Laser application in obstetrics and gynecology

Abstract :

For thelast20years,laser technology has evolved as an important tool in surgical treatment and It is widely used in gynecologyandobstetrics.Especiallyinthetreatmentofvulvarandbenignandpremalignantcervicaldysplasiasitcan be consideredasthegoldstandard.Inprenatalmedicine,lasercoagulationofplacentavesselshasbeenshowntobe superiortoanyotherintrauterinetherapyoftwin-to-twintransfusionsyndromeinmonochorionictwinpregnancies. However, not all expectations in laser technology have been fulfilled. In laparoscopy, for instance, the use of the laser has been abandoned in favor of high-frequency electric surgery. This manuscript gives a short introduction to current therapeutic applications and limits of laser technology in gynecology and obstetrics.:

Introduction

While the history of laser began in1951,the first medical application in dermatology was reported by Goldmanin1962 . Since then, laser technology has evolved as an important tool in surgical treatment and it is widely used in gynecology and obstetrics. Especially in the treatment of benign and premalignant vulvar and cervical dysplasias the standard treatment involves the application of laser energy . In prenatal medicine, laser coagulation of placenta vessels has shown to be superior to any other intrauter in etherapy of twin- to-twin transfusion syndrome(TTTS) in monochorionic twin pregnancies . However ,not all expectations in laser technology have been fulfilled. In laparoscopy for instance, the use of the laser has been abandoned in favor of high-frequency electric surgery [6].

This paper gives a short introduction to current applications of laser techniques in gynecology and obstetrics. It focuses on the medical treatment and on technical aspects of laser therapy.

Laser–tissue interactions :

In short, laser–tissue interactions depend on various physical parameters:

(1)wavelength or wavelength band of the applied laser light

(2)physical properties of the irradiated tissue

(3)irradiance or pulse energy of the laser used

(4) continuous wave(cw) or pulsed irradia- tion;

(5)laser beam size on the tissue and

(6)exposure time or laser pulse length and repetition rate

Physical properties of the tissue include the optical, thermal and mechanical properties, such as the absorption

And scattering coefficients as well as the anisotropy factor and penetration depth, which are wavelength- dependent, and the thermal conductivity, heat capacity and tissue density, which change during laser irradiation. In humans, the main absorption determinant is water, but chromospheres such as hemoglobin or melanin can also lead to an additional absorption effect. In principle,laser–tissue interactions can be classified according to five mechanisms:(1)purely optical–e.g. optical spectroscopy for cancer screening, optical coherence tomography;

(2)photochemical –e.g.photo- dynamic therapy; (3)photo biostimulative e.g. laser acupuncture ,low level laser therapy;(4)photothermal– e.g. laser therapy; and (5)photo mechanical or photo- acoustic–e.g.laser lithotripsy. In medical practice , the desired effect in the target tissue can be reached by selection of the correct laser parameters ,i.e. irradiance and exposure time. Purely optical processesor their combination with photoche-mical or photo biostimulative processes occur at low irradiances and/or energies. With increasing laser power or pulse energies photo thermal interactions start to dominate. If repetitive and very short laser pulses are used,photomechanical effects appear.

Laser systems :

Differences in penetration, absorption, and suitable delivery media for the laser beams dictate clinical application.CO2 and Nd:YAG lasers are the most commonly used laser devices in gynecology and obstetrics. Therefore, the technical aspects described as follows focus on these two different systems.

CO2 laser

The carbon dioxide(CO2) laser emits light at a wavelength of 10,640 nm.Its photo thermal effect on tissue consists of the transformation of water into vapor, which leads to complete cell vaporization. However, as the CO2 light only penetrates 0.3–1mm into the target and 90% of the radiation is absorbed within the first 100 mm due to the high absorption by water, the thermal damage to the tissue beyond the vaporization area is minimal.

Therefore, the ideal use of the CO2 laser is on the endothelium of the cervix, vulva and vagina.

In practical terms, the CO2 laser is applied in a non- contact technique in cw and at about 15W.As the laser light is in the mid-infrared band, visual control can be achieved by the addition of a visible guiding beam, such as a helium-neon or diode laser to mark the aimed focal spot.

It is often used in the super-pulsed wave mode, which produces power peaks that are about ten times higher than the cw mode. This allows application with more precision and less thermal injury as the surrounding tissue can cool down between the power intervals. The CO2 laser can not be used for sealing vessels of more than 0.5mm in diameter.

Nd:YAG laser

The neodymium: YAG (Nd:YAG) laser is a solid-state laser emitting light in the near infrared region(NIR)at a wavelength of 1064nm.The effect on tissue is different from theCO2 laser in terms of penetration and thickness of the damaged tissue. Due to the lower absorption of water , deeper penetration into the tissue and scattering in tissue, the Nd:YAG laser leads to a coagulation of depths of upto3–7mm. In the non-contact technique, fine preparation and super ficial application is not possible. It is therefore an instrument that is applicable for ablation and coagulation– e.g. of liver tissue– a sit offers deep penetration and homogenous destruction with good coagulation effects. One typical application of Nd:YAG lasers is the in trauterine treatment of TTTS in monochorionic twin pregnancies where anastomoses between the two vascular systems have to be coagulated. In gynecology and obstetrics, Nd:YAG lasers are mainly used in a non-contact technique. But there are several other application techniques (contact coagulation, contact cutting, impression, interstitial, intra-luminal), which open new therapeutic options.

Medical treatment:

Application of laser techniques in the treatment of vulvar and vaginal lesions

Benign, premalignant and malignant lesions of the vulva are common diseases in gynecology. The gold standard in the treatment of invasive neoplasiasis radical surgery. However the best treatment for pre- malignant neoplasias, such as vulvar and vaginal intra epithelial neoplasias (VIN and VAIN) is not as clear. Similarly, there is no uniform treatment of condylomata acuminata.

Both diseases could either be treated by destruction or ablation of the respective lesions. The decision about the respective treatment depends–amongst other things– on the certainty of the diagnosis. While condylomata acuminate can be diagnosed by inspection of the lesions.

[pic]

Fig. 1. Condylomata acuminate before (left) and after laser treatment (right).

(Fig. 1), VIN and VAIN lesions necessitate histological examination before therapeutic destruction. The therapeutic approach further depends on the localization, the size of the abnormal tissue, the grade of intraepithelial neoplasia and whether these lesions have been treated before.

Besides cryotherapy, podophyllin and electric cautery, laser vaporization can be considered as a standard procedure in the management of vulvar dysplasias and condylomata acuminata

. Vaporization by CO2 laser energy can be performed under local anesthetic. Baggish and Dorsey pioneered the laser treatment and established the technique in the early 80s, which is still in use.In combination with colposcopy, destruction of the lesions can be limited to the affected tissue with minimal collateral damage to the surrounding healthy tissue. The destruction of condylomata acuminate generally involves vaporization to the level of the basal membrane ,whereas VIN and VAIN lesions require destruction to deeper layers Level III in hairy areas and Reid Level II in hair less areas). CO2 laser vaporization and excision of VIN and VAIN lesions as well as condylomata acuminate result in excellent cosmetic and functional healing(Fig.1). However, due to the risk of recurrence, repeated treatments may be necessary.

Recent research has focused on laser in combination with photo sensitizers in the diagnosis and treatment of VIN lesions (photo dynamic therapy and fluorescence diagnosis).The basic principle consists of the topical or systemic application of photosensitizing agents such as 5- aminolevulinic acid(5-ALA) or meta-tetra hydroxy phenylchlorin, which preferentially accumulates in neoplastic tissue. This is followed by the application of laser light that matches the absorption characteristics of the photosensitizer. Fluorescence diagnosis concentrates on an improved visualization of the abnormal tissue by qualitative or quantitative fluorescence analysis. Photo dynamic therapy aims towards a regression of the lesions by generating singlet oxygen and oxygen radicals with local cytotoxic effects . Hillemanns reported on a regression rate of 64% of VIN lesions after several treatment cycles and fewer post-surgical side effects with photo dynamic therapy compared to laser vaporization and surgical lvulvectomy.

A detailed review of the recent research on fluorescence diagnosis and photodynamic therapy in diseases of the lower genital tract, especially of CIN, VIN and HPV-related genital warts (condylomata acuminata) is given in the contribution of Hillemannsetal.: ‘‘Fluorescence diagnosis and photo dynamic therapy for lower genital tract diseases– A review’’in this issue.

Application of laser techniques in the treatment of cervical lesions

Clinical application of laser techniques in diagnosis and therapy especially focuses on the uteine cervix. Besides the well-established therapeutic application, laser energy could also potentially be used as a diagnostic tool in screening form alignant and premalignant lesions.

Therapeutic application of laser energy mainly concentrates on treatment of early cervical dysplasias.

In technical terms, a CO2 laser is used under colposcopic guidance with the laser coupled via a micromanipulator. Conisation with laser energy appears to cause post-surgical bleeding less often and therefore many clinicians prefer it to classical cold-knife conisation or electricsurgery (LLETZ : large loop electro excision of the transformation zone) . Some authors suggest the combination of electric surgery and laser therapy to improve long-term success .

However, in a Cochrane analysis none of the three concepts have proven to have significant advantages . Classical cold-knife conisation seems to have a higher morbidity rate whereas histological examination of the specimen might be more difficult after laser conisation due to thermal artifacts. In view of a pregnancy following conisation, all three methods increase the risk for preterm delivery to a comparable extent . The risk of persistent or recurrent viral disease is a known entity regardless of the treatment used.

Besides CIN lesions, cervical condylomata acuminata are also in the focus of the laser treatment. Similarly to the vulvar type, CO2 laser energy can be successfully applied with good success rates.

As with VIN lesions, the combination of laser light with photosensitizers also plays an increasing role in the diagnosis and treatment of CIN lesions .The topical application of the photo sensitizer 5-ALA followed by fluorescence analysis offers a real-time analysis of the suspicious tissue. In comparison with colposcopy, the detection rate of CIN III lesions was 94% for qualitative fluorescence analysis and 95% for colposcopy, respectively.The respective false positive rates were 49% and 50% . With quantitative fluorescence analysis ,it was possible to reduce the false positive rate further to 25%. In addition, a differentiation between CIN II/III and CIN I lesions was feasible .

Whether photosensitizers a real so beneficial in the treatment of CIN lesions remains to be determined. In a randomized, double blind trial, photodynamic therapy did not lead to a significant reduction of CIN lesions compared to the placebo treatment. Three months after photodynamic therapy, there were no signs of CIN lesions in only 33% of the patients, in 42% there was no change in the CIN grade and in 25% there was an apparent progression of the disease .

Application of [pic]laser[pic] techniques in the treatment of dysfunctional uterine bleeding
About 20% of women worldwide suffer from menorrhagia, which is one of the leading causes for hysterectomy. As an alternative, destruction of the endometrium by [pic]laser,[pic] electric or thermal coagulation was introduced in order to reduce the morbidity associated with hysterectomy. Using the [pic]laser[pic] device, this could either be performed by photoablation after selective sensibilization of the endometrium with 5-ALA or by direct coagulation during hysteroscopy. Photoablation requires special devices for the intrauterine application of the [pic]laser[pic] light and is less efficient than direct [pic]laser[pic] ablation. Direct [pic]laser[pic] coagulation by the Nd:YAG [pic]laser[pic] is considered to be the gold standard but requires intensive training. It was recently challenged by the endometrial [pic]laser[pic] intrauterine thermal therapy (ELITT) and ELITT requires neither hysteroscopy control nor intensive training. For the ELITT procedure an 830 nm diode [pic]laser[pic] system in combination with a special intrauterine device (GyneLase®; ESC/Sharplan), which consists of three fibres that ensure circumferential diffusion inside the uterine cavity, is used. The cervical canal is first dilated up to 7 mm, and the closed diffuser device is then introduced into the uterine cavity. When it reaches the fundus, the lateral fibres can be open, giving the system an inverted triangular shape that adapts to the uterine cavity. Then, the [pic]laser[pic] is activated for 7 min in a cw exposure mode in three consecutive steps: 20 W during the first 90 s, 18 W during the next 90 s, and 16 W during the final 240 s. A distension fluid is not required for this procedure. [31] A. Perino, A. Castelli, G. Cucinella, A. Biondo, A. Pane and R. Venezia, A randomized comparison of endometrial [pic]laser[pic] intrauterine thermotherapy and hysteroscopic endometrial resection, Fertil Steril 82 (3) (2004), pp. 731–734. Abstract | Article | [pic]PDF (66 K) | View Record in Scopus |Cited By in Scopus (13)
Results of a randomized study, involving 116 patients with menorrhagia, demonstrate that the described ELITT procedure is equally effective compared to transcervical hysteroscopic resection of endometrial (TCRE). At 12 months, the amenorrhea rate was 56% in the ELITT group and 23% in the TCRE group. At 36 months, the figures were 61% for ELITT and 24% for TCRE. No significant complications were recorded for either procedure. the ELITT technique led to the highest amenorrhea rate of all modalities for endometrial ablation such as electrosurgery or intrauterine thermal balloon therapy. The amenorrhea rate after 1 year of follow-up was 71%, and the rate of amenorrhea/severe hypomenorrhea rate was >90%.
Therewith, the ELITT procedure seems to be an inherently safe and simple alternative, providing controlled and effective treatment of the entire endometrium.

Application of [pic]laser[pic] techniques in operative hysteroscopy

Resection of uterine synechiae and submucosa fibroids also belong to the well-established applications of [pic]laser[pic] in gynecology. In order to improve the fertility rate, the normal anatomy of the uterine cavity can be reinstated without major surgical intervention [34] J. Yang, T.L. Yin, W.M. Xu, L.B. Xia, A.B. Li and J. Hu, Reproductive outcome of septate uterus after hysteroscopic treatment with neodymium:YAG [pic]laser,[pic] Photomed [pic]Laser[pic] Surg 24 (5) (2006), p. 625. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (1). After fluid-based distension of the uterine walls, the synechiae or fibroids can be visualized and coagulated by an Nd:YAG or diode [pic]laser[pic] (NIR) in a direct contact technique.

Application of [pic]laser[pic] techniques in the treatment of TTTS

Twin-to-twin syndrome (TTTS) affects about one-third of all monochorionic twin pregnancies between 16 and 24 weeks. About half of those need treatment in order to avoid intrauterine death or handicap. TTTS is caused by an imbalance in the net flow of blood across the placental vascular communications from one fetus, the donor, to the other, the recipient. This exsanguination of the donor into the recipient twin is caused by anastomoses between the two vascular systems, mainly arterio-venous anastomoses, which can be found on the surface of the placenta. Effective treatment for TTTS is provided by endoscopic [pic]laser[pic] coagulation of the communicating placental vessels. Coagulation is generally performed under fetoscopic surveillance with an Nd:YAG or a diode [pic]laser[pic] device (NIR) in a non-contact technique.
[pic]Laser[pic] coagulation is considered to be the gold standard in the treatment of TTTS. In a direct comparison to the alternative therapy – amnioreduction.have shown that after [pic]laser[pic] therapy the survival of at least one fetus was substantially higher and among the surviving fetuses, the rate of neuro developmental handicap was reduced (see also Kagan et al.: “Diagnosis and treatment of twin-to-twin transfusion syndrome (TTTS)” in this issue).

Conclusion

[pic]Laser[pic] therapy in gynecology and obstetrics is well established. CO2 [pic]laser[pic] devices are used in the treatment of vulvar and cervical lesions such as condylomata acuminata and intraepithelial neoplasia. The main advantage is a better cosmetic result (no scars, very accurate preparation). Nd:YAG [pic]laser[pic] energy can be used for endometrium ablation but the main focus lies on the treatment of twin-to-twin transfusion syndrome in monochorionic twins.
The application of [pic]laser[pic] therapy in gynecology and obstetrics is being progressively challenged by the development of high-frequency electric surgery. In the early 90s, coagulation by [pic]laser[pic] was considered to be the gold standard in gynecology and obstetrics. With the enormous improvements in high-frequency electric surgery, the clinical focus may change away from the [pic]laser[pic] towards high-frequency electric surgery .
Concerning clinical handling and practicability at our department high-frequency electrosurgery has proven as the method of choice for endoscopic ablative procedures.In hysteroscopic surgery high-frequency electric surgery can be considered as an equivalent alternative to [pic]laser,[pic] whereas the treatment of vulvar and cervical lesions as well as intrauterine therapy of twin-to-twin transfusion syndrome is still considered to be advantageous using [pic]laser[pic] energy.

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