* Preliminary Q4 net loss of $0.48/shr vs $4.77 yr ago
* Loss from cont ops $0.15/shr vs $2.19 year earlier
* Q4 revenue falls 39 percent to $51 million (In U.S. dollars. Adds background)
TORONTO, Jan 21 (Reuters) - MDS Inc MDS.TO reported a smaller quarterly loss on Thursday as the Canadian health sciences company narrows its focus to nuclear imaging.
In a preliminary report, the company said its loss had narrowed to $58 million, or 48 cents a share, in the fourth quarter ended on Oct. 31 from $575 million, or $4.77 a share, a year earlier.
The loss from continuing operations, which now consist of its Nordion nuclear imaging division, shrank to $19 million, or 15 cents a share, from $264 million, or $2.19 a share.
Last year the company said it had struck a deal to sell its analytical technologies division and would seek buyers for its pharmaceutical division so that it can concentrate on nuclear imaging.
The year-earlier results included a $246 million write-off from the Maple medical reactor project. Government-owned Atomic Energy of Canada Ltd said in May 2008 that it was halting work on the project because of rising costs and technical problems.
Fourth-quarter revenue dropped 39 percent to $51 million as MDS continued to suffer from the prolonged shutdown of the Chalk River nuclear plant, which produces the bulk of its nuclear isotopes.
The plant, which supplies a third of the world's medical isotopes, was shut down in May after a small leak of heavy water was found.
The reactor will not be operational until at least the end of March 2010, operator Atomic Energy of Canada said, but it cautioned late on Wednesday that this could be extended even further, leaving Nordion to scramble for alternatives.
$1=$1.05 Canadian Reporting by Scott Anderson; Editing by Lisa Von Ahn