Gantry angle-dependent correction of dose detection error due to panel position displacement in IMRT dose verification using EPIDs.

PURPOSE: The purpose of this study was to measure the mechanical position displacement of three types of electronic portal image device (EPID) panels at different gantry angles and evaluate the impact of positional displacement on intensity modulated radiation therapy (IMRT) dose verification using an EPID. METHODS: Three types of linear accelerators and EPIDs (aS500, aS1000 and iViewGT) were used. The portal images were taken every 10° within 360° range. The position coordinate difference between the panel center and the portal film center at different gantry angles was measured, then the mechanical position displacement of EPIDs dependent on the gantry angles was analyzed. For the three linear accelerators and EPIDs, five IMRT plans were measured using EPIDs at 0° gantry angel and at the actual treatment angles. The Gamma technique was used to evaluate the resulted dose difference before and after the corrections of the position displacement by a in-house software. RESULTS: For aS500, aS1000 and iViewGT, the maximum mechanical position displacement was 2.9 ± 0.1 mm, 0.2 ± 0.1 mm and 0.1 ± 0.3 mm in the lateral direction and -4.2 ± 0.2 mm, -4.2 ± 0.1 mm and -2.2 ± 0.1 mm in the longitudinal direction, respectively. The position displacement in the longitudinal direction of the three EPIDs can be fitted well with a function. For aS500, aS1000 and iViewGT, the 3%/3 mm gamma pass rates were increased by 6.7%, 2.9% and 0.1% after displacement corrections; and while the 2%/2 mm gamma pass rates were increased by 11.2%, 8.1% and 1.6%. After the displacement correction, there was a slight gamma pass rate difference between the fixed zero degree gantry and the actual treatment angles. CONCLUSION: When the EPIDs were used for IMRT dose verification, there was occasionally large EPID mechanical position displacement, which should be corrected.

A comparative dosimetric study for treating left-sided breast cancer for small breast size using five different radiotherapy techniques: conventional tangential field, filed-in-filed, tangential-IMRT, multi-beam IMRT and VMAT.

BACKGROUND AND PURPOSES: To compare the dosimetry for the left-sided breast cancer treatment using five different radiotherapy techniques. MATERIALS AND METHODS: Twenty patients with left sided breast cancer were treated with conservative surgery followed by radiotherapy. They were planned using five different radiotherapy techniques, including: 1) conventional tangential wedge-based fields (TW); 2) field-in-field (FIF) technique; 3) tangential inverse planning intensity-modulated radiation therapy (T-IMRT); 4) multi-field IMRT (M-IMRT); and 5) volumetric modulated arc therapy (VMAT). The CTV, PTV and OARs including the heart, the regions of coronary artery (CA), the contralateral breast, the left and right lung were delineated. The PTV dose was prescribed 50Gy and V47.5≥95%. Same dose constraint was used for all five plans. The planned volumetric dose of PTV and PRV-OARs were compared and analyzed. RESULTS: Except VMAT (Average V47.5 was 94.72%±1.2%), all the other four plans were able to meet the V95% (V47.5) requirement. T-IMRT plan improved the PTV dose homogeneity index (HI) by 0.02 and 0.03 when compared to TW plan and VMAT plan, and decreased the V5, V10 and V20 of all PRV-OARs. However, the high dose volume (≥ 30Gy) of the PRV-OARs in T-IMRT plan had no statistically significant difference compared with the other two inverse plans. In all five plans, the dose volume of coronary artery area showed a strong correlation to the dose volume of the heart (the correlation coefficients were 0.993, 0.996, 1.000, 0.995 and 0.986 respectively). CONCLUSION: Compared to other techniques, the T-IMRT technology reduced radiation dose exposure to normal tissues and maintained reasonable target homogeneity, VMAT is not recommended for left-sided breast cancer treatment. In five techniques, the dose-volume histogram (DVH) of the heart can be used to predict the dose-volume histogram (DVH) of the coronary artery.

[Efficacy and safety analysis with standardized mite allergen subcutaneous immunotherapy in 90 patients with allergic rhinitis].

OBJECTIVE: To evaluate the three-year efficacy and safety with standardized dust mite subcutaneous immunotherapy in patients with allergic rhinitis. METHODS: Ninety patients who were diagnosed as allergic to mite by skin prick test and serum IgE were include in the standardized allergen-specific dose-escalation regimen. Nasal symptom score (0-3) were collected before treatment and three years after treatment; VAS (visual analogue scale, 0-10) of all nasal symptoms and drug use score were collected every four months; frequency of local and systemic reactions were recorded in the duration of dose escalation and maintenance. RESULTS: Nasal blocking, sneeze, rhinorrhea and nasal itch were significantly improved after 3 years treatment (before treatment: 2[2;3], 2[2;3], 2[2;3], 2[1;2] ; after treatment: all were 0[0;0]; Z value were -8.310, -8.408, -8.377, -8.287, all P were 0.000). VAS of all nasal symptoms and drug use score decreased dramatically after escalation period (before treatment: 8.00[7.00;8.85], 2.00[1.50;2.00]; after treatment: 1.00[1.00;1.50], 0 [0;0]; Z value were -8.287, -8.248, P value 0.086, 0.744), and maintained afterwards (F value were 2.483, 0.296; P value were 0.086, 0.744). Ninety-eight case times (64.47%) local reactions mainly happened in maintenance period; the frequency of systemic reactions was 2.54%. CONCLUSION: The standardized specific allergen immunotherapy for allergic rhinitis is safe and effective.

Diaqua-[5,5'-dicarb-oxy-2,2'-(propane-1,3-di-yl)bis-(1H-imidazole-4-carboxyl-ato)]nickel(II) dihydrate.

In the title complex, [Ni(C(13)H(10)N(4)O(8))(H(2)O)(2)]·2H(2)O, the Ni(2+) cation is six-coordinated by two N atoms and two O atoms from the tetra-dentate anion in equatorial positions and by two water O atoms in axial positions, leading to a distorted octa-hedral environment. The central C atom of the propanediyl unit is disordered over two sites in a 0.531 (6):0.469 (6) ratio. In the crystal, adjacent mol-ecules are linked through O-H⋯O and N-H⋯O hydrogen-bonding inter-actions into a three-dimensional network.