A new technique for the precise localization of the rectum in treatment planning and portal verification for prostate tumors

1841

ASTR Poster Abstracts

Reference Development Smith, V.; Parker, D. L.: Stanley, J. H.; Phillips, T. L.; Boyd, D. P. and Kan, P. T.: Radiology 136:489-493, of a Computed Tomographic Scanner for Radiation Therapy Treatment Planning. 1980.

1.

This

project

was supported

Kishel,

Stephen

Richard

by Toshiba

Corporation.

Russo;~ and Richard

Johnson

Department of Radiation Medicine, Roswell Park Memorial Institute. 666 Elm Street, Bntfalo, USA *Department of Radiotherapy, W.C.A. Hospital, 207 Foote Avenue, Jamestown, S> 14701

NY

1lr26’3 IIsA

The use of lateral treatment portals for prostate tumors may prevent subcutaneous fibrosis, spare. posterior rectal mucosa, help eliminate moist desquamation and provide considerable sparinK 01 the small bowel. The "box technique" as called has a dosimetric advantage of high dose deliverance to a specified treatment An error in p
will

cause

an alteration

of

tumor

dose

and

failure

thr attempt to improve treatment of patients with The plug helps as a means of rectal localization. distribution in relation to tumor dosages.

The plug is an old techniques,

to

cclntro!

performed

we have

prostate

tumors,

evaluate

target volume,

inexpensive, yet valuable method of rectal verifi<,ation using barium for simulation and radiographic anatomy

localizati(jn can now he accurately

disease.

in the treatment

introduced treatment

tht. volume.

rectal rectal

and has proven its Rdvantages over Rectal for portal verification.

of prostate

tumors

with

use of the rectal plug.

of using lateral fields in the treatment of prostate tumors has been proven clinical?! lateral treatment pnrtals require precise posiIn order to achieve such advantages, tioning and verification. With the introduction of a radio opaque rectal plug and the utilization of a films, an attempt has been made tu improve radiation therapy simulator and portal verification the accurate The advantages

over

the

localization

past

years.

of

the

rectum

with

respect

to

the

lateral

portals

in

the

treatment

of

prostate

tumtirs.

P18 IMPROVING

THE REPRODUCIBILITY

Faiz M. Khan, Ph.D., Dept. of Therapeutic

Radiology,

OF TANGENTIAL

Chung K. K. Lee, M.D.,

Box 494 University

FIELDS

FOR BREAST

and Seymour

of Minnesota

TREATMENT

H. Levitt,

Hospitals,

M.D.

Minneapolis,

Minnesota

55455

Setting up tangential fields for breast treatment is a time-consuming procedure. Some of the complex1) matching the superior border of the tangential fields with the inferior border of the ities include: supraclavicular field; 2) matching or achieving a predetermined overlap between the borders of the internal mammary field and the medial tangential; 3) reproducing anatomically the base plane containing the medial and the lateral borders of the tangential fields. Although the above difficulties are well understood, the techniques of solving them vary a lot from one institution to another. A review of some of these techniques has been outlined by Bedwinekl. In this poster we describe an isocentric technique for tangential fields which offers quicker and easier setup as well as improved reproducibility. The salient a) b)

C) d)

features

of the technique

are

setting up the patient with the help of a sagittal laser line, both under the simulator and the treatment machine; predetermining the setup parameters consisting of "setup SSD", L and 8, where the "setup SSD" is measured from sternum at the patient midline, L is the lateral shift of the couch and 8 is the gantry angle; field size is adjusted (without moving the central axis of the beam) to produce the desired match with the internal mammary and supraclavicular field borders; blocking and/or collimator tilt may be necessary to avoid unwanted overlaps.

under

Planning of the setup parameters at the time of simulation the treatment machine will be discussed.

'Bedwinek, John, Treatment of Stage I and II Adenocarcinoma Int. J. Radiat. Oncol. Biol. Phys. 7:1553-1559, 1981.

and the details

of the Breast

of the setup procedure

by Tumor Excision

and Irradiation,