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Objective:To quantify the registration deviation between CT and cone-beam computed tomography (CBCT) images with different breathing rates and motion amplitudes under free breathing state.Methods:Using the QUASAR respiratory motion phantom, breathing rate and motion amplitude in the superior-inferior (SI) direction were changed to simulate free breathing motion under different states. The CT and CBCT images were acquired under different breathing rates and motion amplitudes, and static states, then the registration errors between CT and CBCT images and CT target volume were obtained and subject to quantitative analysis.Results:Using the static CT image as a reference, the changes in breathing rate exerted no significant effect on the registration error when the motion amplitude was constant. When the motion amplitude was 0.5, 1.0, 2.0, and 3.0 cm, the average registration errors were (0.213±0.020), (0.351±0.009), (0.654±0.010), and (0.972±0.022) cm, respectively. When the motion amplitude was 0.5 and 1.0 cm, the CT target volume varied from -16.92% to 18.78%. When the motion amplitude was 2.0 and 3.0 cm, the CT target volume changed from -16.44% to 81.78%.Conclusions:The changes in breathing rate under free-breathing state has no significant effect on the registration error between CBCT and CT images. When the motion amplitude is 0.5 and 1.0 cm, the CT target volume changes and the registration errors are small. When themotion amplitude is 2.0 and 3.0 cm, the registration errors exceed 0.5 cm and the CT target volume changes may exceed 20%.
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Objective:To compare the difference between active breathing coordinator (ABC) technique and free breathing (FB) mode combined with bodyfix stereotactic radiotherapy (SBRT) for chest tumors.Methods:40 thoracic tumor patients receiving SBRT were randomly selected and divided into the ABC technique group and FB model group. After fixation with bodyfix fixing devices in two groups, cone-beam CT (CBCT) scan images before each SBRT were matched with the plan reference images. The setup errors in the left-right (LR), superior-inferior (SI) and anterior-post (AP) directions were obtained. Then, the setup errors were corrected. SBRT was performed and split intra-fraction CBCT was conducted simultaneously, which was repeated until the end of treatment.Results:In the ABC technique group, the setup errors in the LR, SI and AP directions were (0.25±0.21) cm, (0.28±0.21) cm, and (0.21±0.24) cm, significantly less compared with (0.31±0.22) cm, (0.32±0.21) cm and (0.37±0.23) cm in the FB model group (all P<0.05). The V 30Gy of the heart, the V 20Gy and V 30Gy of the lung in the ABC technique group were significantly less than those in the FB model group (0.31%∶7.35%; 24.5%∶32.9%; 19.5%∶25.8%, all P<0.05). Conclusions:ABC technique combined with bodyfix fixation device may be superior to FB mode in SBRT for chest tumors, which remains to be validated by subsequent studies with large samples.
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Magnetic resonance imaging (MRI) plays an important role in abdominal imaging. The high contrast resolution offered by MRI provides better lesion detection and its capacity to provide multiparametric images facilitates lesion characterization more effectively than computed tomography. However, the relatively long acquisition time of MRI often detrimentally affects the image quality and limits its accessibility. Recent developments have addressed these drawbacks. Specifically, multiphasic acquisition of contrast-enhanced MRI, free-breathing dynamic MRI using compressed sensing technique, simultaneous multi-slice acquisition for diffusion-weighted imaging, and breath-hold three-dimensional magnetic resonance cholangiopancreatography are recent notable advances in this field. This review explores the aforementioned state-of-the-art techniques by focusing on their clinical applications and potential benefits, as well as their likely future direction.
Subject(s)
Cholangiopancreatography, Magnetic Resonance , Hand Strength , Magnetic Resonance ImagingABSTRACT
OBJECTIVE: To compare the breathing effects on dynamic contrast-enhanced (DCE)-MRI between controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA)-volumetric interpolated breath-hold examination (VIBE), radial VIBE with k-space-weighted image contrast view-sharing (radial-VIBE), and conventional VIBE (c-VIBE) sequences using a dedicated phantom experiment. MATERIALS AND METHODS: We developed a moving platform to simulate breathing motion. We conducted dynamic scanning on a 3T machine (MAGNETOM Skyra, Siemens Healthcare) using CAIPIRINHA-VIBE, radial-VIBE, and c-VIBE for six minutes per sequence. We acquired MRI images of the phantom in both static and moving modes, and we also obtained motion-corrected images for the motion mode. We compared the signal stability and signal-to-noise ratio (SNR) of each sequence according to motion state and used the coefficients of variation (CoV) to determine the degree of signal stability. RESULTS: With motion, CAIPIRINHA-VIBE showed the best image quality, and the motion correction aligned the images very well. The CoV (%) of CAIPIRINHA-VIBE in the moving mode (18.65) decreased significantly after the motion correction (2.56) (p < 0.001). In contrast, c-VIBE showed severe breathing motion artifacts that did not improve after motion correction. For radial-VIBE, the position of the phantom in the images did not change during motion, but streak artifacts significantly degraded image quality, also after motion correction. In addition, SNR increased in both CAIPIRINHA-VIBE (from 3.37 to 9.41, p < 0.001) and radial-VIBE (from 4.3 to 4.96, p < 0.001) after motion correction. CONCLUSION: CAIPIRINHA-VIBE performed best for free-breathing DCE-MRI after motion correction, with excellent image quality.
Subject(s)
Acceleration , Artifacts , Magnetic Resonance Imaging , Respiration , Signal-To-Noise RatioABSTRACT
Objective To compare and determine the reproducibility of apparent diffusion coefficient (ADC)values of the normal liver parenchyma in respiratory-triggered,breath-hold,and free-breathing diffusion weighted magnetic resonance imaging (DWI). Methods 11 volunteers did three times of breath-hold (excitation number is 1,at the end of the expiration,thickness/gapping=5 mm/1 mm), respiratory-triggered (excitation number is 2,at the end of the expiration,thickness/gapping=5 mm/1 mm),free-breathing (excitation number is 4,thickness/gapping=5 mm/1 mm)and for a total of nine axial liver DWI,the gradient factor was 800 s/mm2 .Then they were all coronally reconstructed (thickness/gapping=8 mm/1 mm).The nonparametric test was used to compare all axial and coronally reconstructed liver ADC values;and the Bland-Altman method was used to evaluate the ADC values’repeatability in coronally reconstructed images.Results The breath-hold DWI’s mean ADC value was (1.09±0.07)×10-3 mm2/s significantly lower than the respiratory-triggered DWI(1.16± 0.09)×10-3 mm2/s and the free-breathing DWI(1.19±0.10)×10-3 mm2/s(P<0.005),the axial and coronal images’results were similar.The ADC values’average difference and scope of consistency of coronal image were (-0.09 to -0.01±0.09 to 0.48)for breath-hold DWI,(-0.04 to 0.01±0.11 to 0.17)for respiratory-triggered DWI,(-0.07 to -0.02±0.11 to 0.18)for free-breathing DWI,respectively.Conclusion The breath-hold DWI’s ADC value of normal liver parenchyma is lower than the respiratory-triggered and free-breathing DWI,and showed more poorer repeatability.It is suggested that the measurement of ADC values of the liver parenchyma should be done within the respiratory-triggered or free-breathing DWI.
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Objective To compare the dose distribution of the target and normal tissues in gastric cancers between three-dimension conformal radiation therapy (3DCRT) and intensity modulated radiation therapy (IMRT) plan when respiratory motion factors integrated in the plan. Methods From January 2005to November 2006, 10 patients with post-operatively radiation of gastric cancer were enrolled in this study.Planning CT were acquired conventionally with free-breath mode and the static treatment plans of the 3DCRT and IMRT were designed respectively. Probability distribution functions (PDF) were generated and convoluted with the static dose distributions from 3DCRT and IMRT plans to obtain the integrated plans. The dose distributions of the target and normal tissues were compared between 3DCRT and IMRT integration treatment plans, such as V45 of clinical target volume, V4o of liver and V15, V18 of left and right kidney.Results In the respiratory integrated treatment planning, the target volume coverage and homogeneity with IMRT are superior to those with 3DCRT ( ( V45 98%∶ 87% (t = -3. 35 ,P =0. 010) ,mean dose 46. 81 Gy ±0. 75 Gy∶45.99 Gy ± 1.12 Gy (t = -0. 31 ,P=0. 020) ). The V40 of teh liver in IMRT are smaller than those in 3DCRT ( 12%∶ 16% ;t=3.75,P=0.010). For the left kidney, the V15 and V18 in IMRT are smaller than those in 3DCRT ( (34%∶ 50% (t = 2. 17 ,P = 0. 050) and 27%∶46% (t = 3. 11 ,P = 0. 020) ),but for the right kidney, V15 and V18 in 3DCRT are smaller than those in IMRT ( ( 15%∶ 21% (t = - 2. 42,P=0.040) and 11%∶15% (t= -2.71,P=0.030)). Conclusions When respiratory motion factor integrated in the treatment plan, IMRT showed advantage both in target coverage and normal tissue sparing in the high dose region of liver and left kidney.
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Objective To assess the impact of respiratory motion on the displacement of target area and to analyze the discrimination between free breathing and active breathing control (ABC) in patients with gastric cancer treated with post-operative radiotherapy. Methods From January 2005 to November 2006, 22 patients with post-operatively confirmed gastric cancer were enrolled in this study. All diseases were T_3/ N +, staging Ⅱ - Ⅳ. Patients were CT scanned and treated by radiation with the use of ABC. Image J software was used in image processing, motion measurement and data analysis. Surgical clips were implanted as fiducial marks in the tumor bed and lymphatic drainage area. The motion range of each clip was measured in the resultant-projection image. Motions of the clips in superior-inferior (S-I), right-left (R-L) and anterior-posterior (A-P) directions were determined from fluoroscopy movies obtained in the treatment position. Results The motion ranges in S-I, R-L and A-P directions were 11.1 mam, 1.9 mm and 2.5 mm (F = 85.15, P = 0. 000) under free breathing, with 2.2 mm, 1.1 mm and 1.7 nun under ABC (F = 17.64, P = 0. 000), and the reduction of motion ranges was significant in both S-I and A-P directions (t = 4.36, P = 0. 000;t = 3.73,P = 0.000). When compared with under free-breathing, the motion ranges under ABC were kept unchanged in the same breathing phase of the same treatment fraction, while significant increased in different breathing phase in all three directions (t = - 4.36, P = 0. 000; t = - 3.52, P = 0.000; t =-3.79, P = 0. 000), with a numerical value of 3.7 mm, 1.6 mm and 2.8 mm, respectively (F = 19.46, P = 0. 000) . With ABC between different treatment fractions , the maximum displacements were 2.7 mm, 1.7 mm and 2.5 mm for the centre of the clip cluster (F =4.07,P =0. 019), and were 4.6 mm, 3.1 mm and 4.2 mm for the clips (F =5.17 ,P =0.007). The motion ranges were significant increased in all the three directions (t = - 4.09, P=0.000 ; t =-4.46, P = 0.000 ; t = - 3.45, P =0.000). Conclusions In the irradiation of post-operative gastric cancer, the maximum displacement of organ motions induced by respiration is in S-1 direction and the minimum in R-L direction under free breathing. The use of ABC can reduce the motions significantly in S-I and A-P directions, and the same changes exist in both inter-and intra-fraction treatment.