The cervical study OCT involved several stages:

OCT does not require additional preparation of the patient and anesthesia.

During the OCT studies, we used a compact portable OCT system developed and constructed at the Institute of Applied Physics of the Russian Academy of Sciences (Nizhniy Novgorod, Russia). The device received Russian regulatory authority certification for clinical use in August 2005.

The unit has the following technical characteristics:

The device is compact and has the following dimensions: 250 × 400 × 450 mm. The weight is 10 kg. All optical and electronic parts of the OCT unit are located inside a console.

The cervical OCT was performed using a detachable, reusable forward-looking OCT probe with an outer diameter 2.7 mm (Fig. 77.1a, b). The probe can be cold disinfected or sterilized. Alternatively, a disposable sterile sheath with an optically transparent membrane (Fig. 77.1b) was used to hold the probe and prevent contamination; in this case the probe was not in direct contact with the patient tissues.

To perform OCT, the probe was applied to the cervical area of interest under the colposcope control. To reduce artifacts related to unintentional movements of the probe and the study object, the distal end of the probe or the sheath membrane was in contact with the tissue.

The obtained images were interpreted directly at the time of the patient examination.

Later, we conducted a comparative analysis of the OCT and histological data. The material obtained by the biopsy, loop electro excision procedure (LEEP), and hysterectomy was subject to histological assessment. The guided biopsy was performed under the colposcopic control immediately after the OCT imaging only when clinically indicated. Cervical histopathology was obtained for 138 out of 205 (67.3 %) patients. The specimen volume and depth were sufficient for identifying the structures in the OCT image with size usually equal to 1.7 × 1.5 mm.

Since the stratified squamous epithelium is well delineated in the normal cervical OCT images, the thickness can be easily measured. This thickness changes significantly depending on the menstrual cycle phase since it is known to be hormonal status dependent. The colpocytological study was performed for ten patients in the group with normal uterine cervix. We used karyopyknotic index (KI) and maturation index (MI) as commonly accepted means to assess hormonal status [30]. Figure 77.4 shows OCT cervical images for two patients in the same age group but with different estrogenic saturation level. For the first patient, 24 years old, the KI on the 24th day of the menstrual cycle was 28 and the MI was 0/44/56, the epithelial thickness was measured 250 μm (Fig. 77.4a) in the OCT image. The second patient, 30 years old, on the 17th day of the menstrual cycle, had KI equal to 0 and MI 0/89/11. Accordingly, the epithelial thickness was 160 μm.

More pronounced differences can be observed between different age groups (Fig. 77.5). Pronounced proliferation with KI = 32 and MI = 0/26/51 was detected for a 29-year-old patient on the 12th day of the menstrual cycle. In the OCT image (Fig. 77.5a), the epithelial thickness was 275 μm. Epithelial atrophy with KI = 0 and MI = 12/88/0 was visualized for a 65-year-old patient (Fig. 77.5b) with the epithelial thickness reduced to 100 μm.

Therefore, OCT visualizes and allows objective in vivo measurement of the epithelial thickness variation in the cervical mucosa, including changes related to the hormonal status.

The normal cervical OCT appearance serves as a good baseline, and changes of this pattern can be associated with different benign and malignant pathological conditions.

Cervical ectopy (or ectropion) is a very common benign cervical condition. According to the histological data, the stromal base of ectopy is loose, infiltrated by inflammatory cells, and has a papillary shape with formation of crypts. The stromal papillae are covered by a single-row cuboidal epithelium. In the majority of cases, ectropion is visualized in the form of a non-layered structural image (Fig. 77.6a) in which chaotically located various shaped and brightness regions are observed. Comparing OCT images and histology slides, we found that bright (strongly scattering) parts correspond to the CTS, while dark (weakly scattering) parts correspond to the mucus-filled space between the stromal papillas.

The squamous regeneration process is accompanied by formation of structural elements (open ducts and cervical glands). The OCT is capable of visualizing these structures in vivo (Fig. 77.7).

Once the formation of a mature metaplastic epithelium is completed, the cervical mucosa is visualized as a sharp double-layered image with an even interlayer interface, resembling original squamous epithelium. However, closed cervical glands are seen under that new squamous epithelium (Fig. 77.8), which makes it different from the normal (original) squamous cervical mucosa.

OCT images of inflammatory cervical changes may look different. OCT images still may have a sharp double-layered appearance. However, the contrast between SSE and stroma can be substantially reduced or completely lost. We associate it with the cellular infiltration changing stromal optical properties. In some OCT images, multiple sharp round and/or linear cavities with a low signal level (Fig. 77.9) can be observed. These cavities can be associated with edema and/or cervical glands.

As in normal cervical mucosa, application of acetic acid reduces the stratification contrast and increase brightness of the upper layer (Fig. 77.10).

In some cases, severe inflammation can completely erase the contrast of the epithelium-stromal interface, creating structureless OCT images (Fig. 77.11).

The inflammatory process can be accompanied by epithelial hyperplasia, acanthosis, and papillomatosis, which are visualized as an increase in the upper moderately scattering layer thickness and discontinuous nature of the interlayer interface (Fig. 77.12).