Establishment of a Modified Ferric Chloride-Induced Superior Sagittal Sinus Thrombosis

In our field, several modeling methods for superior sagittal sinus thrombosis are used. However, the ferric chloride induction method is widely used due to its simplicity and the low cost. We aim to refine the ferric chloride-induced superior sagittal sinus thrombosis model by reducing cortical injury and visualizing sinus thrombus.

To begin, apply ophthalmic ointment to both eyes of an anesthetized rat and shave the scalp hair carefully. Then, secure the rat in a prone position on a rodent operating platform using medical tape. Maintain the body temperature at around 37 degrees Celsius with a heating pad.

Disinfect the shaved scalp thoroughly using 5%povidone-iodine, followed by 75%alcohol, and repeat three times each. After confirming anesthetic depth by toe pinch reflex, make a 15-millimeter peri-median skin incision on the scalp. Using blunt dissection, separate the underlying fascia and periosteum to expose the skull fully.

Thin the skull using a cranial drill until the superior sagittal sinus is clearly exposed, starting from the lambda and extending 10 millimeters anteriorly along the sagittal suture. Employ an intermittent drilling technique to avoid damage to the underlying dura mater and superior sagittal sinus, and repeatedly irrigate the drill bit with normal saline to prevent thermal injury to the cortex. After imaging the baseline conditions, apply a 10-millimeter segment of 2-0 silk suture soaked with 40%ferric chloride solution onto the exposed superior sagittal sinus surface for five minutes.

Replace the suture with a newly soaked segment and apply for another five minutes. Then, rinse the surgical field with 0.5 milliliters of normal saline three times to remove residual ferric chloride. Close the skin using interrupted sutures with 4-0 silk suture, and disinfect the area with povidone-iodine.

Observe the rat until it is fully awake, then return it to its cage. Turn on the laser speckle contrast imaging system and the corresponding software, RF LSI version five. Press the online mode button to activate live imaging.

Adjust the height and position of the instrument until the indicator laser is centered within the field of view. Place the rat on a foam platform, and adjust its position until the superior sagittal sinus aligns with the indicator laser. Adjust the magnification and focus until the image is displayed clearly.

Set the lower and upper limits of the pseudocolor threshold to optimize the visual appearance of the pseudocolor image. Set a circular ROI over the superior sagittal sinus, record venous flow, and save the original and pseudocolor images. Prepare isoflurane, ultrasound gel, disposable razor blades, medical tapes, and check all the instruments required.

Install the three-dimensional acquisition motor onto the imaging system. Then, install the UHF 57X transducer, and initialize the motor. After anesthetizing the rat, place it in a prone position on the thermostatic imaging plate set to 37 degrees Celsius, and gently secure the head and limbs using medical tapes.

Apply ultrasound gel evenly over the exposed scalp. Adjust the position and orientation of the rat relative to the transducer until the superior sagittal sinus and intraluminal thrombus are clearly visualized. Acquire sequential tomographic images of the superior sagittal sinus in the sagittal plane using three-dimensional imaging in B mode with a step size of 0.04 millimeters, followed by tomographic images in the coronal plane using the same settings.

Use color Doppler mode to observe blood flow in the superior sagittal sinus, and apply pulsed-wave Doppler mode to measure blood flow velocity. Discontinue anesthesia and observe the rat until it is fully awake. Then, return the rat to its cage.

Finally, export the acquired images, and analyze them using Vevo LAB software. Record the maximum sagittal and coronal cross-sectional areas and the volume of the thrombus in the superior sagittal sinus, along with the maximum blood flow velocity of the sinus. After local application of ferric chloride, laser speckle contrast imaging detected a significant reduction in local blood flow in the superior sagittal sinus compared with baseline.

On postoperative day seven, small animal ultrasound confirmed thrombus formation in the superior sagittal sinus with partial luminal recanalization. Pulsed-wave Doppler ultrasound demonstrated measurable blood flow velocity within the residual lumen of the superior sagittal sinus. Three-dimensional ultrasound imaging enabled volumetric measurement of the superior sagittal sinus thrombus using serial image slices with a thickness of 0.04 millimeters.

Our refined model is less invasive and more compatible with ultrasound imaging, enabling more reliable, direct therapeutic development and evaluation. Make sure that interoperative laser speckle contrast imaging confirms model's success and postoperative high-resolution ultrasound dynamically monitors thrombus formation, lysis, and lumen recanalization.