Majority Vote and Other Problems when using Computational Tools

Computational tools are essential for most of our research. To use these tools, one needs to know how they work. Problems in application of computational methods to variation analysis can appear at several stages and affect, for example, the interpretation of results. Such cases are discussed along with suggestions how to avoid them. The applications include incomplete reporting of methods, especially about the use of prediction tools; method selection on unscientific grounds and without consulting independent method performance assessments; extending application area of methods outside their intended purpose; use of the same data several times for obtaining majority vote; and filtering of datasets so that variants of interest are excluded. All these issues can be avoided by discontinuing the use software tools as black boxes.     

Quantification of Myocardial Blood Flow in Absolute Terms Using 82Rb PET Imaging: The RUBY-10 Study

ObjectivesThe purpose of this study was to compare myocardial blood flow (MBF) and myocardial flow reserve (MFR) estimates from rubidium-82 positron emission tomography (⁸²Rb PET) data using 10 software packages (SPs) based on 8 tracer kinetic models.BackgroundIt is unknown how MBF and MFR values from existing SPs agree for ⁸²Rb PET.MethodsRest and stress ⁸²Rb PET scans of 48 patients with suspected or known coronary artery disease were analyzed in 10 centers. Each center used 1 of 10 SPs to analyze global and regional MBF using the different kinetic models implemented. Values were considered to agree if they simultaneously had an intraclass correlation coefficient >0.75 and a difference <20% of the median across all programs.ResultsThe most common model evaluated was the Ottawa Heart Institute 1-tissue compartment model (OHI-1-TCM). MBF values from 7 of 8 SPs implementing this model agreed best. Values from 2 other models (alternative 1-TCM and Axially distributed) also agreed well, with occasional differences. The MBF results from other models (e.g., 2-TCM and retention) were less in agreement with values from OHI-1-TCM.ConclusionsSPs using the most common kinetic model—OHI-1-TCM—provided consistent results in measuring global and regional MBF values, suggesting that they may be used interchangeably to process data acquired with a common imaging protocol.     

Comparison of estimates of left ventricular ejection fraction obtained from gated blood pool imaging,different software packages and cameras

Serial measurement of LVEF using gated blood pool (GBP) imaging is an established technique for monitoring LVEF in patients undergoing chemotherapy with cardiotoxic medication and in patients after heart transplants.11,2 The nuclear medicine department at Groote Schuur Hospital performs up to a thousand GBP studies annually. The majority of these studies are for patients receiving cardiotoxic chemotherapy and have a significant impact on patient management.In our hospital, the radiation oncologists consider not starting cardiotoxic chemotherapy if the LVEF is below 50% and terminating chemotherapy if there is a 10% decrease. In patients who have had heart transplants, the cardiologists start patients on glucocorticosteroids if a patient’s LVEF decreases by10%. It is therefore imperative that serial studies on an individual patient are comparable.Two software systems are used in our nuclear medicine department. The Siemens system (Siemens Medical Solutions, Chicago, USA) was introduced in February 2006 and the Hermes system (Hermes Medical Solutions, Stockholm Sweden) in September 2007. After the introduction of the Hermes system, we found large differences between the LVEFs calculated by the two systems. This was confirmed by a pilot study and is consistent with the literature that different software programs for processing equilibrium gated radionuclide studies cannot be used interchangeably.3-7The department also uses two different cameras, a General Electric (GE) Starcam 400 AC single-head and a Siemens Signature Series e.cam dual-head camera to acquire the raw data. These are then transferred to the Siemens and Hermes processing systems.This study was done to determine how the software packages used for processing GBP studies should be integrated into our department and if the use of different cameras for acquisition influences results. The study had two components. The first examined the values and reproducibility of estimates of LVEF from two software packages using data acquired on the GE gamma camera and processed independently by three operators. The second component examined the values and reproducibility of estimates of LVEF calculated with the same software packages using matched pairs of raw data acquired on both gamma cameras (GE and Siemens) processed by one operator.     

C1侧块骨折Magerl技术内固定的数字化模拟及应用

目的 探讨计算机软件应用于C1侧块骨折三维重建、复位以及数字化模拟Magerl技术内固定的方法及临床意义,以指导临床应用.方法 将1具颈椎标本制作成C1侧块骨折类型,进行高速CT薄层扫描,在Mimics中对C1侧块骨折模型进行重建、复位,以Solidworks进行螺钉的设计,并在骨折复位三维模型上进行虚拟Magerl技术内固定.结果 对骨折进行了三维重建、复位,根据三维模型测量数据,完成虚拟螺钉内固定,并成功指导临床手术21例.结论 应用Mimics及Solidworks可在个人电脑上设计出C1侧块骨折数字化螺钉固定,对临床手术有很好的参考意义.     

Dental age estimation in Malaysian adults based on volumetric analysis of pulp/tooth ratio using CBCT data

Forensic odontology plays an important role in human identification and dental age estimation is an integral part of this process. The aim of the study was to investigate the association between chronological age and pulp/tooth volume ratio in a Malaysian population (Malays and Chinese) from cone-beam computed tomography (CBCT) scans, enhanced with Mimics software. Three hundred CBCT scans of 153 males and 147 females, aged between 16 and 65 years were divided into 5 age groups. Volumetric analysis of the pulp/tooth ratio was performed in maxillary left canines, maxillary right canines and maxillary right central incisors. Simple linear regression and Pearson correlation analysis indicated the strongest coefficient of correlation (R) values for maxillary right central incisors (0.83) followed by maxillary right canines (0.74) and maxillary left canines (0.73). Fisher’s Z test indicated that dental age estimation is gender independent. The derived regression equations were further validated on an independent group of 126 teeth. The results indicated mean absolute error (MAE) values of 6.48 and 8.58 years for maxillary right central incisors and maxillary canines respectively. It was also noticed that MAE values were higher among the age groups ranging from 46 to 65 years. This study showed that a volumetric change in the pulp cavity with age is a valuable assessment method for dental age estimation among Malaysian population.     

3D Slicer三维影像重建在颅内动脉瘤夹闭术中的应用

目的 探讨3D Slicer三维影像重建技术在颅内动脉瘤开颅夹闭术中的应用价值。方法 回顾性分析2020年7~9月经翼点入路开颅夹闭术治疗的12例颅内动脉瘤的临床资料。术前利用3D Slicer软件三维重建动脉瘤模型及其周围血管和部分骨性结构,并模拟手术入路,显示手术视野下动脉瘤与毗邻结构的位置关系;术中参考立体模型,寻找动脉瘤并根据解剖结构实时定位,实现精准夹闭。结果 12例均顺利完成三维影像重建,将三维模型与术中所见进行对比,9例正确反映术中真实解剖情况,3例术中对比效果欠佳,小动脉瘤（直径<5 mm）以及小血管重建效果相对较差,但是动脉瘤周围主要血管结构对比一致。12例动脉瘤均顺利实施开颅夹闭术,术中没有出现动脉瘤破裂。术后次日复查颅脑CTA示载瘤动脉通畅,未见新增出血,动脉瘤夹闭良好。术后3个月,复查CTA未见动脉瘤复发;GOS评分5分8例,4分3例,3分1例。结论 3D Slicer三维影像重建制作的颅内动脉瘤三维立体模型,可获得更多的立体解剖信息,加深对病变局部解剖的认识,指导制定手术计划,减少术中动脉瘤破裂的风险,提高手术效果。     

双源 Flash 后处理软件在支气管动脉评价中的应用

目的：探讨双源 Flash 后处理软件(Bone Reading)应用于支气管动脉(BA)CTA 后处理重建中的可行性及时间效率分析。方法由2位放射科医生对70例临床拟诊断为支气管动脉扩张患者的 CTA 影像资料进行评价。首先,利用多平面重组(MPR)、最大密度投影(MIP)及容积再现(VR)技术对支气管动脉的起源、数目、分支类型、走行分布及管腔直径进行评价及测量,记录相关数据及诊断时间;30 d 后再使用后处理软件(Bone Reading)对上述患者的影像资料重新进行评价。结果2位阅片者的诊断一致性无统计学差异,且有良好的相关性;后处理软件(Bone Reading)的使用在诊断时间上有统计学差异,平均减少诊断时间35%。结论后处理软件(Bone Reading)应用于 BA CTA 后处理重建是可行的,可以缩短后处理及诊断所需的时间。