Dosimetric study of inverse-planed intensity modulated, forward-planned intensity modulated and conventional tangential techniques in breast conserving radiotherapy.

OBJECTIVE: The authors present the result of a dosimetric comparison of inverse-planed intensity modulated, forward-planned intensity modulated, and conventional tangential technique in breast conserving radiotherapy. METHOD AND MATERIAL: The breasts (Right side: Left side = 1:1), heart, and lungs of 28 patients were contoured on all the computed tomography (CT)-slice. Three different treatment plans were created: (1) inverse IMRT (iIMRT), (2) forward IMRT (fIMRT), and (3) conventional tangential technique (CVT). The total prescribed dose for all plans was 50 Gy/25 fractions. All treatment plans were normalized at 95% of the prescribed dose covered the entire PTV and used inhomogeneity corrections. RESULTS: For the entire group, the mean breast volume was 517 cc. The V105% for iIMRT, fIMRT and conventional plans was 1.12%, 2.36% and 16.81%, which iIMRT better than fIMRT and CVT (p < 0.001) and fIMRT better than CVT (p < 0.05). The Dmax for the iIMRT plan received 105.03%, which was significantly less than those from the fIMRT(106.6%, p < 0.001) and the conventional (110.68%, p < 0.001) plan. The PTV coverage (V95-105%) for the iIMRT, fIMRTand conventional was 96%, 91% and 87%, which iIMRT better than fIMRT and CVT (p < 0.05) and fIMRT better than CVT (p < 0.05). The PTV CI for the iIMRT technique was 0.704, which was significantly more conformity than those from the fIMRT (0.639, p < 0.001) and the conventional (0.539, p < 0.001) techniques. The PTV CI of fIMRT is significantly better than CVT (p < 0.005). Mean ipsilateral lung dose was 642.7 cGy, 747.6 cGy and 882.25 cGy for iIMRT fIMRT and CVT respectively (p < 0.05) The V20Gy reduced from 14.87% for conventional plan to 12.82% for the fIMRT plan, while 0.88% was obtained for the iIMRT plan (P<0.05). The heart V30 Gy value was 3.124%, 4.65%, and 5.84% for iIMRT, fIMRT and conventional plans, respectively (p < 0.05). The mean dose of contralateral breast was 55.86 cGy, 60.33 cGy, 68.57 cGy for iIMRT, fIMRT and conventional plans, respectively (p < 0.05 both). The mean contralateral lung dose was 57.8 cGy, 43.87 cGy, and 32.28 cGy for iIMRT, fIMRT and conventional plans, respectively (p < 0.005 both). CONCLUSION: The iIMRT technique provides significantly improved PTV Dmax, PTV V105%, PTV V110%, target volume coverage, dose homogeneity and dose conformity throughout the target volume of breast and reduced doses to all critical structures, compared to the fIMRT and conventional techniques. In view of fIMRT technique, it significantly improved the dose distribution and reduced dose to OARs compared to conventional technique, although not better than iIMRT technique.

A two-year experience of implementing 3 dimensional radiation therapy and intensity-modulated radiation therapy for 925 patients in King Chulalongkorn Memorial Hospital.

BACKGROUND AND OBJECTIVE: Three dimensional conformal radiation therapy (3D CRT) and intensity-modulated radiation therapy (IMRT) have been implemented at Department of Therapeutic Radiation and Oncology, King Chulalongkorn Memorial Hospital (KCMH) since July 2005. This is the first study in Thailand to evaluate the pattern of care and utilization of 3D CRT and IMRT for treatment in each individual cancer. MATERIAL AND METHOD: Between July 2005 and July 2007, 925 newly diagnosed cancer patients underwent IMRT or 3D CRT at KCMH. The authors retrospectively reviewed the experience and utilization of 3D CRT and IMRT for each disease site and region. RESULTS: There were 471 males and 454 females. There were 332 patients (35.9%) treated with IMRT. Among the 332 IMRT patients, there were 100, 32 and 27 nasopharyngeal, lung and prostate cancers, respectively. On the contrary, 593 patients (64.1%) were treated with 3D CRT. Among these, breast, cervix and lung cancers were the most common diseases. Except for head and neck as well as genitourinary cancer 3D CRT was still the main technique used in more than 60% of the patients at KCMH. CONCLUSION: 3D CRT and IMRT have been successfully implemented at KCMH for 2 years. Three dimensional conformal radiation therapy was still the main technique used in more than 60% of the patients at KCMH. Prospective studies evaluating tumor control and treatment sequelae are expected.

Radiation dose to medical staff in interventional radiology.

OBJECTIVE: The purposes of the present study were to determine the dose to medical staff in interventional radiology at different locations on the body measured by thermoluminescent dosimeter (TLD) and to relate the medical staff dose to patient dose measured by the dose-area product (DAP) meter. MATERIAL AND METHOD: The present study covered 42 patients in three interventional radiology procedures with three x-ray machines. Thermoluminescent dosimeters were stuck at eight positions on the radiologist's skin during the procedure. In addition, direct reading from the DAP meter placed in front of the collimator of the x-ray tube, was recorded to estimate the patient radiation dose. RESULTS: The surface dose to the primary radiologist showed maximum value at the left forearm of 407 microGy. The ratios between the maximum interventional radiologist surface dose and patient dose are 12.88 microGy per 10 Gycm2 for transarterial oily chemoembolization TOCE (Siemens Polystar), 22.58 microGy per 10 Gycm2 for transarterial oily chemoembolization TOCE (Siemens Neurostar), 148.29 microGy per 10 Gycm2 for percutaneous transhepatic biliary drainage PTBD (Siemens Polystar) and 100.46 microGy per 10 Gycm2for endoscopic retrograde cholangiopancreatography ERCP (GE Advantx). CONCLUSION: The interventional radiologist surface dose can be estimated from the mentioned ratio if the patient dose is measured. This will help the radiologists to avoid receiving an excess dose during their work.

Intensity-modulated radiation therapy in head-and-neck cancer, first report in Thailand.

OBJECTIVE: This is the first report in Thailand to evaluate the efficacy of using intensity-modulated radiotherapy (IMRT) in the primary treatment of head-and-neck cancer. MATERIAL AND METHOD: From July 2005 to March 2006, eighteen patients with head and neck cancer were treated with IMRT, fourteen of which were nasopharyngeal cancer. The median age at diagnosis was 52 years (range 23-58 years). The treatment plan composed of two sequential plans for PTV-low risk (50Gy in 25 fractions) and PTV-high risk (20Gy in 10 fractions). Chemotherapy was given to 13 patients with locoregionally advanced disease (stage T3/T4 and N2/3) using cisplatin (n = 3) or carboplatin (n = 10) every 3 weeks during the course of radiation therapy. RESULTS: The median overall treatment time was 49 days (range, 43-57 days), and 77.8 percent of the patients completed 35 fractions within 50 days. The clinical complete response and partial response rates at 3 months after complete radiation were 71.4% and 28.6%, respectively. However at the median follow-up of 5.6 months, the complete response rate increased to 89%. Treatment break during RT range from 3 to 7 days, was observed in three patients. All of them received concurrent chemoradiation. No distant metastasis was noted. CONCLUSION: The authors' experience of using concurrent chemotherapy with IMRT for a cohort of patients with head and neck carcinoma showed a very high rate response rate at early follow-up. Long-term clinical outcome is expected.