辐照灭菌的剂量分布图怎么做

结论：分布图回答两个问题——最少的地方够不够，最多的地方产品受不受得了

辐照灭菌时，产品在装载中的不同位置接受的剂量是不同的。分布图的作用就是把这个差异测出来，找到剂量下限点和剂量上限点。

两个点对应两个问题：

剂量下限点。 这里的剂量必须达到灭菌所需的水平，否则灭菌不充分。

剂量上限点。 这里的剂量不能超出材料能承受的水平，否则产品性能受损。

灭菌所需剂量与材料耐受剂量之间的区间，就是可用的工艺窗口。 窗口太窄，工艺就难以稳定控制；窗口为负（材料耐受剂量低于灭菌所需剂量），这个灭菌方式就不适用。

分布图的作用

确定剂量范围。 装载中的剂量下限和上限。

确定监控点位置。 日常生产中在哪里放剂量计。

确定装载方式。 什么样的装载能得到可接受的分布。

支持工艺参数设定。 照射时间或传送速度。

支持材料耐受论证。 上限剂量是材料验证的依据。

「监控点位置」是分布图的实际产出之一。 日常生产不可能每次都做完整的分布测定，而是在几个固定位置放剂量计。这些位置的选择依据就是分布图——通常选剂量下限点和剂量上限点，或者与它们有稳定对应关系的位置。

测定的方法

剂量计的选择。 选择适合剂量范围和精度要求的剂量计。

布点。 在装载的各个位置布置剂量计，覆盖可能的下限点和上限点。布点密度要足够，疏了可能漏掉极值点。

装载配置。 按实际生产的装载方式和密度。

重复测定。 多次测定确认结果的重现性。

数据处理。 计算各点剂量、找出极值点、计算不均匀度。

不均匀度的表达。 上限剂量与下限剂量的比值，是分布均匀程度的指标。

「布点密度」是常见的不足之处。 布点太少，真正的极值点可能没被测到，得出的分布图偏乐观。建议先做较密的布点找出规律，之后的验证可以适当简化。

影响分布的因素

「产品密度」是主要因素。 密度大的产品衰减强，内部剂量明显低于表面。所以同样的装载方式，换一个密度不同的产品，分布可能完全不同，需要重新测定。

材料耐受方面的配合

分布图给出上限剂量之后，材料验证要按这个剂量做：

按上限剂量处理样品。 而不是按名义剂量。

考虑重复辐照。 如果允许重复辐照（比如剂量不足需要补照），累积剂量要纳入验证。

检测项目。 力学性能、外观、功能、化学表征。

储存后复测。 前面反复提过——辐照引发的降解可能持续发展。

包装材料一并验证。 包装也会受辐照影响。

「按上限剂量验证」这一条很重要。 按名义剂量验证，而实际生产中某些位置的产品接受了上限剂量，这部分产品的性能就没有被验证过。

剂量设定的思路

灭菌所需剂量的确定。 基于产品的初始污染菌水平和所需的无菌保证水平。

初始污染菌的监测。 需要定期监测，因为它随原材料、环境、工艺变化。

剂量的验证。 用适当的方法验证所设定的剂量确实能达到要求。

工艺窗口的确认。 设定剂量与材料耐受剂量之间要有足够余量。

「初始污染菌水平」是剂量设定的输入。 如果生产环境或原材料变化导致污染菌水平上升，原定的剂量可能不再足够。所以定期监测是必要的，不是可选的。

再确认的时机

产品密度或结构改变；包装改变；装载方式改变；辐照设备或参数改变；初始污染菌水平显著变化；以及定期的再确认。

「产品密度改变」容易被忽略。 产品改了材料、增加了部件、或者包装内增加了缓冲物，密度就变了，剂量分布随之改变。

常规监控与放行

分布图完成之后，日常生产的监控：

每批次放置剂量计。 在确定的监控位置。

剂量计的读取与记录。 每批次的实测剂量。

放行判据。 实测剂量在确认的范围内。

装载核对。 与确认时的装载方式一致。

定期的完整验证。 按规定频次重做分布测定。

「装载核对」容易流于形式。 分布图是基于特定装载做的，实际生产中如果装载方式变了（产品数量、摆放、包装），剂量分布就可能不同。建议用图示规定装载方式并在生产中执行。

包装材料的考虑

辐照对包装材料同样有影响，需要一并验证：

材料强度。 辐照后包装材料是否脆化。

密封强度。 密封处在辐照后是否仍然可靠。

阻隔性能。 阻菌性能是否保持。

外观。 变色影响可读性和客户感受。

释放物质。 包装材料辐照后可能产生新的释放物。

最后一项与产品的化学表征相关。 做表征时样品应当带包装一起经过辐照，这样才能覆盖包装带来的贡献。

剂量计的管理

剂量计本身是测量器具，它的管理影响数据的可靠性：

校准与溯源。 剂量计的响应要能溯源。

储存条件。 温度、湿度、光照都可能影响剂量计。

有效期。 过期的剂量计读数不可靠。

读取时机。 某些剂量计的读数随时间变化，读取时机要规定。

批次差异。 不同批次的剂量计响应可能有差别。

这几项如果失控，测出的分布图就不可信，而分布图是后续所有工作的基础。

我们的做法

做辐照相关的材料验证时，我们会按委托方提供的上限剂量处理样品，并建议同时做储存后的复测。 辐照产生的自由基可能导致持续的降解，只看处理后立即的性能会偏乐观。

检测项目上，我们建议力学性能与化学表征同时做——力学性能反映材料是否降解，化学表征反映是否产生了新的释放物质。 两者角度不同，都有价值。

如果你在做辐照灭菌的材料耐受评估，可以把材料信息和剂量范围发过来一起讨论，或者直接联系：132 4819 8029。能力范围见服务介绍，送检要求见送检要求，其他问题见常见问题。

English version

Conclusion. During irradiation, different positions within a load receive different doses. A dose map measures that variation and locates the minimum and maximum dose positions. Each corresponds to a question. At the minimum dose position, the dose must reach the level required for sterilisation, or sterilisation is inadequate. At the maximum dose position, the dose must not exceed what the materials tolerate, or product performance is impaired. The interval between the dose required for sterilisation and the dose the materials tolerate is the available process window. Too narrow a window makes the process hard to control reliably; a negative window, where material tolerance falls below the sterilising dose, means the method is unsuitable.

Purposes of the dose map. Establishing the dose range, meaning the minimum and maximum within the load. Establishing monitoring positions for routine production. Establishing the loading arrangement that produces an acceptable distribution. Supporting process parameter settings such as exposure time or conveyor speed. And supporting material tolerance justification, since the maximum dose is the basis for material verification. Monitoring positions are one of the practical outputs: routine production cannot repeat a full mapping every time and instead places dosimeters at a few fixed positions, chosen on the basis of the map, usually the minimum and maximum positions or positions bearing a stable relationship to them.

Method. Select dosimeters suited to the dose range and accuracy required. Place them throughout the load, covering the likely minimum and maximum positions, at sufficient density, since sparse placement can miss the extremes. Configure the load as in actual production, in arrangement and density. Repeat the measurement to confirm reproducibility. Process the data to calculate doses, identify the extremes and compute the uniformity ratio. And express uniformity as the ratio of maximum to minimum dose. Placement density is a common shortcoming: too few points may miss the true extremes and produce an optimistic map. Start with dense placement to establish the pattern, after which later verification can be simplified.

Factors affecting distribution. Product density matters most, since dense product attenuates strongly and interior doses fall well below surface doses. Load dimensions matter, since larger loads receive lower doses at the centre. Loading density affects penetration. Product orientation produces different doses. Packaging materials affect distribution through their density and thickness. The source and mode of irradiation have different penetration characteristics. And the conveying arrangement affects the uniformity of accumulated dose. Density is the principal factor: with the same loading arrangement, a product of different density can produce an entirely different distribution and requires remapping.

Material tolerance. Once the map gives the maximum dose, material verification must be performed at that dose rather than at the nominal one. Consider repeat irradiation, where a second pass is permitted for under-dosed loads, and include the cumulative dose in verification. Test mechanical performance, appearance, function and chemical characterisation. Re-measure after storage, as noted repeatedly, since radiation-induced degradation may continue. And verify packaging materials too, since they are also affected. Verifying at the maximum dose matters: verify at nominal and the product that actually received the maximum in production has never been verified.

Setting the dose. The sterilising dose is determined from the product's bioburden and the sterility assurance level required. Bioburden must be monitored periodically, since it varies with raw materials, environment and process. The dose must be substantiated by an appropriate method showing that the set dose achieves the requirement. And the process window must be confirmed, with adequate margin between the set dose and material tolerance. Bioburden is an input to dose setting: if the production environment or raw materials change and bioburden rises, the established dose may no longer suffice. Periodic monitoring is therefore necessary rather than optional.

When to revalidate. After changes to product density or construction. After packaging changes. After loading changes. After changes to equipment or parameters. After significant change in bioburden. And at the scheduled interval. Density changes are easily overlooked: changing materials, adding components or adding packing material within the pack all change density, and the dose distribution changes with it.

How we handle it. For irradiation material verification we process samples at the maximum dose the client provides and suggest re-measuring after storage as well. Free radicals generated by irradiation can drive continuing degradation, so performance measured immediately after processing reads optimistically. On test items we suggest mechanical performance and chemical characterisation together: mechanical testing shows whether the material has degraded and characterisation shows whether new released substances have appeared. The two look from different angles and both have value.

Send us the material information and dose range and we will work through the verification. Phone or WeChat: +86 132 4819 8029.