Enhanced Communication of Tumor Margins Using 3D Scanning and Mapping

Summary

A novel method for 3D scanning and virtual mapping of cancer resections is proposed with the goal of improving communication among the multidisciplinary cancer care team.

Abstract

After oncologic resection of malignant tumors, specimens are sent to pathology for processing to determine the surgical margin status. These results are communicated in the form of a written pathology report. The current standard-of-care pathology report provides a written description of the specimen and the sites of margin sampling without any visual representation of the resected tissue. The specimen itself is typically destroyed during sectioning and analysis. This often leads to challenging communication between pathologists and surgeons when the final pathology report is confirmed. Furthermore, surgeons and pathologists are the only members of the multidisciplinary cancer care team to visualize the resected cancer specimen. We have developed a 3D scanning and specimen mapping protocol to address this unmet need. Computer-aided design (CAD) software is used to annotate the virtual specimen clearly showing sites of inking and margin sampling. This map can be utilized by various members of the multidisciplinary cancer care team.

Introduction

The goal of oncologic resection is the complete removal of cancer with surgical margins microscopically clear of tumor cells. In head and neck cancer, the surgical margin status is the most important pathologic risk factor¹. A positive surgical margin increases the risk of 5-year local recurrence and all-cause mortality by >90%². Despite advances in medical technology and surgical techniques in recent years, positive margin rates in head and neck cancer remain high³. For locally advanced oral cavity cancers, the positive margin rate within the United States is 18.1%⁴.

For head and neck surgeons to ensure complete oncologic resection while minimizing disruption of surrounding structures, intraoperative sampling of margins via frozen section analysis (FSA) is performed. FSA provides a rapid intraoperative pathology consultation that is widely used and is the standard of care^5,6,7,8,9. Fresh tissue is frozen, thinly sliced, placed on a glass slide, and stained for immediate interpretation while the patient is still under anesthesia.

Head and neck oncologic specimens present several distinct challenges in accurately assessing margin status, including the anatomic complexity of head and neck cancer specimens, the minimal reserve in the head and neck region for wide excision given the proximity to vital structures such as the eyes, face, and important nerves and vasculature, and the multiple tissue types often present in the resected specimen (i.e., mucosa, cartilage, muscle, bone)^10,11. Thus, a specimen-based approach to margin analysis requires an enhanced level of communication between surgeon and pathologist¹². A face-to-face conversation is often warranted to ensure correct specimen orientation and discussion of concerning margins. However, this is not always safe or feasible as it requires either the surgeon to leave the operating room (OR) while the patient remains under general anesthesia or the pathologist to leave the gross pathology lab, interrupting their workflow. In addition, there may be a significant travel time between the OR and the pathology lab, or in some cases, the pathology lab may be off-site altogether.

Following FSA, the oncologic specimen is fixed in formalin and formally processed through inking, sectioning, and margin sampling. Slides are created and microscopically interpreted by the pathologist to create a final pathology report. For complex head and neck cancer resection, this can often take 1-2 weeks. Unfortunately, processing of the specimen commonly results in the destruction of the resected cancer specimen. This may create further confusion as the final pathology report, multidisciplinary tumor board discussions, adjuvant radiation therapy planning, and re-resection in the setting of positive margins, must all proceed without a visual record of the oncologic specimen and its pathologic processing.

To address this clinical unmet need, we have developed a 3D scanning and specimen mapping protocol to enhance communication between surgeons, pathologists, and other members of the multidisciplinary cancer care team.

Protocol

This protocol was performed at Vanderbilt University Medical Center under IRB#221597. Patients provided written consent for ex vivo 3D scanning and digital mapping of their surgical specimen prior to surgery and the addition of their scan to a 3D specimen model biorepository. Inclusion criteria were patients 18 and older with a suspected or biopsy-proven head and neck neoplasm undergoing surgical resection. 3D specimen maps were created based on surgeon and pathologist preference and staff availability.

This protocol follows the guidelines of the human research ethics committees of the Institutional Review Board (IRB#221597) at Vanderbilt University Medical Center. All subjects provided written informed consent prior to participation. All patient data have been de-identified.

1. Setting up the 3D scanner

1. Identify a 3 x 2 ft flat workstation available for scanner setup. Ensure the workstation is a dark environment where the scanner is enclosed or that the lights in the room are turned off. Alternatively, perform 3D scanning within a mobile cart setup as seen in Figure 1.
2. Set up the three-legged camera tripod on the flat workstation. Carefully place the 3D scanning camera into the tripod. Angle the camera down toward the workstation at a 60° angle.
3. Connect the two-part power cord to an external power source and the back of the camera.
4. Place the scanner turntable 1 foot in front of the 3D camera and tripod setup. Connect the turntable to the camera using the micro-USB cable.
5. Connect the camera to the laptop computer using the camera to USB cable. See Figure 2 for the labeled setup.
   NOTE: If the laptop computer does not have a USB port, an external USB adapter may be required. An external mouse is recommended.
6. Turn off the lights in the workstation to calibrate the scanner to current lighting conditions.
7. Press and hold the power button on the back of the camera until a blue light appears.
8. Open the 3D capture software on the computer desktop. Center the turntable in the cross projected by the camera.
   ​NOTE: Ensure the camera is powered on and the lights are off prior to opening the software.

2. Specimen handling

1. Obtain the resected oncologic specimen from the surgical team.
2. Rinse the specimen to remove any blood or excess clots from resection. Gently pat dry.
   NOTE: This step is very important to obtain a high-quality scan. The 3D scanner has difficulty picking up data when a specimen is very shiny or has residual blood on the surface.
3. Place the specimen on a flat, clean surface.
4. Using a smartphone camera or digital camera, obtain high-quality 2D images of the specimen. Obtain one photograph of the anterior surface of the specimen. Flip the specimen over exactly 180° and obtain a second photograph of the posterior surface of the specimen.

3. 3D scanning following en bloc resection of solid tumor

1. Place a thin sheet of plastic on the 3D scanner turntable to protect the target points from human tissue. Place the specimen onto the plastic sheet with the anterior surface facing up.
2. Click on the 3D scanner software application on the desktop of the laptop.
3. Click on the 3D scanner icon on the right side of the screen. Click on the New Work button.
4. Create a new folder, using a naming convention that is easy to understand.
   NOTE: Naming convention recommendation: YYYY-MM-DD_SPECIMENTYPE
5. Click on Texture Scan. Leave the open global markers file section blank.
6. Adjust all fixed settings in the menu on the left side of the screen (Figure 3). Select HDR OFF. select the ON option for With Turntable. Set align mode = Turntable Coded Targets, turntable steps = 8, turntable speed = 10, and turntable turns = One Turn.
7. Adjust the brightness by sliding the brightness slider bar to the right to maximize the exposure (redness) on the dark surfaces of the specimen as demonstrated in Figure 3.
   NOTE: Attempt to maximize the exposure (redness) on the dark-colored parts of the specimen (muscle, soft tissue) without overexposing (too red) the light-colored parts of the specimen (bone, teeth).
8. Click on the triangle play button on the right-hand toolbar labeled Start Scan or press the spacebar to start the first round of scanning. Wait for the platform to complete all eight rotations (~4 min). Do not touch the scanner or turntable during this step.
9. Once complete, rotate the scan to see if there are any scan data captured outside the green dots displayed on the screen or any obvious artifact. Once satisfied, click on the checkmark on the right side of the edit screen to proceed to the next half of the scan.
   1. If any artifact is discovered, press Shift and use the cursor to drag a circle around the artifact outside the intended scan. Look for a red circle that appears around the unwanted artifact. Click on the Delete data button on the right-hand toolbar designated by a garbage can icon.
10. Using gloves, flip over the specimen to expose the opposite surface. Adjust the brightness as necessary, and keep all other settings the same. Repeat steps 3.8-3.9.

4. Alignment and meshing

1. The program will attempt to automatically align the specimen. If the alignment is accurate (rare), proceed to step 4.4. If the alignment is poor (see note), continue to step 4.2.
   NOTE: Accurate alignment is characterized by a fully formed specimen without any gapping or overlap on the sides. The yellow portions represent the inside of the scan and optimal alignment shows the least amount of yellow as possible.
2. For manual alignment, press the align button indicated by a puzzle piece on the right-hand toolbar.
3. Perform three-point cross-registration to geometrically align the two 3D scans.
   1. Click and drag one set of scan data (Group 1 and Group 2) into each of the alignment frames. Place Group 1 in the Fixed box and Group 2 in the Floated box.
   2. Use the right-click function to rotate and position the two halves so that one side shows the outside of the specimen (3D scanned surface) and the other half shows the inside of the specimen (yellow). Orient the two halves such that the silhouettes create the same shape if superimposed. Use the middle scroll button on the mouse to zoom in and out on the specimen.
   3. Identify three clear landmarks on each set of scan data to pick as alignment points that are present on both sets of data.
      NOTE: Choose three points that are roughly equidistant from each other on the edges of the specimen. Use the unique topography of the scans to choose these points.
   4. Press shift and left-click to select the first of three corresponding alignment points on each group of data as described above. Following selection by clicking the two corresponding points, look for a red dot that appears in the chosen corresponding positions. Repeat this process 2x and look for green dots to appear for the second set of chosen alignment points and orange dots for the third set.
   5. Look for the alignment result to appear in the larger pane below the two halves. If the scan is aligned well (see NOTE in section 4.1 for optimal alignment recommendations), proceed to step 4.4. To repeat the alignment process, proceed to step 4.3.6.
   6. To re-select the alignment points, simply press the Control key + Z key to undo previous work or click on the X box in the top right corner of each pane and return to step 4.3.1.
   7. Perform these steps until the alignment result preview is accurate.
4. Select the square Global Optimization button on the bottom right toolbar. Proceed through the optimization screens, clicking the Confirm button each time it is prompted.
5. Once optimization is complete, select the triangular Mesh Model button on the bottom right side of the screen.
6. Choose the watertight model option when prompted. Click on the option for Medium Detail.
   NOTE: High detail takes much longer to render and is not visually better than medium detail.
7. Use the slider bars that appear on the left hand side of the screen to adjust the brightness to 50 and the contrast to 0 when prompted.
8. Click on the Save Your Scan button at the bottom right toolbar. Keep the scaling ratio at 100% to preserve all original dimensions of the specimen.
9. Export the model into 3MF and OBJ file formats and save the file within the folder created at the beginning of the scan. Use the naming convention as outlined in step 2.3.

5. Cleanup

1. Using gloves, remove the specimen from the turn table. Return the specimen safely to the pathology team.
2. Remove the plastic sheet and sanitize it with a wipe. Return it to its bag.
3. Return the scanner turntable and camera to their respective slots in the box. Ensure the camera is protected with a plastic bag or a box.
4. Unplug all cords and replace them in the box.
5. Clean the scanning area with a sanitizing wipe.

6. Virtual 3D specimen mapping

1. When the specimen is ready for processing, set up the workstation to work alongside the pathology team member who will be grossing the specimen.
   NOTE: It is helpful to utilize a rolling computer stand to allow for mobility and to facilitate communication with the pathology team.
2. Set up the laptop computer and external mouse on the workstation. Open the computer-aided design software from the laptop desktop to virtually annotate the 3D model.
3. Click on the Import button indicated by the plus sign icon and import the previously saved 3mf file of the raw scan from step 4.9.
   NOTE: This software does not have an erase function; it only allows the user to undo prior work by pressing Ctrl Z. Be wary that the user cannot go back and change or erase markings on the specimen once the map is saved.
4. Virtual inking
   1. Select the paintbrush tool on size setting 15-30 to outline the borders of each inked region. Use the color palette to graphically represent each inked surface using software paint colors concurrent with the true ink colors.
   2. Use the paintbrush tool on size setting 35-45 to fill in each inked section with its corresponding color.
   3. Confirm with the prosector that all inked sides are correct and take note of the anatomic orientation (anterior, posterior, medial, lateral, deep) of each inked side for the key.
5. Margin sampling
   1. Use the paintbrush tool on size setting 20-25 to diagram perpendicular and shave (en face) margins, distinguished using color coding.
      NOTE: For example, use white to denote perpendicular margins and fuschia to denote shave margins.
   2. Label each sampled section with the number or letter that corresponds to the cassette each section is placed within.
6. Plane cuts
   1. For any plane cuts (i.e., breadloaf cuts completely through the specimen), select the Plane Cut tool from the left-side toolbar. Select Keep Both in the upper left hand toolbar.
   2. Draw the plane cuts through the specimen exactly as the prosector performed. Ensure that the cuts are correct and then click on accept.
7. 3D specimen map completion and export
   1. Confirm with the prosector to verify the accuracy of the completed 3D specimen map. Revise any discrepancies and finalize the map.
      NOTE: An example of a completed specimen map is shown in Figure 4.
   2. In the upper toolbar, click File | Save to save the specimen map. Click File | Export | select .3mf to export the file as a .3mf file.

7. Creating a distributable video

1. Open the presentation software from the laptop desktop.
2. Title the slide file with the corresponding name of the specimen that was mapped.
3. Insert the 2D images taken of the specimen and arrange them on one side of the slide.
4. Select Insert from the top toolbar. Click on the rubber duck icon and select Insert 3D model.
5. Import the .3mf file of the raw scan generated in step 4.9 and the .3mf file of the mapped specimen generated in step 6.7.2.
6. Arrange the 3D models with the raw scan and mapped scan side by side. Arrange the two models so they are in the same orientation/alignment and are the same size.
7. Click on Animations on the upper toolbar | select model #1 | select Add animation | Turntable | change the duration to 10 s | select On click.
8. Select model #2 and repeat step 6.8 for the mapped scan, but at the last step, select With previous instead of On click.
9. Select model #1 and repeat step 6.8, but select Effect Options, change the turntable direction to Up, and select After previous.
10. Select model #2 and repeat step 7.9, but at the last step, select With previous.
11. Select the Animation Pane and click on Play all to check that the scans are rotating at the same time in the same direction.
12. To create a shareable video, click on File | Export | Create video | select medium size file to export a .mp4 video to be shared by email or integrated into a presentation.
    NOTE: An example of the final video is shown in Figure 5.

Results

From October 2021 to April 2023, 28 head and neck oncologic specimens were 3D scanned and virtually mapped according to this protocol. These results were previously published¹³. The majority of the surgical specimens were squamous cell carcinoma (SCC) (86%, n = 24), with the most common anatomic subsites being oral cavity (54%, n = 15) and larynx (29%, n = 8).

In all cases, specimen maps were shared with attending surgeons and pathologists prior to the evaluation of the...

Discussion

Traditionally, there is no visual representation of a resected cancer specimen. Pathologic processing often destroys the specimen. Prior work has demonstrated the feasibility and utility of 3D scanning of oncologic specimens followed by virtual annotation of the models to create 3D specimen maps which are representative of pathologic processing^13,14,15. This provides the multidisciplinary care team with a visual model of the ana...

Materials

Name	Company	Catalog Number	Comments
Computer Aided Design Software	MeshMixer		Virtual annotation software for 3D models
Digital Camera or Cameraphone	iPhone		May use iPhone camera or any digital camera available
EinScan SP V2 Platinum Desktop 3D Scanner	Shining 3D		3D scanner hardware
ExScan Software; Solid Edge SHINING 3D Edition	Shining 3D		3D capture software included with purchase of 3D Scanner
External Mouse	Microsoft
Laptop Computer	Dell XP5	00355-60734-40310-AAOEM	Laptop Requirements: USB: 1 ×USB 2.0 or 3.0; OS: Win 7, 8 or 10 (64 bit); Graphic Card: Nvidia series; Graphic memory: >1 G; CPU: Dual-core i5 or higher; Memory: >8 G
Microsoft Office Suite	Microsoft
Mobile Presentation Cart	Oklahoma Sound	PRC450
PowerPoint Software	Microsoft Office		Presentation software
Sit-Stand Mobile Desk Cart	Seville Classics
USB-c Device Converter	TRIPP-LITE	U442-DOCK3-B	Necessary only if laptop does not have USB