therapy shows potential but evidence insufficient for routine adoption.
FDA clearances (informational): FDA clearances/510(k): Warm-Up Active Wound Therapy (1997), MIST Therapy System (2004/2005/2014 UltraMIST), MolecuLight i:X (K191371) — informational only and not determinative for coverage.