## 4 Thermographic Techniques for Breast Cancer Detection
### Dynamic Infrared Thermography
#### 4.2.2 Dynamic IR Thermography Using a Cold Provocation  
The effectiveness of dynamic IR thermography in distinguishing between benign and malignant breast lesions was assessed by [PERSON] et al. [56]. Thermal images of 769 subjects with 187 malignant and 688 benign lesions, previously evaluated through mammography, were acquired in a rapid sequence both before and during the cooling phase. In particular, in this phase, a stream of cold air supplied by a refrigeration chamber was circulated around the breast. The authors reported high sensitivity values (97%) and poor specificity (14%), which, however, was statistically higher in dense breast compared to fatty breast. The authors recognized the value of dynamic IR imaging in conjunction with mammography in determining whether a lesion is benign or malignant.  
The effectiveness of a dynamic IR breast scan, known as Sentinel BreastScan(tm), was evaluated in 2008 by [PERSON] et al. [57], testing 92 women with suspicious breast lesions. The IR system was equipped with an IR camera with a 320 \(\times\) 240 uncooled focal plane array, a sensitivity of 0.08 \({}^{\circ}\)C, and an operating wavelength range of 7-12 \(\upmu\)m. The examination was performed in dynamic conditions using an air cooler supplying a cold air flow directed toward the breasts and a chair equipped with lateral-view side mirrors. More than 100 thermal images were gathered for approximately 4 min for each patient. The authors applied three different modes for analyzing thermal frames, and in particular, a screening mode, a clinical mode based on prior information related to the lesion location, and an artificial neural network. They reported sensitivity values higher than or equal to 90% for each mode, and they concluded that digital IR thermography is a valuable adjunct to mammography and ultrasound, especially in all those cases in which the diagnosis of breast cancer can be difficult (such as in younger women, men, patients with dense breasts, or patients with surgically altered breasts).  
The accuracy of the same IR breast scan employed in the study of [PERSON] et al. was assessed later in 2010 by [PERSON] et al. [58]. These authors subjected 100 women with suspicious breast lesions to IR imaging before their biopsy. For each patient, a sequence of 250 thermal frames was acquired while they were sat on am ergonomic chair with their arms supported at eye level, and a temperature-controlled air flow was directed at the breasts for about 5 min. The recorded images were analyzed using proprietary software. The authors concluded that digital infrared imaging is particularly effective for breast cancer detection in women under 50 years old, for which they observed the maximum values of sensitivity (78%) and specificity (75%).  
[PERSON] and [PERSON] [59] evaluated twenty-six patients affected by IDC of the breast through dynamic infrared thermography before surgery. The examination room was kept at a constant 22-25 \({}^{\circ}\)C with a relative humidity of around 50%. After 15 min for acclimatization, two initial steady-state images of the axillary region were recorded using a Fluke(r) Ti9 IR camera (with an image resolution of 640 \(\times\) 480 pixels and thermal sensitivity \(\leq\) 0.20 \({}^{\circ}\)C at 30 \({}^{\circ}\)C) placed at a distance of 1 m. Then, a cold stress was applied to the same region using a gel pack at 4-8 \({}^{\circ}\)C for 2 min. The successive thermal recovery was recorded for at least 2 min, and sequential thermal frames were taken every 5 s. The authors reported an achieved sensitivity of 83% and a false negative rate of 16% when diagnosing axillary involvement. Finally, dynamic infrared thermography was found to be superior to ultrasound, mammography, and magnetic resonance imaging in detecting malignant lymph nodes.