Search

Purpose To determine whether patients could tolerate the motion of a robotic couch that compensates for breathing-induced tumor motion. Methods and Materials A total of 10 healthy subjects and 23 radio-oncology patients underwent simulated extracranial stereotactic radiotherapy (two 30-min sessions) on a robotic couch programmed to follow a fictitious tumor trajectory of 20×5×5 mm (cranio–caudal, left–right, and anterior–posterior directions, respectively) while rotating 2° around a cranio–caudal axis at a frequency of 5 seconds per loop. Results No session had to be interrupted and no nausea was induced. However, one patient refused the second session due to general deterioration and not all patients could keep their arms elevated for the entire session. Conclusions Our findings showed that most patients tolerated compensatory couch motion and that motion sickness should not pose a problem in the investigation of this tumor-tracking method. more...

Partial coirradiation of both kidneys is an unavoidable consequence of adequate dose delivery in radiation therapy of para-aortic lymph nodes (PLN). Depending on total dose anteroposterior/posteroanterior (AP/PA), opposed-fields or multifield techniques are used. To optimize the treatment of potentially tumor-affected PLN with minimal kidney involvement, we calculated normal tissue complication probabilities (NTCPs) of coirradiated kidneys for four common irradiation techniques used in the PLN area.Planning target volume (PTV) delineation was performed in computed tomography scans of 21 patients with a lateral safety margin of 3 cm from the aorta and 2 cm aside the vena cava. Ventral and dorsal margins of the PTV were delineated 2 cm from the vessels. As previously shown (Nevinny-Stickel M, et al. Int J Radiat Oncol Biol Phys 2000;48:147-151), PTVs optimized by these altered delineations permit inclusion of at least 97% of potentially involved PLN in contrast to standard delineations based on bony structures that are more likely to miss affected lymph nodes. The present study compared NTCPs for individual PTV-based treatment planning with NTCPs for standard planning based on bony structures. For each patient, four hypothetical treatment plans were created: (A) standard AP/PA opposed fields technique with lateral field margins along the tips of the transverse processes of the vertebral bodies; (B) individually planned AP/PA opposed fields with lateral field margins according to the optimized PTV; (C) standard four-field box technique with lateral width as described for (A), with dorsal borders at the center of the vertebral bodies and ventral margins 3 cm in front of the vertebrae; and (D) individually planned four-field box with lateral field margins according to the optimized PTV. Calculation of irradiation-induced complication probability values for nonuniform kidney irradiation was performed for model doses 19.8 Gy, 30.6 Gy, and 50.4 Gy according to the Lyman-Wolbarst model.No dose showed a statistically significant difference (p0.00833, corrected for six multiple interrelated comparisons) in the median of total organ kidney NTCPs between techniques A, C, and D, with technique D intermediately ranging between technique A and C (e.g., for 50.4 Gy: A: median, 0.39; range, 0.01-0.83; C: median, 0.27 range; 0.05-0.68; D: 0.36; range, 0.03-0.72). In comparison to techniques A, C, and D, the individually planned AP/PA opposed-fields technique (B) was accompanied by significantly higher and intolerable overall kidney NTCP rates (e.g., for 50.4 Gy: median, 0.68; range, 0.01-0.99).Conformal four-field planning with individually optimized PTVs (D) resulted in only moderate tissue complication probabilities in both kidneys with the advantage of providing significantly greater inclusion of potentially involved PLNs in comparison to accepted standard procedures (A and C). more...

Purpose: In prophylactic irradiation of infradiaphragmatic lymphatic nodes (LN), the width of the paraaortic and pelvic field is given by a line joining the tips of the transverse processes of the 11th thoracic to the 4th lumbar vertebrae. Then the field boundary follows a straight line to the most lateral point of the acetabulum seen on the simulation film. Another method of setting the field border is to project the lateral contours of the large abdominal vessels from T 1 -weighted coronal MR images of the abdomen onto the simulator radiographs and add a 2-cm margin along the so delineated vessels. In our study, we compared both methods as to full enclosure of paraaortic and pelvic lymphatics or nodal miss. Material and Methods: Abdominal CT scans of 81 patients with involvement of paraaortic lymph node regions with LN sizes not exceeding 2.5 cm were examined. The distance from the center of the appropriate vertebra to the center of the most lateral lymph node was referred to the transverse process as well as to the outside contour of the aorta on the left and the vena cava on the right side. Respectively, the LN were measured referenced to the iliac vessels from the 5th lumbar through to the 2nd sacral vertebra. At the level of the hip joint the distance was measured from the midline as determined by a line through the center of the sacrum, pependicular to a line connecting center of both femoral heads. Results: Our measurements showed that lymph nodes do occur ( 1 ) lateral to the transverse processes of the thoracic and lumbar vertebrae as well as ( 2 ) outside the 2-cm safety margin from the lateral contour of the large abdominal vessels. Conclusion: These data clearly show that the traditional fields for radiation of infradiaphragmatic lymphatic nodes have not been large enough to enclose almost all retroperitoneal and pelvic lymph nodes with certainty. We recommend an expansion of the fields. more...