TOKYO (Reuters) - Toshiba Corp (>> Toshiba Corp) is poised to settle on a preferred bidder for its medical equipment unit with an extraordinary executive meeting planned on Wednesday, people with knowledge of the process said.

Canon Inc (>> Canon Inc) and Fujifilm Holdings Corp (>> FUJIFILM Holdings Corp), both Japanese imaging firms with their own medical device units, are considered the front-runners, having put in bids of more than 600 billion yen (4 billion pounds), other people familiar with the matter have said.

The auction of Toshiba Medical Systems Corp, aimed at shoring up Toshiba's capital after a $1.3 billion accounting scandal, represents an unexpected opportunity for rivals to get their hands on a respected manufacturer of diagnostic equipment such as X-ray and magnetic resonance imaging (MRI) systems.

Konica Minolta Inc (>> Konica Minolta Inc), in partnership with European private equity firm Permira [PERM.UL], also remains in the bidding, one person said.

But the contest for a crucial piece of Toshiba appears to be turning into a match-up between two longtime stalwarts of the Japanese tech industry - Fujifilm Chief Executive Shigetaka Komori and Canon CEO Fujio Mitarai.

"It's a one-on-one fight between two old guys with a lot of pride and neither wants to back down," one source said.

The sources declined to be identified because they are not authorised to speak to the media.

Fujifilm, Canon and Konica Minolta declined to comment. Toshiba also declined to comment on the sale process.

Toshiba Medical, the world's second-largest manufacturer of CT scan machines, had annual revenues of 405.6 billion yen in the financial year ended March 2015.

The sale is part of a massive restructuring after the laptops-to-nuclear company admitted to overstating profits from 2009. The costs of this revamp have forced Toshiba to ask three major Japanese banks for additional loans of about 200 billion yen, sources have told Reuters.

U.S. buyout firm KKR & Co (>> KKR & Co. L.P.), which had teamed up with Japanese trading house Mitsui & Co (>> Mitsui & Co Ltd) has withdrawn from the race as the expected sale price rose too high, a separate source said. KKR declined to comment.

The second round of bidding to grant preferred negotiation rights ended on Friday.

(Reporting by Junko Fujita and Kentaro Hamada; Additional reporting by Emi Emoto; Editing by William Mallard and Edwina Gibbs)

By Junko Fujita and Kentaro Hamada