Chapter 8:

How Thermal Imaging Reveals Hidden Pathology in Pain, Neuropathy, and Vascular Disease

A Clinical Walkthrough with Dr. Phil Hoekstra, MS, CCE, CEP

In clinical medicine, the feet are often overlooked until pain, ulcers, neuropathy, or tissue breakdown force urgent attention. Yet the feet are among the most information-dense regions of the body, reflecting vascular health, nerve integrity, inflammatory patterns, and autonomic regulation. In a guided tour of real patient scans, clinical thermologist Dr. Phil Hoekstra demonstrates how infrared thermal imaging transforms the feet into diagnostic maps—revealing pathology long before structural damage becomes obvious on conventional imaging.

 

Thermal imaging (also called medical thermology) visualizes skin surface temperature as a proxy for underlying physiology. Because blood flow, inflammation, and autonomic nerve activity regulate heat, temperature patterns become functional biomarkers of disease. Dr. Hoekstra’s walkthrough shows how thermography helps clinicians objectively assess conditions such as Complex Regional Pain Syndrome Type II (CRPS II), diabetic microangiopathy, peripheral neuropathy, post-injury autonomic dysfunction, and early pressure-related tissue injury.

 

Thermal Symmetry as a Baseline of Health

One of the foundational principles Dr. Hoekstra emphasizes is bilateral symmetry. In healthy physiology, the left and right feet should present nearly identical thermal profiles. When asymmetry appears—one foot markedly cooler or warmer than the other—it signals dysregulation. In diabetic microangiopathy, for example, thermography often shows a sharp temperature demarcation at the transition from the tarsal region to the toes, reflecting impaired microcirculation to distal tissues. This thermal “cutoff” pattern visually captures what patients experience as cold, numb digits and delayed healing.

 

Thermography also reveals what a normal foot should look like: evenly distributed warmth with slightly warmer nail beds due to dense capillary networks. Deviations from this profile—cool distal digits, patchy hotspots, or abrupt gradients—become clinical clues that something is wrong with perfusion or autonomic control.

 

CRPS II: Making the Invisible Visible

CRPS II is among the most devastating and diagnostically challenging pain disorders. Patients experience severe, disproportionate pain with autonomic instability that alters blood flow and skin temperature. Dr. Hoekstra notes that thermography is uniquely sensitive to this condition, often outperforming electromyography in specificity. Early in CRPS II, the affected limb may appear abnormally warm due to autonomic overdrive; later, it may swing to extreme cold as dysregulation persists.

 

What elevates thermography from static imaging to functional testing is the autonomic challenge. By alternating thermal stimuli—such as immersing hands in cool and warm water—clinicians can observe reflexive temperature modulation in unaffected limbs, while the diseased limb fails to regulate. This lack of modulation is objective evidence of autonomic dysfunction, turning subjective pain into quantifiable physiology. In one patient described by Dr. Hoekstra, this testing confirmed CRPS II following a seemingly minor sports injury, ultimately guiding aggressive neurological intervention.

 

Neuropathy and Dermatomal Mapping

Peripheral neuropathy and radiculopathy often produce burning, tingling, or electric pain in specific distributions. Thermography can visualize these patterns along dermatomes—the “wiring diagram” of the skin mapped to spinal nerve roots. Dr. Hoekstra describes how thermal gradients trace neuropathic pathways, helping localize nerve impingement in the spine or peripheral nerves in the limbs. When combined with autonomic challenge testing, clinicians can differentiate acute inflammatory phases (often warmer) from chronic ischemic or denervated phases (often cooler).

 

This capability is especially valuable in pain management and personal injury contexts, where objective documentation of nerve-related dysfunction supports diagnosis, treatment planning, and medico-legal clarity.

 

 

PART 2:

THERMOLOGY AND THE DIAGNOSTIC VALUE OF ACTIVE SURVEILLANCE FOR EXTREMITY DISORDERS

By: Robert L. Bard & Phil Hoekstra, PhD

 

This chapter established the feet as powerful diagnostic territories—where thermal patterns reveal autonomic dysfunction, neuropathic pain, and vascular compromise long before structural damage becomes obvious. Part 2 advances this conversation from visual insight to measurable intelligence, showing how modern thermography transforms color gradients into quantifiable data that can guide clinical decisions over time. Through Dr. Phil Hoekstra’s clinical walkthrough, thermal imaging emerges not merely as a snapshot, but as a tool for active surveillance—capable of tracking disease progression, treatment response, and emerging tissue risk across oncology survivorship, diabetic foot care, neuropathy, and wound prevention. This section explores how temperature curves, distal thermal drop-offs, and autonomic challenge testing provide objective markers of microcirculatory health and nerve regulation. Positioned alongside conventional imaging and neurologic testing, thermography adds a functional dimension to extremity care—offering clinicians a proactive, non-invasive way to monitor recovery, anticipate complications, and intervene earlier in the disease process.

 

Quantifying Disease: From Images to Data

Beyond visual interpretation, modern thermography provides quantitative analytics. Dr. Hoekstra demonstrates how clinicians plot temperature values between two points along the limb, generating curves that reveal abrupt distal drops consistent with neuropathy or microangiopathy. These thermal gradients are not merely descriptive; they are measurable indicators of disease progression or recovery over time. In active surveillance, repeated scans allow clinicians to monitor whether perfusion improves with treatment, whether autonomic regulation normalizes, or whether pathology advances toward tissue compromise.

 

 Cancer Treatment, Microcirculation, and the Feet

Although cancer does not commonly originate in the feet, oncologic treatments profoundly affect peripheral tissues. Chemotherapeutic agents damage microvasculature and peripheral nerves, contributing to hand-foot syndrome, neuropathy, edema, and skin breakdown. Radiation disrupts autonomic regulation, often creating persistent thermal artifacts in treated regions. Dr. Hoekstra notes that thermography can objectively capture these changes, making it a useful tool for survivorship care—especially in patients with lingering neuropathy, compromised circulation, or delayed wound healing in the lower extremities.

 

Non-Contact Imaging for Wounds and Diabetic Foot

For diabetic foot disease, ulcers, and gangrenous changes, thermography offers a crucial advantage: no contact. Unlike ultrasound gel or manual palpation, infrared imaging does not touch compromised skin. Clinicians can screen for developing hotspots around wounds (suggesting inflammation or infection) or cold zones indicating ischemia. This makes thermography especially valuable for high-risk patients with fragile tissue integrity.

 

Preventing Pressure Injuries Before They Break the Skin

One of the most compelling preventive applications highlighted by Dr. Hoekstra is early detection of pressure-related tissue injury in bedridden or institutionalized patients. Before a bedsore becomes visible, thermography can reveal subtle thermal changes signaling ischemia and tissue stress. Proactive interventions—repositioning, offloading, and targeted care—can then prevent skin breakdown. In an era where pressure injuries carry immense clinical and legal consequences, thermal screening becomes both a patient-safety measure and a quality-of-care standard.

 

Thermography as a Complement, Not a Replacement

Dr. Hoekstra is careful to frame thermography as a complementary modality. It does not replace ultrasound, MRI, nerve conduction studies, or laboratory testing. Instead, it adds a functional layer—revealing how physiology behaves in real time. In extremity care, this functional insight bridges gaps between structure and symptoms, making thermography particularly valuable in chronic pain, neuropathy, diabetic foot management, and post-treatment surveillance.

 

A Diagnostic Future Written in Heat

Through Dr. Hoekstra’s clinical walkthrough, the feet emerge as “informative”—rich with physiological signals that thermal imaging can decode. From CRPS II and neuropathic pain to diabetic microangiopathy, cancer treatment sequelae, and early pressure injury, thermography transforms subtle thermal cues into actionable clinical intelligence. As healthcare moves toward earlier detection and functional diagnostics, thermal imaging of the extremities stands as a powerful, non-invasive ally—one that turns color gradients into clarity, and heat patterns into insight.

 

 THE SOURCE: PODIATRYSCAN 2.0

THERMAL IMAGING (MEDICAL THERMOLOGY) offers a non-invasive, functional window into vascular, neurologic, and inflammatory processes that are often invisible to structural imaging. In this clinical walkthrough, Dr. Phil Hoekstra guides readers through real-world thermal scans of the feet, demonstrating how temperature patterns reveal microangiopathy in diabetes, autonomic dysfunction in Complex Regional Pain Syndrome Type II (CRPS II), dermatomal patterns of neuropathy, and perfusion abnormalities following injury or cancer treatment. By combining static imaging with autonomic challenge testing, thermography provides objective evidence of dysregulated blood flow and nerve-mediated temperature control. The feet emerge as highly informative diagnostic territories, reflecting systemic disease, peripheral nerve injury, and early tissue compromise before visible breakdown occurs. This article positions thermography as a complementary tool for active surveillance in podiatry, pain management, neurology, oncology survivorship, and wound prevention—expanding functional diagnostics for earlier detection, monitoring, and preventive intervention in extremity care.