INFLUENCE OF PHANTOM MATERIALS ON THE DEPTH-DOSE PERCENTAGE FOR RADIATIONS OF DIFFERENT ENERGIES

Journal Article · Mon Jan 01 04:00:00 EST 1962 · Radiologia Clinica (Switzerland) Published 1965-1974 as Radiol. Clin. Biol. Changed to Diagn. Imag.

OSTI ID:4634839

Tori, G; Miceli, R; Corinaldesi, A; Bono, F

By use of several sources of the high-energy radiations (Cs/sup 137/, Co/ sup 60/, and 2-Mev Van de Graaff electrostatic generator) and conventional x rays, comparisons were made of ionimetric data to study the behavior of the radiations generated by each of these sources in phantoms of different materials which are usually employed in experimental radiological dosimetry: water, bolus alba, paraffin, talc, rice, and sodium bicarbonate. Preliminary experiments carried out on these materials, using various energy levels of radiation, indicated instances of analogous behavior between some of them; paraffin showed properties superimposable on those of rice and bicarbonate, bolus alba on those of talc. Water, on the other hand, had characteristics of its own. Thus a detailed examination was made of water, paraffin, and bolus alba with respect to surface and depth doses of radiations of different energies in phantoms of these materials. Changes in the surface dose, measured at the center of the field of irradiation when its area is varied, with 180-kev x rays and Cs/sup 137/, are similar in paraffin and bolus alba, but differ in water. The increase in surface dose according to the area of the field, is less marked for Co/sup 60/ and 2-Mev radiation. These curves relative to Co/sup 60/ and 2-Mev, both in paraffin and in water, are practically identical, the one superimposable on the other, while the Cs/sup 137/ curve has a position midway between them and the 180-kv curve. In bolus alba, on the other hand, the Co/sup 60/ and 2-Mev curves diverge; the depth dose percentage for Co/sup 60/ is considerably greater. The Cs/sup 137/ curve, even though it occupies an intermediate position in this material, is nearer to the high-energy curves than to that of 180 kv. Variations of the dose at a given depth (10 cm) in the materials in relation to the increase of the surface area showed that for the high energies (Co/sup 60/ and 2-Mev electrons) the increase of the depth dose percentage relative to the area of the field is greater in paraffin than in water and bolus alba. For the Cs/sup 137/, on the other hand, the increase of the depth dose percentage shows no variation in the three materials, but 180kv radiation, the increase is greater than for the other energies and is higher in paraffin than in water aid bolus alba. Tests were made to determine which of the three materials approaches most nearly the absorption and diffusion conditions in various body regions irradiated with different energies. Values of the emergent dose in vivo were evaluated during irradiation of various parts of the body (skull, mediastinum, lung, medial abdomen, lateral abdomen, and thigh) in 30 patients. The emergent dose for each part of the body was expressed as a percentage of the incident dose. The ratio between the emergent doses for various irradiated body parts appear less for some than in others. For example, in thorax, since the thickness is made up for the most part by the lung, the values of the emergent dose are 10% of the incident dose in conventional and 39% in Co/sup 60/ radiation. For denser anatomic parts such as the skull, the emergent dose values are, respectively, 6% and 43%. It follows that bolus alba for radiations of 180 kv is nearest to in vivo radiodensity, if the lung is excluded. For Cs/sup 137/, the material whose behavior most resembles that of living tissues is water; the same applies to 2-Mev radiation, again excepting the lung. However, water with Co/sup 60/ gives doses similar to those in living tissues for the mediastinum, thigh, and central abdomen while for the skull and lateral abdomen, paraffin shows the values nearest to those noted in patient dosimetry. (BBB)

• Research Organization: Universita, Bologna
• NSA Number: NSA-17-038675
• OSTI ID: 4634839
• Journal Information: Radiologia Clinica (Switzerland) Published 1965-1974 as Radiol. Clin. Biol. Changed to Diagn. Imag., Journal Name: Radiologia Clinica (Switzerland) Published 1965-1974 as Radiol. Clin. Biol. Changed to Diagn. Imag. Vol. Vol: 31; ISSN RACLA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ABSORPTION
BIOLOGY AND MEDICINE
CALCIUM CARBONATES
CEREALS
CESIUM 137
COBALT 60
LUNGS
MAGNESIUM SILICATES
MAN
MEASURED VALUES
MINERALS
MOCKUP
PARAFFIN
RADIATION DOSES
RICE
SODIUM CARBONATES
SURFACES
TALC
TISSUES
VAN DE GRAAFF ACCELERATORS
VARIATIONS
WATER
X RADIATION