* Australian IPO launches hit by high market volatility
* Private equity firms considering off-market sales
* Australia shares down 6 pct so far in 2015 (Adds IPO market context)
By Byron Kaye
SYDNEY, Oct 1 (Reuters) - Australia's largest X-ray provider I-MED Radiology Network cancelled a A$500 million ($350.45 million) initial public offering because of volatility in global markets, a person with direct knowledge of the situation told Reuters on Thursday.
I-MED's owner, Swedish private equity firm EQT Holdings AB, pulled the sale of a 50 percent stake in the company after company representatives finished a roadshow in Asia, added the source, who asked not to be identified because he was not authorised to comment publicly.
The decision to pull the sale came a day after smaller rival Integral Diagnostics priced its IPO at the bottom of a target range of A$133 million to A$157 million, but the catalyst behind EQT's decision was overall market volatility, said the source.
Australian shares have experienced substantial gyrations in 2015 as concerns about a slowdown in top trading partner China hit commodities prices. Stocks .AXJO are down 6 percent so far in 2015 and the three months to end-September were their worst quarter in four years.
An I-MED spokeswoman and the bank appointed to advise on the IPO, Rothschild, were not immediately available for comment.
Private equity-backed IPOs have slumped accordingly, to about a quarter of 2014's record level, as buyout firms consider holding on to their investments or trade sales to sidestep a skittish market.
In June, South African insurer Hollard Group pulled a listing of its Australian unit that sought to raise nearly A$1 billion while New Zealand wood products firm Carter Holt Harvey delayed a dual Australian-New Zealand IPO worth about the same amount because of investor uncertainty.
The biggest Australian listing of the year so far, software maker MYOB Ltd MYO.AX , is trading below its issue price, while fruit and vegetable producer Costa Group Holdings CGC.AX is trading at a 1 percent premium to its issue price.
($1 = 1.4267 Australian dollars)