The incident took place in the Ballymagorry area near Strabane on Saturday afternoon.
Both officers required medical treatment at the scene before being taken to hospital.
The patrol car was significantly damaged in the collision which followed a separate crash involving the same blue Ford van in the Newbuildings area of Derry at 12.45pm.
Chief Inspector Michael Gahan said the vehicle was driven by a man “believed to have been under the influence of alcohol” and who made off from the scene.
“A short time later the offending vehicle came to the attention of police outside Ballymagorry,” he said.
“Officers attempted to stop the van, however, it continued to drive on at the police vehicle, colliding with it head-on.”
“The driver, a 26-year-old man, got out of the vehicle and assaulted both officers at the scene.
“He was restrained and subsequently arrested on suspicion of a number of driving-related offences, as well as assault on police and resisting police.”
Mr Gahan acknowledged the bravery of police officers as he praised the “true community spirit” of two members of the public who intervened.
“Our officers put themselves on the front line to help keep people safe – they do not deserve to be assaulted for doing their jobs and in this case, attempting to stop a dangerous driver on our roads,” he said.
“I would also like to commend two members of the public who stopped and assisted the officers at the scene as they faced challenging circumstances.
“Their actions were brave and admirable for intervening to help – a reflection of true community spirit.
“Both officers are being supported and receiving the appropriate care and welfare measures from within the Police Service as our enquiries continue.”
Two PSNI officers were injured after their poice car was rammed near Strabane on Saturday afternoon.
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Detectives have appealed to anyone who witnessed what happened or anyone with relevant information that could help with enquiries to call 101, quoting reference number 684 20/09/25.
“We would also be keen to hear from anyone who may have dash-cam, CCTV or other footage of the area,” Mr Gahan added.
“Anyone who may have information can contact PSNI online at or anonymously via Crimestoppers on 0800 555 111”.