The term ablation can be used to refer to the process by which the surface layers of an object are eroded or vaporized. Examples include friction (e.g., a spacecraft entering the Earth’s atmosphere) and radiation (e.g., tumors removed by laser). The term is often found in space physics associated with atmospheric re-entry, glaciology, medicine, and passive fire protection.
In space physics, and astronomy, the term ablation is used when, due to atmospheric friction, a body during re-entry into the atmosphere undergoes a process of vaporization and erosion of the surface layers. The released particles ionize the surrounding atmospheric molecules, which subsequently de-excite to produce the light trails commonly associated with these types of objects.
In some cases this phenomenon can reach to totally consume the body before it reaches the ground. However, the evaporation and the continuous removal of the overheated material allow the body not to undergo strong temperature variations in the internal areas or in the areas not reached by the ablation: the heat produced by the friction with the air is removed and moved away together with the vaporized material. This mechanism, by means of special thermal shields, is exploited to effectively protect spacecraft during re-entry into the atmosphere.
In Geology, however, it represents the process of surface degradation or erosion, with the removal of disintegrated material by water, wind, or ice. Specifically, it is the reduction in volume undergone by a glacier through melting and evaporation as a result of increased temperature.
In glaciology, ablation is used to define the removal of ice or snow from the surface of an ice mass within the so-called ablation basin. This phenomenon is caused primarily by solar radiation. Ablation can refer to melting or sublimation of ice, and produces a thinning of the ice. Ablation deposits are masses of rocky debris left by the surface melting of the glacier.
In medicine, ablation is the removal of a portion (usually superficial) of biological tissue. This technique can be applied to the skin by chemical methods (peeling) or with the help of lasers in order to promote its regeneration. Laser ablation of the cornea is performed in refractive medicine for the correction of visual defects such as astigmatism, myopia and hypermetropia. Surgical ablation can also be performed in otolaryngology, such as for the treatment of snoring.
Laser ablation is applied in the field of minimally invasive procedures (laser interstitial thermotherapy) for the treatment of tumor pathologies in organs such as liver, lung, pancreas and prostate. The heat developed by the laser radiation, which is introduced into the tissue to be treated through the use of one or more optical fibers, determines an irreversible necrosis of the tumor cells. Further applications include laser ablation of benign thyroid nodules.
Ablation techniques are also used in cardiology to treat a variety of arrhythmias such as supraventricular tachycardia, WPW syndrome, ventricular tachycardia and, more recently, atrial fibrillation. Rotoablation is a type of artery cleaning used to treat coronary artery disease in order to restore proper blood flow. Transcatheter ablation is a minimally invasive procedure in which the doctor introduces a thin, flexible tube (catheter) into the blood vessels and maneuvers it up to the heart, canceling (“ablating”) the abnormal electrical pathways present in the heart tissues. If the patient’s atrial fibrillation does not respond to drug therapy, the doctor may recommend the transcatheter ablation procedure.
Bone marrow ablation is a process used when bone marrow cells need to be removed in preparation for a transplant. This process is accomplished through chemotherapy and radiation. This is exactly why physically this process has nothing to do with the other vaporization and erosion techniques explained in the rest of this article.
In dentistry, this means the process of removing tartar (calcium deposits on tooth surfaces) with an ultrasonic instrument (scaler) or with manual instruments such as curettes.