The clinical application of 4D 18F-FDG PET/CT on gross tumor volume delineation for radiotherapy planning in esophageal squamous cell cancer

A combination of four-dimensional computed tomography with ¹⁸F-fluorodeoxyglucose positron emission tomography (4D CT-FDG PET) was used to delineate gross tumor volume (GTV) in esophageal cancer (EC). Eighteen patients with EC were prospectively enrolled. Using 4D images taken during the respiratory cycle, the average CT image phase was fused with the average FDG PET phase in order to analyze the optimal standardized uptake values (SUV) or threshold. PET-based GTV (GTV_PET) was determined with eight different threshold methods using the auto-contouring function on the PET workstation. The difference in volume ratio (VR) and conformality index (CI) between GTV_PET and CT-based GTV (GTV_CT) was investigated. The image sets via automatic co-registrations of 4D CT-FDG PET were available for 12 patients with 13 GTV_CT values. The decision coefficient (R²) of tumor length difference at the threshold levels of SUV 2.5, SUV 20% and SUV 25% were 0.79, 0.65 and 0.54, respectively. The mean volume of GTV_CT was 29.41 ± 19.14 ml. The mean VR ranged from 0.30 to 1.48. The optimal VR of 0.98, close to 1, was at SUV 20% or SUV 2.5. The mean CI ranged from 0.28 to 0.58. The best CI was at SUV 20% (0.58) or SUV 2.5 (0.57). The auto-contouring function of the SUV threshold has the potential to assist in contouring the GTV. The SUV threshold setting of SUV 20% or SUV 2.5 achieves the optimal correlation of tumor length, VR, and CI using 4D-PET/CT images.     

氨基质子饱和转移磁共振成像方法研究

目的:探讨氨基质子饱和转移磁共振成像。方法:介绍化学交换饱和转移磁共振成像的理论、特征以及所受干扰因素等。结果:作为一种新型的分子水平的磁共振成像技术,氨基质子饱和转移磁共振成像是一种可以对人体的蛋白质以及与化学交换效应相关的交换速率进行高分辨成像的技术,也是一种内源性的无创的分子成像方法,具有重要的研究与应用价值。结论:氨基质子饱和转移磁共振成像可以被安全地应用于脑肿瘤以及脑中风等临床科学研究中。     

多源g射束立体定向放射治疗计划系统的剂量计算加速算法研究

回顾了现有多源γ射束立体定向放射治疗计划系统的剂量计算方法,提出了一种基于锥形坐标系和多核并行化的剂量计算加速算法。实验结果表明,该方法在保证剂量计算精度的前提下极大提高了计算速度,速度可提升到传统计算方法的20倍。     

Geometric accuracy of 3D coordinates of the Leksell stereotactic skull frame in 1.5 Tesla- and 3.0 Tesla-magnetic resonance imaging: a comparison of three different fixation screw materials

We assessed the geometric distortion of 1.5-Tesla (T) and 3.0-T magnetic resonance (MR) images with the Leksell skull frame system using three types of cranial quick fixation screws (QFSs) of different materials—aluminum, aluminum with tungsten tip, and titanium—for skull frame fixation. Two kinds of acrylic phantoms were placed on a Leksell skull frame using the three types of screws, and were scanned with computed tomography (CT), 1.5-T MR imaging and 3.0-T MR imaging. The 3D coordinates for both strengths of MR imaging were compared with those for CT. The deviations of the measured coordinates at selected points (x = 50, 100 and 150; y = 50, 100 and 150) were indicated on different axial planes (z = 50, 75, 100, 125 and 150). The errors of coordinates with QFSs of aluminum, tungsten-tipped aluminum, and titanium were <1.0, 1.0 and 2.0 mm in the entire treatable area, respectively, with 1.5 T. In the 3.0-T field, the errors with aluminum QFSs were <1.0 mm only around the center, while the errors with tungsten-tipped aluminum and titanium were >2.0 mm in most positions. The geometric accuracy of the Leksell skull frame system with 1.5-T MR imaging was high and valid for clinical use. However, the geometric errors with 3.0-T MR imaging were larger than those of 1.5-T MR imaging and were acceptable only with aluminum QFSs, and then only around the central region.     

Feasibility study of stereotactic body radiotherapy for peripheral lung tumors with a maximum dose of 100 Gy in five fractions and a heterogeneous dose distribution in the planning target volume

We evaluated toxicity and outcomes for patients with peripheral lung tumors treated with stereotactic body radiation therapy (SBRT) in a dose-escalation and dose-convergence study. A total of 15 patients were enrolled. SBRT was performed with 60 Gy in 5 fractions (fr.) prescribed to the 60% isodose line of maximum dose, which was 100 Gy in 5 fr., covering the planning target volume (PTV) surface (60 Gy/5 fr. − (60%-isodose)) using dynamic conformal multiple arc therapy (DCMAT). The primary endpoint was radiation pneumonitis (RP) ≥ Grade 2 within 6 months. Toxicities were graded according to the Common Terminology Criteria for Adverse Events, version 4.0. Using dose–volumetric analysis, the trial regimen of 60 Gy/5 fr. − (60%-isodose) was compared with our institutional conventional regimen of 50 Gy/5 fr. − (80%-isodose). The enrolled consecutive patients had either a solitary peripheral tumor or two ipsilateral tumors. The median follow-up duration was 22.0 (12.0–27.0) months. After 6 months post-SBRT, the respective number of RP Grade 0, 1 and 2 cases was 5, 9 and 1. In the Grade 2 RP patient, the image showed an organizing pneumonia pattern at 6.0 months post-SBRT. No other toxicity was found. At last follow-up, there was no evidence of recurrence of the treated tumors. The target volumes of 60 Gy/ 5 fr. − (60%-isodose) were irradiated with a significantly higher dose than those of 50 Gy/5 fr. − (80%-isodose), while the former dosimetric parameters of normal lung were almost equivalent to the latter. SBRT with 60 Gy/5 fr. − (60%-isodose) using DCMAT allowed the delivery of very high and convergent doses to peripheral lung tumors with feasibility in the acute and subacute phases. Further follow-up is required to assess for late toxicity.     

Gray matter volume increases induced by intragastric balloon treatment and their associations with neuroinflammation: A magnetic resonance study

ObjectiveWe simultaneously performed structural MRI, ¹H magnetic resonance spectroscopy, and whole-body hydration status assessment to evaluate brain changes in patients with morbid obesity treated with intra-gastric balloon (IGB) for six months. We asked, if changes in myo-inositol ratios (marker of neuroinflammation) are related to brain volume increases accompanying IGB-induced weight loss.MethodsTwenty five patients with morbid obesity (OB, 43.9 ± 11.8 years, BMI = 49.1 ± 7.2, 12 females, 9 without co-morbid conditions) were treated with IGB for six months. They underwent magnetic resonance imaging at 3T one month before IGB insertion, three months after insertion (N = 19), and one month after IGB removal (N = 14).ResultsInsertion of IGB lead to 8.9% and 12.3% weight reduction over the first three months and over the entire treatment, respectively. Over the entire treatment, total gray matter volume increased by 2.0% (p = 0.009). These changes were mostly pronounced in the left precuneus and in the right frontal pole (>1.9%, p < 0.009). The increases in cortical volume in the right hemisphere and the left posterior cingulate cortical thickness over the entire treatment were significantly related to decreases in myo-inositol ratios measured over the first three months of the treatment (r < −0.740, p < 0.006).ConclusionsIGB treatment lead to brain structural improvements consistent with earlier studies of bariatric patients without co-morbid conditions. Our results also pointed to improvements in brain regions, where atrophy in other studies was related to type 2 diabetes and hypertension. The correlations point to neuroinflammation as one of the potential processes behind brain volume reductions in patients with morbid obesity.