What is Gantry (medical)?

In a medical facility such as a hospital or clinic, a gantry houses radiation detectors and/or radiation sources for diagnosing or treating a patient's disease.Radiation sources may produce gamma radiation, X-rays, electromagnetic radiation or magnetic fields, depending on the purpose of the device.

CT scanner 

The gantry of a computed tomography (CT) scanner is a ring or cylinder in which the patient is placed.The x-ray tube and x-ray detector rotate rapidly in the gantry as the patient moves in and out of the gantry. A CT scanner produces a 3-dimensional X-ray image of the patient.

MRI

The MRI gantry remains stationary and contains cryogenically cooled superconducting electromagnets and radio transmitters that flip the protons in the body's hydrogen atoms through proton nuclear magnetic resonance.The machine then listens and processes the signals from the hydrogen atoms as the protons flip over to create a 3D image of the inside of the patient's body.

Radiation therapy

The gantry of the external beam radiation therapy machine moves the radiation source around the patient.A linear accelerator (linac) is built into the top of the gantry in the photo on the right.The rectangular screen to the right of the gantry is a cone-beam X-ray detector used to help position the patient prior to treatment.The gantry is supported by drive mounts that rotate the gantry on a fixed horizontal axis as the linac rotates around the patient.A klystron in a drive bracket behind the gantry provides RF energy to the linac.A linear accelerator accelerates a pencil-sized beam of electrons horizontally.After leaving the linac, the electrons are deflected by magnets and focused downward, causing the electrons to strike a tungsten target.The target stops electrons, and the sudden deceleration causes bremsstrahlung in X-rays.The photo below is a different gantry rotated to about 45°.The unit mounted on the left side of the gantry is the cone-beam X-ray source, with the X-ray detector on the right.Prior to treatment, a cone beam X-ray system is used to align the patient's tumor with radiation.