The Laser and its many uses in medical diagnosis and treatment

On the silver screen a laser sword is usually depicted as a destructive weapon with which an alien in outer space fights a rival. In the movie Star Wars, Obe-Van- Kenobi and Darth Wader fight each other with laser swords. In the movie Goldfinger, Sean Connery as James Bond is strapped to a couch. The laser beam steadily approaches his crotch. Goldfinger is seen leaving the room when Sean Connery asks him” do you expect me to talk?” ” No Mr. Bond ” says Goldfinger ” I expect you to die” Then of course James Bond manages to convince Goldfinger that he has some useful information relating to Goldfinger’s Operation Grandslam and Goldfinger stops the laser beam from advancing further at the very last minute..

Therefore the use of the Laser in surgery would come as a surprise to most people who associate surgery with images of blood-stained sheets and razor sharp knives. It is also rather ironical that the very idea of inventing an instrument such as the laserscope had first occurred to a cardiologist while watching a popular science fiction movie where two of the major characters clashed with laser swords!

☝️ One of the unique aspects of medical treatment since the previous century has been the use of extremely sophisticated instruments to assist physicians in diagnosing diseases and surgeons in performing delicate operations. But very few products of modern technology have proved to be as useful as the laser (acronym for ‘light amplification by stimulated emission of radiation’).

The light from the sun or that from an electric bulb spreads in all directions and in many wavelengths. On the other hand, laser produces a powerful, monochromotic (i.e. single frequency) and coherent beam of light. Stimulated emission which is the principle on which the laser works is the emission of a photon, by an atom in an excited quantum state, as a result of the impact of a photon from outside of exactly equal energy which is the principle on which the laser works is the emission of a photon, by an atom in an excited quantum state, as a result of the impact of a photon from outside of exactly equal energy.

Thus, the stimulating photon is augmented by the one emitted by the excited atom. The greatest advantage of stimulated emission is that it is in ‘phase’.When focussed to a width lesser than a pinpoint a laser beam attains a temperature of 10,000° F. It is so powerful that it can punch holes in diamonds in a fraction of a second, slice through a steel beam, cut cloth for several suits at lightning speed, and surge through fibre optics carrying 80,000 simultaneous telephone calls.

The Laser’s utility and versatility have also been proved of immense use in the medical field. By destroying overgrown blood vessels in the eyes it can cure glaucoma; by welding a tissue graft to a perforated eardrum it can restore hearing; it can vaporise a tumour in the brain, cauterise a bleeding stomach ulcer, restore a detached retina to its original place and can erase a tattoo or a birthmark. Ear, nose and throat specialists, dermatologists, neurosurgeons and gastro-enterologists, have for more than two decades been making use of laser, because of the many advantages it has over conventional surgery which involves removal of tissue with the scalpel or with heat or cold.A laser beam can reach areas in the inner-most recesses of the body where the knife cannot reach as its beam can be bent with fibre optics. Since the beam can be aimed with precision neigh­bouring tissues are left undamaged, thus reducing post-operative complications. It seals off the small blood vessels while it cuts, thus preventing bleeding which obscures the surgeon’s vision. It also simultaneously sterilises the wound by burning away unwanted tissues.

Apart from this, since the laser cauterises blood vessels, no haemostats are required for clamping them as in the case of surgery. Since laser also cuts with great speed the patient spends comparatively lesser time under anaesthesia and recovers faster.

Surgeons have started using laser in gyna­ecology also. The Laser has proved extremely useful in removing infectious warts in the genital regions as well as in treating precancerous lesions on the surface tissue of the cervix—a condition known as cervical intraepithelial neoplasia (CIN).

Of late, surgeons have found a new use for laser in cauterising the lining of the uterus to stop a condition known as menorrhagia, i.e. prolonged and excessive menstrual bleeding. In this technique called photo vaporisation which laser is used along with fibre optics, a hysteroscope (an illuminated inspecting instrument) is inserted into the uterus and then a fine optical fibre is passed through the instrument. After a systematic search the laser is used to cauterise the uterine lining, while a surgeon guides the fibre to areas where bleeding occurs. Already photo vaporisation has begun to replace conventional hysterectomy in many procedures.

Women who have CIN can be given local anaesthesia for performing laser surgery. The patient is made to lie on a table. The anaesthetic is then applied to the cervix which is viewed through a speculum. Looking through the binocular eyepiece of a coloscope (a lighted surgical microscope) the surgeon can locate the diseased tissue or tumour . By properly aiming and regulating the time of exposure and the intensity of the blast the surgeon can make the lesion disappear. The patient feels very little discomfort. Doctors are also inclined to believe that the results obtained with Lasers are better than those from conventional methods, such as cryosurgery.

The main goal of colposcopy is to prevent cervical cancer by detecting and treating precancerous lesions early Human Papilloma virus (HPV) is a common infection and the underlying cause for most cervical cancers. Smoking also makes developing cervical abnormalities more likely. Other reasons for a patient to have a colposcopy include, a congenital abnormality of the cervix or as the result  of a sexual assault necessitating forensic examination .Colposcopy is done using a colposcope, which provides a magnified and illuminated view of the areas, allowing the colposcopist to visually distinguish normal from abnormal appearing tissue, such as damaged or abnormal changes in the tissue lesions), and take directed biopsies for further pathological examination if needed. Looking through the binocular eyepiece of a coloscope (a lighted surgical microscope) the surgeon can locate the diseased tissue. The doctor then manoeuvres the red dot on to the lesion. By properly aiming and regulating the time of exposure and the intensity of the blast the surgeon can make the lesion disappear in a puff of steam. The patient feels very little discomfort apart from a slight sensation of warmth. Doctors are inclined to believe that the results obtained with lasers are better than those from conventional methods such as cryosurgery and thermocautery which use cold and heat respectively to destroy unwanted tissues.

The main part of surgical laser, i.e. the substance that determines the wavelength and power of its beam is either a ruby crystal in the shape of a rod or a gas such as carbon dioxide or argon in a glass cylinder. In the ruby laser chromium ions are stimulated to emit photons having been previously excited by an intense flash of light. In a gas laser, a low pressure gas is excited by a continuous electrical discharge through it. In laser radiation, the beam is amplified greatly by additional stimulated emissions during multiple relfections between two mirrors, one reflecting and the other semi-reflecting.

The beam emerging from the semi-reflecting mirror is extremely powerful. The argon laser contains an emerald green beam and is useful in eye surgery as the fluid in the eye does not absorb the energy of the beam. The carbon dioxide laser emits a beam in infrared region and it requires an accompanying dot of visible light to enable the doctor to guide the laser beam to its target.

In gynaecology lasers are particularly useful since the beam is absorbed by any substance containing water and as tissue contains almost 80 per cent water a carbon dioxide laser simply vaporizes the diseased cells.

Doctors are now hopeful of using lasers in the treatment of diseased fallopian tubes, the particular tunnels through whicle female egg passes from ovary to the uterus. If these tubes are blocked due to disease or deformity, fertilisation is not possible. This condition has usually been corrected by a procedure known as ‘insufflation’, i.e. blowing carbon dioxide gas through the tubes. Surgery is resorted to in more severe cases but it has a low success rate of 20 to 30 per cent.

One surgeon in the United States, was the first to apply laser microsurgery to treat blocked fallopian tubes. He had performed operation on 120 patients of two categories, those in whom con­ventional surgery had been unsuccessful and also those rejected for surgery because of the extent of the disease. Of these 120, 21 had become pregnant and similar success was expected in 80 other cases also.

There has been some criticism that the equipment and other infrastructure required for laser surgery are too expensive. While surgeons agree that such considerations are relevant in cases involving routine operations they feel that financial constraints should not come in the way while planning operations for saving life or improving the reproductive ability.

Another major breakthrough in this connection is the invention of an instrument called the laserscope by an eminent cardiologist of the University of California at Davis. Doctors hope that it will become a powerful tool in the treatment of arteriosclerosis. This condition starts in early childhood when fats begin to get deposited in the arteries.

Over the years they grow into plaques which cause obstruction to the flow of blood leading to heart attacks or strokes depending upon the region of the body in which the affected artery is situated. Arteriosclerosis is usually treated by a bypass surgery or balloon angioplasty.

In a bypass operation a vein taken from the patients limb is grafted to the diseased artery to circumvent the obstruction. In angioplasty a catheter is inserted into the artery and pushed till it reaches the plaque. It is inflated to flatten the plaque deposit against the arterial wall and thus widen the channel available for blood flow. Balloon angioplasty can be used instead of bypass surgery in only 10 per cent of the population having arteriosclerosis (in the rest of the cases the arteries are either too clogged for the catheter to be inserted or the deposits too hard to be flattened).

Even if the procedure is successful the condition recurs after a while since the artery becomes clogged once again. A Californian cardiologist first carried out experiments on diseased vessels taken from cadavers to examine the effect of heat on fat deposits. He found that the fat evaporated. Extending the idea he replaced the soldering iron with a laser which not only vaporised the fat but the connective tissue and calcium as well. He then built a laser device for being tested on blood vessels of live animals .The laser is attached to the end of a catheter or tube about one-eighth of an inch in diameter.

The tube which contains three channels is inserted into the artery The first channel has quartz fibres which conduct the laser beam; the second has optical fibres that enable the doctor to look inside the artery; the third channel sprays fluid to flush clear the target site and vacuum away the vapour and solid debris after the laser is fired.

Packed around the channels are optic fibres that illuminate the inside of the artery. The catheter also has a balloon near its tip which is inflated before the laser is switched on.This stems the flow of blood leaving a clean line of fire for the laser beam (otherwise the beam damages the blood vessels and causes clots to form).

He found that within two to three seconds the laser can burn through a plaque. Since the laser is only aimed at the centre of the thick plaque, the arterial walls are left undamaged despite the high temperatures.

This cardiologist was however, humble enough to admit that a lot of research has to be done before the laserscope can be used in regular medical treatment as a substitute for bypass or other conventional treatment. More data has to be collected regarding the damage that can occur due to a bad aim. The vaccuming system has to be per­fected. He plans to attach a video camera system so that the difficulty of having to see through an eye piece is eliminated.

He also hopes to make use of computers to calculate and adjust precisely the necessary duration and intensity of the blast. The laserscope in its present form can be used to clear clogged arteries on the legs but to be used on arteries in regions such as the heart its diameter would have to be reduced to less than a tenth of an inch.

It would have to be designed to work faster and to keep to an absolute minimum the duration for which blood circulation to the heart would have to be stopped by the balloon. He would like to use the carbon dioxide laser but this is not possible unless a technique is developed to conduct its radiation safely and efficiently into a blood vessel.