Computer-Aided Three-Dimensional Visualization in the Treatment of Locally Advanced Thyroid Cancer

Summary

In diagnosing and treating locally advanced thyroid cancer, the application of computer-aided three-dimensional reconstruction can provide additional information regarding the tumor scope and anatomic characteristics, thereby assisting in risk assessment and surgical planning.

Abstract

The diagnosis and treatment of locally advanced thyroid carcinoma are challenging. The challenge lies in the evaluation of the tumor scope and the formulation of an individualized treatment plan. Three-dimensional (3D) visualization has a wide range of applications in the field of medicine, although there are limited applications in thyroid cancer. We previously applied 3D visualization for the diagnosis and treatment of thyroid cancer. Through data collection, 3D modeling, and preoperative evaluation, we can obtain 3D information regarding the tumor outline, determine the extent of tumor invasion, and conduct adequate preoperative preparation and surgical risk assessment. This study aimed to demonstrate the feasibility of 3D visualization in locally advanced thyroid cancer. Computer-aided 3D visualization can be an effective method for accurate preoperative evaluation, the development of surgical methods, shortening the surgical time, and reducing the surgical risks. Furthermore, it can contribute to medical education and doctor-patient communication. We believe that the application of 3D visualization technology can improve outcomes and quality of life in patients with locally advanced thyroid cancer.

Introduction

Thyroid cancer is the seventh most common malignancy in China¹, and surgery is the most important treatment method^2,3. Complete resection of the tumor is strongly associated with high survival rates and a good quality of life in patients with locally advanced thyroid cancer^3,4; however, this type of resection is challenging. The neck contains important organs and tissues, such as the trachea, esophagus, and common carotid artery. Resection for advanced thyroid cancer is even more risky and difficult considering the proximity of such tumors to important organs and large blood vessels in the neck and mediastinum^5,6. Thus, adequate preoperative evaluation is necessary.

Currently, computed tomography (CT), magnetic resonance (MRI), and color Doppler ultrasonography, which are widely used in clinical settings, provide a two-dimensional (2D) view, which limits the evaluation of the tumor volume, boundaries, and relationships with important surrounding structures^7,8. Substantial clinical experience and efficient trial and error are required before surgeons can translate 2D images into 3D space. Computer-aided 3D visualization can use 2D imaging to create a more intuitive 3D model that can be used for preoperative planning and treatment plan selection, thereby making doctor-patient communication more intuitive and reducing doctor-patient disagreements. Although the model provides 3D visualization, it is intangible. This 3D-guided preoperative evaluation and preparation can shorten the surgical time and reduce the surgical risks. The 3D approach has been widely used in hepatobiliary surgery, orthopedics, and oral and maxillofacial surgery^9,10. In thyroid cancer, 3D visualization is currently used to assist in ultrasonic diagnosis and in the formulation of surgical plans^{11,12,13,14,15}.

Therefore, we believe that 3D visualization can be conveniently applied to the diagnosis and treatment of locally advanced thyroid cancer. This visualization method includes CT acquisition, computer-aided 3D modeling, and preoperative evaluation using 3D models. The 3D models can be used to determine surgical difficulties, surgical risks, and the potential postoperative functional status. Surgeons can engage in detailed doctor-patient communication, surgical plan formulation, and the corresponding surgical preparation¹⁶. Furthermore, this method can provide an adequate preoperative assessment of patients, reduce the surgical risks, and improve patient satisfaction without increasing patient trauma.

Protocol

This study protocol was approved by the Ethics Committee of Sichuan Cancer Hospital (Approval date: September 27, 2019). All the procedures involving human participants were performed in accordance with the ethical standards of the institutional and national research committees, as well as the 1964 Declaration of Helsinki and its later amendments. Written informed consent was obtained from all the patients before surgery.

1. Inclusion and exclusion criteria

1. Include patients if (1) they have pathologically confirmed thyroid cancer and require surgical treatment; (2) they have extensive local tumor infiltration, such as T3-T4 (American Joint Committee on Cancer TNM staging, eighth edition), or if metastatic lesions have invaded important structures such as the trachea, esophagus, and large vessels; (3) they and their family members volunteer for computer-aided 3D visualization; and (4) they had no contraindications to anesthesia.
2. Exclude patients if they do not undergo surgical treatment.

2. Imaging acquisition

1. Obtain plain and enhanced CT (including venous and arterial phases) images of the patients using a 256-layer spiral CT system. The scanning parameters are as follows: 120 kV, 120 mA, 512 x 512 matrix, 0.625 mm layer thickness, 150 HU threshold, and 10-20-s arterial scan delay.
2. Obtain the scan data from the CT system in DICOM format.

3. Computer-aided 3D modeling

1. Import the data into the 3D visualization software (Figure 1A).
   1. Click on the Open button to select the document containing the patient data in DICOM format. Import the data into the software.
   2. Process the data for Gaussian smoothing if the original data contain a lot of image noise (Figure 1B). Select the data with the right mouse button, and then click on the Gaussian Smoothing button.
2. Reconstruct different structures in the target area (chest and neck) individually.
   1. Select Different Models (for example, skin and bone) in the software according to the structure to be reconstructed (Figure 2A).
   2. Set the Color, Maximum Threshold, and Minimum Threshold based on the reconstructed structure on CT (Figure 2B). Set different thresholds for the bone and skin. Adjust the upper and lower thresholds based on the observed preview effect (Figure 2C).
   3. Click on the Calculation button to complete the preliminary 3D model reconstruction (Figure 2D).
3. Modify the segmented data.
   1. Once the segmentation data of structures such as the blood vessels, skin, and bones are obtained (Figures 3A-C), use the Smoothing Algorithm button to optimize the segmented data and ensure the reconstructed saw-tooth edges match the real tissue.
   2. Then, use the One-Click Navigation button to locate the 2D and 3D images (Figure 3D), and determine whether the segmentation effect was accurate. Use the Pen or Brush tool to fix the incorrect layers (Figure 3E).
      ​NOTE: The 3D modeling is achieved after obtaining the segmentation data of all the structures.

4. Preoperative evaluation

1. View the 3D model, and pay close attention to the tumor volume and location and the relationships between the tumor and the adjacent tissues using the Magnification, Rotation, Tissue Transparency, and Separation functions and a combination of various structures. For example, observe the extent of tumor invasion in the common carotid artery, esophagus, and trachea.
2. Determine the scope of surgical resection, the degree of functional impairment after resection, and the postoperative adjuvant therapy plan based on the 3D model evaluation. Implement effective and intuitive doctor-patient communication to satisfy the patient's expectations and explain the surgeon's treatment plan.

5. Surgery

1. Remove the tumor according to the preoperative plan and the intraoperative observations of the tumor and the affected vital organs.
2. Perform tumor-reducing surgery with intraoperative labeling for postoperative adjuvant therapy in the absence of a repair plan.
3. Repair defects caused by the resection, and perform functional reconstruction as necessary based on the operative plan and intraoperative situation.

Results

From December 2017 to July 2021, 23 patients with locally advanced thyroid cancer underwent 3D modeling. Of these 23 patients, 4 were excluded from surgery owing to surgical risks, and the remaining 19 patients were treated with surgery following 3D modeling (Table 1). All 19 patients had locally advanced thyroid cancer, including 14 for whom this was the initial diagnosis, 16 who had varying degrees of dyspnea, and 18 who had large tumors in the neck (primary thyroid tumor or metastatic lymph node) that...

Discussion

For recurrent and metastatic differentiated thyroid carcinoma (DTC), surgical treatment is still preferred¹⁷. The 5 year disease-specific survival rate of patients with DTC and R0 resection is 94.4%, which is significantly higher than that of patients with R1 resection (67.9 %)². Achieving disease control in the neck is crucial for attaining a better quality of life and disease-specific survival for patients⁴. Medullary thyroid carcinoma is mainly tr...

Materials

Name	Company	Catalog Number	Comments
Brilliance 256-layer spiral CT system	Philips Healthcare, Andover, MA, USA	N/A	Used for plain and enhanced CT imaging
3D-Matic digital medical software application	Anhui King Star Digital S&T Co. Ltd.	N/A	Used for computer-aided 3D visualization reconstruction