【APT 白皮书】Philips 3D APT (7)

How does the dedicated APT-weighted image color scale simplify interpretation?

APT 加权专用彩图是如何简化图像的解读的？

APTw images are shown in a rainbow-type color scale ranging from green (0% APTw%) to red (5% APTw%). This scale is standardized across all APTw images to facilitate fast and easy reading, as well as to enable comparison among hospitals or between pre- and post-treatment images. The advanced reconstruction algorithm combines all information and generates the final color-coded APTw image volumes, using APTw% and a standardized scale of ±5% for display. As additional anatomical reference, image reconstruction also provides an S0 image volume.

APT 加权图像使用彩虹色条进行显示，从绿（0% APTw%）到红（5% APTw%）。所有 APT 加权图的这一尺度都是标准化的，从而使得图像解读更加快捷简便；而且，不同医院做的图像或治疗前后的图像都可以进行比较。高级的重建算法联合所有信息生成最终的彩色 APT 加权图像，并使用 APTw% 与 ±5%标准化范围进行显示。为了提供额外的解剖参照，还重建了 S0 图。

For tumor grading, normal white and grey matter typically appears green, while areas of APTw hyper intensities, appearing yellow or red, may indicate solid tissue areas of grade III and IV gliomas. For treatment follow-up, normal white and grey matter and treatment necrosis typically appear green, while areas of APTw hyper intensities, appearing yellow or red may indicate tumor recurrence in solid tissue areas. Adhering to routine radiology procedures, all acquired image contrasts are viewed in concert, aiding identification of potential solid tumor areas via anatomical T1w, T2w and/or fluid-enhanced FLAIR images that can be scored for APTw hyper-intensity (yellow/red) to assist tumor grading.

对于肿瘤分级，正常的脑白质与脑灰质通常呈现绿色，而 APT 加权高的区域呈现黄色或红色，可能提示三四级胶质瘤的实性组织区域。对于治疗后随访，正常脑白质和脑灰质，还有治疗后坏死通常呈现绿色，而 APT 加权高的区域表现为黄色或红色，可能提示在实性组织区域有肿瘤的复发。除了 APTw，常规的影像检查还是要坚持做，获得的不同对比的图像都要进行观察，这样能够通过 T1w，T2w 和/或 FLAIR 解剖像帮助鉴别肿瘤可能的实性组织，帮助对 APTw 高信号（黄/红）进行评分从而进行肿瘤的分级。

In the literature on APTw MRI, it is common to show brain images in which the skull and the fat around the skull have been removed. Skull stripping is not performed for APTw imaging on the system, because such algorithms are often not reliable and could potentially conceal tumor tissue for example near the cortex. Thus, a colored rim related to fatty tissue in the skull may be visible around the brain, which is visually distinct from the relevant brain areas and is easily disregarded during the radiological reading process.

在磁共振成像 APTw 相关文献中，在显示 APTw 图像时通常将颅骨与颅骨周围的脂肪给去除。在 MR 系统上并不会去除颅骨，因为这样的算法通常不是十分可靠，并且可能会把肿瘤组织给去掉，比如靠近皮层的肿瘤。因此，在颅脑周围可能会看到一圈彩带，它是颅骨中的脂肪组织，它与相对的颅脑组织看起来不同，那么在阅读图像时可以不用理会。

For ROI-based measurements on APTw images it is important to note that the contrast should be assessed using the difference between normal appearing brain (white or grey matter, preferably contra-lateral to the lesion) and tumor tissue values, which is called ∆MTRasym. The APTw technique may show a small overall offset - less than 0.5% APTw% - if comparing absolute APTw% values, therefore it is important to follow the procedures described in the literature for ROI definitions in grading applications. Furthermore the highest tumor grade found in sub-regions of the lesion is the determinant for the overall grade. Thus, in the literature, several small regions of interest (ROI) were defined on APTw images guided by the highest levels of APTw contrast observed in solid parts of the lesion. Alternatively, a histogram can be calculated within a large ROI including the tumor region and the highest grade shown by APTw contrast is assessed via the 90-percentile of the signal distribution.

还可以在 APTw 图上画 ROI 进行测量，但一定要注意，需要评估正常表现的脑组织（最好取病灶对侧的脑白质或灰质）与肿瘤组织之间对比的差值，这称之为 ∆MTRasym。如果比较 APTw% 的绝对值，APT 加权技术能显示很小的偏差，小于 0.5% 的 APTw% 值。因此，在肿瘤分级时遵循文献中所给的定义 ROI 的方法很重要。此外，病变整体的级别由病变亚区域所发现最高的级别来决定。因此文献中，在病变实体部分所画的 ROI 中最高 APTw 对比决定了最终的等级。或者，可以画一个包括肿瘤部分的大的 ROI，然后计算直方图，取 90-百分位的值作为最高的 APTw 值。

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【译者注】

什么是 90-percentile? 请看下面例子：from perfmatrix.com

‘Percentile’ – a common but most important term, especially in performance testing. From the day first when we started analysing any performance testing report, we heard about 90th percentile. Even our mentor gave more stress on 90th percentile figures for response time. So, what is this 90th percentile exactly?

Let’s try to understand with an example. If you had 10 sheep and each sheep eat some KGs of grass on a daily basis. One day you weighted the grass and noted the figures of each sheep’s intake. Refer to the below table:

Now, you need to find out what amount of grass has been consumed by 90% of sheep? So simply you need to sort the number with respect to consumed grass and ignore the last value.

90^th percentile value in 10 entries is a 9^th value which is 4, so just ignore S4 with 4.8 (keep it hungry for some days, it eats so much).

The conclusion is 90% of total sheep either eat 4 KGs grass or below, so you got an upper limit of grass consumption. In terms of performance testing, you need to sort response time of a particular transaction or request in increasing order and then ignore 10% of the total count having high values. The last highest number in the remaining values will be 90^th percentile.

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Besides gliomas, other lesion types - in particular meningiomas, lymphomas, and metastases - may be depicted as APTw hyper-intensity, however to date there is insufficient evidence to understand the implications of high APTw signals in these pathologies. Furthermore, fatty tissues or tissue fluids, for example cysts, blood vessels or hemorrhage, may show up as APTw hyper-intensity due to their high protein content. It is therefore of utmost importance to read the APTw images carefully and always in combination with images from a standard multi-parametric tumor protocol.

除了胶质瘤，其他类型的病变——尤其是脑膜瘤、淋巴瘤和转移瘤——在 APTw 图上也会表现为高信号，然而到目前为止没有充分的理论来解释这些病理组织表现为高 APTw 信号有什么含义。此外，脂肪或液体组织，比如囊肿、血液或出血，在 APTw 上也会表现为高信号，因为它们富含蛋白成分。因此，这也是在解读 APTw 图像时至关重要、最需要小心的地方，一定要结合其他多参数的解剖像一起观察。