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Objective@#To compare the accuracy of two automatic segmentation softwares (Smart Segmentation and MIM Atlas) in organs at risk (OARs) contouring for nasopharyngeal carcinoma (NPC).@*Methods@#Totally 55 NPC patients were retrospectively reviewed with manually contoured OARs on CT images, in which 30 cases were randomly selected to create a data base in the Smart Segmentation and MIM Atlas. The remaining 25 cases were automatically contoured with Smart Segmentation and MIM as test cases. The automatic contouring accuracies of two softwares were evaluated with Dice coefficient(DSC), Hausdorff distance(HD), and absolute volume difference(△V) using manual contours as a golden standard.@*Results@#The overall DSC, HD and △V of all organs contoured by MIM Atlas and Smart Segmentation were (0.79±0.13) vs. (0.62±0.24) (t=14.06, P<0.05), (5.50±3.84)mm vs.(8.38±4.88)mm (t=-11.40, P<0.05), and (1.52±2.46) cm3 vs. (2.38±3.57) cm3 (t=-4.70, P<0.05), respectively. The average DSC of 11 organs (brain stem, optic chiasm, bilateral lens, bilateral optic nerve, bilateral eyeballs, bilateral parotid gland, spinal cord) delineated by MIM Atlas was statistically greater than that of Smart Segmentation (t=5.27, 4.41, 6.34, 5.70, 10.62, 7.45, 3.96, 4.26, 6.25, 5.42, 7.23, P<0.05). The average HD of 10 organs (brain stem, optic chiasm, bilateral lens, bilateral optic nerve, bilateral eyeballs, left parotid gland, spinal cord) delineated by MIM Atlas was statistically less than that of Smart Segmentation (t=-4.51, -4.49, -3.92, -3.45, -5.36, -5.56, -3.89, -3.90, -3.60, -3.68, P<0.05). The average △V of 6 organs (brain stem, optic chiasm, left len, bilateral optic nerve, right eyeball) delineated by MIM Atlas was statistically less than that of Smart Segmentation (t=-2.83, -3.39, -2.56, -2.27, -2.43, -2.51, P<0.05).@*Conclusions@#Both softwares have reasonable contouring accuracy for larger organs. The accuracy decreased with the decrease of organ volumes and blurred boundary. Generally, MIM Atlas′s performs better than Smart Segmentation does.
ABSTRACT
Objective To compare the accuracy of two automatic segmentation softwares ( Smart Segmentation and MIM Atlas) in organs at risk ( OARs) contouring for nasopharyngeal carcinoma ( NPC) . Methods Totally 55 NPC patients were retrospectively reviewed with manually contoured OARs on CT images, in which 30 cases were randomly selected to create a data base in the Smart Segmentation and MIM Atlas. The remaining 25 cases were automatically contoured with Smart Segmentation and MIM as test cases. The automatic contouring accuracies of two softwares were evaluated with Dice coefficient( DSC) , Hausdorff distance( HD) , and absolute volume difference(△V) using manual contours as a golden standard. Results The overall DSC, HD and △V of all organs contoured by MIM Atlas and Smart Segmentation were (0.79±0.13) vs. (0.62±0.24) (t= 14.06, P<0.05),(5.50±3.84)mm vs.(8.38±4.88)mm ( t=-11. 40, P<0. 05 ) , and ( 1. 52 ± 2. 46 ) cm3 vs. ( 2. 38 ± 3. 57 ) cm3 ( t = -4. 70, P<0. 05 ) , respectively. The average DSC of 11 organs ( brain stem, optic chiasm, bilateral lens, bilateral optic nerve, bilateral eyeballs, bilateral parotid gland, spinal cord) delineated by MIM Atlas was statistically greater than that of Smart Segmentation ( t=5. 27, 4. 41, 6. 34, 5. 70, 10. 62, 7. 45, 3. 96, 4. 26, 6. 25, 5. 42, 7. 23, P<0. 05) . The average HD of 10 organs ( brain stem, optic chiasm, bilateral lens, bilateral optic nerve, bilateral eyeballs, left parotid gland, spinal cord) delineated by MIM Atlas was statistically less than that of Smart Segmentation ( t=-4. 51, -4. 49, -3. 92, -3. 45, -5. 36, -5. 56, -3. 89, -3. 90,-3. 60, -3. 68, P<0. 05). The average △V of 6 organs (brain stem, optic chiasm, left len, bilateral optic nerve, right eyeball) delineated by MIM Atlas was statistically less than that of Smart Segmentation ( t=-2. 83, -3. 39, -2. 56, -2. 27, -2. 43, -2. 51, P<0. 05 ) . Conclusions Both softwares have reasonable contouring accuracy for larger organs. The accuracy decreased with the decrease of organ volumes and blurred boundary. Generally, MIM Atlas's performs better than Smart Segmentation does.
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Objective To investigate the dosimetric differences among three types of breath hold mode ( free breath:FB, thoracic deep inspiration breath hold: T-DIBH, abdomen deep inspiration breath hold:A-DIBH) and to explore the optimal breath hold method in the postoperative radiotherapy of left-side breast cancer patients with minimum dose to normal tissues and organs at risk. Methods A total of eighteen patients with left-side breast cancer patients who underwent postoperative radiotherapy were enrolled in this study. Three CT simulation scans with three different breath hold method ( FB, T-DIBH, and A-DIBH ) were performed for each patient. Dosimetric differences were compared among plans generated on these three different CT image sets. Results There was no significant difference in the volume, mean dose, and homogeneity of planning target volume ( PTV) among plans generated from three different image sets (P>0. 05). The mean heart dose, mean LAD dose and mean ipsilateral lung dose in plans generated from CT image sets with FB, T-DIBH and A-DIBH were (3. 21 ± 1. 02), (1. 74 ± 0. 51), (1. 31 ±0. 41) Gy (W =171, P <0. 05), (34. 61 ± 13. 51), (14. 38 ±10. 20), (9. 21 ± 6. 53) Gy (W=171, P<0. 05), and (8. 31 ±2. 75), (7. 46 ±1. 96), (6. 89 ±1. 79) Gy (W=171, P<0. 05), respectively. Conclusions Compared with plans with FB, plans with DIBH ( T-DIBH and A-DIBH ) achieved lower cardiac, LAD and pulmonary doses. A-DIBH achieved a better normal dose reduction than T-DIBH.
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Objective To compare the dosimetric results of postoperative intensity modulated radiation therapy (IMRT) using single-energy or mixed-energy photons in invasive thymoma patients.Methods Simulation CT images were acquired and clinical target volume (CTV),planning target volume (PTV) and organs at risk (OARs) were defined.Three sets of fixed-field IMRT planning were generated using 6 MV,10 MV and mixed 6/10 MV photons for each case.Monitor Units (MUs) for each plan were recorded after optimization,and parameters of PTV such as conformity index (CI),homogeneity index (HI) and dose to OARs were evaluated on dose-volume histograms.Results Near-Maximal dose (D2％) received by PTV was better in mixed-energy IMRT as compared with 6 MV(t =3.107,P ＜0.05).HI was better in mixed-energy than in 6 MV(t =2.924,P ＜0.05).There were statistically significant differences in CI among three IMRT plans.MU was higher in 6 MV than in both 10 MV and mixed-energy IMRT.The percentages of lung volumes receiving 5 Gy (V5),10 Gy(V10),20 Gy (V20),30 Gy (V30) and the mean lung dose (D) were also significantly different in most plans.V30 and V40 of the heart were comparable between 6 MV and mixed energy plans but better than in 10 MV plan.Conclusions If the reasonable choice of beam angles and number,and capability of energy selection according to beam directions,with combined advantages of low and high energy photons,mixed IMRT plans can improve the quality of IMRT plans in general and has clinical potential for postoperative radiotherapy of invasive thymomas.
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Objective To investigate the value of diffusion-weighted magnetic resonance imaging (DWI) and apparent diffusion coefficients (ADC) in detecting metastatic lymph nodes from nasopharyngeal carcinoma (NPC),and predicting the response of these nodes to concurrent chemoradiation (CRT).Methods Eighteen patients with pathologically proven NPC received conventional magnetic resonance imaging (MRI) and DWI before treatment,weekly during treatment,and one month after treatment.DWI was performed using a single-shot echo-planar (SSEPI) MR imaging sequence with b values of 0 and 1500 s/mm2.ADC maps were reconstructed for all patients and ADC values were calculated for each lymph node and tongue muscle.Totally fifty-two morphologically abnormal lymph nodes were analyzed.The ADC values of the metastatic lymph nodes before treatment were compared between those with the short axis≥10 mm (n=32) and those with the short axis<10 mm (n=20),and the dynamic changes in ADC values of the lymph nodes before,during,and after therapy were observed and recorded.Results The average ADC of the 32 lymph nodes with the short axis ≥ 10 mm was (0.71±0.12) x 10-3mm/s,not significantly different from that of the 20 lymph nodes with the short axis < 10 mm [(0.73±0.16) x 10-3mm/s,t = 1.11 ,P =0.27].The average ADC values of these lymph nodes before treatment was significantly lower than that of the tongue muscle (t = 19.35,P < 0.0001).During CRT,the ADC values of the lymph nodes increased gradually,with the most evident change in the first two weeks before reaching a relatively flat plateau thereafter.The ADC value of the residual lymph nodes after CRT was significantly higher than that before treatment (t = 12.72,P < 0.0001),however,not statistically significant different from that of the normal tongue muscle (t = 0.34,P = 0.73).Conclusions DWI plays an important role in diagnosing the metastatic lymph nodes from NPC and is feasible for observation of the early response of the lymph nodes to IMRT,thus helping the clinicians make appropriate treatment planning and replanning in the course of radiotherapy.
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Objective To evaluate treatment outcomes and quality of life (QOL) in glioma patients treated with postoperative intensity-modulated radiotherapy (IMRT), and to explore the possible clinical factors of affecting QOL. Methods From 2007 to 2009, 37 patients with low or high grade glioma were analyzed retrospectively. All patients were operated by tumor resection below microscopy. IMRT began at 2-4 week postoperstion with 2.0 Gy/fractior, 5 fractions/week and to shrink portal and to add dose to 50-60 Gy/25-30 fractions after 40-50 Gy. The gross tumor volume (GTV) was defined as preoperation T2WI MRI high sign area and postoperation tumor cavity for low grade glioma, and with preoperation T1WI MRI enhanced abnormity area and postoperation tumor cavity for high grade glioma. The clinical target volume ( CTV ) was defined as GTV with a margin of 1.5 cm for low grade glioma and a margin of 2.5 cm for high grade ghoma, the planning target volume (PTV) with CTV plus 0.4 cm margin for setup errors according to the European Organization for Research and Treatment of Cancer ( EORTC ).The treatment outcomes and QOL were assessed. Results The half-year and one-year survival rates for all the patients were 100% and 79.2%, respectively. The median progression-free survival time was 10 months. The main side-responses after postoperative IMRT were fatigue and mild memory decline or cognitive disabilities, which were radiation dose-dependent. Conclusions Postoperative IMRT is an effective and safe modality of therapy for glioma patients.
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Objective To analyze the volumetric and dosimetric variations in radiation treatment planning(RTP) using CT images based on normal and extended reconstructed field-of-view(FOV). Methods Original data of CT scans from 16 cases of nasopharyngeal carcinomas were reconstructed to form 2 sets of CT images with Dermal(45 cm)and EFOV(65 cm),which were then exposed to RTP. Contouring of targets/OAR including GTV(gross tumor volume),CTV(clinical target volume,CTV),brain stem, lens, parotids and cord was made on normsl FOV CT set.A 7-field equi-angular IMRT (intensity modulated radiation Therapy)plan was generated with prescribed GTV dose of 70 Gy.Two sets 0f CT images were fused in DICOM coordinate system and targets/OARs on normal FOV CT were copied to EFOV CT.IMRT plans were then transplanted from normal FOV to EFOV CT,with the same isocenter on DICOM coordinates.Volumetric and dosimetrie variations including GTV,CTV brain stem,lens, parotids and cord were calculated on dose-volume-histogram(DVH).For dosimetric verification,IMRT plans were input into fluence maps of Mapcheck 1175 phantom based on normal FOV and EFOV, and DTA(distance to agreement)was used to analyze the passing rate of calculated/measured absolute doses at 5 cm depth.Paired-t test was used to compare the passing rate of field 1-7 of IMRT plans based on 2 CT sets.Results Volumes of targets and OARs on 2 CT sets of different FOVs were statistically different.with larger calculated volume on norlual FOV in all cases.There was no statistic difference in the maximal(Dmax) doses received by all targets and OARs except the small-volume lens, in which the dose was higher on normal CT than that on EFOV CT(t=-3.14,P<0.007).The mean doses(Dmean)to the CTV(clinical target volume)and GTV(gross tumor volume)were higher on EFOV than normal FOV CT(t=-6.45,-5.65,P<0.001).There was no statistic difference in Dmean received by OARs and the minimal dose (Dmin)by all targets and OARs(P>0.05).There was also no statistic difference in the passing rate of field 1-7 of IMRT plans based on 2 CT sets.Conclusions There were volumetric and dosimetric variations as evaluated on DVH using different reconstructed FOV during CT simulation,though the difference between the passing rates as verified in 2 dimensional fluence map was not significant.