High-Resolution Ultrasonography for the Analysis of Orthotopic ATC Tumors in a Genetically Engineered Mouse Model

This protocol helps users to utilize high-resolution ultrasonography to scan, monitor, and measure tumors in the mouse model of anaplastic thyroid carcinoma. Ultrasonography has been proven reliable in mice for imaging tissues that occupy similar body locations as human tissues, including the liver, thyroid, and fetus. To begin, turn on the ultrasonography system, and create a new folder for capturing the images and collecting data.

Then, select the 40-megahertz line probe, click on superficial tissue pattern to activate the superficial tissue transducer, and use the resultant B mode for thyroid imaging. Clean the animal imaging platform, and switch on the heating button for the platform temperature to reach 38 to 40 degrees Celsius before placing the animal on it. Anesthetize the mouse, and place it on the heated platform.

Cover the snout with a nose cone connected to the anesthesia outlet. Then, with the mouse in a supine position, use adhesive tape to fix its limbs to the heated platform. For tumor imaging, adjust the imaging system to optimize the resolution.

Set the two-dimensional gain to 25 to 30 decibels, image depth to 10 millimeters, and center to three to six millimeters. After setting the parameters, liberally apply ultrasound gel to the area of bare skin achieved by using a depilatory cream. Holding the probe, place it into contact with the ultrasound gel on the chest.

Then, scan from the chest toward the neck to locate the thyroid. Identify the anaplastic thyroid carcinoma tumors from the trachea and strap muscles depending on the anatomical location and ultrasound echo. Based on the impression of the total tumor, confirm the image section with the largest left-to-right tumor diameter.

Then, press the freeze button, and measure the anteroposterior and left-to-right tumor diameters using the ultrasound caliper. After completing the scans, wipe the ultrasound gel, and remove the restraining tape from the animal's limbs. The ATC tumor size of the right and left lobes were measured over four time intervals.

On the fourth measurement, the average right ATC size had grown to 11.844 square millimeters, while the tumor size of the left lobe had grown to 9.280 square millimeters, making the total an average size increase to 15.843 square millimeters. Interestingly, in the mouse labeled P92, the tumor size had grown to almost four times larger than the size on the initial measurement. The main advantage of this technique is that ultrasound is flexible and can be performed in real time without any radiation.