Evaluation of Parotid Gland Function following Intensity Modulated Radiation Therapy for Head and Neck Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: This study was undertaken to determine the parotid gland tolerance dose levels following intensity modulated radiation therapy (IMRT) for treating patients who suffered with head and neck cancer. MATERIALS AND METHODS: From February 2003 through June 2004, 34 head and neck patients with 6 months of follow-up were evaluated for xerostomia after being treated by IMRT. Their median age was 59 years (range: 29~78). Xerostomia was assessed using a 4-question xerostomia questionnaire score (XQS) and a test for the salivary flow rates (unstimulated and stimulated: USFR and SSFR, respectively). The patients were also given a validated LENT SOMA scale (LSS) questionnaire. Evaluations were performed before IMRT and at 1, 3 and 6 months after IMRT. RESULTS: All 34 patients showed significant changes in the XQS, LSS and Salivary Flow rates (USFR and SSFR) after IMRT. No significant changes in the XQS or LSS were noted in 12 patients who received a total parotid mean dose of 3,100 cGy, significant increases in the XQS and LSS were observed. The USFR and SSFR from the parotid glands in 7 patients who received 2,750 cGy were significantly lower than the baseline values at all times after IMRT. CONCLUSION: We suggest that the total parotid mean dose should be limited to < or =2,750 cGy to preserve the USFR and SSFR and so improve the subsequent quality of life.

Feasibility Study of the Real-Time IMRT Dosimetry Using a Scintillation Screen / 대한방사선종양학회지

PURPOSE: To study the feasibility of verifying real-time 2-D dose distribution measurement system with the scintillation screen for the quality assurance. MATERIALS AND METHODS: The water phantom consisted of a scintillation screen (LANEX fast screen, Kodak, USA) that was axially located in the middle of an acrylic cylinder with a diameter of 25 cm. The charge-coupled device (CCD) camera was attached to the phantom in order to capture the visible light from the scintillation screen. To observe the dose distribution in real time, the intensity of the light from the scintillator was converted to a dosage. The isodose contours of the calculations from RTP and those of the measurements using the scintillation screen were compared for the arc therapy and the intensity modulated radiation therapy (IMRT). RESULTS: The kernel, expressed as a multiplication of two error functions, was obtained in order to correct the sensitivity of the CCD of the camera and the scintillation screen. When comparing the calculated isodose and measured isodose, a discrepancy of less than 8 mm in the high dose region was observed. CONCLUSIONS: Using the 2-D dosimetry system, the relationship between the light and the dosage could be found, and real-time verification of the dose distribution was feasible.

Evaluation of Xerostomia Following Intensity Modulated Radiotherapy (IMRT) for Head and Neck Cancer Patients / 대한방사선종양학회지

PURPOSE: This study was done to evaluate xerostomia following intensity modulated radiotherapy for patients with head and neck cancer, and to analyze the correlation between the dosimetric parameters and xerostomia parameters. MATERIALS AND MEHTODS: From February till October 2003, 13 patients with 3 months of follow-up were evaluated for xerostomia after being treated for head and neck cancer with IMRT. Their median age was 57 years (range: 43~77). Xerostomia were assessed with a 4-question xerostomia questionnaire score (XQS) and a test for salivary flow rates (unstimulated and stimulated). The patients were also given a validated LENT SOMA scale (LSC) questionnaire. The evaluations were completed before radiation therapy (pre-RT) and at 1 and, 3 months after radiation therapy (RT). We evaluated xerostomia at pre-RT, 1 and, 3 months after RT. The association between the xerostomia parameters (XQS and LSC) and salivary flow rates (unstimulated and stimulated: USFR and SSFR) was assessed at 1 and 3 months after RT. RESULTS: All 13 patients showed no significant changes in XQS, LSC and Salivary Flow rates. As a result, we couldn`t find out about xerostomia development. Based on the total mean parotid dose, 3,500 cGy, we divided these patients into two groups. The 8 patients ( or =3,500 cGy), there was a significant increase in USFR and, SSFR at 3 months after RT, and for the XQS and, LSC at 1 and 3 months after RT. The correlation between XQS and, LSC, and USFR and, SSFR in all patients (13) was significant at 3 months after RT. The correlation had a tendency to the decrease for USFR and, SSFR in proportion to the increase of XQS and, LSC. CONCLUSION: Based on the results of this study, IMRT seem to be an effective treatment to significantly decrease the xerostomia. XQS and, LSC seem to be a effective tool for predicting the xerostomia. A total parotid gland mean dose of <3,500 cGy should be a planning goal if substantial sparing of the gland function is desired. Furthermore, patients should be enrolled in a study to define a more accurate threshold dose for the parotid gland.