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ABSTRACT: This study aimed to identify the potential benefits and limitations of a new volumetric modulated arc therapy (VMAT) planning system in Monaco, compared with conventional intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT). Four-dimensional CT scans of 13 patients with abdominal lymph node metastasis from hepatocellular carcinoma were selected. Internal target volume was defined as the combined volume of clinical target volumes (CTVs) in the multiple 4DCT phases. Dose prescription was set to 45 Gy for the planning target volume (PTV) in daily 3.0-Gy fractions. The PTV dose coverage, organs at risk (OAR) doses, delivery parameters and treatment accuracy were assessed. Compared with 3DCRT, both VMAT and IMRT provided a systematic improvement in PTV coverage and homogeneity. Planning objectives were not fulfilled for the right kidney, in which the 3DCRT plans exceeded the dose constraints in two patients. Equivalent target coverage and sparing of OARs were achieved with VMAT compared with IMRT. The number of MU/fraction was 462 ± 68 (3DCRT), 564 ± 105 (IMRT) and 601 ± 134 (VMAT), respectively. Effective treatment times were as follows: 1.8 ± 0.2 min (3DCRT), 6.1 ± 1.5 min (IMRT) and 4.8 ± 1.0 min (VMAT). This study suggests that the VMAT plans generated in Monaco improved delivery efficiency for equivalent dosimetric quality to IMRT, and were superior to 3DCRT in target coverage and sparing of most OARs. However, the superiority of VMAT over IMRT in delivery efficiency is limited.
Journal of Radiation Research 06/2012; 53(5):769-76. · 1.68 Impact Factor
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ABSTRACT: The purpose of this study was to define individualized internal target volume (ITV) for hepatocellular carcinoma (HCC) using 4D computed tomography (4DCT), and to determine the geometric and dosimetric benefits of respiratory gating. Gross tumor volumes (GTVs) were contoured on 10 respiratory phases of 4DCT images for 12 patients with HCC. Three treatment plans were prepared using different planning target volumes (PTVs): (1) PTV(3D), derived from a single helical clinical target volume (CTV) plus conventional margins; (2) PTV(10 phases), derived from ITV(10 phases), which encompassed all 10 CTVs plus an isotropic margin of 0.8 cm; (3) PTV(gating), derived from ITV(gating), which encompassed three CTVs within gating-window at end-expiration plus an isotropic margin of 0.8 cm. The PTV(3D) was the largest volume for all patients. The ITV-based plans and gating plans spared more normal tissues than 3D plans, especially the liver. Without increasing normal tissue complication probability of the 3D plans, the ITV-based plans allowed for increasing the calculated dose from 50.8 Gy to 54.7 Gy on average, and the gating plans could further escalate the dose to 58.5 Gy. Compared with ITV-based plans, the dosimetric gains with gating plan strongly correlated with GTV mobility in the craniocaudal direction. The ITV-based plans can ensure target coverage with less irradiation of normal tissues compared with 3D plans. Respiratory-gated radiotherapy can further reduce the target volumes to spare more surrounding tissues and allow dose escalation, especially for patients with tumor mobility >1 cm.
Medical dosimetry: official journal of the American Association of Medical Dosimetrists 01/2011; 36(2):213-8. · 1.26 Impact Factor
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ABSTRACT: The planning dose distribution of intensity-modulated radiation therapy (IMRT) has to be verified before clinical implementation. The commonly used verification method is to measure the beam fluency at 0 degree gantry angle with a 2-dimensional (2D) detector array, but not the composite dose distribution of the real delivery in the planned gantry angles. This study was to investigate the angular dependence of a 2D diode array (2D array) and the feasibility of using it to verify the composite dose distribution of IMRT.
Angular response of the central detector in the 2D array was measured for 6 MV X-ray, 10 cmx10 cm field and 100 cm source axis distance (SAD) in different depths. With the beam incidence angle of 0-60 degrees, at intervals of 10 degrees, and inherent buildup of the 2D array (2 g/cm2), the array was irradiated and the readings of the central diode were compared with the measurement of thimble ionization chamber. Using a combined 30 cmx30 cmx30 cm phantom which consisted of solid water slabs on top and underlying the 2D array, with the diode detectors placed at 8 g/cm2 depth, measurements were taken for beam angles of 0 degrees-180 degrees at intervals of 10 degrees and compared with the calculation of treatment planning system (TPS) that pre-verified with ion chamber measuring.
Differences between the array detector and thimble chamber measurements were greater than 1% and 3.5% when the beam angle was larger than 30 degrees and 60 degrees, respectively. The measurements in the combined phantom were different from the calculation as high as 20% for 90 degrees beam angle, 2% at 90 degrees+/-5 degrees and less than 1% for all the other beam angles.
The 2D diode array is capable of being used in composite dose verification of IMRT when the beam angles of 90 degrees+/-5 degrees and 270 degrees+/-5 degrees are avoided.
Chinese journal of cancer 06/2010; 29(6):617-20.
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ABSTRACT: To study the impact of different planning target volume (PTV) margin settings on surface and superficial dose distribution and explore the resolution of high superficial dose when the target area is close to the surface during head and neck intensity-modulated radiotherapy (IMRT).
A typical superficial target volume was designed in an circular neck phantom. Two experimental inverse IMRT plans were conducted with 8MV X ray, and in plan A, the superficial side of PTV margin ranged from 0 to 5 mm, while other side margins were 5 mm; in plan B, an suppositional machine dosimetry data for IMRT optimization was established in which the build-up dose was eliminated, and this machine data was used to optimize the inverse IMRT plan followed by recalculation of the planned dose distribution with the actual clinical machine dosimetry data. The variation of the surface and superficial dose resulting from set-up error and the dose distribution to CTV were compared. The adequate PTV margin was analyzed when the CTV approached the surface.
In plan A, the high dose greater than the prescribed dose was found in the surface and superficial region when the superficial sparing distance was between the surface and PTV d<3 mm, and the 3 mm set-up margin increased this superficial dose remarkably. Reducing the superficial side of PTV margin lowered the high superficial dose effectively and allowed maintenance of the prescribed dose to the CTV. To avoid reduction of the dose to the CTV to below 95% of the prescribed dose, the superficial side of PTV margin should be greater than 1 mm. Plan B effectively lowered the surface doses and maintained the prescribed dose to the CTV.
With appropriate techniques for optimizing inverse IMRT, more homogeneous superficial dose can be achieved.
Nan fang yi ke da xue xue bao = Journal of Southern Medical University 04/2010; 30(4):891-4.
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ABSTRACT: The aim of this study was to use four-dimensional CT (4DCT) in the planning of 3D conformational external beam radiation therapy (3DCRT) for patients with early stage breast cancer. A total of nine Chinese women who received breast conservation treatment were included in this study. Target localization and movement (range of motion) during normal respiration were assessed using ultrasound and 4DCT. Plans based on 3DCT and 4DCT scans were developed in accordance to RTOG0319 guidelines and dose delivery comparisons were made between these plans. The mean ranges of motion of the excision cavity volume as determined using 4DCT were 1.03 +/- 0.51, 2.08 +/- 0.92, and 1.27 +/- 0.58 mm in the right-left, anterior-posterior, and superior-interior directions, respectively. There were no significant differences between the mean and maximum PTV-E doses or the volume receiving 95% of the prescribed dose (V95). 4D plan prescribed dose levels were significantly lower (p < 0.05) than 3D plan levels for all of the following: ipsilateral breast V100, ipsilateral lung V30, and contralateral lung V5. Maximum contralateral breast and thyroid doses were also significantly lower with the 4D plan (p < 0.05). This study highlights the usefulness of 4DCT for the planning of 3DCRT in breast cancer patients. Our findings suggest that the use of 4DCT can lead to improvements in target definition and decreases in normal tissues irradiation.
Oncology Research Featuring Preclinical and Clinical Cancer Therapeutics 01/2010; 18(10):503-7. · 1.30 Impact Factor
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ABSTRACT: To determine the feasibility of using limited four-dimensional computed tomography (4DCT) images for treatment planning.
The 4DCT scans of 16 patients with hepatocellular carcinoma (HCC) were analyzed. Gross tumor volumes (GTVs) were manually contoured on all 10 respiratory phases, and different internal clinical target volumes (ICTVs) were derived by encompassing volumes of the respective CTVs. Volume, position, and shape of ICTVs were calculated and compared.
The ICTV(2 phases), ICTV(3 phases), ICTV(4 phases), and ICTV(6 phases) all showed excellent agreement with ICTV(10 phases), and the ICTV(2 phases) encompassed ICTV(10 phases) by 94.1+/-1.8% on average. The 3D shift between the centers of mass of the ICTVs was only 0.6mm. The surface distance between ICTV(10 phases) and ICTV(2 phases) was 1.7+/-0.8mm in the left-right (LR) and anteroposterior (AP) directions.
Contouring two extreme phases at end-inhalation and end-exhalation is a reasonably safe and labor-saving method of deriving ITV for liver radiotherapy with low and medium tumor motion amplitude (1.6 cm). Whether the larger tumor movement affects the results is the subject of ongoing research.
Radiotherapy and Oncology 07/2009; 92(2):255-9. · 5.58 Impact Factor
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ABSTRACT: To define individualized internal target volume (ITV) for hepatocellular carcinoma using four-dimensional computed tomography (4DCT).
Gross tumor volumes (GTVs) and clinical target volumes (CTVs) were contoured on all 10 respiratory phases of 4DCT scans in 10 patients with hepatocellular carcinoma. The 3D and 4D treatment plans were performed for each patient using two different planning target volumes (PTVs): (1) PTV(3D) was derived from a single CTV plus conventional margins; (2) PTV(4D) was derived from ITV(4D), which encompassed all 10 CTVs plus setup margins (SMs). The volumes of PTVs and dose distribution were compared between the two plans.
The average PTV volume of the 4D plans (328.4+/-152.2cm(3)) was less than 3D plans (407.0+/-165.6cm(3)). The 4D plans spared more surrounding normal tissues than 3D plans, especially normal liver. Compared with 3D plans, the mean dose to normal liver (MDTNL) decreased from 22.7 to 20.3Gy. Without increasing the normal tissue complication probability (NTCP), the 4D plans allowed for increasing the calculated dose from 50.4+/-1.3 to 54.2+/-2.6Gy, an average increase of 7.5% (range 4.0-16.0%).
The conventional 3D plans can result in geometric miss and include excess normal tissues. The 4DCT-based plans can reduce the target volumes to spare more normal tissues and allow dose escalation compared with 3D plans.
Radiotherapy and Oncology 10/2007; 84(3):272-8. · 5.58 Impact Factor
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ABSTRACT: Accurate definition of target volume is difficult in three-dimensional conformal radiotherapy (3D CRT) for liver tumors because of the wide moving extent of tumors with respiration. This study was to define individualized internal target volume (ITV) using four-dimensional computed tomography (4D-CT), and compare planning target volumes (PTVs) and dose distribution of 3D planning with 4D planning for hepatocellular carcinoma (HCC).
Seven primary HCC patients received 4D-CT scanning. Gross tumor volumes (GTVs) and clinical target volumes (CTVs) were contoured on all 10 respiratory phases of CT images. The 3D and 4D treatment plans were made for each patient using different PTVs, namely, PTV-3D derived from a single CTV plus conventional margins; PTV-4D derived from ITV-4D which encompassing all 10 CTVs plus setup margins (SM). The two plans were designed at the 20% respiratory phase CT images using 3D treatment planning system and compared with respect to PTVs, dose distribution to normal tissues, normal tissue complication probability. The prescription dose and design of irradiating fields were identical for both plans.
The average PTV was (417.6+/-197.7) cm(3) in 3D plan and (331.9+/-183.1) cm(3) in 4D plan, decreased by 20.50% (12.60%-34.40%). PTV coverage and dose uniformity were similar in the 2 plans. 4D plans spared more normal liver, kidney, stomach, and small intestine than 3D plans, especially for the liver. The V30 and V40 of the liver were lower in 4D plans than in 3D plans (33.59% vs. 38.77%, 22.62% vs. 27.32%); the mean dose to normal liver was decreased from 24.13 Gy to 21.5 Gy; liver complication probability was decreased from 21.57% to 15.86%. Without increasing the normal tissue complication probability, the prescription dose was higher in 4D plans than in 3D plans [(54.86+/-2.79) Gy vs. (50.57+/-1.51) Gy], increased by 9.72% (4%-16%).
The 3D plans have pitfalls of geometric miss or over coverage of target volume. The 4D plans can accurately definite target volume to spare more normal tissues and make dose escalation as compared with 3D CRT.
Ai zheng = Aizheng = Chinese journal of cancer 02/2007; 26(1):1-8.
