This procedure aims to diagnose melanoma or other types of skin cancer non-invasively using dynamic infrared imaging. Start by taking a white light photograph of the lesion and the surrounding healthy tissue, followed by a reference infrared image of the same region of the skin. Next, cool, the lesion and surrounding skin.
Then remove the cooling stress and record an infrared movie of the reheating process termed thermal recovery. Finally, perform the data analysis and image processing of the captured white light and infrared images to measure the temperature of the skin as a function of time during the thermal recovery process, compare the skin temperature at the location of the lesion and far away from the lesion to evaluate differences in the thermal response as an indication of increased metabolic activity that may be related to skin cancer. Ultimately, results can be obtained that show heat generation through dynamic thermal imaging.
Dynamic infrared imaging is a noninvasive objective and quantitative method that allows detection of melanoma at an early stage of the disease. This method can help answer key questions in the field, such as whether I pick man signal lesions is metabolically active and measure the level of metabolic activity combined with increased blood supply. This can be linked to cancer staging.
This method entails some complexity of acquiring accurate surface temperature data using infrared imaging techniques and compensating for involuntary movement of the subject during the imaging process. So Dr.Mcg Miguel Perini, a postdoc from my lab and myself will now demonstrate the procedure, Organize a temperature controlled exam room equipped with an infrared camera and a PC for infrared image acquisition and storage, as well as a data acquisition card connected to a computer. In order to monitor the room and skin surface temperatures, attach thermocouples to a data acquisition card during the patient study and store measurement data on a computer.
Since lesion detection in the thermal image requires a cooling effect, use a square adhesive marker to localize the pigmented lesion of interest and its surroundings with the digital camera. Acquire a bright light image of the pigmented lesion and the adhesive window. Then connect a dermatoscope to a digital camera and capture oscopy images.
The lab view software captures and saves all infrared images using the lab view software. Capture a steady state infrared image with a Merlin midway infrared camera. Proceed to apply a stream of cold air to the area of the patient's skin containing the lesion, as well as a 50 millimeter diameter of surrounding region.
After one minute, remove the cooling stress to allow the skin to rewarm at room temperature for three to four minutes. During this thermal recovery phase, capture infrared images of the pigmented lesion every two seconds in order to obtain accurate transient temperature distributions on the skin surface. Analyze the IR images using a MATLAB code customized for this purpose, including several calibration steps and a multimodal image analysis system.
Start by applying a landmark detection algorithm to the bright light image for localizing the corners of the adhesive marker. Next, identify the corresponding points in the reference IR image, compensate for involuntary body or limb movement of the patient by using these points as landmarks in a quadratic motion model for aligning the IR image sequence during recovery phase. Next, use the random walker to spatially guide the segmentation by placing seed points to create a mask image delineating the lesion.
Once the shape of the lesion is determined, identify the corresponding region in each of the registered IR images. Select random points inside the lesion and away from the lesion representing the lesion and the healthy tissue respectively. Then compare the transient thermal responses of both sites.
Finally, prepare a table including all the digital oscopy color-coded IR images of the lesion and surrounding area recorded at ambient conditions and two seconds after the cooling excitation, as well as the transient thermal responses of the lesion and corresponding healthy tissue. In a patient study in which patients who possess a pigmented lesion with a clinical indication for biopsy are selected for imaging, the increased metabolic activity of the melanoma lesion can be detected by dynamic infrared imaging. Once data is collected from the patient's study, a precise thermal response curve is obtained with motion correction.
There is no difference in temperature between the benign pigmented lesion and the healthy skin tissue in the infrared image or during thermal recovery. Thermal imaging proves a particular advantage in malignant skin lesions based on the infrared images. A significant temperature and color difference is observed during the thermal recovery, only at the location of the melanoma lesion in the infrared image.
Once fully optimized and automated, this technique can be done in two, three minutes if it is performed properly. This imaging procedure is harmless. There are no hazards involved, and this is essential in clinical diagnostics.
While attending this procedure, it's important to remember that the subject needs to remain as motionless as possible following this procedure. Other methods like biopsy can be performed in order to answer additional questions like the staging and penetration level of the cancer and second lesion.
