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ABSTRACT: To assess the dosimetric effect of using a split-organ delineation approach during intensity-modulated radiotherapy (IMRT) treatment planning for advanced T-stage nasopharyngeal carcinoma (NPC).
Twenty NPC patients with T3-4 tumours were studied. A reference (REF) IMRT plan was generated based on a standard treatment planning protocol, with a set of user-defined dose constraints for optimisation. An investigative (INV) IMRT plan was then generated based on the same protocol, but treating several organs at risk (OARs; parotid glands, temporal lobes, cochlea, auditory nerves and planning organ at risk volume [PRV] of the brainstem) as split organs consisting of target-overlapping and non-target-overlapping sub-segments. These sub-segments were assigned independent dose constraints. The REF and INV plans were compared with respect to target coverage and OAR sparing. Target coverage was evaluated by the Dmin (minimum dose), V66/V60 (percentage volume of gross target volume [GTV]/planning target volume [PTV] receiving 66 Gy/60 Gy), target conformity index (CI), and tumour control probability (TCP). The sparing of OARs was evaluated by the commonly used dose end points for the respective OAR, and normal tissue complication probability (NTCP).
For PTV coverage, the INV plan was superior to the REF plan in terms of Dmin (P=0.000), CI (P=0.005) and TCP (P=0.002). This is attributed to an increase in dose to the PTV-OAR overlapping sub-segments. Regarding the sparing of OARs, there was a significant reduction in the mean dose of the parotid glands (P=0.002), and a slight, but non-significant, increase in NTCP of the temporal lobes, cochlea and brainstem.
Using a split-organ delineation approach in IMRT treatment planning for advanced T-stage NPC, a significant improvement in the target coverage and TCP could be achieved, whereas the mean dose of the parotid was reduced significantly. There was insignificant change in the NTCP of the temporal lobe, parotid gland, cochlea and brainstem, but a significant change in the NTCP of the auditory nerve. The approach provides the planner extra room to manipulate the dose constraints during optimisation, and to obtain the desired result in less attempts. This approach also has the potential to be used in a broader context for IMRT planning for other tumour sites.
Clinical Oncology 04/2008; 20(2):134-41. · 2.07 Impact Factor
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ABSTRACT: We evaluated the role of chemoradiotherapy (CRT) for patients with inoperable squamous esophageal cancer.
Patients with locally advanced or metastatic squamous esophageal carcinoma who received CRT were recruited. The CRT consists of continuous infusion of 5-fluorouracil at 200 mg/m(2)/day, and cisplatin at 60 mg/m(2) on days 1 and 22, with concurrent radiotherapy for a total of 50 to 60 Gy in 25 to 30 fractions over 6 weeks. Efficacy was assessed by endoscopy and computed tomographic scan before and 8 weeks after completion of the treatment program. Median survival and the need for palliative esophageal stenting were compared with another group of patients who received endoscopic stenting.
From 1996 to 2003, a total of 36 consecutive patients (33 male, mean +/- SD age 63.2 +/- 9.5 years) with T4 disease (81%) with or without cervical nodal metastasis (50%) received CRT, while 36 patients treated with endoscopic stenting alone were recruited as controls. Both groups were comparable in demographics, pretreatment dysphagia score, comorbidities, and tumor characteristics. CRT was completed in 32 patients (89%). There was no treatment-related mortality. Tumor volume was greatly reduced after CRT in 19 patients. Four patients (11%) received salvage esophagectomy 9 to 42 months after CRT. Compared with the stenting group, CRT statistically significantly improved 5-year survival (15% vs. 0%, P = .01), median survival (10.8 months vs. 4.0 months, P < .005), and need for stenting (22% vs. 100%, P = .005).
Palliative CRT can effectively improve the symptoms of dysphagia in patients with inoperable squamous esophageal carcinoma. It results in better survival compared with endoscopic stenting in these patients.
Annals of Surgical Oncology 02/2008; 15(2):576-82. · 4.17 Impact Factor
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ABSTRACT: To assess the dosimetric effect of using interpolated contours in planning intensity-modulated radiation therapy (IMRT) for advanced T-stage nasopharyngeal carcinoma. The present study focused on T3-T4 tumours where the proximity of targets to neurological organs poses a stringent test on the feasibility of such an approach. Contours of targets and organs were delineated on CT images of 2.5-mm interval and a reference IMRT plan was generated. An investigative (INV) IMRT plan was then generated with the same planning protocol, but based on interpolated contours that replaced deleted contours on alternate slices. The reference and INV plans were compared. Regarding target coverage, all targets in the INV plans met the acceptance criteria except for the PTV in one case. Regarding organs, the mean dose to 1% volume of the brainstem and spinal cord in the INV plans were kept below their dose limits. No significant differences in the mean doses to others organs were found. Satisfactory target coverage and protection of critical organs to a degree similar to full-scale contouring could be achieved with use of interpolated contours. The saving in manpower time for contouring is expected to significantly improve the throughput of the IMRT planning process.
Australasian Radiology 11/2007; 51(5):480-4. · 0.51 Impact Factor
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ABSTRACT: The aim of this study is to evaluate the deficiencies in target coverage and organ protection of 2-dimensional radiation therapy (2DRT) in the treatment of advanced T-stage (T3-4) nasopharyngeal carcinoma (NPC), and assess the extent of improvement that could be achieved with intensity modulated radiation therapy (IMRT), with special reference to of the dose to the planning organ-at-risk volume (PRV) of the brainstem and spinal cord. A dosimetric study was performed on 10 patients with advanced T-stage (T3-4 and N0-2) NPC. Computer tomography (CT) images of 2.5-mm slice thickness of the head and neck were acquired with the patient immobilized in semi-extended-head position. A 2D plan based on Ho's technique, and an IMRT plan based on a 7-coplanar portals arrangement, were established for each patient. 2DRT was planned with the field borders and shielding drawn on the simulator radiograph with reference to bony landmarks, digitized, and entered into a planning computer for reconstruction of the 3D dose distribution. The 2DRT and IMRT treatment plans were evaluated and compared with respect to the dose-volume histograms (DVHs) of the targets and the organs-at-risk (OARs), tumor control probability (TCP), and normal tissue complication probabilities (NTCPs). With IMRT, the dose coverage of the target was superior to that of 2DRT. The mean minimum dose of the GTV and PTV were increased from 33.7 Gy (2DRT) to 62.6 Gy (IMRT), and 11.9 Gy (2DRT) to 47.8 Gy (IMRT), respectively. The D(95) of the GTV and PTV were also increased from 57.1 Gy (2DRT) to 67 Gy (IMRT), and 45 Gy (2DRT) to 63.6 Gy (IMRT), respectively. The TCP was substantially increased to 78.5% in IMRT. Better protection of the critical normal organs was also achieved with IMRT. The mean maximum dose delivered to the brainstem and spinal cord were reduced significantly from 61.8 Gy (2DRT) to 52.8 Gy (IMRT) and 56 Gy (2DRT) to 43.6 Gy (IMRT), respectively, which were within the conventional dose limits of 54 Gy for brainstem and of 45 Gy for spinal cord. The mean maximum doses deposited on the PRV of the brainstem and spinal cord were 60.7 Gy and 51.6 Gy respectively, which were above the conventional dose limits. For the chiasm, the mean dose maximum and the dose to 5% of its volume were reduced from 64.3 Gy (2DRT) to 53.7 Gy (IMRT) and from 62.8 Gy (2DRT) to 48.7 Gy (IMRT), respectively, and the corresponding NTCP was reduced from 18.4% to 2.1%. For the temporal lobes, the mean dose to 10% of its volume (about 4.6 cc) was reduced from 63.8 Gy (2DRT) to 55.4 Gy (IMRT) and the NTCP was decreased from 11.7% to 3.4%. The therapeutic ratio for T3-4 NPC tumors can be significantly improved with IMRT treatment technique due to improvement both in target coverage and the sparing of the critical normal organ. Although the maximum doses delivered to the brainstem and spinal cord in IMRT can be kept at or below their conventional dose limits, the maximum doses deposited on the PRV often exceed these limits due to the close proximity between the target and OARs. In other words, ideal dosimetric considerations cannot be fulfilled in IMRT planning for T3-4 NPC tumors. A compromise of the maximal dose limit to the PRV of the brainstem and spinal cord would need be accepted if dose coverage to the targets is not to be unacceptably compromised. Dosimetric comparison with 2DRT plans show that these dose limits to PRV were also frequently exceeded in 2DRT plans for locally advanced NPC. A dedicated retrospective study on the incidence of clinical injury to neurological organs in a large series of patients with T3-4 NPC treated by 2DRT may provide useful reference data in exploring how far the PRV dose constraints may be relaxed, to maximize the target coverage without compromising the normal organ function.
Medical Dosimetry 02/2007; 32(4):263-70. · 1.00 Impact Factor
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Advanced Functional Materials 01/2007; 17(4):555 - 562. · 10.18 Impact Factor
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ABSTRACT: Nanoribbons and nanowires of different metal phthalocyanines (copper, nickel, iron, cobalt, and zinc), as well as copper hexadecafluorophthalocyanine (F(16)CuPc), have been grown by organic vapor-phase deposition. Their properties, as a function of substrate type, source-to-substrate distance, and substrate temperature, were studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and absorption measurements. The size and morphology of the nanostructures were found to be mainly determined by the substrate temperature. The crystal structure was dependent on the substrate temperature as well. At substrate temperatures below 200 degrees C, in addition to straight nanoribbons, twisted nanoribbons were found for all investigated materials except F(16)CuPc, which formed helical nanoribbons upon exposure to an electron beam. The formation of different nanostructures (nanoribbons, twisted nanoribbons, and helical nanoribbons) is discussed.
The Journal of Physical Chemistry B 10/2006; 110(35):17406-13. · 3.70 Impact Factor
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ABSTRACT: Dye-sensitized solar cells based on perpendicular titania nanotube arrays were fabricated. Titania nanotube arrays were prepared by anodization of Ti foil. The cell performance as a function of nanotube length and anodization method was investigated. Short circuit current density and cell efficiency increased with the nanotube length. Device performance was also affected by anodization method, spacer layer thickness, and annealing conditions. With optimized device structure and titania annealing procedure, short circuit current density of 3.28 mA/cm2 could be achieved under AM 1.5 simulated solar irradiation.
Applied Physics Letters 07/2006; 89(2):023508-023508-3. · 3.84 Impact Factor
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ABSTRACT: In1−xGaxN nanowires were fabricated in a tube furnace by chemical vapour deposition, with Ga, In and NH3 as the starting materials and Au as the catalyst. Scanning electron microscopy showed that a mixture of straight and helical In1−xGaxN nanowires was obtained. Transmission electron microscopy (TEM) revealed that both types of nanowire exhibited core–shell structures. The crystal structure of the samples was studied by high resolution TEM and x-ray diffraction, and both cubic and hexagonal phases were found. Energy dispersive x-ray spectroscopy showed that the core had a high In content and the shell had a low In content. The nanowires were also characterized by photoluminescence. The mechanism of formation for the helical nanowires and core–shell structure is discussed.
Nanotechnology 04/2006; 17(9):2330. · 3.98 Impact Factor
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ABSTRACT: To evaluate the efficacy of using intensity-modulated radiotherapy (IMRT) in the primary treatment of nasopharyngeal carcinoma (NPC), including the role of dose escalation above 66 Gy level.
Between July 2000 and September 2002, 63 newly diagnosed NPC patients were treated with IMRT. The disease was Stage I in 9 (14%), Stage II in 18 (29%), Stage III in 22 (35%), and Stage IV in 14 (22%). The prescribed dose was 66 Gy to the gross tumor volume (GTV) and positive neck nodes, 60 Gy to the planning target volume (PTV), and 54-60 Gy to the clinically negative neck. All 20 (100%) patients with T1-2a tumors received intracavitary brachytherapy (ICB) boost, and 15/42 (36%) patients with T2b-T4 tumors received conformal boost (8 Gy/4 fractions). Nineteen patients with advanced stage disease also received either neoadjuvant or concurrent chemotherapy. Acute and late normal tissue effects were graded according to the Radiation Therapy Oncology Group (RTOG) radiation morbidity scoring criteria. Local relapse-free survival (LRFS), nodal relapse-free survival (NRFS), distant metastasis-free survival (DMFS), and overall survival (OS) were estimated using the Kaplan-Meier method.
With a median follow-up of 29 months (range 8-45 months), 4 patients developed local in-field failure, 1 patient developed regional relapse, and 13 patients developed distant metastases. All 4 patients with local failure had either T3 or T4 disease before primary treatment and did not have ICB or conformal boost. The 3-year actuarial LRFS, NRFS, DMFS, and OS were 92%, 98%, 79%, and 90%, respectively. Multivariate analysis showed that dose escalation above 66 Gy was significantly associated with better PFS and DMFS, whereas GTV size was a significant adverse factor for OS. The worst acute mucositis was Grade 1 or 2 in 36 (59%), and Grade 3 in 25 (41%) patients. Acute dysphagia requiring tube feeding occurred in 5 (8%) patients. The proportion of patients with Grade 2-3 xerostomia was 57% at 3 months, and 23% at 2 years after IMRT. Within the subset of patients with a mean parotid dose of <31 Gy, the proportions with Grade 2-3 xerostomia were 30% and 17% at 3 months and 2 years, respectively.
Our experience of using IMRT in the primary treatment of NPC showed a very high rate of locoregional control and favorable toxicity profile. Furthermore, we found that dose escalation above 66 Gy of IMRT-based therapy was a significant determinant of progression-free survival and distant metastasis-free survival for advanced T-stage tumors. Distant metastases represent the predominant mode of treatment failure.
International Journal of Radiation OncologyBiologyPhysics 12/2004; 60(5):1440-50. · 4.11 Impact Factor
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Anthony T C Chan,
Brigette B Y Ma,
Y M Dennis Lo,
S F Leung,
W H Kwan,
Edwin P Hui,
Tony S K Mok,
Michael Kam,
Lisa S Chan,
Samuel K W Chiu,
K H Yu, K Y Cheung,
Karen Lai,
Maria Lai,
Frankie Mo,
Winnie Yeo,
Ann King,
Philip J Johnson,
Peter M L Teo,
Benny Zee
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ABSTRACT: PURPOSE: To assess the efficacy of neoadjuvant paclitaxel and carboplatin (TC) followed by concurrent cisplatin and radiotherapy (RT) in patients with locoregionally advanced nasopharyngeal carcinoma (NPC) and to monitor treatment response with plasma Epstein-Barr virus (EBV) DNA. PATIENTS AND METHODS: Thirty-one patients with International Union Against Cancer stages III and IV undifferentiated NPC had two cycles of paclitaxel (70 mg/m2 on days 1, 8, and 15) and carboplatin (area under the curve 6 mg/mL/min on day 1) on a 3-weekly cycle, followed by 6 to 8 weeks of cisplatin (40 mg/m2 weekly) and RT at 66 Gy in 2-Gy fractions. Plasma EBV DNA was measured serially using the real-time quantitative polymerase chain reaction method. Results All patients completed planned treatment. Response to neoadjuvant TC was as follows: 12 patients (39%) achieved partial response (PR) and 18 achieved (58%) complete response (CR) in regional nodes; five patients (16%) achieved PR and no patients achieved CR in nasopharynx. At 6 weeks after RT, one patient (3%) achieved PR and 30 patients (97%) achieved CR in regional nodes, and 31 patients (100%) achieved CR in nasopharynx; 29 patients (93%) had EBV DNA level of less than 500 copies/mL. Neoadjuvant TC was well tolerated, and the most common acute toxicity of cisplatin plus RT was grade 3 mucositis (55%). At median follow-up of 33.7 months (range, 7 to 39.3 months), six distant and three locoregional failures occurred. Plasma EBV DNA level increased significantly in eight of nine patients who experienced treatment failure but did not increase in those who did not. The 2-year overall and progression-free survival rates were 91.8% and 78.5%, respectively. CONCLUSION This strategy was feasible and resulted in excellent local tumor control. Serial plasma EBV DNA provides a noninvasive method of monitoring response in NPC.
Journal of Clinical Oncology 09/2004; 22(15):3053-60. · 18.37 Impact Factor
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ABSTRACT: Ten registered nurses working in a neonatal intensive care unit in Hong Kong were interviewed to explore their experiences of caring for infants whose disease is not responsive to curative treatment, their perceptions of palliative care, and factors influencing their care. Eight categories emerged from the content analysis of the interviews: disbelieving; feeling ambivalent and helpless; protecting emotional self; providing optimal physical care to the infant; providing emotional support to the family; expressing empathy; lack of knowledge and counselling skills; and conflicting values in care. The subtle cultural upbringing and socialization in nurse training and workplace environment also contributed to their moral distress. Hospital and nurse administrators should consider different ways of facilitating palliative care in their acute care settings. For example, by culture-specific death education, peer support groups, bereavement teams, modification of departmental policies, and a supportive work environment. Future research could include the identification of family needs and coping as well as ethical decision-making among nurses.
Journal of Clinical Nursing 10/2001; 10(5):651-9. · 1.12 Impact Factor
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ABSTRACT: We isolated by differential screening a 1.2 kb cDNA from an Arabidopsis thaliana ecotype Columbia cDNA library that is highly expressed in stem and root. In situ hybridization studies on stem sections and root sections showed that the mRNA is expressed in stem sclerenchyma and root cortex, respectively. The isolation and sequence analysis of four other overlapping cDNA clones from two independent A. thaliana cDNA libraries confirmed that these cDNAs lack a significant open reading frame that has recognizable homology to any known proteins. We have obtained from A. thaliana ecotype Columbia three corresponding genomic clones and nucleotide sequence analysis of these clones revealed that we have isolated a retroposon, TSCL, that is flanked by two 13 bp direct repeats, is intronless, and has a poly(A)+ tract at the 3' end. The site of transcription initiation mapped by primer extension analysis lies 48 bp downstream from an external TATA box. Results from Southern blot analysis suggest that TSCL occurs as a single-copy insert in the genomes of A. thaliana ecotype Columbia (Col-0) and Col-2 but is absent in the genomes of Brassica napus. Brassica juncea and A. thaliana ecotypes Be-0, Oy-0 and Ler-0. This suggests that Col-0 and Col-2 are phylogenetically more closely related to each other than to Be-0, Oy-0 and Ler-0, and that the Laibach Landsberg seeds Redei received, from which ecotypes Col-0, Col-2 and Ler-0 originated, were heterogeneous for TSCL.
Plant Molecular Biology 01/1998; 35(6):893-903. · 4.15 Impact Factor
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ABSTRACT: Clones encoding beta-1,3-glucanase have been isolated from a Hevea cDNA library prepared from the latex of Hevea brasiliensis using a probe Nicotiana plumbaginifolia cDNA encoding beta-1,3-glucanase, gnl. Nucleotide sequence analysis showed that a 1.2 kb Hevea cDNA encoding a basic beta-1,3-glucanase showed 68% nucleotide homology to gnl cDNA. Northern blot analysis using the Hevea cDNA as probe detected a mRNA of 1.3 kb which was expressed at higher levels in latex than in leaf. In situ hybridization analysis using petiole sections from Hevea localized the beta-1,3-glucanase mRNA to the laticifer cells. Genomic Southern analysis suggested the presence of a low-copy gene family encoding beta-1,3-glucanases in H. brasiliensis.
Plant Molecular Biology 11/1995; 29(2):397-402. · 4.15 Impact Factor
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ABSTRACT: ZnO nanorods have been grown by a hydrothermal method on titania/titanate nanowires. The resulting branched structures were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL) measurements. The influence of seeding on the nanorod growth was investigated, and the large-scale synthesis of branched ZnO/TiOx heterostructures has been demonstrated. The ZnO nanorods grow along [0 0 0 1] direction and emit UV and visible (yellow–green) luminescence, as expected for samples grown by a hydrothermal method.
Journal of Crystal Growth 307(2):348-352. · 1.73 Impact Factor
