Lee H. Gerig

A prospective comparison of three systems of patient immobilization for prostate radiotherapy

PURPOSEnThe study compared the setup reliability of 3 patient immobilization systems, a rubber leg cushion, the alpha cradle, and the thermoplastic Hipfix device, in 77 patients with cT1-T3, N0, M0 prostate cancer receiving conformal radiotherapy.nnnMETHODS AND MATERIALSnPort films were analyzed and compared to simulation films to estimate the setup errors in the three coordinate axes (anterior-posterior, cranial-caudal, medial-lateral). A total vector error was calculated from these shifts.nnnRESULTSnThe Hipfix was found significantly superior to the other two devices in reducing mean setup errors in all axes (p < 0.005). The average field-positioning error with the Hipfix ranged from 1.9 mm to 2.6 mm for all axes, whereas the deviation for the other two systems ranged from 2.7 to 3. 4 mm. Errors greater than 10 mm were virtually eliminated with the Hipfix system. There was a reduction in the mean total vector error in the alpha cradle and Hipfix patient cohorts over time, reflecting improved efficacy as a result of experience.nnnCONCLUSIONnThere was a significant difference in the performance of each immobilization device. The Hipfix was consistently more reliable in reducing setup errors than the other devices.

Effects of urethrography on prostate position: considerations for radiotherapy treatment planning of prostate carcinoma

PURPOSEnRetrograde urethrography is commonly used to define the prostate apex at simulation. This study evaluated the hypothesis that urethrography causes prostate displacement, resulting in an error in treatment planning.nnnMETHODS AND MATERIALSnForty-five patients with carcinoma of the prostate were evaluated. Gold seeds were placed in the apex, posterior wall, and base of the gland. In the first 20 patients, the position of the seed-defined apex was compared at simulation (with urethrogram) and on day 1 of treatment (without urethrogram). In the second cohort of 25 patients, the effects of urethrography on prostate position were evaluated directly at simulation by comparing the position of apex pre- and post-urethrography. An analysis was performed to estimate the possible impact of urethrogram-induced prostate motion on target coverage.nnnRESULTSnThe mean superior displacement in the first and second cohort was 5.2 mm and 6.8 mm, respectively (combined mean shift 6.1 mm). With a 10-mm field margin below the tip of the urethrogram cone, 56% of patients in this study would have inadequate planning target volume (PTV) coverage.nnnCONCLUSIONnRetrograde urethrography causes a significant superior shift of the prostate. Strict reliance on urethrography in determining the inferior field margin could result in inadequate treatment.

Brain metastases with an unknown primary: a clinical perspective

A review of 43 patients with cerebral metastases, an unknown primary, and no other sites of metastases is presented. 27/43 (62.7%) had solitary metastases and 37.2% (16/43) had multiple metastases. Surgical treatment involved complete resection in 30.2%, subtotal resection in 37.2% and biopsy alone or no surgical procedure in the remainder. 39/43 patients underwent whole brain irradiation with the majority receiving 3000–4000 rads/10–20 fractions. Overall survival was 52% at six months and 20% at one year, and was significantly better in patients with solitary as opposed to multiple metastases (p < 0.03). A failure analysis including autopsy data demonstrates that (28/41) 68.3% of patients died of progressive intracranial disease without extracerebral metastases. Implications for treatment strategies are discussed.

Development and clinical application of a patient-position monitoring system

We have developed and clinically tested a computer vision system capable of real time monitoring of the position of an oncology (cancer) patient undergoing radiation therapy. The system is able to report variations in patient setup from day to day, as well as patient motion during an individual treatment. The system consists of two CCD cameras mounted in the treatment room and focused on the treatment unit isocenter. The cameras are interfaced to a PC via a two channel video board. Special targets, placed on the patient surface are automatically recognized and extracted by our 3D vision software. The three coordinates of each target are determined using a triangulation algorithm. System accuracy, stability and reproducibility were tested in the laboratory as well as in the radiation therapy room. Beside accuracy, the system must ensure the highest reliability and safety in the actual application environment. In this paper we also report on the results of clinical testing performed on a total of 23 patients having various treatment sites and techniques. The system in its present configuration is capable of measuring multiple targets placed on the patient surface during radiation therapy. In the clinical environment the system has an accuracy and repeatability of better than 0.5 mm in Cartesian space over extended periods (> 1 month). The system can measure and report patient position in less than 5 seconds. Clinically we have found that the system can easily and accurately detect patient motion during treatment as well as variations in patient setup from day to day. A brief description of the system and detailed analysis of its performance in the laboratory and in the clinic are presented.

Asymmetric ARC technique for posterior pharyngeal wall and retropharyngeal space tumors

PURPOSEnTumors of the posterior pharyngeal wall and nasopharyngeal cancer with retropharyngeal extension can partly encircle the cervical vertebrae. Treating the patient within spinal cord tolerance can cause a geographic miss. A simple technique has been developed to avoid this problem.nnnMETHODS AND MATERIALSnThe standard fields for posterior pharyngeal wall and nasopharyngeal tumors are used up to 36-40 Gy. A planning computed tomography (CT) scan is taken during the second or third week of treatment with the patient fitted in a new shell ensuring that the cord is straight and parallel to the treatment couch. The asymmetric arc technique consists of two posterior arcs with closure of one jaw beyond the central axis. Each arc delivers the total dose to each ipsilateral side, while the median region of the U-shaped volume is treated by the summation of both arcs.nnnRESULTSnWe have treated 10 patients using asymmetric arcs in the last 3 years. This technique proved to be a versatile way of treating targets wrapped around the spine. The technique allows better individualization for target volume irregularities than the partial rotation with a central bar.

Complications of microwave hyperthermia treatment of psoriasis

Three healthy men with psoriatic plaques unresponsive to tar, anthralin, and UVB were treated with 2450 MHz microwave heating for 30 minutes at 42 degrees C. Two patients had plaques over bony prominences. Pain developed in both patients, and one had a hypotensive episode during the first treatment. The third patient, whose plaque was greater than 2 cm and was not located over a bony prominence, completed the 5 weeks of biweekly treatments with complete resolution of the plaque and no complications.

The development and clinical application of a patient position monitoring system

We have developed and clinically tested a computer vision system capable of real time monitoring of the position of an oncology (cancer) patient undergoing radiation therapy. The system is able to report variations in patient setup from day to day, as well as patient motion during an individual treatment. The system consists of two CCD cameras mounted in the treatment room and focused on the treatment unit isocentre. The cameras are interfaced to a PC via a two channel video board. Special targets, placed on the patient surface are automatically recognized and extracted by our 3-D vision software. The three coordinates of each target are determined using a triangulation algorithm. System accuracy, stability and reproducibility were tested in the laboratory as well as in the radiation therapy room. Beside accuracy, the system must ensure the highest reliability and safety in the actual application environment. In this paper we also report on the results of clinical testing performed on a total of 23 patients having various treatment sites and techniques. The system in its present configuration is capable of measuring multiple targets placed on the patient surface during radiation therapy. In the clinical environment the system has an accuracy and repeatability of better than 0.5 mm in Cartesian space over extended periods (> 1 month). The system can measure and report patient position in less than 5 seconds. Clinically we have found that the system can easily and accurately detect patient motion during treatment as well as variations in patient setup from day to day. A brief description of the system and detailed analysis of its performance in the laboratory and in the clinic are presented.