Laser Surgical Planning With Magnetic Resonance Imaging–Based 3-Dimensional Reconstructions for Intralesional Nd:YAG Laser Therapy of a Venous Malformation of the Neck FREE

LARGE VENOUS malformations with their mostly subcutaneous involvement make magnetic resonance imaging (MRI) an essential diagnostic tool and therapeutic prerequisite. Especially for the minimally invasive intralesional laser therapy of venous malformations, MRI can be a valuable diagnostic method to define the true anatomical extent and involvement of the lesion.

The numerous vascular abnormalities are classified in different groups according to their pathological and anatomical features. According to the Hamburg classification of 1988, arterial, venous, lymphatic, arteriovenous, and combined malformations with a further subdivision in truncular and extratruncular, circumscribed, and infiltrating malformations should be differentiated. Truncular malformations are based on a dysembryogenesis of mature blood vessels, whereas extratruncular malformations are derived from the primitive capillary network.^1- 3

We report a case of a 27-year-old woman with a venous extratruncular infiltrating malformation of the neck since birth. Treatments with the flashlamp pumped dye laser, percutaneous laser therapy, and 1 session of intralesional Nd:YAG laser therapy were performed.

The Nd:YAG laser produces a continuous-wave infrared light at 1064 nm, penetrating into the dermis to a depth of 5 to 7 mm. In the treatment of cavernous vascular tumors and voluminous malformations, good results can be achieved.^4- 7 Two different methods of Nd:YAG laser light applications are emphasized in this article: the percutaneous laser light application and the intralesional photocoagulation. In percutaneous application, the laser light is transmitted into the lesion directly through the overlying skin, resulting in coagulation and shrinking of the vascular lesion.⁶ Adverse effects such as necrosis and scarring can be reduced by protecting the skin from serious heat damage. For this purpose, the skin surface should be cooled simultaneously with ice water or ice cubes.^4,6,8- 11 Intralesionally, the laser light is applied into the vascular tissue directly via a flexible bare quartz fiber. The tissue is penetrated using a 16-gauge needle, and the fiber is inserted through the needle. The position of the fiber can be controlled by ultrasound, by palpation, or by the red light of the pilot laser shining through the skin surface.^1,12- 13

Understanding the complex anatomical involvement of vascular malformations based on sectional MRIs remains a difficult task for clinicians. Magnetic resonance imaging–based 3-dimensional (3-D) reconstruction of the lesion could help the dermatologist in comprehensive laser surgical planning. This technique, which has been widely used in complex neurosurgical procedures for several years,¹⁴ has to be adapted for dermatological requirements. Using advanced computer graphics workstations, clinicians can achieve the task by applying the 3-D reconstruction techniques, surface rendering and volume rendering.

For surface rendering, a structure has to be defined on each sectional image by an experienced user. To create a 3-D model, the points on all sectional images are connected. Using a visualization pipeline, clinicians form the surface (based on these points) and visualize it with virtual light sources. Because of the manual-user interaction, this technique is very time-consuming. On the other hand, it allows precise depiction of pathological structures and is less demanding regarding the computing power.

Volume rendering describes a method, that uses all voxels in a magnetic resonance data set. Each voxel is defined by a specific value for opacity, color, and reflection. This approach is less time-consuming because no manual image processing is necessary. There is, however, extensive need of graphics computer power. For dermatological laser surgical planning, we applied a hybrid technique using surface and volume rendering in one comprehensive model.

A 27-year-old woman presented with a large but symptomless venous malformation of the right part of the neck that had been there since birth (Figure 1). Until now she had not undergone any treatment. Findings from clinical examination revealed a mass of compressible, bluish, and bulky nodes below the chin and a subcutaneous swelling of the right part of the neck.

Before planning intralesional laser therapy, 4 percutaneous laser treatments of the superficial area were performed with the Nd:YAG laser (MED 100-L Jenlas; Aesculap Meditec, Jena, Germany) with varying parameters (1064 nm, 25-35 W, continuous wave, 0.3- to 1.0-second pulses, 2- to 3-mm spot size) under general anesthesia at 3-month intervals. The laser light was applied to the lesion percutaneously with simultaneous surface cooling with ice water. No adverse effects occurred. For laser surgical planning of the intralesional Nd:YAG laser therapy of the subcutaneous part of the venous malformation, a diagnostic MRI was performed with reconstruction of a virtual 3-D model of the venous malformation to show the pathological involvement and extent of the lesion.

A diagnostic MRI was performed to appreciate the true anatomical extent and involvement of the lesion. Imaging was performed on a 1.5-T MR scanner (MAGNETOM Symphony; Siemens Medical Solutions, Erlangen, Germany) using a head coil. Gadolinium-enhanced (Gd-DTPA; Magnevist, Schering, Berlin, Germany) T1-weighted MRI sequences (3-D fast low-angle shot) were acquired. Additionally, fat suppressed T1- and T2-weighted spin echo sequences were performed. On these sequences the tumor was clearly depicted as a bright structure. The fat-suppressed sequences revealed the expansion of the vascular malformation within the parotis and submandibular gland.

Using the T2-weighted axial MRIs, clinicians created 3-D models of the venous malformation and the surrounding tissue on a Silicon Graphics O2 computer workstation (Silicon Graphics Inc, Mountain View, Calif) with Virtuoso3D software (Siemens Medical Solutions, Erlangen, Germany). The venous malformation, the jugular vein, the parotis, and submandibular gland were outlined separately on the axial images. Semiautomatic intensity–based segmentation with manual fine editing was applied to reduce the processing time. The surrounding anatomy consisting of skin, muscles, and eyes was reconstructed using the volume-rendering technique. For an experienced radiologist, this procedure takes about 60 minutes. A comprehensive 3-D visualization of the complex venous malformation related to the facial anatomy was achieved (Figure 2, Figure 3, and Figure 4) with consecutive 3-D reconstructions. This resulted in a better understanding of the pathological involvement for the planning of intralesional laser therapy.

The patient was treated with a combined laser therapy under general anesthesia. The subcutaneous node at the neck was treated intralesionally with the Nd:YAG laser (6 W, continuous wave, 1- to 2-second pulse) using a 600-µm bare fiber. After penetrating the tissue with a puncture cannula, the fiber was inserted through the needle. The position of the fiber was first controlled by ultrasound (10 MHz). Additionally the exact position of the fiber was optimized by comparing the 3-D images, the ultrasound image, and the red light of the pilot laser shining through the skin surface. In the correct position, the laser light was applied directly into the vascular tissue. This procedure was repeated several times, applying the laser light to mostly all areas of the complex malformation. Finally, the superficial red area was treated with the flashlamp pumped dye laser (SPTL 1B; Candela Corporation, Wayland, Mass) without cooling device (spot size, 10 mm; 4.5 J/cm²; pulse duration, 450 microseconds).

No complications occurred after laser surgery. Eight weeks after the first intralesional laser treatment, the patient showed satisfactory regression of the bulky lesions of the neck. The follow-up period was about 3 months after the last treatment. Figure 5 shows the patient 4 months after the treatment with intralesional laser therapy.

In the meantime, a second combined percutaneous and intralesional laser therapy under general anesthesia was performed with similar parameters. The bulky lesions of the neck showed regression again, but a new MRI to control the anatomical extent of the subcutaneous involvement in correlation to the clinical appearance was not then available.

As a result of the 3-D reconstruction, the application of the intralesional laser treatment could be performed more exactly because the dermatologist could understand much better the complex anatomy of the venous malformation; especially the anatomical situation near the submandibular gland was elucidated by studying the 3-D images before laser surgery. Color reprints of 3-D reconstructions, together with sectional 2-D MRI, were shown to the dermatologist during laser surgery. Furthermore, it is notable that a 3-D reconstruction of a venous malformation with axial and sagittal sequences could be easily performed by an experienced radiologist within 1 hour.

The Nd:YAG laser produces light at 1064 nm, which penetrates to a depth of 5 to 7 mm due to relatively low absorbance but high scattering in the skin.¹⁵ The absorption of the light induces an increase in temperature in the vascular lesion and results in the coagulation of vessels, even those located deep in the dermis.¹⁶ To reduce epidermal and dermal damage and scarring and to minimize the swelling that typically occurs, especially in regions such as lips and eyelids, laser treatment should be performed with intraoperative cooling of the skin surface. Additional cooling after laser treatment is helpful. Within a few days after percutaneous therapy, blisters and scabs are formed. Normally, wound healing is completed after 2 to 4 weeks.¹⁷

The advantages of intralesional photocoagulation are the direct penetration of the target tissue without thermal damage of the skin and the possibility of deeper application of the laser light after inserting the fiber through the needle. The laser light is applied directly into the vascular tissue. A size reduction of the lesion is obtained by producing thrombosis and coagulation necrosis of the tissue.⁹ Possible complications of intralesional laser therapy include injury to the facial nerve or thermal necrosis of the lower surface of the skin due to an incorrect setting, ie, too superficial fiber position or high power output. The former can be prevented by intraoperative facial monitoring that allows confirmation of the electrical integrity of the nerve during surgery.^15,18 Common in both techniques is the physical property to cause an internal and nonspecific shrinkage and heating of vessels.

In our experience, combining the percutaneous and intralesional laser treatment is useful in therapy for complex malformations because both deep and superficial vessels can be treated with the optimal parameters and acceptable risk of adverse effects. The number of laser treatments as well as the energies necessary for regression mainly depend on the ectasia of vessels, the type, and the location of the lesion. The smaller the proliferating part of the vascular lesion, the more effective the response.⁶ High-flow lesions with marked arterial circulation or arteriovenous shunting generally respond unsatisfactorily to Nd:YAG laser treatment because the circulating blood acting as "cooling circuit" probably prevents effective coagulation of the lesion. Laser treatment of mucosal vascular tumors achieves better results than on nonglabrous skin because tumor vessels are mostly located superficially and easily accessible to the laser light.⁶ Multiple laser treatments are preferred to aggressively performed single treatments because the latter bear an increased risk of adverse effects due to excessive thermal necrosis (scarring, prolonged swelling, infection, or nerve injury).

Another well-known method for the treatment of complex venous malformations is percutaneous sclerotherapy^19- 20 or, in the case of arteriovenous malformations, transcatheter embolization.^21- 22 With this kind of therapy, results almost similar to intralesional laser therapy can be achieved.²³ The most common complication of liquid agents is local tissue injury such as skin necrosis or peripheral nerve damage.^24- 27

The complex 3-D network character of venous malformations and their excellent signal characteristics on fat-suppressed T2-weighted and contrast-enhanced sequences make MRI a potential diagnostic standard in assessing these malformations.²⁸ However, computed tomographic scans with contrast enhancement can also define the extent of involvement. Because of known adverse effects of iodinated contrast media and the high radiation dose, this modality precludes routine surgical planning for the mostly young patients. In our experience, it remains a difficult task for nonradiologists to understand the complex anatomical involvement of venous malformations based on 2-D images. Invasive diagnostic methods such as phlebography or arteriography do not provide more useful information than noninvasive techniques.²⁹ Doppler ultrasonography (duplex scans) can demonstrate superficial and deep areas of the venous system with dilatation or ectasia also in 2 dimensions and can be used to follow the course of the disease.³⁰ The problem consists of the exact anatomical and 3-D localization of the venous malformation in the patient before intralesional laser therapy, especially regarding the tendency of venous malformations to collapse depending on the position of the patient. For this purpose, 3-D reconstructions of MRI data can be a extremely useful tool that allows a comprehensive 3-D visualization of the complex venous malformation related to the surrounding facial anatomy. From the radiologist's point of view, a routine MRI gives the same information as a 3-D reconstruction, but in our experience, the use of 3-D reconstructions can significantly help the planning of laser surgical procedures. To our knowledge, the technique of MRI-based 3-D visualization, which has been used in subtle neurosurgical procedures for several years, has never been described for surgical dermatological procedures like intralesional laser therapy. In particular, the minimally invasive dermatological laser therapy could be improved by an accurate 3-D surgical planning in complex anatomical regions like the face. Having a 3-D "road map" of the lesion including the surrounding tissue gives dermatologists a better understanding of the pathological involvement and extent for the intralesional laser therapy.

Combined percutaneous and intralesional Nd:YAG laser therapy is a valuable tool in the management of vascular malformations, especially of the predominantly venous type. Output power, spot size, pulse duration, and the total energy dose must be individually adapted to size, color, and consistency of the malformations. With the use of MRI-based 3-D reconstructions, an exact planning and positioning for intralesional treatment is possible. Using this technique, the risk of adverse effects can be reduced.

Accepted for publication June 20, 2001.

We thank Christine Ross-Cavanna, Christine Fabritius, and Ruth Nowack for performing the clinical photography.

Corresponding author: Alexander Glaessl, MD, Department of Dermatology, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93042 Regensburg, Germany (e-mail: alexander.glaessl@klinik.uni-regensburg.de).