Malignant eccrine spiradenoma is an exceedingly rare tumor. A case of a 72-year-old women with this highly aggressive malignancy arising from a long-standing lower leg lesion is reported. Management during the course of disease included surgery, radiation therapy (RT), hyperthermic limb perfusion chemotherapy, and chemotherapy. The patient died of her disease, with widespread metastatic disease 20 months after the diagnosis. A review of the literature is presented, and treatment considerations are summarized.
Purpose: To compare the electron cutout output factor (COF) of small fields measured by two methods: radiographic film (Kodak X‐Omat V) and the Seven29 (PTW) 2D small volume ion chamber array. Method and Materials: The COFs for four small electron fields were measured on a Varian‐2100C accelerator with a 10 cm × 10 cm cone at 6 MeV. Radiographic film and Seven29 array ion chamber were set perpendicular to the central axis of the beam. The film and effective point of measurement for the 2D array were both set at dmax. Solid water was used for build up in both cases, and 100 cm SSD was set at the top surface of the solid water. The data were measured using 10 to 400 monitor units (MU) for Seven29 and 30 to 200 MU for the film. The open 10 cm × 10 cm insert data from film measurement was used to compute the film parameters of maximum optical density (OD) and sensitivity based on a single hit model. These parameters were used later to convert the measured cutout data from OD to dose for the COF calculation. The OD was read from a Digital Densitometer II. Results: The Seven29 ion chamber array behaved linearly as a function of MU as expected, which provided an identical COF regardless of the number of MU's used (less than 1% difference). The COF results from the Seven29 and from film measurements showed a maximum difference of 1.6%. Conclusion: The 2D ion chamber array can be used to measure the COF for a small electron fields. Using the Seven29 to measure small field COF will save measurement time compared to using film dosimetry, and in addition, this is also beneficial to filmless departments.
Purpose: To evaluate the response of in‐vivo diodes for IMRT delivery under new calibration condition. Materials and Method: In‐vivo diodes (QED p‐type, 6–12 MV and 15–25 MV, Sun Nuclear Inc) with model 1131 dosimeter were calibrated with actual patient IMRT (sliding window technique) treatment fields (hereafter referred to as IMRT diodes). A 6–12 MV diode was placed on top of a solid water phantom at 100 cm SSD with an ion chamber (Capintec PR‐06) at dmax. First a 10×10 static open field was delivered to obtain the ion chamber reference reading. Then an IMRT breast patient's medial field was delivered, and the ion chamber reading was converted to dose based on the reference reading. This dose number was used to calibrate the diode. A 15–25 MV diode was calibrated the same way with an IMRT prostate's PA field delivered. Regular diodes were calibrated to dmax dose under standard conditions (100 cm SSD, 10×10 FS). The response of both regular and IMRT diodes under IMRT delivery were measured with a farmer chamber at dmax used as reference. Results: Diodes calibrated with the new method, i.e. IMRT diodes over‐responded by 2.0% for 18 MV photons and 1.0% for 6 MV photons respectively for IMRT delivery when compared with their corresponding regular diodes, indicating IMRT diodes sensitivity increased by about 2.0% for 18 MV photons and about 1.0% for 6 MV photons respectively. Conclusion: A new method to calibrate diode for IMRT delivery was presented. The responses were compared with regular diodes. IMRT diodes over‐responded when compared with regular diodes by 2.0% for 18 MV photons and 1.0% for 6 MV photons with IMRT delivery. The evaluation of field size dependence, gap dependence and SSD dependence of the diodes for IMRT delivery have also been submitted to this conference.
Purpose: In IGRT, couch shifts are needed to align the target to account for organ motion. In some rare cases treatment SSD may differ significantly (up to 1.0 cm) from the plan after these shifts. TMR ratio method is proposed to correct SSD changes so dosimetric accuracy of IGRT with IMRT delivery can be preserved. Method and Materials: A prostate patient CT was contoured in Eclipse TPS (Varian Medical Systems, v7.3) as test body. A bolus was added surrounding the body with either 1.0 cm or 2.0 cm thick bolus, (simulating 1.0 cm and 2.0 cm SSD change, respectively). An IMRT prostate clinical plan using 18 MV photons was exported to each of the three test bodies to create verification plans. TMRs were then read from our clinical data table according to different depths in the three test bodies. The TMR ratios were generated based on the non‐bolus plan. To apply the TMR ratio to the beams, the prescription percent isodose line in each plan was lowered by the corresponding TMR ratios to increase MUs. By doing this, all other treatment parameters, including dynamic MLC configuration were kept the same. The corrected plans were exported to corresponding bodies and doses were calculated. The DVHs of prostate and critical organs were then compared. Results: DVHs for prostate and critical organs were identical for all three scenarios after TMR ratio correction. Conclusion: The TMR ratio method was applicable for IMRT plans to correct for small SSD changes in IGRT. For regular IMRT plans, if SSD changes are caused by other reasons like weight loss, this method is still valid assuming PTV does not change. However, if SSD change is larger than 1.0 cm, it is prudent to re‐CT scan the patient and re‐calculate plan because the PTV might have changed.
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