Steve Suh

City of Hope National Medical Center, Duarte, California, United States

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Publications (4)11.91 Total impact

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    ABSTRACT: The objectives of the study were to evaluate the effect of intravenous contrast in the dosimetry of helical tomotherapy and RapidArc treatment for head and neck cancer and determine if it is acceptable during the computed tomography (CT) simulation to acquire only CT with contrast for treatment planning of head and neck cancer. Overall, 5 patients with head and neck cancer (4 men and 1 woman) treated on helical tomotherapy were analyzed retrospectively. For each patient, 2 consecutive CT scans were performed. The first CT set was scanned before the contrast injection and secondary study set was scanned 45 seconds after contrast. The 2 CTs were autoregistered using the same Digital Imaging and Communications in Medicine coordinates. Tomotherapy and RapidArc plans were generated on 1 CT data set and subsequently copied to the second CT set. Dose calculation was performed, and dose difference was analyzed to evaluate the influence of intravenous contrast media. The dose matrix used for comparison included mean, minimum and maximum doses of planning target volume (PTV), PTV dose coverage, and V45 Gy, V30 Gy, and V20 Gy organ doses. Treatment planning on contrasted images generally showed a lower dose to both organs and target than plans on noncontrasted images. The doses for the points of interest placed in the organs and target rarely changed more than 2% in any patient. In conclusion, treatment planning using a contrasted image had insignificant effect on the dose to the organs and targets. In our opinion, only CT with contrast needs to be acquired during the CT simulation for head and neck cancer. Dose calculations performed on contrasted images can potentially underestimate the delivery dose slightly. However, the errors of planning on a contrasted image should not affect the result in clinically significant way.
    No preview · Article · Sep 2014 · Medical Dosimetry
  • S Suh · A Liu · J Wong · T Schultheiss
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    ABSTRACT: Purpose: To evaluate the reconstructed 3D dose from the Tomotherapy detector response as a pre‐treatment patient‐specific dose verification tool by comparing the reconstructed dose with the 3D dose from the Tomotherapy treatment planning system (TPS). Methods: A simple dry‐run of a patient plan was performed to capture the fluence sinogram with the detectors. Then, DosimetryCheck™ (DC) was used to calculate the 3D dose using the detector sinogram, CT images, and treatment delivery parameters. The couch attenuation was corrected mathematically. The reconstructed dose was compared with the Tomotherapy TPS 3D dose in the patient anatomy. Results: TPS dose and DC reconstructed dose were compared for 5 prostate plans, 1 head and neck plan, and 1 SRS plan. For the prostate plans, the average dose differences of the bladder, rectum, femur, and prostate were 3.0+−1.8%, 4.2+−1.1%, 3.0+−2.0%, and 0.1+−1.1% (+−S.D.). For the head and neck plan, the average differences of the spinal cord, parotid, mandible, and PTV were 6.9%, 8.6%, 1.2%, and 0.2%. For the SRS plan, the average differences of the brain stem, optical chiasm, left eye, and the PTV were −0.5%, 0.6%, 1.5%, and −3.4%. The overall gamma factor (3%, 3mm) passing rate was >90% for all the cases. Conclusion: It is feasible to perform patient specific QA without Tomotherapy phantom DQA. The QA is more meaningful beca use the dose difference is visualized over patient anatomy instead of over a phantom. The statistics with prostate plans show a consistent match between the measured and planning dose. The head and neck plan suggests that DC Pencil Beam algorithm may need improvement in accuracy for areas with dramatic electron density changes. The SRS plan indicates DC accuracy is independent of jaw width and pitch. All the differences between the Tomotherapy TPS and the reconstructed doses were within clinical tolerance.
    No preview · Article · Jun 2013 · Medical Physics
  • Steve Suh · Timothy E Schultheiss
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    ABSTRACT: Purpose: To compare Tomotherapy's megavoltage computed tomography bony anatomy autoregistration with the best achievable registration, assuming no deformation and perfect knowledge of planning target volume (PTV) location. Methods and materials: Distance-to-agreement (DTA) of the PTV was determined by applying a rigid-body shift to the PTV region of interest of the prostate from its reference position, assuming no deformations. Planning target volume region of interest of the prostate was extracted from the patient archives. The reference position was set by the 6 degrees of freedom (dof)-x, y, z, roll, pitch, and yaw-optimization results from the previous study at this institution. The DTA and the compensating parameters were calculated by the shift of the PTV from the reference 6-dof to the 4-dof-x, y, z, and roll-optimization. In this study, the effectiveness of Tomotherapy's 4-dof bony anatomy-based autoregistration was compared with the idealized 4-dof PTV contour-based optimization. Results: The maximum DTA (maxDTA) of the bony anatomy-based autoregistration was 3.2 ± 1.9 mm, with the maximum value of 8.0 mm. The maxDTA of the contour-based optimization was 1.8 ± 1.3 mm, with the maximum value of 5.7 mm. Comparison of Pearson correlation of the compensating parameters between the 2 4-dof optimization algorithms shows that there is a small but statistically significant correlation in y and z (0.236 and 0.300, respectively), whereas there is very weak correlation in x and roll (0.062 and 0.025, respectively). Conclusions: We find that there is an average improvement of approximately 1 mm in terms of maxDTA on the PTV going from 4-dof bony anatomy-based autoregistration to the 4-dof contour-based optimization. Pearson correlation analysis of the 2 4-dof optimizations suggests that uncertainties due to deformation and inadequate resolution account for much of the compensating parameters, but pitch variation also makes a statistically significant contribution.
    No preview · Article · Jul 2012 · International journal of radiation oncology, biology, physics
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    ABSTRACT: To define setup variations in the radiation treatment (RT) of anal cancer and to report the advantages of image-guided RT (IGRT) in terms of reduction of target volume and treatment-related side effects. Twelve consecutive patients with anal cancer treated by combined chemoradiation by use of helical tomotherapy from March 2007 to November 2008 were selected. With patients immobilized and positioned in place, megavoltage computed tomography (MVCT) scans were performed before each treatment and were automatically registered to planning CT scans. Patients were shifted per the registration data and treated. A total of 365 MVCT scans were analyzed. The primary site received a median dose of 55 Gy. To evaluate the potential dosimetric advantage(s) of IGRT, cases were replanned according to Radiation Therapy Oncology Group 0529, with and without adding recommended setup variations from the current study. Significant setup variations were observed throughout the course of RT. The standard deviations for systematic setup correction in the anterior-posterior (AP), lateral, and superior-inferior (SI) directions and roll rotation were 1.1, 3.6, and 3.2 mm, and 0.3°, respectively. The average random setup variations were 3.8, 5.5, and 2.9 mm, and 0.5°, respectively. Without daily IGRT, margins of 4.9, 11.1, and 8.5 mm in the AP, lateral, and SI directions would have been needed to ensure that the planning target volume (PTV) received ≥95% of the prescribed dose. Conversely, daily IGRT required no extra margins on PTV and resulted in a significant reduction of V15 and V45 of intestine and V10 of pelvic bone marrow. Favorable toxicities were observed, except for acute hematologic toxicity. Daily MVCT scans before each treatment can effectively detect setup variations and thereby reduce PTV margins in the treatment of anal cancer. The use of concurrent chemotherapy and IGRT provided favorable toxicities, except for acute hematologic toxicity.
    No preview · Article · Jan 2012 · International journal of radiation oncology, biology, physics