Use of surface markers for MR radiotherapy planning.

PURPOSE: For the precise planning of radiotherapy treatment ports, the delineation and control of their borders has to be performed with X-ray and other imaging procedures before and during the therapy. MATERIALS AND METHODS: Conventional planned therapy ports are checked with the help of MR-imaging with new gel-markers, as a further development to formerly used fluid filled tubes, on the skin of the patient in different regions. We describe the essentials of these gels and report about their first practical use. RESULTS: Principal considerations to the technique and practical applications are given with imaging examples. The essential physical qualities of the gels are introduced with separate NMR experiments. It turns out, that multiplanar MR-imaging in combination with field markers on the skin is a fast simple and useful help for the control and the improvement of treatment planning. CONCLUSION: MR-imaging with gel-markers on the skin in many cases can show the tumor and the field-ports in one picture. Thus the therapy planning is refined with simple means. On the one hand the target volume can be seized completely and on the other hand sensitive organs can better be protected.

[Optimization of the image intensifier-assisted technique of lumbar sympathetic block. Computed tomographic simulation of a paravertebral puncture access]. / Optimierung der Bildverstärker-gesteuerten Technik lumbaler Sympathikusblockaden. Computertomographische Simulation eines paravertebralen Punktionszugangs.

The paravertebral approach is the most common technique for local anaesthetic and neurolytic lumbar sympathetic blocks. However, guidelines on the site of needle insertion differ. As there have been several case reports on accidental trauma to the ureter and the kidney, this study was undertaken to evaluate the site of paravertebral needle insertion and the fluoroscopic landmarks for lumbar sympathetic blocks by computed tomographic puncture simulation. METHODS. CT scans of 73 patients at the level of L2-4 were analysed with respect to the location of kidneys, the vertebral insertion of the diaphragm, the distance of the sympathetic trunk from the ventral and lateral border of the lumbar vertebrae, the paravertebral distance of a tangent from the sympathetic trunk through the kidney surface and the frequency of inadvertent puncture of major organs by different paravertebral approaches. For needle insertion distances of 6, 8, 10 and (at the level of L4) 12 cm lateral to the midline were simulated. RESULTS. Simulating a paravertebral approach of 6 cm resulted in perforation of the right (or left) kidney only at the level of L2 in 1.4% (2.8%) of cases. The incidence of accidental renal puncture due to a paravertebral approach of 8 cm was 26.0%, 4.1% and 0 (26.0%, 2.7% and 0) at the levels L2, L3 and L4, respectively. A more lateral insertion of needles 10 cm from the spinous process increased the frequency of anticipated renal puncture to 57.5%, 19.2% and 1.4% (65.8%, 26.0% and 1.4%); in addition, perforation of liver parenchyma was detected in two cases. Although the lower pole of the kidney reached the mid-vertebral level of L4 in only 23.3 (15.1)% of cases, a lateral approach 12 cm from the midline still showed a 8.2 (4.1)% incidence of kidney perforation and inadvertent trauma to the intestine in two cases. The mean distance from the sympathetic trunk to the ventral border of the lumbar vertebra (in simulation of a lateral fluoroscopic view) was 0.80, 0.66 and 0.59 cm, analogous measurements to the lateral border averaged 0.37, 0.43 and 0.50 cm at L2, L3 and L4, respectively. At the level of L2 the medial insertion of the diaphragm was identified in 45% of patients in close anatomical relationship to the psoas fascia. CONCLUSION. In order to reduce the risk of accidental trauma to major organs the paravertebral distance of insertion of the needles from the midline should not exceed 6, 7 and 10 cm for lumbar sympathetic blocks at the levels of L2, L3 and L4, respectively. However, a paravertebral approach of less than 6 cm may cause a lateral and ventral deviation of the needle from the sympathetic chain. Under fluoroscopy a correct needle position is obtained at an average distance of 0.5-0.8 cm dorsal to the anterior vertebral border, advancing the needle to the ventral border may cause an accidental puncture of the vena cava in more than 20% of patients undergoing nerve block of the right sympathetic chain. Furthermore, at the level of L2 inadvertent placement of the needle tip within the vertebral insertion of the diaphragm must be considered as a reason for atypical spread of contrast medium.

[The initial clinical experiences with a dynamic FLASH-2D sequence in tumors of the head and neck area]. / Erste klinische Erfahrungen mit einer dynamischen FLASH-2D-Sequenz bei Tumoren im Kopf- und Halsbereich.

28 patients with clinically confirmed head and neck tumours were examined by MRI. The results of a dynamic FLASH-2D sequence and a Gd-DTPA enhanced T1-weighted sequence were analysed and retrospectively compared with surgery and pathological findings. The extent of tumours was clearly defined by the dynamic technique in 21 cases. Furthermore, it was found to be superior for the purpose of demonstrating contrast behaviour and concerning T-classification. Here the dynamic FLASH-2D sequence proved to be an important supplement for preoperative diagnosis.