In the broad, varicolored canvas of malpractice law, Jack Olender's request to place an advertisement last month in the New England Journal of Medicine was no more than a background brush stroke. But it was a detailed part of the picture that needs to be noticed if the complexities of suits, verdicts and victims' rights are to be lucidly sorted.

His request, accompanied by a check for $185, was for an advertisement that would run under the headline, ''Tragedy With Cat Scanner.'' It read: ''Important message to those who rely on CT scans: In Washington, D.C., a settlement of $3 million was obtained from a hospital that performed the CT scan and a subsequent hospital where neurosurgery was done. The 8800 G.E. CT Scanner was involved. The right and left sides of the film were reversed, and normal brain tissue from a 16-year-old girl was removed. Result: Permanent short-term memory loss. Answer: Inform other practitioners of this risk. Use a marker on the head rest showing left versus right. Make sure computer is programmed correctly -- feet first. Use check list.''

Olender's effort to place the ad was the follow-up of a pledge he made in late May to alert hospital staffs to heed the details. Olender was in a position to know. On May 21, he was the attorney for the family that won the $3 million settlement mentioned in the ad. In 1982, surgeons at Georgetown University Hospital operated on the wrong side of the girl's brain, following the incorrect labeling of an X-ray by a technician at George Washington University Hospital. Cases have occurred in which surgeons have amputated a healthy limb or left instruments inside the sewn-up body. This time, a cut was performed for a tumor, but the wrong side of the brain was opened.

The patient, now 19, will need lifetime round-the-clock care. On the day of the settlement, the girl's father told a reporter that his brain-damaged daughter can learn nothing new and remembers things for only five to 30 minutes: ''It placed my daughter in another world.''

It also placed her in Jack Olender's world. At 50, he is one of the nation's premier trial lawyers. His specialty is the catastrophic injury case. If malpractice were baseball, Olender would be a starting pitcher in the annual all-star game. His record includes 18 cases with victories and settlements, each worth more than $1 million.

Olender is not little league. Nor is he another malpractice lawyer obsessed with attacking doctors and hospitals. ''If I had 90 percent fewer malpractice cases coming in my door,'' he said last week in his Washington office, ''I'd still have too much business to handle.'' His effort to place the ad in the New England Journal of Medicine was part of his own reconciliation program with doctors. He intended it as a comradely reaching out to the other side.

''I keep seeing the same mistakes over and over,'' he says. ''With the medical technology that's available and with the learning that doctors have, people are being needlessly hurt by plain, careless, dumb human error.''

sk Here the story turns sour. Olender's ad was rejected by the New England Journal of Medicine. The $185 check was returned with a brief note saying that under the editorial discretion of the magazine, the ad ''has not been accepted.'' When asked later by a reporter about the rejection, the advertising director declined to offer specifics.

Other medical magazines have also refused Olender's ad. Medical Economics, circulation 170,000, said it was a piece of ''clinical instruction and we are not a clinical-instruction magazine.''

As more rejection slips come in, Olender is having little trouble getting the message: ''I was naive. I should have known better than to think that the medical industry would cooperate with me to help doctors help themselves and their patients. The medical journals are controlled by doctors. Doctors are so paranoid about malpractice that they reject any help from a plaintiff's lawyer, even when I wanted to pay for the ad to help them.''

The malpractice issue, whether called a crisis or a breakdown, has four sides: patients, doctors, lawyers and insurers. With immense sums of money at stake, doctors nearsightedly see lawyers as enemies and patients as potential enemies. That leaves the insurers free to raise malpractice rates to unprecedented heights. Of the three professional groups, the insurers have been making the weakest justifications for their soaring fees.

The tale of Jack Olender and the medical magazines exemplifies the hardness of the battle lines. Ways need to be found for lawyers and doctors to be on the same side, that of the person who is called client by one group and patient by the other. Olender's way was a fair-minded start. He wasn't acting from greed, though trial lawyers are routinely depicted that way. His gesture was the peacemaker's.