Grace Tang

China Three Gorges University

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T LoSasso

Memorial Sloan Kettering Cancer Center

C Yu

University of Maryland, Baltimore

Suzanne M. Garland

Royal Women's Hospital

S Lim

Memorial Sloan Kettering Cancer Center

Cosette M. Wheeler

New Mexico Cancer Center

Laura A. Koutsky

University of Washington

Gonzalo Pérez

Hospital Universitario Río Hortega

Daron G. Ferris

Augusta University

Marc Steben

Université de Montréal

Sepp Leodolter

University of Vienna

Cooperative Institutions

University of Hong Kong

Queen Mary Hospital

Memorial Sloan Kettering Cancer Center

Chinese University of Hong Kong

Merck & Co., Inc., Rahway, NJ, USA (United States)

United States Military Academy

University of Washington

Danish Cancer Society

University of Melbourne

Royal Women's Hospital

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Intensity-modulated arc therapy: principles, technologies and clinical implementation

Physics in Medicine and Biology (2011)

C Yu Grace Tang

Intensity-modulated arc therapy (IMAT) was proposed by Yu (1995 Phys. Med. Biol. 40 1435–49) as an alternative to tomotherapy. Over more than a decade, much progress has been made. The advantages and limitations of the IMAT technique have also been better understood. In recent years, single-arc forms of IMAT have emerged and become commercially adopted. The leading example is the volumetric-modulated arc therapy (VMAT), a single-arc form of IMAT that delivers apertures of varying weights with a single-arc rotation that uses dose-rate variation of the treatment machine. With commercial implementation of VMAT, wide clinical adoption has quickly taken root. However, there remains a lack of general understanding for the planning of such arc treatments, as well as what delivery limitations and compromises are made. Commercial promotion and competition add further confusion for the end users. It is therefore necessary to provide a summary of this technology and some guidelines on its clinical implementation. The purpose of this review is to provide a summary of the works from the radiotherapy community that led to wide clinical adoption, and point out the issues that still remain, providing some perspective on its further developments. Because there has been vast experience in IMRT using multiple intensity-modulated fields, comparisons between IMAT and IMRT are also made in the review within the areas of planning, delivery and quality assurance.

Tomotherapy

10.1088/0031-9155/56/5/r01

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Citations (174)

Non-surgical sterilization using phenol-mucilage: Acceptability versus efficacy

Contraception (1988)

Grace Tang Marie Kwan

Sterilization

Mucilage

Female sterilization

10.1016/0010-7824(88)90006-6

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Citations (4)

[Studies on urinary metabolites of perlolyrine in rats].

PubMed (2000)

Guohui Jiang Grace Tang S Wang Chong-tai WANG Lei Zheng

To study the metabolism of perlolyrine in rats, which is an active ingredient from the traditional Chinese herb, Ligusticum Wallichii Franch.After administration of perlolyrine and deuterated perlolyrine, the rat urines were hydrolyzed with glucuronidase, basified with NaHCO3-Na2CO3, extracted with ethyl ether--iso-propyl alcohol. The organic phases (neutral and basic fractions) were concentrated for trimethylsilyl (TMS) derivatives. The aqueous phase were acidified with sulfuric acid, taken to dryness and extracted with methanol (water soluble acidic fractions) and concentrated for TMS derivatives. The TMS derivatives were determined by gas chromatograph mass spectrometry (GC-MS).Perlolyrine and one metabolite were found from the neutral and basic fractions, and two different metabolites were found from the water soluble acidic fractions.It was proposed that the major metabolic pathways of perlolyrine were that the hydroxylation of perlolyrine and the oxidation of its hydroxylmethyl group.

Hydroxylation

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Helical Tomotherapy vs. Single-arc Intensity Modulated Arc Therapy (IMAT): A Collaborative Dosimetric Comparison between Two Institutions

International Journal of Radiation Oncology*Biology*Physics (2009)

Yajing Rong Grace Tang James S. Welsh B Paliwal C. X. Yu

Tomotherapy

Multileaf collimator

Monitor unit

Collimator

10.1016/j.ijrobp.2009.07.1515

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Citations (0)

Further study of sexual functioning following treatment of carcinoma of the cervix in Chinese patients

Journal of Psychosomatic Obstetrics & Gynecology (1988)

Hys Ngan Grace Tang

Reports on sexual functioning following treatment for carcinoma of the cervix are many and the results are conflicting. The modalities of treatment have been considered to play a significant role. A study of 99 patients showed that 20 (20.2%) of them became sexually inactive after treatment. For those who remained sexually active, the degree of change of sexual functioning did not vary significantly between patients who were treated by radiotherapy, by surgery or by a combination of the 2 methods. Despite physical changes in the vagina following irradiation, it did not seem to be the major cause of sexual dysfunction in patients who received radiotherapy. It is apparent that alteration in sexual functioning has a multifactorial basis.

Sexual Functioning

Treatment modality

10.3109/01674828809016794

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Citations (5)

TH‐C‐350‐02: Is Dose Rate Variation Crucial for Single‐Arc Radiation Therapy Delivery?

Medical Physics (2008)

Grace Tang M Earl S Luan C Wang S Naqvi

Purpose: Recent arc therapy techniques such as arc‐modulated radiation therapy (AMRT) developed at the University of Maryland and Varian's RapidArc™ allow variable segment‐weightings in order to expand the optimization domain. As a result, these plans may require a varying dose rate (DR) for delivery. To evaluate the necessity of DR variation in arc therapy delivery, the variable‐DR plans were translated in such a way that they can be delivered with a constant DR. Method and Materials: Four cases were selected for this study: 1 HN, 1 lung, 1 prostate and 1 brain. A single‐arc AMRT plan was generated for each case. Planning of AMRT started with optimization of ideal intensity maps with 36 equi‐spaced beams in Pinnacle followed by segmentation of the intensity maps into a deliverable AMRT MLC sequence. During leaf‐sequencing, the segment weightings are allowed to vary. In translating variable‐DR AMRT plans into constant‐DR plans, the angular spacing of the original beams were changed from equi‐spacing to spacing according to their weightings. Hence, apertures with more MUs occupy a greater angular range. To account for any field shifting in the process, a field shape correction was applied ensuring proper target coverage. Results and Conclusion: DVH comparisons show that constant‐DR plans were comparable to the corresponding variable‐DR plans in 3 of the 4 cases. Significant degradation occurred in the constant‐DR plan of the prostate case due to the large MU variations in the original variable‐DR plan, causing the beams to deviate significantly from their original positions. The estimated delivery times of the constant‐DR plans are 3 to 30 times longer than the variable‐DR plans due to large MLC shape variation within a small beam interval. It is hereby shown that DR variation is crucial to AMRT delivery in order to maintain excellent plan quality and efficient delivery time.

Pinnacle

Constant (computer programming)

Field size

10.1118/1.2962827

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Citations (0)

Effects of androgens on fertilizing capacity of human spermatozoa

Contraception (1983)

Siu Yuen Chan L. C. H. Tang Grace Tang P. H. Chan

Capacitation

Dihydrotestosterone

Mesocricetus

10.1016/0010-7824(83)90079-3

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Citations (11)

Serum immunoreactive beta-endorphin in the human ovulatory cycle.

PubMed (1987)

L. C. H. Tang Siu Yuen Chan Grace Tang Hope Okechukwu K

Daily serum immunoreactive beta-endorphin (IR-beta-EP) levels, in conjunction with luteinizing hormone, follicle-stimulating hormone, 17 beta-oestradiol, progesterone, and prolactin, were measured during the ovulatory cycle in five healthy Chinese women. Standardization of raw data by conversion to the statistical "Z scores" and composite plot of the five cycles showed that serum IR-beta-EP levels fluctuated during the follicular, late luteal, and menstrual phases. A preovulatory rise occurred two to three days prior to the luteinizing hormone surge, followed by a postovulatory dip for two to three days. The concentrations of IR-beta-EP were (mean +/- S.E.M.): 85.5 +/- 10.5 pg/mL (n = 36) in the follicular phase; 92.4 +/- 36.5 pg/mL (n = 5) in the ovulatory phase; 72.3 +/- 16.6 pg/mL (n = 7) in the early luteal phase; 100.0 +/- 10.7 pg/mL (n = 38) in the late luteal phase. The values in the luteal phase were the highest of any in the ovulatory cycle. The findings suggest that the fluctuation of endogenous beta-EP is under the influence of, among other factors, ovarian sex steroids. The significance of beta-EP in the regulation of gonadotropin release during normal menstrual cycles is discussed.

Gonadotropin

BETA (programming language)

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Citations (6)

SU-GG-T-96: IMRT Leaf Sequencing with Intensity-Based Segment Weight Optimization

Medical Physics (2008)

S Luan C Wang Grace Tang D Chen C Yu

Purpose: Dose distribution based segment weight optimization can significantly improve the quality of IMRT plans after leaf sequencing despite it is computationally very time-consuming. This research aims to develop a leaf sequencing algorithm that has built-in intensity-based segment weight optimization with minimal additional running time. Method and Materials: The new algorithm is named LSWISW (for leaf sequencing with intensity-based segment weight optimization). Its input includes: (1) (continuous) intensity patterns; (2) MLC leaf leakage ratio (typically ranges from 1% to 3%); either (3) the number of MLC segments, k, specified by the user or (4) an upper bound on the error between the computed intensity pattern and original ideal intensity pattern. If (3) is specified, a plan of k segments that best approximates the ideal intensity pattern is calculated. If (4) is specified, a plan of the minimum number of segments whose error is within the error bound is produced. In LSWISW, the leaf sequencing is modeled as a constrained shortest path problem and solved using dynamic programming; segment weight optimization is modeled and solved as a nonnegative least square optimization. Results: The performance of our leaf sequencing algorithm was tested on three treatment sites (head-and-neck, lung, and prostate). Our target delivery system is the Varian LINAC, whose MLC allows interdigitiation. In all the cases, our algorithm produces IMRT plans that rival those from Pinnacle planning system with afterward dose-based segment weight optimization. Execution times of no more than 1 minute for our algorithm were observed on a laptop computer with a Pentium M Processor of 2.0 GHz. Conclusion: We presented an IMRT leaf sequencing algorithm with built-in intensity-based segment weight optimization. Compared with the leaf sequencing and dose-based segment weight optimization modules from Pinnacle planning system, our new leaf sequencing algorithm is much more effective and efficient.

Pinnacle

Intensity

10.1118/1.2961848

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Citations (1)

Variable dose rate single-arc IMAT delivered with a constant dose rate and variable angular spacing

Physics in Medicine and Biology (2009)

Grace Tang Matthew A. Earl C Yu

Single-arc intensity-modulated arc therapy (IMAT) has gained worldwide interest in both research and clinical implementation due to its superior plan quality and delivery efficiency. Single-arc IMAT techniques such as the Varian RapidArc deliver conformal dose distributions to the target in one single gantry rotation, resulting in a delivery time in the order of 2 min. The segments in these techniques are evenly distributed within an arc and are allowed to have different monitor unit (MU) weightings. Therefore, a variable dose-rate (VDR) is required for delivery. Because the VDR requirement complicates the control hardware and software of the linear accelerators (linacs) and prevents most existing linacs from delivering IMAT, we propose an alternative planning approach for IMAT using constant dose-rate (CDR) delivery with variable angular spacing. We prove the equivalence by converting VDR-optimized RapidArc plans to CDR plans, where the evenly spaced beams in the VDR plan are redistributed to uneven spacing such that the segments with larger MU weighting occupy a greater angular interval. To minimize perturbation in the optimized dose distribution, the angular deviation of the segments was restricted to

Constant (computer programming)

10.1088/0031-9155/54/21/001

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Citations (28)