Simulation of a MR-PET protocol for staging of head-and-neck cancer including Dixon MR for attenuation correction

Purpose

To simulate and optimize a MR protocol for squamous cell cancer of the head and neck (HNSCC) patients for potential future use in an integrated whole-body MR–PET scanner.

Materials and methods

On a clinical 3T scanner, which is the basis for a recently introduced fully integrated whole-body MR–PET, 20 patients with untreated HNSCC routinely staged with 18F-FDG PET/CT underwent a dedicated MR protocol for the neck. Moreover, a whole-body Dixon MR-sequence was applied, which is used for attenuation correction on a recently introduced hybrid MR–PET scanner. In a subset of patients volume-interpolated-breathhold (VIBE) T1w-sequences for lungs and liver were added. Total imaging time was analyzed for both groups. The quality of the delineation of the primary tumor (scale 0–3) and the presence or absence of lymph node metastases (scale 1–5) was evaluated for CT, MR, PET/CT and a combination of MR and PET to ensure that the MR–PET fusion does not cause a loss of diagnostic capability. PET was used to identify distant metastases. The PET dataset for simulated MR/PET was based on a segmentation of the CT data into 4 classes according to the approach of the Dixon MR-sequence for MR–PET. Standard of reference was histopathology in 19 cases. In one case no histopathological confirmation of a primary tumor could be achieved.

Results

Mean imaging time was 35:17 min (range: 31:08–42:42 min) for the protocol including sequences for local staging and attenuation correction and 44:17 min (range: 35:44–54:58) for the extended protocol. Although not statistically significant a combination of MR and PET performed better in the delineation of the primary tumor (mean 2.20) compared to CT (mean 1.40), MR (1.95) and PET/CT (2.15) especially in patients with dental implants. PET/CT and combining MR and PET performed slightly better than CT and MR for the assessment of lymph node metastases. Two patients with distant metastases were only identified by PET.

Conclusion

We established a potential MR-protocol to be used for HNSCC patients in a recently introduced MR–PET scanner. The proposed protocol can be performed in an acceptable time frame and did not lead to a loss of diagnostic capability compared to PET/CT.     

Growth guidance of angular lower limb deformities using a one-third two-hole tubular plate

Purpose

The eight-plate system for angular deformity correction is well known, reliable and effective at any age during growth. Due to high implant costs, we sought to evaluate the effectiveness and safety of a less expensive alternative.

Methods

Between 2006 and 2011, 41 children with angular deformities were managed using a two-hole one-third tubular plate in cases where an eight plate would normally be indicated. Inclusion criteria in this retrospective study were: genu valgum and genu varum. X-ray documentation was performed before and after surgery and patients were followed clinically every 3 months after surgery. The cost per implant was 361.40 Sfr (Swiss Francs) compared to the eight plate at 737 Sfr.

Results

Mean time for correction was 13 months. A mean LDFA/MPTA after correction of 89.9°/86.8° was recorded, as well as a mean correction angle of 6.8°/6.6°. The complication rate was 6.6 % (one superficial wound infection and one insufficient correction in an older child). These results compare favourably with published data on the eight plate.

Conclusion

The two hole one-third tubular plate seems to be a clinically and also cost effective alternative to the eight plate. Full deformity correction is gained for a fraction of the cost. Level of Evidence: Level III     

溶血对酮胺氧化酶法测定糖化清蛋白结果的影响与校正

目的评价标本溶血对酮胺氧化酶法测定糖化清蛋白(GA)的影响,并建立有效的校正方法。方法酮胺氧化酶法测定无溶血血清GA浓度及其对应人工溶血血清GA浓度、溶血指数;分析溶血对GA检测结果的影响及二者的相关性;利用多元回归分析建立纠正公式,用于临床溶血标本的GA测定值的数学纠正。结果溶血降低酮胺氧化酶法GA测定结果(P0.01),溶血程度与GA浓度呈负相关(R~2=0.943 4);以无溶血血清GA浓度为Y,其对应人工溶血血清GA浓度为Z,溶血吸光度值为X,经多元回归分析,纠正公式为Y=2.468X+Z-0.015 73;溶血标本GA浓度经公式纠正后GA浓度偏移均小于10%。结论标本溶血可导致酮胺氧化酶法GA检测结果降低,运用纠正公式可有效校正溶血对GA测定的干扰,符合临床要求。     

The impact of a corrective tether on a scoliosis porcine model: a detailed 3D analysis with a 20 weeks follow-up

Purpose

Non-fusion treatment for adolescent idiopathic scoliosis generates interest due to the potential for growth preservation and mobility. Using an established porcine scoliotic model, this study aims to evaluate the global alignment and the morphology of the spine with and without application of a non-fusion corrective tether.

Methods

At 12 weeks of age, 21 immature Yorkshire pigs had an induction of scoliosis. Once a 50° Cobb angle was obtained; animals were placed into one of the following groups: a scoliosis model group (SM, n = 11) where animals were euthanized, tether release group (TR, n = 5) where the inducing tether was removed, and an anterior correction group (AC, n = 5) where the inducing tether was removed and non-fusion corrective tether was applied. TR and AC were observed for a further 20 weeks and then euthanized. Post-mortem CT scans were used to create 3D spinal reconstructions to obtain global and morphologic parameters.

Results

Maximal Cobb angle of the scoliotic deformity was significantly lower for AC (27.9° ± 12.0°) than for the two other groups (TR 52.7° ± 10.0°, SM 48.3° ± 7.6°). AC experienced an increase in kyphosis (24.2° ± 15.9°) compared to TR (7.1° ± 6.4°). Correction in the axial plane was also observed in AC versus TR. Correction of vertebral wedging was found for AC compared to SM and TR in the three apical vertebrae.

Conclusions

3D realignment of scoliotic curves was observed with application of the corrective tether. The correction was the product of both mechanical action and growth modulation. These findings are encouraging for future development of a non-fusion device for the treatment of immature scoliotic curves.     

The imprecision in heart rate correction may lead to artificial observations of drug induced QT interval changes

Because of the known limitations of the Bazett and other heart rate correction formulas, it has been proposed that studies of drug induced QT interval changes should use several different heart rate correction formulas and that the consistency of findings by a majority of such formulas should be considered as valid. The aim of this article was to show that such an approach is inappropriate. Using the database of the EMIAT trial, data of QT and RR intervals were taken from electrocardiograms of the first postrandomization visit of 1,402 patients. Of these, 309 were on amiodarone and beta-blockers, 395 on amiodarone and off beta-blockers, 318 on beta-blockers and off amiodarone, and 380 off amiodarone and off beta-blockers. An investigation of drug induced QT interval changes was modeled by evaluating the corrected QT (QTc) interval differences between patients on and off amiodarone, and on and off beta-blockers. A set of 31 previously published heart rate correction formulas was used. In addition to calculating the QTc difference between on and off drug for each formula, the success of heart rate correction was judged by computing correlation coefficients between QTc and RR intervals (ideally corrected QTc values should be independent of heart rate). The difference between on and off drug QT intervals was also evaluated by logarithmic regression models between uncorrected QT and RR intervals in data taken from patients on and off treatment. The QTc interval prolongation on amiodarone was confirmed by all heart rate correction formulas but the extent of the prolongation differed from formula to formula and ranged from 13.6 to 30.9 ms. Of the 31 formulas, 3 reported QTc interval shortening on beta-blockers (up to -11.8 ms) and 28 reported QTc interval prolongation (up to +16.8 ms). The distribution of the results provided by the different formulas suggested that beta-blocker treatment led to a QTc interval prolongation by approximately 7 ms (e.g., +7.4 ms by the Fridericia formula, P = 0.002). The on treatment QTc changes obtained by different formulas were closely correlated to their correction success. Formulas that provided QTc intervals almost independent of the RR intervals estimated approximately 20 ms QTc prolongation on amiodarone and no QTc change on beta-blockers. QT/RR regression analysis confirmed that while amiodarone led to substantial QT prolongation, there was no change of QT interval on beta-blockers beyond the change in heart rate. The study showed that the concept of "majority voting" by different heart rate correction formulas is inappropriate and may lead to erroneous conclusions.     

结合峰值检测的前列腺磁共振成像偏移场平滑拟合

目的研究前列腺磁共振图像中灰度不均匀现象(偏场)的校正方法。材料与方法从几组前列腺磁共振扫描数据中截取的横断面图像。将真实图像的分段常量特性与偏移场的平滑变化特性表达到图像模型中,构造一个能量函数,通过能量函数的最小化实现偏移场评估和组织分割。利用峰值检测技术自动获得能量函数的初始化参数,并用结合三角函数与多项式函数的一组基函数实现对偏移场的平滑拟合。结果定性的实验表明笔者的方法能对前列腺磁共振图像中的偏场现象进行有效的校正。另外通过与其他方法在变化系数、均方根、Jaccard相似度等指标下的定量对比发现,笔者的方法有更好的校正结果。结论结合峰值检测的偏移场校正方法能对前列腺磁共振图像中的灰度不均匀现象有效改善。     

非刚性配准运动校正算法与双扇区重组对改善冠状动脉CTA图像质量的对比分析

目的一种基于非刚性配准的运动校正算法智能边缘修复技术(intelligent boundary registration,IBR)已应用于冠状动脉CTA成像。通过与双扇区重组图像质量的比较,评估IBR技术应用于冠状动脉成像的效果。方法本回顾性研究经医院伦理委员会批准,并获得患者的知情同意。收集本院行能谱CT冠状动脉CTA检查且平均心率为65次/min(范围58~75次/min)的70例可疑心肌缺血患者,在最佳心动时相进行双扇区图像重组(SSB2),即为SSB2组;在最佳心动时相进行单扇区图像重组,基于最佳单扇区重组执行IBR重组以生成IBR图像,即为IBR组。采用5分制评分(5=图像质量优秀;1=不能满足诊断要求),评价指标包括:整体图像质量、血管的评估(连续性、有无运动伪影、血管的边缘模糊与否)。由两位心血管放射学医师通过双盲和独立观察比较,对SSB2和IBR处理后的图像分别进行冠状动脉整体水平和冠状动脉节段评分。结果共分析了70位患者冠状动脉的984个节段。两位医师的评分结果具有良好的一致性(k0.81),SSB2组和IBR组的平均评分分别为(4.02±1.28)和(4.45±1.01),两者间的差异具有统计学差异(Z=-9.22,P0.01)。在基于冠状动脉节段的分析中,可接受的图像质量不低于3分的百分比分别为88.3%和91.2%,具有统计学差异(X~2=5.68,P0.05);可接受的图像质量不低于4分的百分比为分别为73.3%和88.5%,具有统计学差异(X~2=6.47,P0.05)。在重组的血管中不可评估的节段IBR组明显低于SSB2组,差异具有统计学意义(4.2%与9.5%,X~2=12.13,P0.01)。结论能谱CT冠状动脉IBR技术可以提高冠状动脉CTA的图像质量,减少阶梯状伪影。     

利用蒙特卡罗模拟评估空气间隙对点扫描质子治疗的剂量影响

目的:利用蒙特卡罗模拟探究空气间隙对点扫描质子治疗的剂量影响。方法:利用通用蒙特卡罗程序Geant4平台构建使用射程移位器的治疗头末端的点扫描质子束流模型,并进行验证。模拟计算不同能量、不同射程移位器、不同束斑尺寸、不同束斑数目在不同空气间隙条件下的质子束流在水模体中的剂量沉积,并通过获得的积分深度剂量生成剂量修正因子对剂量的差异进行比较。结果:不同空气间隙会造成剂量损失,随空气间隙增大而增大,随水模体中深度增加而减小。对于能量更高的射束和使用水等效厚度更薄的射程移位器,剂量损失越大。束斑尺寸改变和束斑数目增加较少时造成的剂量损失与同条件下单一束流无显著差别。结论:当使用射程移位器、肿瘤位置较浅、空气间隙较大时,建议建立剂量修正因子数据库应用于治疗计划系统对剂量进行修正。