Biomedical subjects

Shidong Tong

Publications and source records attributed to Shidong Tong.

5 recordsLinked to original sources

PubMed2003

Partial breast brachytherapy after lumpectomy: low-dose-rate and high-dose-rate experience.

PURPOSE: The use of partial breast brachytherapy (PBB) after lumpectomy for selected patients with early-stage breast cancer reduces the adjuvant radiotherapy treatment time to <1 week. Despite the advantages of accelerated treatment, maintaining an acceptable cosmetic outcome is important. In a cohort of patients who received low-dose-rate (LDR) or high-dose-rate (HDR) PBB after lumpectomy, the clinical characteristics and treatment parameters were analyzed to identify predictors for an unfavorable cosmetic outcome. METHODS AND MATERIALS: Early-stage breast cancer patients with clear resection margins and 0-3 positive lymph nodes were eligible for PBB. Uniform guidelines for target definition and brachytherapy catheter placement were applied. The HDR PBB dose was 34 Gy in 10 fractions within 5 days, and the LDR dose was 45 Gy given at a rate of 50 cGy/h. The end points included incidence of radiation recall reaction, telangiectasias, and cosmetic-altering fibrosis. RESULTS: Between 1995 and 2000, 44 patients with early-stage breast cancer received PBB without adjuvant external beam radiotherapy after lumpectomy (31 HDR PBB, 13 LDR PBB). After a median follow-up of 42 months (range 18-86), all patients remained locally controlled. The overall rate of good/excellent cosmetic outcome was 79.6% overall and 90% with HDR PBB. Radiation recall reactions occurred in 43% of patients (6 of 14) who received adriamycin. LDR PBB and adriamycin were significant predictors for late unfavorable cosmetic changes in univariate analysis (p = 0.003 and p = 0.005, respectively). CONCLUSION: Although a high rate of local control and good/excellent cosmetic outcome is provided with HDR PBB, the risk of unfavorable cosmetic changes when treated with both LDR PBB and adriamycin is noteworthy. This suggests that HDR PBB is preferred in patients for whom adriamycin is indicated.

Adult↗

PubMed2002

Technical considerations in the application of intensity-modulated radiotherapy as a concomitant integrated boost for locally-advanced cervix cancer.

The technical aspects of IMRT applied to cervix cancer are discussed in this paper, as well as issues related to tumor delineation, target volume definitions, inverse planning, and IMRT delivery. A theoretical example illustrating how IMRT can accurately mimic dose distributions obtained using conventional planning plus HDR brachytherapy is also shown. The notion of clinical optimization parameters is introduced to account for the radiation delivery variables, which affect the overall treatment time. This is especially relevant to the possible introduction of intrafractional movement and resulting inaccuracy, as well as facility efficiency.

Brachytherapy↗

PubMed2002

Clinical application of intensity-modulated radiotherapy for locally advanced cervical cancer.

Intensity-modulated radiotherapy (IMRT) offers technical advantages over conventional external beam radiotherapy (CXRT) that might prove clinically advantageous in the management of gynecologic malignancies. Especially in the case of locally advanced cervical cancer, IMRT provides an opportunity to improve the therapeutic ratio by allowing a selective combination of normal tissue dose reduction and/or concomitant integrated boost dose to the tumor. The clinical and biologic rationale for IMRT in this setting is presented here, and pertinent technical considerations such as the delineation of relevant clinical and planning target volumes are discussed. The capacity for IMRT-mediated normal tissue sparing is illustrated by example and review of the literature. Furthermore, for a small cohort of patients with locally advanced or recurrent cervical cancer treated with concomitant integrated boost IMRT and concurrent chemotherapy, preliminary clinical observations of toxicity and tumor response are presented. Concomitant integrated boost IMRT appears clinically tolerable and efficacious in this setting, and formal clinical investigation is warranted as a means of exploiting the fraction-size dependence of radiosensitizers in common clinical use.

Female↗

PubMed2002

Reducing dose calculation time for accurate iterative IMRT planning.

A time-consuming component of IMRT optimization is the dose computation required in each iteration for the evaluation of the objective function. Accurate superposition/convolution (SC) and Monte Carlo (MC) dose calculations are currently considered too time-consuming for iterative IMRT dose calculation. Thus, fast, but less accurate algorithms such as pencil beam (PB) algorithms are typically used in most current IMRT systems. This paper describes two hybrid methods that utilize the speed of fast PB algorithms yet achieve the accuracy of optimizing based upon SC algorithms via the application of dose correction matrices. In one method, the ratio method, an infrequently computed voxel-by-voxel dose ratio matrix (R = D(SC)/D(PB)) is applied for each beam to the dose distributions calculated with the PB method during the optimization. That is, D(PB) x R is used for the dose calculation during the optimization. The optimization proceeds until both the IMRT beam intensities and the dose correction ratio matrix converge. In the second method, the correction method, a periodically computed voxel-by-voxel correction matrix for each beam, defined to be the difference between the SC and PB dose computations, is used to correct PB dose distributions. To validate the methods, IMRT treatment plans developed with the hybrid methods are compared with those obtained when the SC algorithm is used for all optimization iterations and with those obtained when PB-based optimization is followed by SC-based optimization. In the 12 patient cases studied, no clinically significant differences exist in the final treatment plans developed with each of the dose computation methodologies. However, the number of time-consuming SC iterations is reduced from 6-32 for pure SC optimization to four or less for the ratio matrix method and five or less for the correction method. Because the PB algorithm is faster at computing dose, this reduces the inverse planning optimization time for our implementation by a factor of 2 to 8 compared with pure SC optimization, without compromising the quality or accuracy of the final treatment plan.

Algorithms↗

PubMed1999

Three dimensional transrectal ultrasound imaging of the prostate: initial experience with an emerging technology.

PURPOSE: A three-dimensional ultrasound system (3-D US) was evaluated for its clinical utility in transrectal prostate imaging, in comparison with the current standard 2-dimensional transrectal ultrasound (TRUS) imaging system. METHODS AND MATERIALS: The computer program developed in our laboratory was coupled with a commercially available ultrasound transducer. Geometric validation and volumetric assessment was performed with "stretched-string" wire models and solution-containing balloons respectively. Anatomic correlation of 3-D TRUS images was performed with cadaveric prostates. Intraprostatic lesion localization by 3D-TRUS was assessed clinically by 2 observers in 11 patients prior to radical prostatectomy and the data compared with those yielded by 2-D TRUS. RESULTS: Geometric assessment by 3D TRUS in comparison with the "between strings in the phantom" model (true dimensions) had an error of up to 1.2%. Volume measurement by 3-D TRUS had an error, compared to the true volume, of 0.9%. The correlation coefficient (r) was 0.99985 for the end-firing probe and 0.978 for side firing. The 3-D images provided accurate representation of the true anatomy in the sagittal, transverse and most uniquely, the coronal plane. Two observers achieved better diagnostic accuracies with intraprostatic abnormalities using 3-D instead of standard 2-D TRUS. The negative predictive value and the specificity were improved. CONCLUSION: 3-D TRUS appears to provided accurate representation of the true anatomy with geometric and volumetric validation. Areas of potential clinical application of 3-D TRUS include treatment monitoring with volume measurements and various intervention and therapeutic procedures for both benign and malignant prostatic disorders.

Journal Article↗