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Cutaneous T-cell lymphomas are a relatively rare group of mature T-cell lymphomas mainly manifesting in the skin, and its common subtype is mycosis fungoides. Total skin electron irradiation is one of the important conventional treatment methods, but there are many disadvantages, such as uneven dose distribution, poor position repetition, and long treatment time, which affect the clinical efficacy and patient prognosis. With the emergence and gradual popularization of helical tomotherapy in recent years, more and more medical institutions are gradually expanding their applications in total skin irradiation due to their ability to treat ultra-long targets and achieve dose-sculpted distribution, aiming to further explore its good or bad, and confirm whether it can replace the traditional total skin electron irradiation. In this article, research progress on total skin irradiation using helical tomotherapy was reviewed, the development of treatment technology, clinical efficacy and current concerns and controversies were illustrated.
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Objective:To study the changing characteristics and impact factors of helical tomotherapy (HT)for longitudinal dose fall-off outside the target, in order to guide the plan junction or pretreatment target and implementation efficiency in clinical.Methods:Eight patients with head and neck tumors admitted to the Department of Oncology Radiotherapy of the First Affiliated Hospital of Zhengzhou University in December 2019 were retrospectively selected as the research objects. The planning target area and dose drop structure were outlined in the head and neck images with a thickness of 1 mm obtained by Siemens SOMATOM Definition AS positioning computerized tomography (CT). Different field widths (FW, 5.0 cm/2.5 cm/1.0 cm) and pitches (0.430/0.287/0.215) were assembled for planning with the same modulation factor (1.8), finest does calculation grid (0.195 cm ×0.195 cm) and other planning parameters were consistent. The plans were designed by different parameters, and the result was analyzed by univariate analysis.Results:The that different pitch curves coincided under the same field width by comparative analyzing, so pitchs had no effect on dose drop. The different field width curves were independent of each other, indicating that the field width had an effect on dose drop in the head and foot direction. The relationship between the longitudinal dose drop speed outside the target and the change of the field width was inversely correlated: the larger field widths meant the slower dose fall-off and the larger penumbra, while the smaller field widths meant the faster fall-off and the smaller penumbra. When the dose fall-off to 50% of the prescribed dose, the distance from the target was approximately equal to half the field widths, and the pitchs had not affect the rate of dose-drop, while the dose at different distances from the target boundary could be calculated by the fitting formulas. The field widths and pitchs had little effect on the CI and HI index of the target, relatively, the target area was best when the field width was 2.5 cm. The total beam-on time gradually decreased with the increase of the field widths and pitches.Conclusions:When segment target therapy needs to consider planning junction, execution efficiency, and controlling longitudinal dose fall-off and considered the execution, the optimal planned parameters such as field widths and pitches could be selected or the target at the junction regions could be adducted according to the longitudinal dose drop formula, so as to achieve the ideal dose distribution.
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Objective@#To investigate the dosimetric differences between TomoDirect (TD) and Helical Tomotherapy (HT) in total body irradiation (TBI), as well to evaluate the plan quality and delivery efficiency of TD.@*Methods@#Eight patients with acute leukemia at an average height of about 120 cm who had undergone TBI in the first affiliated hospital of Zhengzhou university were retrospectively reviewed and replanned with the TD and HT techniques for dosimetric comparison. Identical planning parameters were configured for both techniques except that TD plans were designed with 2-12 equally spaced odd number fields and with an initial angle of 180 or 0 degree. Dosimetric differences in mean dose of plan target volume (PTVDmean), homogeneity index (HI), dose of organs at risk (OARs), as well as delivery time were compared between the TD and HT plans.@*Results@#The TD plans with 9 fields or more had similar PTVDmeanand HI compared with HT plans, while TD plans with less than 9 fields had a significant different PTVDmean(t=-3.12, -5.41, -20.33, -4.56, -7.22, -11.27, P<0.05) and HI (t=-2.94, -5.18, -15.66, -4.31, -5.51, - 9.13, P<0.05) compared with those of HT. In terms of OARs, the TD plans with 7 fields or more had no significant dosimetric differences in the mean dose of left and right lung compared with the HT plans. The TD plans with 3 fields had significant different maximum dose in the left lens plan risk volume(PRV) (2.14±0.60) Gy and the right lens PRV (3.05±0.10) Gy (t=0.77, 0.63, P<0.05) compared with the HT plans. No significant difference in delivery time was observed. The initial angle of the TD plans had no effects on PTVDmean, HI, OAR dosimetry and delivery time.@*Conclusions@#The TD plans with 9 fields or more can achieve similar plan quality in terms of target coverage, OAR sparing and delivery time, but have an advantage in the maximum dose to lens PRV compared with the HT plans.
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Objective Because of high precision and mild side effects,intensity-modulated proton therapy (IMPT) has become a hot spot in the radiotherapy field.Nevertheless,the precision of IMPT is extremely sensitive to the range uncertainties.In this paper,a novel robust optimization method was proposed to reduce the effect of range uncertainty upon IMPT.Methods Firstly,the robust optimization model was established which contained three types of range including the increased range,the normal range and the shortened range.The objective function was expressed in quadratic function.The organ dose contribution matrix of each range was calculated by proton pencil beam algorithm.The range deviation was discretized and the probability of each range was obtained based on the Gauss distribution function.Finally,the conjugate gradient method was adopted to find the optimal solution to make the actual dose coverage of the target area and the organs at risk distributed within the expected dose as possible.Results The 3 sets of simulation tests provided by the AAPM TG-119 Report were utilized to evaluate the effectiveness of this method:nasopharyngeal carcinoma,prostate and "C"-type cases.Compared with conventional IMPT optimization approach,this novel method was less sensitive to the range uncertainty.When the range deviation occurred,the dose coverage of the target area and organs at risk of the nasopharyngeal carcinoma and prostate cases almost reached the expected dose,and the high dose coverage of the target area and organs at risk protection were improved in the"C"-type cases.Conclusions To compensate for the range uncertainty,this novel method can enhance the dose coverage of the target area and reduce the dose coverage of the organs at risk.
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Objective To investigate the dosimetric differences between TomoDirect ( TD) and Helical Tomotherapy ( HT ) in total body irradiation ( TBI ) , as well to evaluate the plan quality and delivery efficiency of TD. Methods Eight patients with acute leukemia at an average height of about 120 cm who had undergone TBI in the first affiliated hospital of Zhengzhou university were retrospectively reviewed and replanned with the TD and HT techniques for dosimetric comparison. Identical planning parameters were configured for both techniques except that TD plans were designed with 2-12 equally spaced odd number fields and with an initial angle of 180 or 0 degree. Dosimetric differences in mean dose of plan target volume ( PTVDmean ) , homogeneity index ( HI) , dose of organs at risk ( OARs) , as well as delivery time were compared between the TD and HT plans. Results The TD plans with 9 fields or more had similar PTVDmean and HI compared with HT plans, while TD plans with less than 9 fields had a significant different PTVDmean(t=-3. 12, -5. 41, -20. 33, -4. 56, -7. 22, -11. 27, P<0. 05) and HI ( t=-2. 94, -5. 18,-15. 66,-4. 31,-5. 51,- 9. 13, P<0. 05) compared with those of HT. In terms of OARs, the TD plans with 7 fields or more had no significant dosimetric differences in the mean dose of left and right lung compared with the HT plans. The TD plans with 3 fields had significant different maximum dose in the left lens plan risk volume(PRV) (2.14±0.60) Gy and the right lens PRV (3.05±0.10) Gy (t=0.77, 0.63, P<0.05) compared with the HT plans. No significant difference in delivery time was observed. The initial angle of the TD plans had no effects on PTVDmean , HI, OAR dosimetry and delivery time. Conclusions The TD plans with 9 fields or more can achieve similar plan quality in terms of target coverage, OAR sparing and delivery time, but have an advantage in the maximum dose to lens PRV compared with the HT plans.
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Objective@#To study the lumber spine imaging process of dual-energy X-ray absorptiometry (DXA) and parameters used to optimize the image quality.@*Methods@#A computational voxel phantom was constructed from patient computed tomography (CT) data. Using the Monte Carlo radiation transport method, a dual energy x-ray beam was simulated to scan the phantom of lumbar spine to generate a bone density image. The Figure of Merit (FOM) of each image was claculated. Parameters including the combination of the high and low energy tube voltage, the thickness of Cu filter, and the ratio of two beam energy incident photon number were optimized, which based on FOM.@*Results@#FOM reaches a minimum of 1.59 × 10-2 with the tube voltage combination of 75 and 200 kVp. With the thickness of the Cu filter from 0 mm to 3 mm, FOM decreases from 6.30×10-2 to 1.87×10-2, showing a gradually slow-down trend. With the incident photon number ratio (low energy/high energy) increasing from 1∶3 to 19∶1, FOM decreases firstly and then increases, reaching a minimum of 1.40×10-2 at 3∶1.@*Conclusions@#According to the simulation results, the combinations of low tube voltage from 70 kVp to 85 kVp and high tube voltage from 160 kVp to 200 kVp, 0.3 mm Cu filter and beam incident photon number ratio from 1 to 5 can yield the best lumbar spine image quality with the lowest patient dose.
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Objective To develop an online organ doses reporting software VirtualDose-IR, which can compute the radiation doses and provide an easy access to evaluation and control of patients ′radiation doses.Methods Monte Carlo method was applied to simulating various interventional radiology ( IR) processes , which included various parameters such as different patient models at different ages and with different weights , different projection angles and regions of interest , and other parameters .All of the dose data was acquired and then integrated into a database , and displayed with hyper text markup language (HTML), so only a web browser was necessary for users .Results A web-based software that reports organ doses for patients under IR progress was developed .The organ doses assessed with VirtualDose-IR were compared with other experiment and simulation data , and the results were basically consistent with each other .Conclusions VirtualDose-IR is a easy and efficient method to assess patients′radiation doses of IR.