Perfusion computed tomography in predicting treatment response of advanced esophageal squamous cell carcinomas.

BACKGROUND: The purpose of this study was to prospectively evaluate the predictive value of perfusion computed tomography (CT) for response of local advanced esophageal carcinoma to radiotherapy and chemotherapy. MATERIALS AND METHODS: Before any treatment, forty-three local advanced esophageal squamous cell carcinomas were prospectively evaluated by perfusion scan with 16-row CT from June 2009 to January 2012. Perfusion parameters, including perfusion (BF), peak enhanced density (PED), blood volume (BV), and time to peak (TTP) were measured using Philips perfusion software. Seventeen cases received definitive radiotherapy and 26 received concurrent chemo-radiotherapy. The response was evaluated by CT scan and esophagography. Differences in perfusion parameters between responders and non-responders were analyzed, and ROCs were used to assess predictive value of the baseline parameters for treatment response. RESULTS: There were 25 responders (R) and 18 non-responders (NR). Responders showed significantly higher BF (R:34.1 ml/100 g/min vs NR: 25.0 ml/100 g/min, p=0.001), BV (23.2 ml/100g vs 18.3 ml/100g, p=0.009) and PED (32.5 HU vs 28.32 HU, P=0.003) than non-responders. But the baseline TTP (R: 38.2 s vs NR: 44.10 s, p=0.172) had no difference in the two groups. For baseline BF, a threshold of 36.1 ml/100 g/min achieved a sensitivity of 56%, and a specificity of 94.4% for detection of clinical responders from non-responders. CONCLUSIONS: The results suggest that the perfusion CT can provide some helpful information for identifying tumors that may respond to radio-chemotherapy.

A comparison of the different 3D CT scanning modes on the GTV delineation for the solitary pulmonary lesion.

OBJECTIVES: To investigate the impacts of the different three-dimensional CT (3DCT) scanning modes on the GTV delineation for solitary pulmonary lesion (SPL) based on four-dimensional CT (4DCT), and to evaluate the feasibility of using the spiral CT scan in CT simulation. MATERIALS AND METHODS: Twenty-one patients with SPL underwent axial CT scan, spiral CT scan and 4DCT simulation scan during free-breathing, respectively. The same clinical radiation oncologist delineated the gross tumor volume (GTV) under the same CT window setting. GTVA and GTVS were created from the axial and spiral images, respectively. ITVMIP was created from the maximum intensity projection (MIP) reconstructed 4D images. The target volumes and position between GTVA, GTVS and ITVMIP were compared. The matching index (MI) between GTVA and GTVS, and the correlation between MI and GTVS were evaluated. RESULTS: ITVMIP was significantly larger than GTVA and GTVS (ps = 0.000). The ratios of ITVMIP to GTVA and GTVS were 1.57 ± 0.54 and 1.66 ± 0.61, respectively. There was no significant difference between GTVA and GTVS(p = 0.16). A comparison of the centroidal positions in x, y, and z directions for GTVA, GTVS and GTV4Dmip showed no significant difference (px = 0.17, py = 0.40, pz = 0.48). Additionally, there was no difference between distances from the centroidal positions of GTVA and GTVS to the origin of coordinates (p = 0.51). MI between GTVA and GTVS was 0.41 ± 0.24 (range 0-0.89), and it was positively correlated with the tumor volume (r = 0.64, p = 0.002). CONCLUSION: There was no impact on the volume or centroidal position of GTV by the axial scan or spiral scan in 3DCT simulation for SPL. MI between GTVA and GTVS was small. A positively correlation was found between MI and GTVS. Relative to axial scanning mode, spiral CT scan was more timesaving and more efficient, it was feasible in 3DCT simulation for SPL.

Comparison of primary target volumes delineated on four-dimensional CT and 18 F-FDG PET/CT of non-small-cell lung cancer.

BACKGROUND: To determine the optimal threshold of 18 F-fluorodexyglucose (18 F-FDG) positron emission tomography CT (PET/CT) images that generates the best volumetric match to internal gross target volume (IGTV) based on four-dimensional CT (4DCT) images. METHODS: Twenty patients with non-small cell lung cancer (NSCLC) underwent enhanced three-dimensional CT (3DCT) scan followed by enhanced 4DCT scan of the thorax under normal free breathing with the administration of intravenous contrast agents. A total of 100 ml of ioversol was injected intravenously, 2 ml/s for 3DCT and 1 ml/s for 4DCT. Then 18 F-FDG PET/CT scan was performed based on the same positioning parameters (the same immobilization devices and identical position verified by laser localizer as well as skin marks). Gross target volumes (GTVs) of the primary tumor were contoured on the ten phases images of 4DCT to generate IGTV10. GTVPET were determined with eight different threshold using an auto-contouring function. The differences in the position, volume, concordance index (CI) and degree of inclusion (DI) of the targets between GTVPET and IGTV10 were compared. RESULTS: The images from seventeen patients were suitable for further analysis. Significant differences between the centric coordinate positions of GTVPET (excluding GTVPET15%) and IGTV10 were observed only in z axes (P < 0.05). GTVPET15%, GTVPET25% and GTVPET2.0 were not statistically different from IGTV10 (P < 0.05). GTVPET15% approximated closely to IGTV10 with median percentage volume changes of 4.86%. The best CI was between IGTV10 and GTVPET15% (0.57). The best DI of IGTV10 in GTVPET was IGTV10 in GTVPET15% (0.80). CONCLUSION: None of the PET-based contours had both close spatial and volumetric approximation to the 4DCT IGTV10. At present 3D-PET/CT should not be used for IGTV generation.

Influence of intravenous contrast medium on dose calculation using CT in treatment planning for oesophageal cancer.

OBJECTIVE: To evaluate the effect of intravenous contrast on dose calculation in radiation treatment planning for oesophageal cancer. METHODS: A total of 22 intravein-contrasted patients with oesophageal cancer were included. The Hounsfield unit (HU) value of the enhanced blood stream in thoracic great vessels and heart was overridden with 45 HU to simulate the non-contrast CT image, and 145 HU, 245 HU, 345 HU, and 445 HU to model the different contrast-enhanced scenarios. 1000 HU and -1000 HU were used to evaluate two non-physiologic extreme scenarios. Variation in dose distribution of the different scenarios was calculated to quantify the effect of contrast enhancement. RESULTS: In the contrast-enhanced scenarios, the mean variation in dose for planning target volume (PTV) was less than 1.0%, and those for the total lung and spinal cord were less than 0.5%. When the HU value of the blood stream exceeded 245 the average variation exceeded 1.0% for the heart V40. In the non-physiologic extreme scenarios, the dose variationof PTV was less than 1.0%, while the dose calculations of the organs at risk were greater than 2.0%. CONCLUSIONS: The use of contrast agent does not significantly influence dose calculation of PTV, lung and spinal cord. However, it does have influence on dose accuracy for heart.

[Comparison of three methods to delineate internal gross target volume of the primary hepatocarcinoma based on four-dimensional CT simulation images].

OBJECTIVE: To compare the position and magnitude of internal target gross volume (IGTV) of primary hepatocarcinoma delineated by three methods based on four-dimensional computed tomography (4D-CT) and to investigate the relevant factors affecting the position and magnitude. METHODS: Twenty patients with primary hepatocarcinoma after transcatheter arterial chemoembolization (TACE) underwent big bore 4D-CT simulation scan of the thorax and abdomen using a real-time position management (RPM) system for simultaneous record of the respiratory signals. The CT images with respiratory signal data were reconstructed and sorted into 10 phase groups in a respiratory cycle, with 0% phase corresponding to end-inhale and 50% corresponding to end-exhale. The maximum intensity projection (MIP) image was generated. IGTVs of the tumor were delineated using the following three methods: (1) The gross tumor volume (GTV) on each of the ten respiratory phases of the 4D-CT image set was delineated and fused ten GTV to produce IGTV10; (2) The GTVs delineated separately based on 0% and 50% phase were fused to produce IGTV(IN+EX); (3) The visible tumor on the MIP image was delineated to produce IGTV(MIP). Twenty patients were divided into groups A and B based on the location of the target center,and were divided into groups C and D based on the tumor maximum diameter. The patients were divided into groups E and F based on the three-dimensional (3D) motion vector of the target center. The position of the target center, the volume of target, the degree of inclusion (DI) and the matching index (MI) were compared reciprocally between IGTV10, IGTV(IN+EX) and IGTV(MIP), and the influence of the tumor position and 3D motion vector on the related parameters were compared based on the grouping. RESULTS: The average differences between the position of the center of IGTVs on direction of X, Y and Z axes were less than 1.5 mm, and the difference was statistically not significant. The volume of IGTV10 was larger than that of IGTV(IN+EX), but the difference was not significant (t = 0.354, P = 0.725). The volume of IGTV10 was larger than that of IGTV(MIP) but the difference was not significant (t = -0.392, P = 0.697). The ratio of IGTV(IN+EX) to IGTV10 was 0.75 +/- 0.15 and the ratio of IGTV(MIP) to IGTV10 was 0.78 +/- 0.14. The DI of IGTV(IN+EX) in IGTV10 was (74.85 +/- 15.09)% and that of IGTV(MIP) in IGTV10 was (68.87 +/- 13.69)%. The MI between IGTV10 and IGTV(IN+EX), IGTV10 and IGTV(MIP) were 0.75 +/- 0.15 and 0.67 +/- 0.13, respectively. The median of ratio of IGTV(IN+EX)/ IGTV10 was 0.57 in group A versus 0.87 in group B, statistically with a significant difference between the groups A and B (Z = -3.300,P = 0.001). The median of ratio of IGTV(MIP)/IGTV10 was 0.51 in the group A and 0.72 in group B, with a significant difference between the groups A and B (Z = -3.413, P = 0.001). The median of ratio of IGTV(IN+EX)/IGTV10 was 0.79 in group C versus 0.74 in group D, with a difference not significant (Z = -0.920, P = 0.358). The median of ratio of IGTV(MIP)/IGTV10 was 0.85 in group C versus 0.80 in group D, with a non-significant difference (Z = -0.568, P = 0.570). The median of ratio of IGTV(IN+EX)/IGTV10 was 0.87 in group E versus 0.68 in group F, with a significant difference between the two groups (Z = -2.897, P = 0.004). The median of ratio of IGTV(MIP)/IGTV10 was 0.85 in the group E versus 0.81 in the group F, with a non-significant difference (Z = -0.568, P = 0.570). CONCLUSIONS: The center displacement of the IGTVs delineated separately by the three techniques based on 4D-CT images is not obvious. IGTV(IN+EX) and IGTV(MIP) can not replace IGTV10, however, IGTV(IN+EX) is more close to IGTV10 comparing with IGTV(MIP). The ratio of IGTV10 and IGTV(MIP) is correlated to the 3D motion vector of the tumor. When the tumor is situated in the upper part of the liver and with a 3D motion vector less than 9 mm, IGTV10 should be the best IGTV.

[Displacement of the silver clips in surgical cavity based on four-dimensional CT images for patients undertaking external-beam partial breast irradiation after breast-conserving surgery].

OBJECTIVE: To explore the displacement of the selected clips and the center of the geometry consisted of all the clips in the surgical cavity measured on the basis of four-dimensional computed tomography (4D-CT) simulation images. METHODS: Fourteen breast cancer patients after breast-conserving surgery were recruited for external beam partial-breast irradiation (EB-PBI), and received large aperture CT simulation. The 4D-CT image data sets were collected when the patient was in the free breathing state. Using the Varian Eclipse treatment planning system, the selected four clips in the cavity were separately delineated on the CT images from 10 phases of the breath cycle, and all of the clips in the cavity were marked to obtain the geometry. Then the displacement of the four selected clips and the center of the geometry in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions were measured. The differences of the displacement were compared. RESULTS: The displacements in the AP and SI directions were always greater than the displacement in LR direction for the same selected clip. The difference of the displacements in the same direction of the different selected clips was not statistically significant (P>0.05). The displacements of the geometry center consisted of all of the clips in the LR, AP, SI directions were (1.34±0.39) mm, (2.01±1.02) mm and (1.89±1.03) mm, respectively, and the difference of the displacements between LR and AP, LR and SI were all statistically significant (P<0.05). In the same directions (LR, AP and SI), the displacement of geometry center was always greater than the displacement of the selected clips, and the difference except SI direction was all statistically significant (P<0.05). In the SI direction, the association between the displacement of geometry center and the upper clip, geometry center and the lower clip was statistically significant (P<0.05). CONCLUSION: When the target for EB-PBI is defined on the basis of 4D-CT simulation images, the displacement of the selected clips at the border of the surgical cavity is not qualified to substitute the displacement of the target defined basing on all of the clips in the surgical cavity.

Comparison of the planning target volume based on three-dimensional CT and four-dimensional CT images of non-small-cell lung cancer.

BACKGROUND AND PURPOSE: To compare positional and volumetric differences of planning target volumes (PTVs) based on axial three-dimensional CT (3DCT) and four-dimensional CT (4DCT) for the primary tumor of non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Twenty-eight patients with NSCLC underwent 3DCT and 4DCT scans of the thorax during normal free breathing. PTV(vector) was defined on 3DCT using the individual tumor motion vector measured by 4DCT accounting for tumor motion; PTV(4D) was defined on all phases of 4DCT images. In addition, a 7mm margin for microscopic disease and a 3mm setup margin were used for above PTVs, respectively. The differences in target position, volume and coverage between PTV(vector) and PTV(4D) were evaluated for tumors in different lobes, respectively. RESULTS: The median motion vector for tumors located in the upper lobe (group A) and in the middle lower lobe (group B) was 2.8 and 7mm, respectively. The mean centroid shifts between PTV(vector) and PTV(4D) in the LR, AP and CC directions for group A and B were close to zero. The median size ratio of PTV(4D) to PTV(vector) was 0.75 and 0.52 for group A and B. The motion vector showed a significant correlation to the ratio of PTV(4D) to PTV(vector) for group A and B (p=0.008 and 0.003). The median DI of PTV(vector) in PTV(4D) was 69.19% for group A and 51.60% for group B. The median DI of PTV(4D) in PTV(vector) was 98.99% for group A and 99.94% for group B. CONCLUSION: It is necessary to expand the internal margin isotropically in a single direction for 3DCT treatment planning due to the uncertainty of the 3DCT-based target position. The 3DCT-based PTV using individual margins provides a good coverage of the 4DCT-based PTV, meanwhile encompasses relatively large normal tissues, especially for middle and lower lobe tumors. We should be cautious about the use of the individual PTV derived from 3DCT in treatment planning.