Related Study About Target Delineation In Radiation Therapy For Nasopharyngeal Carcinoma

1. Related study about target delineation of the primary tumor for nasopharyngeal carcinoma1.1 Impact of contrast media on target delineation and dose calculation of nasopharyngeal carcinoma treated with radiotherapyPurpose To compare the results of target delineation with and without intravenous contrast during CT scan for nasopharyngeal carcinoma (NPC), and to assess the potential changes in dose calculation.Methods and Materials CT-simulation with (C-) and without (C+) intravenous contrast media was performed in seven NPC patients. All the scanning images were transferred to the treatment planning system and undergone C-/C+ image registration. Three radiation oncologists were asked to delineate gross tumor volume (GTV), contours of the eye, brainstem and the spinal cord both on the C- and C+ images independently. Another radiation oncologist was asked to delineate the concordance volume and then calculate the concordance index (CI). Two treatment plans were carried out on C- and C+ images. In each patient dose distributions were formally compared for both plans, and the increment in monitor units (MU) needed to compensate for the presence of contrast media was assessed. Paired t test or Wilcoxon test was used to compare the defference between the CIs with and without contrast media.Results The mean CI of the eye, brainstem and the spinal cord of the seven patients on the C- images was 94.23 ± 0.96, 82.40 ± 2.94, and 82.07 ± 3.51, respectively; And the accordingly CI on the C+ images was 94. 63 ± 0.93, 83.25 ± 2.58, and 82.53 ± 3.08, respectively (p=0.44, p=0.14, and p=0.50, respectively). The CI of GTV on C- and C+ images changed from 38.79 to 58.54 and from 54.73 to 75.01, respectively. The contrast media decreased interobserver variability in delineateing GTV(p=0.02). The average mean MU increment with intravenous contrast was 0. 54%±0.27(p=0. 001).Conclusions Intravenous contrast media used during CT simulation decreases interobserver variability in GTV delineation, but not in delineation of theeye, brainstem, and the spinal cord. And the contrast media moderatelyimproves MU in NPC patients treated with 3D-CRT.1.2 A Comparative study of CT and HRI registration methods in nasopharyngeal carcinomaObjective To explore and evaluate the difference among three methods for CT and MRI registration in patients with nasopharyngeal carcinoma (NPC).Methods and materials CT and MRI scans of 10 NPC patients were carried on in treatment position with immobilized mask. All images were transformed to the treatment planning system, and undergone CT/MRI registration using the following three methods, respectively:①Links and Marks, ②Interactive, ③ Normalized Mutual Information. The time needed for the above three methods to complete CT/MRI registration was recorded. And registration errors of each method was measured. Friedman test was used to compare the differences among the registration errors of the above three CT/MRI registration algorithms, as well as differences among the time needed to complete CT/MRI fusion.Result The maximum registration error of the three methods at X axis was all less than 1.10mm (p=0.72) . And the maximum registration error at Y axis was less than 1.40mm(p=0.25). The maximum error between the center of the maxillary sinus shown on CT and MRI at the X axis was less than 0.60mm(p=0.33), and less than 0.72mm at the Y axis(p=0.27). And less than 1.51mm at the Z xis(p=0.72). The time needed to complete CT/MRI registration was longest for Links and Marks method (p=0.001), while there was no difference between the time needed for Interactive and Normalized Mutual Information method.Conclusion All the three registration methods-Marks and Links, Interactive, Normalized Mutual Information-can achieve good CT/MRI registration result. But more time is needed for the Marks and Links method.1. 3 The role of MRI on decreasing interobserver variability in target delineation of nasopharyngeal carcinomaPurpose To explore and evaluate the interobserver variability in delineatinggross tumor volume (GTV) of nasopharyngeal carcinoma (NPC), contours of theeye, brainstem, and spinal cord with CT and MRI, respectively.Methods and materials CT and MRI scans of 10 untreated patients withnasopharyngeal carcinoma were carried out in treatment position withimmobilized mask. CT/MRI registration was performed by Normalized MutualInformation method. Three experienced radiation oncologist in the NPCtreatment group were asked to delineate GTV, contours of the eye, brainstem,and spinal cord according to CT and MRI, respectively. (named GTV-CT and GTV-MR,STEM-ct and STEM-mr, EYE-ct and EYE-mr, CORD-ct and CORD-mr). Another radiationoncologist was asked to delineate the concordance area of the above organs,and concordance index (CI) was calculated. Paired t test was used to comparethe difference between CI of GTV-CT and GTV-MR, STEM-ct and STEM-mr, EYE-ctand EYE-mr, CORD-ct and CORD-mr.Result The mean CI of the EYE-ct and EYE-mr was 94.65 ± 0.82 and 94.81±1.01,respectively (p=0. 62). The mean CI of STEM-ct and STEM-mr was 83.19±2.59 and92.79±0.97, respectively (p=0.00). The mean CI of CORD-ct and CORD-mr was 85.15±2.03 and 94.35±1.45, respectively(p=0. 00). The mean CI of GTV-CT and GTV-MRwas 68.63±4.92 and 90.89±1.56, respectively (p=0.00).Conclusion Compared with CT, MRI decreases interobserver variability indelineating GTV, contours of the brainstem and spinal cord.1.4 A comparative study of gross tumor volume (GTV) shown on CT and MRI of nasopharyngeal carcinomaPurpose To compare gross tumor volume (GTV) of nasopharyngeal carcinoma (NPC), brain stem, eye, and spinal cord delineated according to CT and MRI, respectively.Methods and Materials CT and MRI scans were obtained for 62 NPC patients with the head fixed with thermoplastic mask. The slice thickness for CT and MRI scan was 5mm and 6mm, respectively. All the images were transferred to the treatment planning system (TPS) according to DICOM protocol, MRI/CT registration was performed using normalized mutual information method. The GTV, contours of the brain stem, eye, and spinal cord were delineated by anexperienced radiation oncologist according to CT and MRI, respectively (named GTV-CT and GTV-MR, STEM-ct and STEM-mr, EYE-ct and EYE-mr, CORD-ct and CORD-mr). Wilcoxon test and/or Paired t test was used to compare the differences between the volumes of GTV-ct and GTV-mr, STEM-ct and STEM-mr, EYE-ct and EYE-mr, CORD-ct and CORD-mr.Results Of the 62 cases, 9 were with T1 disease, 20 with T2, 12 with T3, and 21 with T4. The mean volume of EYE-ct and EYE-mr was 9.62±0.93 cm~3 and 9.67 ±0.98cm~3, respectively(p=0.48). The mean volume of CORD-ct and CORD-mr was 8.55±1.47cm~3 and 7.04±1.26cm~3, respectively. CORD-ct was 21.45% larger than CORD-mr (p=0.000). The mean volume of STEM-ct and STEM-mr was 23.41 ± 3.83cm~3 and 20.64 ± 3.74 cm~3, respectively. STEM-ct was 13.42% larger than STEM-mr (p=0.000). Further analysis showed that CORD-ct and STEM-ct was always larger than CORD-mr and STEM-mr, irrespective of T stage. On the average, GTV-MR was larger than GTV-CT (p=0.002). But for T1 disease, there was no statistical difference between GTV- MR and GTV- CT (p=0. 859). For T2 lesion, GTV- CT was larger than GTV- MR (p=0.007). For T3 and T4 disease, GTV- MR was larger than GTV- CT. (p=0.028 and p=0.002, respectively). Six patients' GTV-CT could cover GTV- MR completely. Twenty-two patients' GTV- MR could cover GTV- CT completely. The rest thirty-four patients' GTV- CT and GTV- MR were complementary to each other.Conclusion The contours of brainstem and spinal cord shown on MRI are smaller than that on CT. CT and MRI are complementary in delineating the GTV. 2. Related study about target delineation of metastatic node for nasopharyngeal carcinoma2.1 Analysis of CT-Based Distribution of Cervical Nodal Metastases in Nasopharyngeal CarcinomaPurpose The application of intensity-modulated radiation therapy (IMRT) for nasopnaryngeal carcinoma (NPC) requires a precise delineation of the nodal area and nodal clinical target volume (CTV) on CT images. And the prerequisite is to find out the patterns of CT-based distribution of metastatic lymph nodesfrom NPC. But few such reports and documents were found. This study was designed to analyze the patterns of CT-based distribution of nodal involvements from NPC according to the guidelines of nodal levels proposed by Radiation Therapy Oncology Group (RTOG).Methods and Materials From July 2003 to November 2003, 259 cases of newly diagnosed NPC patients received radiotherapy at Fudan University Affiliated Cancer Hospital. All patients had transversal contrast enhanced CT scan before treatment. The scanning range was from the base of skull to the clavicle. Diagnostic radiologists and radiation oncologists assessed together the nodal distribution in each RTOG nodal levels. Differences between T stage and nodal metastasis rate were tested by chi-square test. The neck was further divided into three regions by the level of the hyoid bone and the inferior border of the cricoid cartilage to assess leap metastasis of the nodes.RESULTS A total of 218 patients (84.2%) had nodal involvement. The distribution was as follows: 0 in level Ⅰa, 6 (2.8%) in level Ⅰb, 115(52.8 %) inlevel Ⅱa, 192 (88.1%) in level Ⅱb, 78(35.8%) in level Ⅲ, 20(9.2 %) in level Ⅳ, 65(29.9%) in level Ⅴ, 0 in level Ⅵ, 157(72.0%) in retropharynx, and 2(0. 9%) at preauricular area. Leap metastasis was found in only 5 cases (2.3%) . No significant correlation was found between T stage and nodal involvement.CONCLUSION NPC has a high probability of nodal metastases. Our preliminary data showed that nodes in level Ⅱa, Ⅱb and retropharynx were most likely to be involved. Nodal metastases development appeared from the upper to the lower level, and from the proximal to the distal part, with a very low skip metastasis rate. The relationship between T stage and nodal involvement did not reach statistical significance.2.2 Feasibility of RTOG suggested nodal classification guidelines in delineation of nodal CTV for intensity modulated radiation therapy of nasopharyngeal carcinomaPurpose To evaluate the pattern of nodal metastases from nasopharyngeal carcinoma (NPC) and to explore the feasibility of RTOG suggested nodal classification guidelines in delineation of nodal CTV for intensity modulatedradiation therapy of NPC.Methods and Materials 259 consecutive NPC patients received contrast-enhanced transverse CT scan from July to November in 2003, the scanning range extended from the skull base to the inferior border of the clavicle. Interpretation of the images and assessment of the involved nodes distribution were performed by the group of radiation oncologists and diagnostic radiologists according to RTOG suggested classification guidelines of the neck. And the applicability of RTOG guidelines was further analyzed in nodal CTV delineation for IMRT.Results 218 cases (84.2%) had nodal involvements. According to RTOG guidelines, nodal distributions were 0 in Ⅰa, 6 in Ⅰb, 115 in Ⅱa, 192 in Ⅱ b, 78 in Ⅲ, 20 in Ⅳ, 65 in Ⅴ, 0 in Ⅵ, 157 in retropharynx, respectively. And among the 192 cases with level Ⅱb nodal metastases, 29(15.1%) had involved nodes whose cranial edge reached the level of half the first cervical vertebra(C1), and 9 (4.7%) reached the cranial edge of C1. And 2 cases had lesions at the preauricular area. Extracapsular spread was rarely seen with nodes less than 1. 5cm in diameter. Nodes more than 3. 0cm in diameter were all associated with extracapsular spread. 67% of nodes between 1. 5 and 3. 0cm in diameter had extracapsular spread.Conclusions The RTOG nodal classification guideline did not fully cover level Ⅱb nodes, it would be better to set the cranial edge of Ⅱb at the cranial border of C1. CTV boundaries described by RTOG guidelines was applicable for patients with nodes less than 1.5cm in diameter, but not for patients with nodes more than 3. 0cm in diameter.3. Applicability of 99mTc-labeled HL91 as a hypoxic marker to detectnasopharyngeal carcinomaPurpose: To investigate the 99mTc -labelled amine oxime (99mTc -HL91) as apotential noninvasive clinical marker of tumor hypoxia in nasopharyngealcarcinoma (NPC).Materials and Methods: Twenty-four newly diagnosed NPC patients wereimmobilized with thermoplastic mask and underwent SPECT scans two hours after99mTc-HL91 (740 MBq per person) injection. Distribution of the tracer was assessed, and Region Of Interest(ROI) technique was used to calculate the uptake ratio of both the primary tumor and involved node to the background. Student t test was used to test the difference between the ratios of the primary and the involved node.Results: All of the twenty-four patients showed obvious uptake of 99mTc-HL91 by the nasopharyngeal cancer. The uptake ratio of nasopharyngeal cancer to background was 3.25±0.44. Of the 15 patients with lymph node metastases, fourteen (93. 3%) showed uptake of at the nodal site. The uptake ratio of the involved node to background was 2. 74 + 0. 36. The ratio of nasopharyngeal cancer to background was higher than that of involved node to background(p=0.002).Conclusion 99mTc-HL91 shows good potential as a clinical marker for detection of nasopharyngeal carcinoma. But further study is required to test its hypoxia specificity.