o

RADIOLOGY WITH ~-RADIATORS

I t is well known that the interaction of B-panicles With matter results in the production of radiation in the x-ray region in the form of characteristic x-rays or b~em~ralung. However, up to the present t ime. no attempts have been made to exploit this effect for use in med ic~e as a radiolog~eal dlagno~Ic t o o l

!

Fig. 1, Experimental arrangement, 1) 'ucecium shield; ~ object being irradiated;

casctte.

In the work being reported here a medical appli- cator COml~islng of �9 $ ~ - T ~~ complex is used as �9

�9 source of 8-radiat lon. The source, with a working di- �9 meter of 5 ram, Is placed at the end of a 16-cen~l- n~eter rod. A circular plastic shield l~ used as prorec- tlon against radiation when ~he appllcato~ is adJu~ed, The $~u in th�9 source is in equilttxium with ym ir, an �9 mount such tha~ the ~u~face Intcnsipj of the r~dlatlon is 330 fea/sec. The radiation consists of B-panic'~les ~.Ch energies of 0.537 Mev trained in the transmt~ta- l~on of Sr ~ in~.o Y ~ , and B-Panlcles wJx~h energle~ of

x I /

~.~ ,, .~-"

Fig. 2. X-ray picture of the t dy of �9 rat. Focal distasted is 10 cm. Len I th of exposure 5

minutes.

9.18 Mev emitted in the transmutation o fY m into �9 uzble L~otope of zlxconium. The mean energy of the B" tadlatlan for Sz m is 0.22 Mev and fotY m is 0.7 M(~v. The half-life for Sr m is ap~oxlmately twenty years and

�9 ) nadioZogy 67o S.4xe r

that o f t ~ is about 82 hours.

The source has a metal shield consisting of 0.05 mm of stainless steel a~d 0.?.5 mm of alum!num, equiva- Ion! to a i00 mg/cm ~ filter. Because of the shielding, the number of 8"particles produced in the decay of Sr ~4 and Y~ is reduced to 3 per cent and 60 per cent of the original number,respectively.

A shield of lutecium0 1.2 cm thick~ is placed between the source and the object being investigated to absorb the ~-r

The interaction of the g-radiation with the material in the source'ttself and In the absorber produces bronX. st:alung and characteristic x-ray radiation which can be used to make x-ray pictureS. In Fig. 1 are shown the details of the experimental apparatus. In Fig. 2 and Fig. 3 are shown x-ray pictures of the body of a rat and �9 human hand.

The radiographs would seem to indicate that x-radiation is given off by ordina~ medical applicators. This radiation is due to the following: a) internal bremst~alung produced in the interaction of the ,q-particles wRh nuclei In the material; h) external bremstralung produced as the 8-panicles are brought to a stop by the nuclei

, . .

~ . ~ . . ~.., ~.' ~ f i

. . . . . i

Fig. 3. X-ray picture of a human hand. Focal dL~ance 10.5 cm. Length of exposure 5 minutes.

able for radiology of various parts of the body.

in the absorber, and c) characteristic x-ray radiation due ~o the interaction of B-particles with orbital electrons in the material of the source, shell, and absorber. The inter- hal brem~:ralung arises in the ~rontium-yRerblum com- plex; the external bwmstralung in the absorbing layers of the source and surrounding material. Since only 3 per cent of the ~-radiation of the strontium penetrates the shield, it may be assumed that some pan of the absorbed g7 per cent of the 8-panicles is transformed into characterL~Ic x-rays and b~em~ralung.

The characto~L~[c x-rays, produced by 8-particles from Sr~'-Y g~ In the foil amount to I x 10 ' z photons for each 8-partlele while the yield of bremstralung for par- deles with higherenergy is approximately 6 x 10"~8-par- ticl~. The internal bremstralung of Srs~ N with energl.cs from I0-150 key exhibits �9 maximum at about 06 key; the radiation produced by the B'panicles of a preparation in tin have two maxima: ~25 kev for the characterlnic radiation and 55 key for the bremnralung. The correspon- ding data for B'Particles of Sr m and ym for interaction In gecl and aluminum are not known. P:elLmlnary measure- ments of the emission spectrum of the radiation Indicate that this radiation is nonuniform and h ~ several hard coln- ponents.

The x-ray pictures obtained with this simple and rel~,- tively weak nuclear source(300 mcurie0 show very good definition and conura~ in spite of the large "working di- ameter" of the source{5 ram) and the short focal length. BeRet x-ray piotures can be obtained by using a source with a smaller working diameter and using other B-radiators In conjunction with materials which emit radiation mote suit-

It Is evident from the x-ray pictures which have been presented ~ t pure B-radiators can be t~ed to obtain radiation which is wRable for medical radlolo~.

L L.