[Physical and methodological aspects of multimodality imaging and principles of treatment planning in 3D conformal radiotherapy]

Comparison of measured and calculated doses in a Rando phantom with a realistic lung radiotherapy treatment plan including heterogeneities

In this work, dose measurements were performed to evaluate an external radiotherapy treatment plan and, particularly, to validate dose calculations for a lung lesion case. Doses were calculated by the Varian Eclipse treatment planning system using the AAA anisotropic analytical algorithm. The measurements were performed using a Rando anthropomorphic phantom and TLD700 thermoluminescent dosimeters. The comparison between doses calculated and doses measured by means of thermoluminescence (TL) shows compatibility except for a few points, due to the limitations in the heterogeneity correction used for the case studied here. The deviation between the calculated and measured doses is about 6.5% for low (< 0.5 Gy) doses and about 1% for higher doses (> 0.5 Gy).The deviation between AAA-calculated and TL-measured doses was also found to be higher in proximity to heterogeneous tissue interfaces.

[Progress in radiation therapy and integration in Tenon hospital (AP-HP) of new advances in routine practices of radiotherapy for non-small-cell lung cancer]

Much progress has been made in recent years in administration modalities for external radiotherapy of non-small-cell lung carcinoma. Three-dimensional conformal radiotherapy with or without intensity modulation, with respiratory gated radio-therapy (4D radiotherapy), and image-guided radiotherapy (IGRT) can be considered as a third revolution in radiation therapy after total dose fractionation and the development of megavoltage radiation therapy equipment. We describe progress in the three-dimensional radiotherapy technique and the integration of this technique in the department of Radiation Oncology at Tenon hospital (AP-HP).

Automatic image registration of three-dimensional images of the head of cats and dogs by use of maximization of mutual information

OBJECTIVE

To validate mutual information criterion as a ready-to-use technique for automated alignment (ie, registration) of 3-dimensional (3-D) multimodal image data of the head of cats and dogs.

SAMPLE POPULATION

Corresponding 3-D magnetic resonance imaging (MRI) and computed tomography (CT) brain scans of a 6-month-old Doberman Pinscher with a brain cyst; CT images of the head of a European shorthair cat with a meningioma before and immediately, 3, and 6 months after surgical resection; and CT and corresponding stacked anatomic cryosection images of the entire head of a 2-year-old sexually intact female Beagle.

PROCEDURE

All images were matched retrospectively by use of an in-house computer program developed on the basis of a mutual information image registration algorithm. Accuracy of the resulting registrations was evaluated by visual inspection.

RESULTS

All registrations were judged to be highly accurate. Additional manual corrections were not necessary.

CONCLUSIONS AND CLINICAL RELEVANCE

Mutual information registration criterion can by applied to 3-D multimodal head images of cats and dogs for full automatic rigid-body image registration. The combination of such aligned images would considerably facilitate efforts of veterinary clinicians as indicated by its widespread use in brain surgery and radiation therapy of humans.

[Computerized tomography for dosimetry purposes: technical factors in helical acquisition. Importance and limits of this technique in target-volume delineation and dose calculation]

The computerized tomography (CT) used for target volumes contouring is an essential step of the radiotherapy process. The CT technical factors must be adapted to explored organs and anatomic regions: data acquisition parameters and reconstruction algorithm, digestive or intravenous contrast. The choice of these parameters and its consequences for contouring are discussed. Respiratory motion must be considered for some organs. Helical CT allow a data acquisition during one apnoea. Knowledge of these technical factors is essential for good contouring and for the future use of multiple row detectors. Precise exams protocols depending on lesions, on treatment methods and patients are demanded. Close cooperation between radiation oncologists, physicists and radiologists is not only a wish but becomes a necessity.