Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We have issued our report dated February 6, 2007, accompanying the consolidated financial statements of TomoTherapy Incorporated and Subsidiaries contained in the Registration Statement and Prospectus. We consent to the use of the aforementioned report in the Registration Statement and Prospectus, and to the use of our name as it appears under the caption “Experts.”

/s/  Grant Thornton LLP

Madison, Wisconsin

February 7, 2007