As hospitals digitize patient records and amass huge amounts of data, many are relying on companies such as Microsoft, SAS Institute Inc., International Business Machines Corp. and Oracle Corp., whose data-mining technologies can help them detect patterns and improve medical care. The analytics industry generated more than $30 billion in revenue last year, according to research firm IDC. That is forecast to increase to $33.6 billion this year as the healthcare industry becomes a bigger customer. The use of data-mining technology has already led to some measurable improvements in patient care.