Standards and protocols in Clinical Thermographic Imaging

Introduction

These guidelines are noted to adhere to quality assurance for the use of thermal imaging in clinical practice. The information is based on a review of the current and past peer-reviewed indexed literature, consultation with authorities in relevant fields of expertise, standards and guidelines issued by other qualified organizations, and clinical experience concerning the application of thermal imaging. It is not the purpose of this organization to regulate clinical thermography, but rather to promote scientific validity and quality imaging. The information that follows has been compiled to insure the highest standards in clinical thermal imaging and patient safety.

The guidelines have been divided into the following sections:

1. Definition of Clinical Thermography
2. Laboratory Requirements
3. Equipment Guidelines
4. Patient Management Protocols
5. Imaging Protocols
6. Image Interpretation and Reporting
7. Summary

1. Definition of Clinical Thermography: Thermography, when used in a clinical setting, is a prognostic or diagnostic imaging procedure that detects, records, and produces an image (thermogram) of a patient’s skin surface temperatures and/or thermal patterns. The procedure uses equipment that can provide both qualitative and quantitative representations of these temperature patterns. Thermography does not entail the use of ionizing radiation, venous access, or other invasive procedures; therefore, the examination poses no harm to the patient. Clinical thermography is appropriate and germane to health care practice whenever a clinician feels a physiologic imaging test is needed for differential diagnostic purposes. Clinical thermography is a physiologic imaging technology that provides information on the normal and abnormal functioning of the sensory and sympathetic nervous systems, vascular system, musculoskeletal system, and local inflammatory processes. The procedure also provides valuable diagnostic information with regard to dermatologic, endocrine, and breast conditions.

Clinical thermography may contribute to the diagnosis and management of the patient by assisting in determining the location and degree of irritation, the type of functional disorder, and treatment prognosis. The procedure may also aid the clinician in the evaluation of the case and in determining the most effective treatment. Clinical thermography is an acceptable analytical procedure that may be performed by a doctor or technician who has been adequately trained and certified by a recognised organisation. However, it is strongly recommended that the interpretation of the thermal images be made only by health care providers who are licensed to diagnose and hold credentials as board certified clinical thermographs or fellows from a recognised organisation or a regulated software. This is meant to insure that directed care and proper follow-up recommendations will be made available to the patient if warranted by the interpretation of the images.

There are two currently recognised methods of clinical thermographic imaging: electronic infrared telethermography and liquid-crystal thermography. The following terminology is commonly used interchangeably for clinical thermographic analysis and computer interfaced infrared thermography systems: thermal imaging, thermography, infrared imaging, digital infrared imaging, digital infrared thermal imaging, computed thermal imaging, and computerised infrared imaging among others.

2. Laboratory Requirements 
3. a) Room Design: As part of image quality control, the design and environmental conditions of the room should conform to the thermodynamic attributes required in thermal image acquisition. The room itself should be of adequate size to maintain a homogenous temperature. There must be sufficient space for the placement of equipment and freedom of movement for both the technician and patient. It should also be large enough to allow for patients of all sizes to be positioned adequately for each anatomic image. A room approximately 8’x 10′, or dimensions similar in square footage, is adequate to meet these requirements. Larger rooms may also be used as long as a steady ambient temperature can be maintained (see Environmental Controls section below). During the examination, the patient should be able to be placed relatively equidistant and adequately spaced from each wall. The room should be carpeted. If this is not possible, a well-insulated area rug will suffice. A complete infrared survey of the room should be performed to inspect for any infrared sources and leakage (i.e. windows, heating ducts, light fixtures, hot water pipes). Any significant findings need to be remedied. All windows must be covered or shielded to prevent outside infrared radiation from entering the room. Shades or blinds may be adequate for this purpose depending on the amount of direct infrared radiation. The room must be free from drafts. Windows and doors should be adequately sealed to prevent airflow in the area where the patient is positioned. Heat and air conditioning sources must be minimised in the room and kept well away from the patient. Vents should be directed away from the patient and thoroughly diffused or turned off during the examination. Incandescent lighting should not be used during the examination due to the amount of infrared radiation produced. Standard fluorescent lighting is adequate.

2. b) Environmental Controls: The temperature of the room should be such that the patientʼs physiology is not altered to the point of shivering or perspiring. The temperature range should be maintained between 18 and 23 degrees C. Room temperature changes during the course of an examination must be gradual so that steady state physiology is maintained and all parts of the body can adjust uniformly. The temperature of the room should not vary more than one degree Celsius during the course of a study. The humidity of the room must also be controlled such that there is no air moisture build up on the skin, perspiration, or vapor levels that can interact with radiant infrared energy. The examining room must have an ambient temperature thermometer to accurately monitor the temperature of the room.
3. Equipment Guidelines: In order to provide quality image production and accurate clinical interpretations, certain minimum equipment standards should be maintained. There are two currently recognised types of thermographic imaging equipment: electronic infrared telethermography (IRT) and liquid crystal thermography (LCT). Liquid Crystal Thermography: LCT utilises a range of interchangeable “screens” or “pillows” impregnated with cholesterol methyl-ester derivatives that change colour as a function of their temperature. The “screens” or “pillows” are touched to the anatomic surface for development. A 35mm or Polaroid picture of the image is taken for later analysis and archive. The thermal precision and resolution of the equipment is well within accepted limits for clinical interpretation.
4. a) Electronic Infrared Telethermography: IRT equipment incorporates single or multiple infrared detectors that sample the field-of-view in two directions simultaneously. The process does not involve contact with the surface of the skin. A current review of the literature suggests that in order to produce accurate and reproducible diagnostic images the following minimum specifications should be incorporated in the design of clinical IRT hardware and software systems:

• Detector(s) response greater than 5 microns and less than 15 microns with the spectral bandwidth encompassing the 8-10 micron region.
• Repeatability and precision of 0.1 degree C detection of temperature difference.
• Accuracy of +/- 2% or less.
• Spatial resolution of 1 sq. mm at 40 cm from the detector(s).
• Limiting temperature windows of 5 and 10 degrees C.
• Significantly variable contrast (level) settings.
• A maximum scanning time of 4 seconds or less with real-time capture preferred.
• Ability to perform accurate quantitative differential temperature analysis with a precision of 0.1 degree C.
• Ability to capture images in hi-resolution grayscale.
• High-resolution image display for interpretation.
• Ability to archive images for future reference and image comparison.
• Software manipulation of the images should be maintained within strict parameters to insure that the diagnostic qualities of the images are not compromised.

4. Patient Management Protocols: Proper management of the patient, both before and during the examination, decreases the chance of thermal artefacts and increases the accuracy of the images.
5. a) Pre-examination Preparation: Pre-examination preparation instructions are of great importance in decreasing thermal artifacts. The following is a minimal list of instructions that should be given to the patient prior to the examination:

• No sun bathing of the area to be imaged 5 days prior to the exam.
• No use of lotions, creams, powders, or makeup on the body area to be imaged the day of the exam.
• For upper body imaging, no use of deodorants or antiperspirants the day of the exam.
• If any body areas included in the images are to be shaved, this should be done the evening before the exam or at least 4 hours prior to examination.
• No physical therapy, EMS, TENS, ultrasound treatment, acupuncture, chiropractic, physical stimulation, hot or cold pack use for 24 hours before the exam.
• No exercise 4 hours prior to the exam.
• If bathing, it must be no closer than 1 hour before the exam.
• If not contraindicated by the patientʼs doctor, avoid the use of pain medications and vasoactive drugs the day of the exam. The patient must consult with their doctor before changing the use of any medications.

1. b) Intake Forms: Intake forms should be used and formatted to cover the areas of complaint with specific pain diagrams, previous tests and examinations, and a current and past history of any diagnoses, surgeries, and traumas.
2. c) Patient Acclimation: Prior to imaging, the patient’s body must be given sufficient time to equilibrate with the ambient conditions of the laboratory such that an approximate steady physiologic state of thermodynamic equilibrium can be reached. A minimum equilibration period of 15 minutes should be observed; further equilibration results in minimal surface temperature changes. During the equilibration period, and the subsequent examination, the area to be imaged should remain completely uncovered of clothing or jewellery. To provide a level of modesty prior to certain examinations, a loose fitting gown may be worn during the equilibration period provided that it does not restrict airflow or constrict the skin surface in any way that would produce an artefactual result on the thermogram. Special gowning procedures, specific to the clinic or examination, may be required and are permitted as long as the above stipulations are observed. Due to the individual anatomy of each patient, special positioning during the equilibration period and examination may be needed.
3. d) Clinical Examination: When appropriate to the individual case, a clinical examination may be performed after thermal imaging to correlate specific findings. The examination may include visual inspection, palpation, neurologic, orthopedic or other forms of analyses as deemed necessary by the interpreting clinician.
4. Imaging Protocols: The guidelines given for strict laboratory environmental controls and patient preparation provide for a subject that is physiologically ready for thermal imaging. A thermographic series consists of one or more images, captured on archival media, which permit the evaluation of the body surface area relevant to the purpose of the examination. Each thermographic series should include all or as many body surfaces as possible that are relevant to the patients complaint and symptomatology, along with any anatomically and physiologically related areas. A single thermographic series is considered diagnostic if performed under the conditions previously outlined. Note: It is strongly recommended that the capturing of thermal images for health care purposes be made only by personnel who hold credentials as clinical thermographic technicians, board certified clinical thermographs, or fellows from a recognised organisation.
5. a) Patient Positioning: The use of both electronic infrared and liquid crystal thermographic systems incorporate basic standardised patient and equipment positioning for each area of the body imaged. Typically, the entire upper body or lower body is imaged in order to analyse the physiology related to these areas. Specialised or limited views may be added, or taken as an individual study, as needed. With certain patients, additional views may be necessary to image specific surface areas that are obscured due to the individual’s anatomy.
6. b) Imaging: Combined positioning of the equipment and the patient is critical to accurate imaging. Electronic infrared telethermography studies should be performed with the detector(s) as perpendicular as possible to the surface to be viewed. If other than perpendicular views are required, the angle must be kept exactly the same for comparable bilateral views. To maintain adequate spatial resolution and interpretation accuracy, the body part(s) of interest should be brought close enough to the detector(s) to fill the viewable image area. When multiple views are required for bilaterally equivalent areas of the body, the equipment settings (or temperature scale “screen” selection with LCT) must not be altered for the two views. Liquid crystal thermography studies should be performed using the proper temperature scale “screen” for the body area imaged, along with an adequate number of images to cover the surface area(s) of interest. Additional Studies: Stress studies involving symptom exacerbation, autonomic challenge, or alcohol spray (i.e. thyroid studies) may be performed following a baseline thermographic series. The use of an autonomic nervous system challenge (a.k.a. cold challenge) is defined as dynamic thermography. The procedure entails the use of a cold stimulus (ice water or equivalent temperature stimulus) applied to the hands, feet, or lower half of the central thoracic spine. The test is commonly performed via hand or feet immersion in an ice water bath for a minimum of 45 seconds (or until pain tolerance) followed by repeated imaging (a single duplicate study or a timed cooling/warming series may be used) of the body area(s) under study. Warmer water (i.e. tap water in temperate climate zones) may not provide a strong enough stimulus to the sympathetic nervous system and is considered questionable as to its reliability. The cold challenge may be added to an examination to clarify the extent of the nervous system’s involvement in a suspected pathologic process. The addition of a cold challenge test is up to the discretion of the interpreting doctor and not the technician. The use of the cold challenge in thermal breast imaging is intended to enhance the detection of the neoangiogenic process.
7. c) Documentation: Each thermographic image, captured on archival media, should contain an indication of the anatomic view along with the following minimum information; either included with the original image or immediately traceable to other archived documents:

• The patientʼs name or identification code and imaging date
• The imaging facility name and address

6. Image Interpretation and Reporting:
7. a) Thermogram Interpretation by Technician: Interpretation of thermal images is based on a knowledge of thermography and its relation to human physiologic systems and processes. Interpretation provides information on the normal and abnormal functioning of the sensory and sympathetic nervous systems, vascular system, musculoskeletal system, endocrine system, and local inflammatory processes. Combining the information gained from the thermal images with clinical data allows for the formation of a clinical impression. Note: It is strongly recommended that the interpretation of thermal images for health care purposes be made only by health care providers who are licensed to diagnose and hold credentials as board certified clinical thermographers or fellows from a recognized organization.
8. b) Thermogram Interpretation by software: Software solutions from Aarca Research uses advanced image processing techniques to interpret thermal images. This eliminates the human error of interpreting the minute changes in temperature variations. Our software is peer-reviewed and medically validated.
9. c) Written Reporting: The format for reporting should include as a minimum the following information:

• Imaging facility address and phone number
• Patient name and age
• Date of examination
• Clinical data
• Symptomatology
• Relevant thermographic findings
• Impression
• Recommendations (if appropriate)
• Signature of qualified interpreter

7. Summary: The guidelines in this document are designed to assist practitioners in the use of thermal imaging and to provide outside agencies with knowledge in the application of the procedure. The guidelines, however, should not be considered permanent. Research in this field is ongoing internationally within private practices, hospitals, and universities. This research can be expected to impact the utilization of thermal imaging on a continuous basis ensuring that there is progression and growth in knowledge and understanding of the benefits and role of thermal imaging in the health care delivery system. As the results of such research begin to have a practical impact, the utilization of thermal imaging will change and future guidelines will have to take such changes into account. Some practitioners and equipment manufacturers may disagree with certain individual recommendations and guidelines included in this document. It is the responsibility of these individuals or companies to take the initiative to establish a research base from which changes could be made. Justification for such changes must be made available in the form of research papers published in the peer-reviewed literature. It is only through published research that significant advances in clinical thermal imaging can occur.