G. Shan

Fox Chase Cancer Center, Philadelphia, PA, United States

Are you G. Shan?

Claim your profile

Publications (14)35.63 Total impact

  • L. Chen · G. Shan · Q. Xu · J. Fan · X. Chen · C. Ma
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: This work investigates the dosimetric changes due to inter‐factional organ motion during the treatment course for IMRT of prostate cancer with in room CT guidance. Methods: Fifteen prostate cancer patients were recruited for this retrospective study. For each patient, MR and CT images were fused. IMRT treatment planning was performed on the simulation CT images. Inter‐fractional organ motion during the course of treatment was corrected using a Siemens CT‐on‐rails system. The prostate, rectum, bladder and femoral heads were outlined on both the original treatment plan and the subsequent daily CT images for 98 treatment factions by the same investigator. Dose distributions on these daily CT images were recalculated with the isocenter shifts relative to the simulation CT images. The doses from the subsequent daily CTs were co‐registered and compared with the original doses planned on the simulation CT. Results: Our results based on 15 patients (98 daily CT sets) with anatomical matching (i.e., matching the prostate contours from simulation CT scans with the prostate on daily CT‐on‐rails scans) showed that 7.1% of the treatment fractions exhibited poor target coverage (Dmin < 65Gy). For critical structures, 27.6% and 26.5% of the treatment fractions violated our rectal criteria of V65 < 17% and V40 < 35% for the rectum and 10% and 6% of the treatment fractions violated our bladder criteria of V65 < 25% and V40 < 50% for the bladder, respectively. Conclusion: The IGRT procedure for target localization using 3D imaging for prostate cancer is still not ideal if only anatomy matching is used. Future studies are warranted for improvements in target dose coverage using adaptive therapy through re‐planning or other target localization techniques such as that to match prescription isodose surfaces with target volumes to correct for both translational and rotational organ motion.
    No preview · Article · Jun 2013 · Medical Physics
  • C. Ma · G. Shan · W. Hu · I. Emam · Q. Xu · J. Li · R. Price · L. Chen

    No preview · Article · Nov 2012 · International Journal of Radiation OncologyBiologyPhysics
  • C Ma · G Shan · W Hu · Q Xu · I Mohamed · J Fan · L Chen
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: Advanced imaging techniques have been developed to facilitate patient setup and target localization for advanced prostate radiotherapy. These techniques work well for translational, interfractional organ motion but may Result in poor target coverage for some cases where the effects of rotational motion and organ deformation are not corrected. This work investigates the feasibility of the use of 3D dose distributions to match the target volume to improve target coverage and critical structure sparing. Methods: Fifteen previously treated prostate patients were selected for this retrospective study. Siemens CT-on-rails scans were performed before and after the IMRT treatment weekly. Ninety-eight post-treatment CT-on-rails scans were used to reconstruct the dose distributions. The isodose distributions and DVH were compared with those of the original plans. Target localization was also performed using the prescription isodose surface from the original plan to match the target volume and a new isocenter shift was applied in the dose reconstruction, which was evaluated against the original plans and the reconstructed dose distributions using the standard contour-based target-localization technique. Results: The results show that for contour/anatomy matching, 7.1% of the 98 treatment fractions exhibit poor target coverage (Dmin<65Gy). For the rectum, 27.6% fractions violated our rectal criterion of V65<17% and 26.5% fractions violated the criterion of V40<35%. After the isocenter realignment based on 3D dose/target volume matching, all the fractions delivered >65Gy to the target, and the percentages of fractions that violated the rectal criteria (V65<17% and V40<35%) were reduced to 14.3% and 18.4%, respectively. Conclusions: The current IGRT procedure for isocenter alignment based on contour/anatomy matching is not ideal due to poor soft-tissue contrast, residual translational/rotational organ motion and organ deformation. Target localization based on 3D dose/target volume matching provides better target dose coverage and critical structure sparing that reduces the need for adaptive re-planning.
    No preview · Article · Jun 2012 · Medical Physics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To quantify changes of the transverse diameter and volume and dosimetry, and to illustrate the inferiority of non-replanning during intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) patients. Fifty-three NPC patients who received IMRT in 33 fractions were enrolled in this prospective trial. Before the 25th fraction, a new simulation computed tomography (CT) scan was acquired for all patients. The dose-volume histograms of the phantom plan were compared with the initial plan. Significant reduction of the transverse diameter of the nasopharyngeal, the neck, and 2 parotid glands volume was observed on second CT compared with the first CT (mean reduction 7.48 ± 4.45 mm, 6.80 ± 15.14 mm, 5.70 ± 6.26 mL, and 5.04 ± 5.85 mL, respectively; p < 0.01). The maximum dose and V-40 of the spinal cord, mean dose, and V30 of the left and right parotid, and V-50 of the brain stem were increased significantly in the phantom plan compared with the initial plan (mean increase 4.75 ± 5.55 Gy, 7.18 ± 10.07%, 4.51 ± 8.55 Gy, 6.59 ± 17.82%, 5.33 ± 8.55 Gy, 11.68 ± 17.11% and 1.48 ± 3.67%, respectively; p < 0.01). On the basis of dose constraint criterion in the RTOG0225 protocol, the dose of the normal critical structures for 52.83% (28/53) of the phantom plans were out of limit compared with 1.89% (1/53) of the initial plans (p < 0.0001). Because of the significant change in anatomy and dose before the 25th fraction during IMRT, replanning should be necessary during IMRT with NPC.
    Full-text · Article · Dec 2011 · Medical dosimetry: official journal of the American Association of Medical Dosimetrists
  • H. Yang · W. Wang · C. Yu · G. Shan · W. Hu
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: The aim of replanning at the midcourse and the latter course was to illustrate the superior timing of replanning during intensity‐modulated radiotherapy(IMRT) for nasopharyngeal carcinoma (NPC) patients. Methods: Twenty‐three NPC patients received IMRT in 33 fractions were enrolled. Each patient with two repeated CT scans before the 16 fraction and before the 25 fraction, respectively. The anatomic changes were determined in the three CT scans. The differences of the dose distribution were compared in inital plan vs. phantom plan 1 and replanning 1vs. phantom plan 2. Results: The mean decrements of the transverse diameter of nasopharyngeal level (d1) and the transverse diameter of the neck level (d2) were 4.66mm, 2.63mm and 7.94mm, 5.78mm before the 16th and 25th fraction. The target volume reduced mainly in the first half. The mean decrements of volume GTVnx and GTVnd were 12.20cc, 8.91cc and 18.25cc, 13.71cc before the 16th and 25th fraction. While the volume of the parotid glands reduced mainly in the second half. The mean decrements of the left and right parotid glands volume were 1.40cc, 1.98cc and 6.31cc, 6.08cc before the 16th and 25th fraction. But the dose changes of bilateral parotids were more prominent in the first half than in the second half. There was a statistically significant increase in the mean dose and V30 to the bilateral parotid only in the first half (P < 0.05). Based on dose constraint criterion in the RTOG0225 protocol, the dose of the normal critical structures for 39.13% (9/23) were out of limit comparing to in the first half than 17.39(4/23) in the second half. Conclusions: Replanning at the midcourse may reach more benefits both in the coverage of the targets and sparing of normal structures for NPC patients. This study was supported by Zhejiang Provincial Medical and Health science Foundation of China (2008B198).
    No preview · Article · Jun 2011 · Medical Physics
  • W. Hu · Z. Zheng · G. Shan · C. Yu · H. Zhu · H. Yang · B. Wang · W. Ding · X. Liang · Y. Wang

    No preview · Article · Jun 2010 · Medical Physics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To quantify the target and normal structures on dose distributing variations during intensity-modulated radiotherapy (IMRT) and to assess the value of replanning for nasopharyngeal carcinoma (NPC) patients. Twenty-eight NPC patients treated with IMRT were recruited. The IMRT was delivered in 33 fractions, to 70 to 76Gy, to the gross tumor volume (GTV). Before the 25th fraction of IMRT, a new simulation computed tomography (CT) scan was acquired for all patients. According to the dose constraint criterion in the Radiation Therapy Oncology Group (RTOG) 0225 protocol, the replanning was generated on the new simulation CT. With the Quality Assessment Center of a CORVUS 6.3 treatment planning system, a phantom plan was generated for each patient by applying the beam configurations of the initial plan to the anatomy of the new simulation CT. The dose-volume histograms of the phantom plan were compared with the replanning. The percentage of prescription dose delivered to the clinical target volume (CTV1) was significantly increased by 4.91% +/- 10.89%, whereas the maximum dose to the spinal cord, mean dose to the left parotid, and V30 to the right parotid were significantly decreased by 5.00 +/- 9.23Gy, 4.23 +/- 10.03Gy, and 11.47% +/- 18.89% respectively in the replanning, compared with the phantom plan (p < 0.05). Based on the dose constraint criterion in the RTOG0225 protocol, 50% of phantom plans (14/28) were out of limit for the dose to the normal critical structures, whereas no plan was out of limit in replanning (p < 0.001). Replanning for patients with NPC before the 25th fraction during IMRT helps to ensure adequate dose to the target volumes and safe doses to critical normal structures.
    Full-text · Article · Feb 2010 · International journal of radiation oncology, biology, physics
  • C. Ma · G. Shan · W. Hu · Q. Xu · J. Fan · I. Mohamed · L. Chen

    No preview · Article · Nov 2009 · Fuel and Energy Abstracts
  • L. Jin · J. Li · J. Fan · L. Wang · L. Chen · Q. Xu · R. Price · G. Shan · Cm Ma
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: In conventional photon breast therapy, the effect of setup and breathing motion is accounted for by adding a margin to the clinical target volume (CTV). In modulated electron radiation therapy (MERT), since the electron beams can be arranged nearly along the direction of the organ motion, the effect of breathing motion is greatly reduced. This work is aimed to estimate the dosimetric changes caused by setup and breathing motion for MERT of breast cancer.Method and Materials:Monte Carlo(MC) based inverse treatment planning was used based on the CT data of a breast phantom. The dosimetric accuracy of the MERT delivery using the Siemens photonMLC (pMLC) was verified previously. In this work, five Monte Carlo calculated plans were compared with different static displacements (along the beam direction) of the phantom from its normal position, i.e. ±1cm, ±0.5cm and 0cm. Comparisons were performed in terms of 2D isodose distributions, dose‐volume histograms (DVHs), minimum dose (Dmin), mean dose (Dmean) and maximum dose (Dmax). Results: For ±1cm target displacements, dose differences from the nominal plan (without target motion) are relatively large in both 2D dose distributions and DVHs. For example, the difference in Dmean for this case is about 3.4%, indicating a visible target dose reduction. For ±0.5cm target displacements, a minor difference is seen for the 90% isodose lines, and the difference in Dmean is less than 2%. The integrated dose distributions remain unchanged, indicating the effect of breathing motion on the dose coverage of the target is ignorable. Conclusions: Due to the relatively small SSDs used for pMLC‐based MERT the effect of patient setup may become significant (displacement >0.5cm). Breathing motion has little effect for en‐face electron irradiation. The magnitude of the setup effect can be estimated with the inverse‐square relationship with an accurately determined “effective” SSD.
    No preview · Article · Jun 2009 · Medical Physics
  • G. Shan · L. Chen · W. Hu · Q. Xu · J. Fan · I. Mohamed · C. Ma
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: This work is aimed to evaluate the dose distributions delivered by image‐guidedradiation therapy(IGRT) for prostate cancer using the in‐room CT technique. Methods and Materials: A Siemens CT‐on‐rails system was used for image‐guided target localization for intensity‐modulated radiation therapy(IMRT) of prostate cancer. Fifteen previous treated prostate patients were selected for this study. CT‐on‐rails scans were performed before and after the IMRTtreatment once a week under local IRB approval. A total of 15 original simulation CT scans and 98 post‐treatment CT scans were contoured by the same oncologist to delineate the prostate target, bladder and rectum. IMRT plans were generated on the original simulation CTs and the same MUs and leaf sequences were used to compute the dose distributions for post‐treatment CTs. These dose distributions represent what the patients have actually received by the IGRT procedure. For some dose distributions that showed poor target coverage, isocenters were shifted to match the prescription isodose surfaces with the target volumes and the dose distributions recalculated. Results: The results showed that using the standard IGRT procedure based on anatomy matching, 7.1% of the treatment fractions exhibited poor target coverage (Dmin<65Gy) while 27.6% and 26.5% of the treatment fractions violated our rectal criteria of V65<17% and V40<35%, respectively. After matching the prescription isodose surfaces with the target volumes, all the fractions delivered >65Gy to the target, and the percentages of fractions that violated the rectal criteria (V65<17% and V40<35%) were reduced to 14.3% and 18.4%, respectively. Conclusions: The current IGRT procedure for prostate cancer is still not ideal if only anatomy matching is used for target localization due to poor soft‐tissue contrast and organ deformation (rectal and bladder filling). Improvements in target coverage after matching prescription isodose surfaces with target volumes indicate our current margins are adequate with optimal target localization.
    No preview · Article · Jun 2009 · Medical Physics
  • Q. Xu · J. Li · G. Shan · I. Veltchev · I. Emam · J. Fan · T. Lin · L. Jin · L. Chen · C. Ma
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: The Beacon rotation angles reported by the Calypso system have not been utilized clinically due to the difficulties in rotating the patient. The actual prostate rotation angle is affected by Beacons&apos; migration, prostate&apos;s shrinkage and deformation due to rectal/bladder filling. This work investigates the actual prostate rotation angles between the planning CT and the treatment CBCT and to compare those reported by the Calypso system. Method and Materials: The Calypso system reports centroid shifts and rotation angles of the 3 implanted Beacons, relative to their locations on the planning CT.CBCT scans were obtained for 9 treatment fractions of 5 patients. The same sets of the Beacons in the planning CT and post‐treatment CBCT were segmented according to their high intensities and aligned according to their centroid positions. An iterative closest point (ICP) method was developed to find the best matching iteratively between two sets of Beacons after rotation and translation. Results: The maximum inter‐Beacon distance varied from 1.1 to 4.7 mm with inter‐Beacon distances from 14.4 to 40.4 mm. The mean Beacon rotation angle reported by the Calypso system in each plane was 4.7±3.8°, which were likely caused by the inter‐Beacon distance change. After the best 3D matching of the Beacons, our method reported a mean rotation angle of 1.5±1.7° for all the fractions. If the projected inter‐Beacon distance was >9mm there was good agreement between our method and the Calypso system. As the inter‐Beacon distance decreased, the uncertainty in the reported rotation angle increased. Conclusion: The actual rotation angles for the prostate were smaller than those for the Beacons reported by the Calypso system. It is recommend to avoid small (<9mm) projected inter‐Beacon distances to reduce the uncertainty in the reported rotation angle.
    No preview · Article · Jun 2009 · Medical Physics
  • H. Yang · W. Hu · W. Wang · W. Ding · G. Shan · C. Yu · B. Wang · Y. Yan · H. Zhu · Q. Xu

    No preview · Article · Jan 2009 · Medical Physics
  • W. Hu · H. Yang · B. Wang · W. Ding · M. Shao · C. Yu · G. Shan · W. Wang · H. Zhu · Q. Xu

    No preview · Article · Jan 2009 · Medical Physics
  • J. Li · L. Chen · G. Shan · C. Ma

    No preview · Article · Jan 2009 · Medical Physics

Publication Stats

52 Citations
35.63 Total Impact Points

Institutions

  • 2009-2012
    • Fox Chase Cancer Center
      • Department of Radiation Oncology
      Philadelphia, PA, United States
  • 2010-2011
    • Wenzhou Medical College
      Yung-chia, Zhejiang Sheng, China