Volker Sturm

Three dimensional image correlation of CT, MR, and PET studies in radiotherapy treatment planning of brain tumors

Abstract A treatment planning system for stereotactic convergent beam irradiation of deeply localized brain tumors is reported. The treatment technique consists of several moving field irradiations in noncoplanar planes at a linear accelerator facility. Using collimated narrow beams, a high concentration of dose within small volumes with a dose gradient of 10-15%/mm was obtained. The dose calculation was based on geometrical information of multiplanar CT or magnetic resonance (MR) imaging data. The patients head was fixed in a stereotactic localization system, which is usable at CT, MR, and positron emission tomography (PET) installations. Special computer programs for correction of the geometrical MR distortions allowed a precise correlation of the different imaging modalities. The therapist can use combinations of CT, MR, and PET data for defining target volume. For instance, the superior soft tissue contrast of MR coupled with the metabolic features of PET may be a useful addition in the radiation treatment planning process. Furthermore, other features such as calculated dose distribution to critical structures can also be transferred from one set of imaging data to another and can be displayed as three-dimensional shaded structures.

Computerized optimization of 125I implants in brain tumors

A computer program for treatment planning for the interstitial radiotherapy of brain tumors with 125I stereotactic implants is presented. To minimize brain traumatization only 1-3 catheters loaded with several seeds are implanted. It is possible to position the catheters very accurately due to CT guided stereotactic techniques. Precise treatment planning is necessary because of the high dose gradient of the radiation field. Two planning methods are available: conventional planning with interactive optimization of source configurations and an automatic optimization procedure. The goal of optimization is to identify source parameters (catheter positions and seed activities) for which a prescribed dose at the target surface is approximated as closely as possible.

Intracavitary Irradiation of Cystic Craniopharyngiomas

Craniopharyngiomas comprise 2.5% of adult and 7% of childhood intracranial neoplasms. They arise from remnants of squamous epithelium in Rathke’s pouch, usually within the tuber cinereum and pituitary infundibulum [18], and extend into the sellar-suprasellar region. Rarely, these tumors extend into the frontal (2%–5%), posterior (1%–4%), or middle cranial fossae (2%) [15]. Approximately 60% of craniopharyngiomas are exclusively cystic; 9% are predominantly cystic with a smaller solid part; 15% are equally cystic and solid; and 16% are solid [17]. Because of papillary extensions and reactive gliosis, both cystic and solid craniopharyngiomas adhere closely to the surrounding brain tissue [7, 23]. This feature makes radical operative removal hazardous or even impossible, especially in larger tumors (those with diameters exceeding 3 cm) [20].

Diagnostic value of the stereotactic approach to focal lesions in the deep brain of children and adolescents

Since it is relatively harmless, stereotactic biopsy has become in recent years a useful method for the diagnostic assessment of lesions deep in the brain, which are not accessible to open surgery. With the aid of stereotaxis, focal lesions only a few millimeters in diameter can be approached in every location in the brain with high precision. Since stereotaxis does not require general anesthesia, or at most requires only a very shallow anesthesia, it can also be applied to young infants or persons of advanced age. Experience with stereotactic biopsy exploration of lesions of various kinds in the deep brain of 74 children and adolescents, out of a sample of 260 patients of all age groups who received stereotactic biopsy, is reported. Our aim is to demonstrate and discuss the advantage of this contemporary method for child neurology and neurosurgery. In many medical centers in the world where stereotactic tumor biopsy has been established, it has become an important criterion for the choice of treatment.

Stereotactic Brachytherapy for Brain Tumors

Brachytherapy for the treatment of brain tumors has a very long history and for selected indications still represents a safe, minimally invasive and effective local treatment option, offered by specialized centers. In the following chapter we review stereotactic brachytherapy (SBT) for brain tumors, including the history, physical aspects, surgical procedure, and indications, which are introduced and discussed in the context of the available literature.

Research on Diagnosis and Therapy

In the battle against cancer, diagnosis has a crucial strategic significance. Diagnostic shortcomings will be difficult to counteract by therapy.

Diagnostik- und Therapieforschung

Im Kampf gegen den Krebs hat die Diagnostik eine entscheidende strategische Bedeutung. Was diagnostisch versaumt wird, last sich therapeutisch schwer wieder gut machen.