A doctor who once cared for sick children at Don Imus' (search) New Mexico ranch has sued the tart-tongued radio personality for slander, claiming he made false derogatory comments about him on his "Imus in the Morning" show.

Dr. Howard Allen Pearson (search) says in court papers that on at least four days last year, Imus said Pearson "was one of the worst doctors in the world and did not care if children suffered."

Pearson's lawsuit says Imus apparently misunderstood the physician's response to a morning call to treat a child for pain in July 2004.

Pearson left the main house and began a quarter-mile walk to the infirmary. Because the nurse had said there was no emergency, Pearson declined a ride offered by Imus' wife, court papers say.

The doctor says he gave the child pain medicine, and she resumed normal activities. About 45 minutes later, Imus, armed with a gun and a knife, pulled up in his truck, jumped out and began yelling and cursing at Pearson, the papers say.

Reached by telephone at his ranch near Ribera, N.M., Imus confirmed and repeated his disparaging comments about Pearson. He said the lawsuit was "disgraceful."

Imus said Pearson was called to treat "a 16-year-old girl from Afghanistan (search) who had been up all night in abject agony and pain. The place was a quarter mile away and he refused to get in the truck."

Pearson's lawsuit, filed in a Manhattan court Friday, names Imus, NBC, MSNBC and Westwood One Inc., as defendants. It asks unspecified damages for "distress, shock, humiliation and economic loss."

A spokesman for NBC and MSNBC said he had no comment on the lawsuit. Westwood One could not be reached for comment.

Pearson's lawyer did not return calls for comment.

Imus invites children who have been ill to visit his ranch in groups of 10 in the summer and spring.