Treatment Techniques for the Pelvis Region - Prostate - (- Cervix Ca -) Uwe Götz, Bernd Schicker...

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Treatment Techniques for the Pelvis Region

- Prostate-(- Cervix Ca -)

Uwe Götz, Bernd Schicker Institute of Radiation Oncology Limburg,

Germany

Treatment Techniques for the Pelvis Region - Prostate

Textbook TechniquesTreatment Techniques for the Pelvis Region - Prostate

Perez & Prady – Principles and Practice of Radiation Oncology

... A variety of techniques have been used, raging from parallel anteroposterior portals with perineal appositional field to lateral portals (box techniques) or rotational fields to supplement the dose to the prostate.In recent years, three-dimesional conformal radiotherapy (3-D CRT) and intensity modulated irradiation techniques have been used increasingly in selected centers.

My Opinion:- Treatment Planing based on Radiograph should be history !- CT based Treatment Planning should be standard – 3-D CRT!

3-D Conformal Treatment Planning

Definition of 3-D CRT:- CT Dataset for Treatment Planning, Spaceing 1-0.5 cm.- Delination and Definition of the Organs at Risk (OR) and Target Volume in each CT slice. - Definition of the field (gantry and collimator angle and field borders) under the Beams Eye View (BEV) of the Treatment Planning System (TPS) - Planning and optimisation of the Dose distribution in each CT slice.- Dose Distribution conformal to TV and OR; ICRU Recomondations

Target Volume

- CT Dataset with 22 CT Slices- Spaceing 0.5 cm.

Treatmen Planning – AP / PA Fields

Treatmen Planning – AP / PA

DVH – AP / PA Fields

Treatmen Planning – Box Fields

DVH – Box Fields

DVH – AP / PA Fieds vs Box Fields

Improvement – Box Fields

Homegneous Dose Distribution the Target Volume Quality Index of 94

High Dose to the Oragn atRisk (Rectum)

NOT OK !!!

Improvement – Box Fields

High Dose to the Organ atRisk (Rectum)

NOT OK !!!

Solution:

Find the area at the ORwith high dose level

Find the Area at the ORwith a high dose level

Modification of the AP / PA Fields

Area that should be protected to reduce the dose dowards the OR

Solution:Shielding by a satelite or Multi Leaf Collimator

Field Setup of the Box Technique

180° Field / Collimator Rotation to 270°

Dose Volume Histohgram

DVH – Box vs Improved Box

Advanced Techniques - Crossfire Technique -

Clinical Case:70-year old patientDiagnosis: Adenocarcinoma of the prostate. PSA- Increase to 8.22 ng/ml.Histology: Medium- to low graded differentiated adenocarcinoma of the prostate; tumor stadium pT3a, N0, M0, G2, R1 (Gleason-Grading: 7).Therapy: Status after radical perineal prostaticovesiculectomy. For a better tolerance, at an aimed total dose of 76.4 Gy, the therapy starts with the boost series applied to the tumor bed (Dose per fraction: 2.0 Gy; total dose: 26.0 Gy). The main series provides the box of the prostate and the loco regional lymphatic drainage area with a dose per fraction of 1.8 Gy at an total dose of 50.4 Gy.

Advanced TechniquesTreatment Techniques for the Pelvis Region - Prostate

Target Volume Definition:The target volume of the primary series contains the primary tumor and the lymph nodes. Normally the target volume contains the primary tumor which means the prostate and the seminal vesicles. In the case of smaller tumors the seminal vesicles could be excluded from the target volume. In the cranial area the target volume begins at the bifurcation of the A. iliaca communis in the A. Iliaca interna and externa.

Target Volume:

Patient Modell:Room View

Target Volume (red)Urinary Bladder (blue)Tectum (green)

Beam Setup:A monoisocenter technique composed by eight fixed fields with individual absorbers and wedges are arranged around the patient in a nearly equidistant angle was developed. The lateral fields only cover the whole target volume. The fields with a diagonal beam direction respectively limit to one side of the target volume and enable in this way an adaption to its biconcave shape. 54

Physical Treatment Planning:The common isocenter of all fields is located in the center of the body, in this case 6 cm in the dorsal direction of the cranial edge of the symphysis. Here the eight fields are divided intothree groups. The first two groups forma self- contained functional unit in which the field- and absorber borders as well as the weighting have to be reconciled with each other.

Group I - Field 1 to 3:Dose adaption to the concave part in the direction to the urinary bladder and the cranial divided area of the target volume.

For the beam direction of the field 2and 3 in the beam´s eye view a gantryposition is searched in which the tangent to the ventral tip of the target volume coincides with the center of the“bottom” of the target volume.

Fie ld 2 Fie ld 3

An individual absorber in field 2 (in field 3 correspondingly symmetrical) protects in the complete cranial part of the target volume the contra lateral side of the target volume (arrow). Caudalward both fields cover the target volume at its complete width. Because of the half sided absorbing in the cranial part a symmetrical underdosage is the result, which is compensated through a separate field (field 1). Its beam direction is at gantry position 0° and enables with the central absorber, especially in the bipartite area of the target volume, a maximum protection of the healthy tissue. The caudal field boundary of field 1 geometrically coincides with the caudal edge of the absorber of field 2 (and 3) what can be seen in the beam’s eye view.

Fie ld 2

The caudal field boundary of field 1 geo-metrically coincides with the caudal edge of the absorber of field 2 (and 3) what can be seen in the beam’s eye view.

Fie ld 5

Group II - Field 4 to 6Dose adaption to the concave area to the rectum and in the cranial divided part of the target volume.

The interplay of the field 4 to 6 is similar.Here the absorber (arrow) is shown which enables to adapt the course of the isodosesto the concave shape of the target volume in the area of the rectum. Cranialward the field ends near the bifurcation of the target volume. Cranialward field 4 from 180° links up to the fields 5 and 6.

Group II - Field 4 to 6

Cranialward field 4 from 180° links up to the fields 5 and 6.

Group III - Field 7 and 8Relief of the normal tissue ventral- and dorsalward of the target volume.

The fields 7 and 8 are a variation of the conventional “Box”-Technique. But they are inclined dorsalward in that way (here 2°), that the dorsal field boundaries coincides in the relevant area of the rectum.

All fields with a diagonal beam direction are equipped with a 60° wedge (with the tip in the lateral direction), to relieve thearea which is covered by all the fields and is situated in the center of the target volume (yellow area).

Field configuration in the middle section of the target volume.

Beam Parameter:

Dose Distribition

D o s e D is tr ib u t io n in th e D ig ita lly R e c o n str u c te d S e c t io n

Fron ta l section La te ral sag itta l section M edian sagitta l sec tion

1 0 0%

8 5% 8 0% 7 0%

3 0 % 1 0%

Dose Distribution

Dose Volume Histogram

2nd International Symposium on Target Volume Definition - Limburg - May 30 - June 01 2002

Conformal Technique for

CERVIX CARCINOMA

Short Overview

Bernd Schicker

Uwe Götz and I. Chr. Kiricuta ISRO-Limburg - Germany

TARGET VOLUME DEFINITION

LIMBURG-TECHNIQUE

Field set up in the „V“-shape area of the PTV

Field set up in the cranial and caudal part of the PTV

How to use the marker in the „V“-shaped area of the PTV

FIELD PARAMETER

How to use a MLC

DOSE DISTRIBUTIONin sagittal reconstructed slices

A B C BC A

DOSE DISTRIBUTION in CT-slices

DOSE VOLUME HISTOGRAM

Thank You Very Much

Treatment Techniques for the Pelvis Region - Prostate - (- Cervix Ca -) Uwe Götz, Bernd Schicker...

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