LOOKING AT LUNGS

      IN THE WAR AGAINST CANCER, AN MRI IS A GREAT DOCTOR'S TOOL, ABLE TO SPOT
A TUMOR WHEN A REGULAR X-RAY NEVER COULD.  MRI'S WORK BECAUSE THEY MAP OUT
WATER IN YOUR BODY, SPECIFICALLY THE PROTONS IN THE WATER.  AN MRI CONSISTS OF
TWO PARTS, FIRST A MAGNETIC FIELD THAT LINES UP THE PROTONS AND SETS THEM
WHIRLING AROUND LIKE LITTLE TOPS. THESE PROTONS GIVES OFF RADIO WAVES, JUST
LIKE YOU HEAR OVER THE RADIO  HE SECOND PART OF THE MRI CAN TUNE INTO THESE
FREQUENCIES, TO MAP THEM AND  RECONSTRUCT A PICTURE OF THE BODY.   THE
PROBLEM IS IT DOESN'T WORK IN THE LUNGS, SAYS PHYSICIST WILLIAM HAPPER AT
PRINCETON UNIVERSITY,

     Happer: "the lungs are mostly empty space.  they're designed to hold air. If you had a lot of
water in them you would . . . be in a lot of trouble.  so they're just no transmitters in your lungs that you
can look at." 

     TO AN MRI THE LUNGS LOOK LIKE JUST A LOT OF WHITE NOISE. BUT HAPPER
THINKS HE'S FOUND A SOLUTION.  YOU CAN'T PUT WATER IN THE LUNGS, BUT YOU CAN
STILL GET RADIO WAVES OUT.  HAPPER AND HIS COLLEAGUES HAVE USED LASERS TO
LINE UP NUCLEI IN HELIUM, INSTEAD OF PROTONS IN WATER.  THE PATIENT THEN TAKES A
DEEP BREATH OF THE HELIUM, FILLING THEIR LUNGS WITH THESE PERFECTLY LINED UP
NUCLEI.  THESE SPIN AROUND IN THE BODY,  GIVING OFF THE RIGHT FREQUENCY AGAIN. 

     Happer: "People who are used to looking at images of lungs can hardly believe the resolution,
it's very much better than anything that's available now."
     
     THE TECHNIQUE HASN'T BEEN TESTED ON HUMANS YET, BUT HAPPER SAYS TRIALS
ARE SCHEDULED FOR THIS SUMMER.  FOR VICTIMS OF LUNG DISEASE, THE SPECIAL
HELIUM SHOUD BE A BREATH OF FRESH AIR.