© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

8.4.1.3 Low-Resolution Thermographics

Even simple thermographic maps may have great utility. If the deviation from mean temperature to 3 significant figures (~0.01°C accuracy requiring ~10 bits/measurement) is resampled at ~10 Hz, then 0.1°C/sec gradients may be detected in each of ~10⁵ voxels (volume ~1 cm³/voxel) using ~10⁵ resident thermographicytes, producing a 10⁷ bit/sec dataflow. A dermal thermographic network divided into 1 cm² squares requires ~20,000 resident nanorobots and produces a ~2 x 10⁶ bit/sec whole-network dataflow at 0.01°C accuracy (vs. 0.5-1.0°C accuracy for traditional thermograms ).⁸⁹⁹ In either case, each thermographicyte in the network (Section 7.3) maintains in its ~10¹⁰-bit memory (Section 7.2.6) the entire continuously updated network map and can store ~1 hour of historical data (~7 x 10⁹ bits) for the whole-body thermographic map or ~1 year of historical data (~3 x 10⁹ bits) taken at its own position.

Measured skin temperature can be used for macrosensing (Section 4.9). As a simple example, knowledge of average skin temperature allows estimation of the environmental wind chill (air temperature and velocity) and relative wind direction using the theoretical equation given by Lampietro⁸⁹⁰ or the experimental data compiled by Mitchell et al⁸⁹³ over the range of 10-50°C and wind velocities of 1-5 m/sec, although the presence of clothing may be a complicating factor.

Thermal patterns appearing on centimeter-resolution volume or surface maps may be useful either for macrosensing or for the determination of various medically relevant states. Some examples of measurable patterns include:

1. bimodal thermal variations on the soles of the feet, while the patient is standing on a cold concrete floor or a hot asphalt pavement;

2. cooling of the back and seat after settling into a chair whose surface is initially at room temperature (chair material may be inferred from the subsequent temperature warm-up profile);³³³⁰

3. warm pattern of a hand placed on the chest while patient hears the national anthem at a sports event;

4. cool vertical lines caused by tears running down cheeks;

5. asymmetric temperature profile caused by lying on one side or the other, in bed or at the beach;

6. warmth or coolness on palm and thumb of one hand while carrying a hot or cold plate of food, or grasping a cold can of beer;

7. cool knee spots while kneeling on a cold floor;

8. comparison of facial and scalp temperatures permitting inference of hair length and coiffure;

9. patterns of muscle warmth indicating physical activity involving specific tendons, limbs or appendages;

10. approximate arrangement and density of clothing;³³³²

11. increased warmth of the sexual organs, during excitation or tumescence, or of the skin, stomach, and liver, following a meal;

12. dangerous thermal gradients (e.g., hand placed on stove) detected in 0.1 sec, faster than the usual ~0.2 sec human response time; and

13. specific thermographic dermal patterns that signal the presence of a wide variety of medical conditions such as ischemic limbs, Raynaud's Syndrome, cerebral apoplexy, reflex sympathetic dystrophy, muscular injuries, abnormal joints, ankylosing spondylitis (Pott's disease), spinal root syndrome, osteoarthritis, tennis elbow, osteoid osteomas, headaches, breast cancers, or melanomas.⁸⁹⁹

Assuming exogenous positional information is available to fixed thermographicytes, a population of these devices can constitute a permanent monitoring network that can issue alerts and detect:

1. temperature profiles of internal or external lesions located anywhere in the body;

2. thermal anomalies reflecting the presence of interior hematomas, lipomas, myomas, edemas and hydromas, new fibrous deposits or air pockets, or dental caries;

3. slowly growing tumors (e.g., by searching for localized, shallow, but monotonic thermal gradients in the ~microkelvin/sec range in the historical data);

4. unusual skin patterns due to defects in nervous control of the peripheral circulation;

5. intestinal surface patterns reflecting identifiable thermal characteristics of materials passing through the bowels, or alterations in cell metabolism resulting from food toxins or inflammatory reactions; or

6. alterations in the thermal behavior of individual organs at specific times of day, under varying workloads, or over long timespans, possibly indicating a change in functionality or general health (measurable by taking advantage of the different thermal characteristics of body tissues; Table 8.12).

Mobile nanorobots passing near any thermographicyte can interrogate the device's thermographic data library and thus may examine all or part of the current whole-body coarse thermal map. Similarly, historical and current data can be transmitted to medical personnel who interrogate the network.

Last updated on 20 February 2003