Av Thomas Sjøberg, MD, Consultant reconstructive surgeon, Department of plastic and hand surgery, University Hospital of North Norway
Throughout history warfare has been a strong force in technological development. However, many new inventions also find their use for civilian purposes, including medicine. “Heat-seeking” cameras are among these technical devices, that now are being utilized at the University Hospital of North Norway to support reconstructive surgery, especially after breast cancer treatment. Breast cancer it the most common cancer type among women in Norway, striking almost one out of ten before the age of 75. Luckily the chance to recover after the diagnosis has become much better during the last decade, due to earlier diagnosis and advances in treatment.
Breast reconstruction on the rise
According to American figures approximately 40% of all women will have their breast reconstructed after breast cancer treatment. There is a strong trend towards immediate breast reconstruction, meaning that the breast is re-built in the same operation as the cancer is treated. Furthermore, some women are carriers of a genetic disorder rendering them more prone to developing breast cancer during their life, the so-called BRCA1 or BRCA2 genetic mutations. In these situations, healthy breasts are removed as a prophylactic measure and a direct breast recomsatruction can be performed. The procedure is frequently performed on young women, as early removal of the breast gland reduces the risk for cancer.
There are many different techniques to reconstruct a breast. The most common way is to use a breast implant, usually filled with soft silicone. The implant will be put under the skin and breast muscle to re-create the shape of a breast. Another strategy is to use “extra” tissue from the woman’s own body to build up a new breast. This can be done by using surplus tissue in a so called “flap” made up of fat and skin, sometimes including muscle (Figure 1). The available tissue can be voluminous enough on its own to reconstruct a breast or one can combine the flap with a small breast implant. Anyhow, the flap tissue is dependent on adequate blood circulation. In case of insufficient blood perfusion the tissue will suffer and might die, resulting in an unsuccessful breast reconstruction.
Blood circulation is crucial
The first acknowledgement of reconstructive surgery is from an Ancient Egyptian medical text dated to 3000-2500 years BC. Ever since there has been a constant struggle to explore new and safer operative techniques. The surface of the body (skin and subcutaneous fat) can be divided into sections based on the pattern of the blood vessels catering for each particular area. These tiny vessels with a diameter of 1-2 mm, often called perforators, are the mainstay of tissue transfer in reconstructive surgery.
The precise location of these perforators and larger source vessels might vary with each individual. Therefore it is important to know exactly where the blood vessels are and which of them is the most reliable to supply the flap. As a result, a number of different techniques have been developed to find and assess the quality of blood vessels under the skin.
Mapping the landscape of skin perfusion
The most commonly used tool is a hand-held Doppler ultrasound machine, which will generate harmless ultrasound waves that can penetrate the skin and register the echo bouncing back from moving blood cells in superficial subcutaneous vessels. The technique is simple and easily available, but cannot give very reliable information on the quality and exact location of blood vessels. In breast reconstruction with flaps specifically, computer tomography angiography (CTA) scans are popular. A CT scan is basically a repeated x-ray investigation of a certain area of the body, whereby the tissue can be evaluated as a stack of multiple x-ray pictures on top of each other, enabling the radiologist to acquire precise information on the anatomy of that particular area and also to create 3D images of the structures. Both the size and the location of blood vessels can be registered. However, this comes with a price. A CT scan always exposes the patient to an amount of electromagnetic radiation that can be harmful. Repeated x-ray investigations during a long period of time might give rise to cell mutations and eventually cancer. Although the risk is low, it is still an unwanted side effect of medical x-rays. In addition some people are not able to go through a CT scan for blood vessel mapping because of other health conditions. Hence, there is a need for harmless but precise blood vessel mapping.
Heat radiation unveils blood vessels
Heat-sensitive cameras (thermographic cameras, infrared cameras) have been used in different fields of interest for a long time. The technology was firstly developed for military purposes, starting at the late 1920s. There was a tremendous development throughout the 20th century and eventually infrared cameras were popularized also for civil purposes during the 1990s. This includes environmental control, building/art analysis and car guidance and collision avoidance systems.
The use of infrared camera is clinical medicine is called medical thermography, commonly used to detect increased temperature due to inflammation (in joints or related to cardiovascular disease), newly developed blood vessels (associated with cancer) or neurological problem (chronic pain). Circulatory problems related to reduced or altered blood perfusion can be easily detected.
The thermographic camera registers the heat radiation from a surface and displays this information in a thermographic image. Using a special colour pattern different temperature can be represented by different colors (Figure 2). As the major source of heat radiating from a body surface is warm blood in the vessels, these can be seen as warm areas. In reconstructive surgery we are especially interested in the so-called “hot-spots”. These can be thought of as volcanoes under the skin, bringing hot material from the depth towards the surface. The vessels conveying this heat are the perforators (Figure 3).
Safe surgery without drawbacks
Thermograpic imaging is totally harmless, as no x-radiation or other potentially harmful substances are needed to assess the blood circulation in the skin. The camera is positioned at a distance from the body surface and will therefore allow the surgeons to continue their work without having to alter the working conditions in the operating room. The blood perfusion in the area where the flap is harvested, also called the donor-site, is also evaluated with thermography before surgery. Thermography can also provide essential information on the adequacy of the blood perfusion to the flap in the period after the operation and allows for early detection of any circulatory problems. The cameras come in different sizes but many are highly portable and can be easily brought to wherever needed for additional check-ups. No extra equipment is needed to register and display the information, although all data can be saved for later processing, as needed. The thermal images are logical and easily comprehended by most trained personnel, thereby avoiding the need for support from other professionals.
As such thermography has become a handy complement to other investigations to reduce the risk of unwanted events in advanced surgical treatment.
The future is in thermography
Thermographic investigations have already shown their value in relation to breast reconstruction using skin and fat tissue from the stomach (DIEP flaps). Another commonly used donor site is the back. A TDAP-flap can be raised from just below the shoulder blade and thereafter transposed to the front of the body accordingly. Doppler ultrasound or CT scans are frequently used techniques to assess the perforators in this area. Based on our earlier experience with thermographic imaging, a new project is planned at the Department of plastic and hand surgery in co-operation with the Radiology department at the University Hospital of North Norway and the Institution for Cardiovascular research at the University of Tromsø. The aim of the study is to explore the value of thermography in breast reconstruction with TDAP-flaps. The proposed idea is that infrared imaging can provide the same information as CTA. This has several advantages. Not only is CTA a more expensive technique, it is also more labour intensive. There are also advantages for the patients as they do not become exposed to ionizing irradiation and intravenous contrast medium. Thermography can supposedly be used throughout the surgical treatment and make surgery safer at a low cost. The research project is part of a thesis by the author. It is our belief that heat sensitive cameras will be useful tools also in other types of reconstructive surgery in the future – to the benefit of patients and professionals.