Comparison between optical coherence tomographic and histopathologic appearances of artifacts caused by common surgical conditions and instrumentation

Abstract

Objective: To document the appearance of artifacts created by commonly encountered surgical conditions and instrumentation on optical coherence tomography (OCT) and to compare these findings with histopathology.

Study design: Ex vivo study.

Animals: Five canine cadavers.

Methods: Skin, subcutaneous fat, skeletal muscle, and fascia samples were obtained from fresh canine cadavers. Blood pooling, hemostatic crushing, scalpel blade cut, monopolar electrosurgery, bipolar vessel sealing device, and ultrasonic energy surgical artifacts were induced on each tissue type. Each specimen was imaged with OCT and subsequently histologically processed.

Results: Most surgical instrumentation used for tumor excision created a high-scattering region with local architectural disruption. Blood pooling was visible as a high-scattering layer overlying tissue with normal architecture. Only the scalpel blade created a focal, low-scattering area representing a sharply demarcated cut within the tissue distinct from the appearance of other instrumentation.

Conclusion: Common surgical instruments and conditions encountered during tumor excision produced high-scattering OCT artifacts in tissues commonly seen at surgical margins.

Clinical significance: The clinical value of OCT hinges on the ability of personnel to interpret this novel imaging and recognize artifacts. Defining and describing the appearance of common surgical artifacts provides a foundation to create image libraries with known histological and OCT interpretation, ultimately improving the diagnostic accuracy of OCT for assessment of surgical margins.

FIGURE 1

Photographs illustrating the use of a spectral domain OCT system for in vivo and ex vivo tissue analysis. A, Handheld OCT probe is used intraoperatively to evaluate a resection bed after digit amputation. B, OCT probe is held in light contact with the tissue surface and systematically swept along the lateral and deep margins of an excised tissue specimen for image acquisition. OCT, optical coherence tomography

FIGURE 2

Blood pooling artifact on adipose tissue. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). No histopathologic abnormalities are visible. Normal adipose tissue appears as vacuolated and honeycomb in appearance (thin white arrow, B) with OCT imaging. The area of increased scatter on the tissue surface (thick white arrow, B) represents blood pooling artifact. OCT, optical coherence tomography

FIGURE 3

Blood pooling artifact on skeletal muscle. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). No histopathologic abnormalities are visible. OCT image exhibits the normal, homogenous architecture of skeletal muscle (thin white arrow, B). A high-scatter region (thick white arrow, B) on the surface of the skeletal muscle represents blood pooling. Small, focal low-scatter regions (asterisk, B) represent the uneven surface of skeletal muscle and resultant air pockets. OCT, optical coherence tomography

FIGURE 4

Blood pooling artifact on fascial tissue. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). No histopathologic abnormalities are visible. A high-scattering layer on the superficial aspect of the fascia (thick white arrow, B) represents blood pooling artifact. Interspersed within this area is the normal architecture of the fascia (thin white arrows, B). OCT, optical coherence tomography

FIGURE 5

Crushing artifact on skeletal muscle. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). No histopathologic abnormalities are visible. OCT image reveals multiple, focal, low-scatter regions (thin white arrow, B) that represent air pockets from poor tissue contact. Smaller, punctate, high-scatter regions (thick white arrows, B) within this area resulted from crushing and compression of the tissue. OCT, optical coherence tomography

FIGURE 6

Crushing artifact on fascia. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). No histopathologic abnormalities are visible. OCT image reveals interspersed adipose tissue (thin white arrow, B) and trapped air pockets (thick white arrow, B) overlying the fascial tissue (dagger, B). The crushing artifact has changed the conformation of the tissue, creating a serrated appearance and high-scatter region (asterisk, B) on the most superficial aspect of the fascia. OCT, optical coherence tomography

FIGURE 7

Scalpel blade artifact on fascia. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). No histopathologic abnormalities are visible. OCT image reveals a focal, low-scatter area (arrow B) that represents the scalpel blade cut. The architecture of the fascia is normal (left and right sides of image), reflecting a lack of disruption to surrounding tissues. The area of low scatter is a consequence of decreased contact between the probe-tissue interface and reflects the scalpel blade defect that has been created. OCT, optical coherence tomography

FIGURE 8

Monopolar electrosurgery (5 W) artifact on fascia. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). Histopathology identifies areas of fascia that are expanded, fragmented, and filled with necrotic material (black arrows, A). The OCT image is composed of a very high-scattering layer (thin white arrow, B) on the surface of the fascia consistent with thermally induced injury. This leads to extremely superficial light penetration and lack of visualization of the underlying tissues (thick white arrow, B). OCT, optical coherence tomography

FIGURE 9

Monopolar electrosurgery (15 W) artifact on fascia. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). Histopathology identifies areas of fascia that are expanded, fragmented, and filled with necrotic material (black arrows, A). The OCT (B) image illustrates a transition from normal fascia (thin white arrow) to an area of abnormal, thermal injury (thick white arrows). Normal fascia contains linear stratifications, whereas the artifact has thin, high-scatter striations present at the fascia surface (thick white arrows). Beneath this, there is a lack of penetration of light waves to deeper tissues. The focal, low-scatter regions present just beneath the thick white arrows represent trapped air pockets from an irregular tissue surface. OCT, optical coherence tomography

FIGURE 10

Monopolar electrosurgery (25 W) artifact on fascia. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). Histopathology identifies areas of fascia that are necrotic material. The OCT image reveals a focal, high-scatter line (thin white arrows, B) present at the surface of the fascia beneath which there is poor visualization of the underlying tissue. Small amounts of normal fascia at the periphery have retained their normal structural characteristics (thick white arrow, B). OCT, optical coherence tomography

FIGURE 11

Optical coherence tomographic image of monopolar electrosurgery (5 W) artifact on adipose tissue. Thermal injury is created in the superficial connective tissue with adjacent high-scatter regions (thick white arrow) and comparatively low-scatter regions (thin white arrows) that represent air pockets or tissue irregularity. Note the ability to visualize adipose tissue beneath the areas of thermal injury

FIGURE 12

Optical coherence tomographic image of monopolar electrosurgery (15 W) artifact on adipose tissue. There is a zone of transition between normal adipose tissue (thick white arrow) and abnormal adipose tissue secondary to thermal injury (thin white arrows). The normal adipose tissue has a homogenous honeycomb appearance. The abnormal adipose tissue contains areas of high scatter, with some retention of its normal vacuolated appearance

FIGURE 13

Optical coherence tomographic image of monopolar electrosurgery (5 W) artifact on skeletal muscle. This image illustrates the transition between the normal and organized appearance of skeletal muscle (thin white arrow) progressing to an area of abnormal thermal injury induced by monopolar electrosurgery (white outlined area). The area of injury consists of a high-scattering and disrupted tissue surface preventing light from penetrating deeper within the skeletal muscle. Note the presence of focal, low-scatter regions (air or fluid pockets) on the irregular tissue surface (thick white arrow)

FIGURE 14

LigaSure artifacts on adipose (A), skeletal muscle (B), and fascia (C). Histopathology (top images) with hematoxylin and eosin stain and OCT images (bottom images). Histopathology of skeletal muscle (B, top) contained focal areas of degeneration with characteristic loss of striations of myocytes. Histopathology of fascia (C, top) contained expanded and fragmented tissue filled with necrotic material (black arrows). Each OCT image (A,B,C bottom) contains a focal, low-scattering cleft (thin white arrows) outlined by a high-scatter layer (thick white arrows in A and B, outlined area in C) representing the cutting and sealing functions of the device, respectively. The irregular surface of the tissue has also created pinpoint, low-scatter regions (B, bottom, asterisk) representing air pockets. OCT, optical coherence tomography

FIGURE 15

Harmonic scalpel artifact on adipose tissue. Histopathology with hematoxylin and eosin stain (A) and OCT image (B). Histopathology identifies haphazardly arranged and fragmented collagen fibers with accumulation of eosinophilic debris (black arrow, A). The adipose tissue in the OCT image (B) appears heterogenous, with a layer of high-scatter interposed with low-scattering regions (thin white arrow). This represents a layer of necrotic adipose tissue secondary to thermal injury. The layer of tissue deep to this (thick white arrow) is low-scattering and, likely, more structurally normal adipose tissue. OCT, optical coherence tomography