Volume 34, Issue 6, June 2007
Index of content:
- Therapy Continuing Education Course: Room M100A
- CE‐Therapy: Accurate Clinical Measurements
34(2007); http://dx.doi.org/10.1118/1.2761610View Description Hide Description
Radiation therapy is rapidly moving into the direction of image guidance, functional target volumes, hypofractionation, dose escalation and 4D deliveries. In this era of joint imaging‐therapy developments, accurate dosimetry techniques are often considered an issue of the past. However, clinical reality increasingly requires dealings with non‐protocol compliant reference dosimetry as well as complex charged particle disequilibrium measurements and their interpretation. This presentation consists of two parts: the first part will review principles of measurementdosimetry, definitions of detectors and phantoms, reference dosimetry for conventional as well as non‐protocol compliant technologies. The second part will review principles of relative dosimetrymeasurements, focusing on scanning and integrated measurements usually performed at time of beam commissioning. We will conclude with a discussion of dosimetry in special cases including the photon build‐up region as well as narrow and dynamic fields.
1. To understand the principles of clinical measurementdosimetry.
2. To get an overview of detectors and phantoms for reference and relative dosimetry.
3. To understand reference dosimetry techniques in protocol compliant and non‐compliant beam arrangements.
4. To understand relative dosimetry techniques for the purpose of 3D dose distributions and to grasp areas of complication.
5. To understand integrated relative dosimetrymeasurements in photon and electron beams.
6. To be aware of non electronic equilibrium types of measurements in the photon build‐up and for small photon fields.
- CE‐Therapy: Multimodality and 4D Image Registration: Methods and Clinical Use
34(2007); http://dx.doi.org/10.1118/1.2761626View Description Hide Description
Acquisition of anatomic and functional data from magnetic resonance imaging and nuclear medicine studies is becoming increasingly common for patient management in radiation therapy. These data can help improve tumor localization and normal tissue delineation for treatment planning and may provide information about treatment efficacy during or after a course of radiotherapy. Time series data from serial and 4D CT before and during the treatment course, including CT data acquired in the treatment room at the time of treatment, is also helping to estimate motion and shape changes of relevant anatomy which can be used to accumulate dose and possibly adapt treatments.
In order to fully realize the benefits of the multitude of data we can now acquire, the different imaging studies must be registered to each other or to a common coordinate system. The geometric transformation required to register the image data can range from simple rotate‐translate to account for differences in patient orientation to 3D or 4D deformation models to account for changes in internal anatomy during and over the course of therapy. Once registered, data derived from the various studies such as anatomic outlines and computed dose can be integrated or fused to help construct a more complete and accurate representation of the patient.
This lecture will focus on the mechanics of registering and displaying data from different imaging studies using distinct modalities or a single modality over time. A description and taxonomy of the different methods will be described. Methods for display and interaction with multimodality data will also be presented. The overall goal is to provide the basic knowledge required to understand what is happening “under‐the‐hood” of the different registration systems one might encounter in the clinic, the different ways these systems are being used and their limitations.
1. Understand the basic mechanics of multi‐modality and 4D image registration techniques.
2. Understand the different techniques used to combine, display & interact with multimodality/4D image and dose data.
3. Understand the clinical use and limitations of these techniques for Tx planning, Tx delivery and plan adaptation.