B. Kimmig

MRI and MRA in treatment planning of subdiaphragmatic radiation therapy

Radiotherapy treatment planning needs optimum definition of target volume in its relative position to normal tissue. The aim of our study was to achieve individual field definition in subdiaphragmatic radiotherapy by visualization of the target volume using fast, breath-held MRI and MR angiography. A modified rapid acquisition SE technique (SE 150/10) was used to obtain a coronal image within a 14 s breath-holding period, displaying kidneys, spleen, and lumbar spine on one slice. Coronal MR angiography acquisition in breath-hold technique was performed using a sequential FLASH-2D sequence (FLASH-2D 30/10/30 degrees). For reconstruction of the MR angiogram in coronal view, we used a maximum intensity projection algorithm. A computer program superimposed the MR angiogram onto the MR image. Correct magnification of the superposition image allowed direct projection onto the simulation film. Problems of distortion and different projection techniques were taken into account and quantified by phantom measurements. The localization error measured in a reference plane was less than 5 mm within a radius of 140 mm. Fourteen cases of Hodgkin disease and non-Hodgkin lymphomas were treated employing the novel technique. By superposition of the MR image and the MR angiogram, demarcation of vascular architecture from parenchymatous organs was achieved. Projection of the MR superposition onto the simulation film yielded accurate and convenient field definition using noninvasive imaging techniques.

External Stereotactic Focal Irradiation

“Radiosurgery” is a somewhat provocative term for a special concept of radiotherapy (Leksell 1951). It describes a percutaneous, stereotactically guided irradiation delivering a single high dose with collimated narrow beams. The precise stereotactic localization of the target point and a steep dose gradient outside the target volume allow the administration of high doses to a lesion without damage of adjacent normal tissue.

Individual Treatment Planning of Subdiaphragmatic Radiation Therapy Using Magnetic Resonance Tomography and Magnetic Resonance Angiography

The target volume in subdiaphragmatic radiation therapy of malignant lymphoma is commonly defined on plain X-ray simulation film [1]. Both correct inclusion of lymphatic tissue adjacent to blood vessels and the exclusion of radiosensitive organs are obligatory [7]. This is facilitated by a combination of several imaging techniques. Thus, imaging information as obtained by intravenous nephrogram, lymphogram, computed tomography, and ultrasound is transferred onto simulation film [3, 4]. Computed tomography and ultrasound, however, lack the possibility of direct image projection onto simulation film, which makes data transfer more difficult. For identification of the splenic pedicle, which shows marked anatomical variations in its vicinity to the left kidney, even surgical clipping or intravenous digital subtraction angiography is employed [6]. In clinical routine, however, the complete set of diagnostic information, which partly is obtained by invasive methods, is rarely available.

Magnetic Resonance Imaging and Magnetic Resonance Angiography in Treatment Planning and Response Monitoring of Single High-Dose Radiotherapy in Intracerebral Arteriovenous Malformations

Arteriovenous malformations (AVM) are regarded as congenital anomalies consisting of a racemose convolution of pathological vessels which predispose to intercerebral bleeding. The bleeding risk is about 4% per year, with a combined rate of major morbidity and mortality of 2.7% per year (Ondra et al. 1990). Cerebral AVM can be graded according to Spetzler et al. (1986). This system is based on the size of the AVM, localization of draining veins, and eloquence of adjacent brain tissue. It is derived from the potential postoperative complications, such as neurological deficits and mortality. AVMs of grade I or II are easily resectable, while those of grade IV or V are correlated with a high risk of major postoperative neurological deficits. This grading allows comparison with other therapeutic approaches: (a) embolization is very helpful preoperatively in preventing excessive bleeding but does not obliterate a large AVM alone (Fox et al. 1990); (b) stereotactic single high-dose radiotherapy, or “radiosurgery,” shows good results for complete occlusion of the AVM after a latency of approximately 2 years (Engenhart et al. 1989).