Purpose

Radiochromic film (RCF) is a detector that can obtain a two-dimensional dose distribution with high resolution; it is widely used in medical and industrial fields. Several types of RCFs exist based on their application. The type of RCF mainly used for mammography dose assessment has been discontinued; however, a new type of RCF (LD-V1) has been distributed as a successor. Since the medical use of LD-V1 has rarely been studied, we investigated the response characteristics of LD-V1 in mammography.

Methods

Measurements were performed using Mo/Mo and Rh/Ag on a Senographe Pristina mammography device (GE, Fairfield, CT, USA). The reference air kerma was measured using a parallel-plate ionization chamber (PPIC) (C-MA, Applied Engineering Inc, Tokyo, Japan). Pieces of LD-V1 film model were irradiated at the same position where the reference air kerma in air was measured by the PPIC. Irradiation was performed using the time scale method based on the load on the equipment. Two methods of irradiation were considered: placing the detector in air and on the phantom. The LD-V1 was scanned five times at 72 dpi in RGB (48 bit) mode using a flatbed scanner (ES-G11000, Seiko Epson Corp, Nagano, Japan) 24 h following irradiation. The response ratio of the reference air kerma and the air kerma obtained from the LD-V1 were compared and examined for each beam quality and air kerma range.

Results and discussion

When the beam quality was altered, the response ratio varied from 0.8 to 1.2 with respect to the measurement value of the PPIC; however, some outliers were observed. Response ratios were highly variable in the low-dose range; however, as the air kerma increased, the ratios approached 1. Thus, LD-V1 does not need calibration for each beam quality used in mammography. LD-V1 enables air kerma evaluation by creating air kerma response curves under certain X-ray conditions used in mammography.

Conclusion

We suggest that the dose range be limited to 12 mGy or more to keep the response variation with beam qualities below ±20%. If further measurement is required for reducing the response variation, the dose range should be shifted to a higher dose range.

中文翻译：

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使用乳腺放射线束质量表征新型放射变色薄膜 (LD-V1)

目的

放射致色膜（RCF）是一种可以获得高分辨率二维剂量分布的探测器；它广泛应用于医疗和工业领域。根据其应用，存在多种类型的 RCF。主要用于乳腺X线摄影剂量评估的RCF类型已停产；然而，一种新型 RCF (LD-V1) 已作为后续产品发布。由于 LD-V1 的医学用途很少被研究，我们研究了 LD-V1 在乳房 X 线摄影中的响应特征。

方法

使用 Mo/Mo 和 Rh/Ag 在 Senographe Pristina 乳房 X 线摄影设备（GE，Fairfield，CT，USA）上进行测量。使用平行板电离室 (PPIC)（C-MA，Applied Engineering Inc，东京，日本）测量参考空气比释动能。LD-V1 薄膜模型的碎片在 PPIC 测量空气中参考空气比释动能的同一位置受到照射。照射是根据设备的负荷使用时间尺度法进行的。考虑了两种照射方法：将探测器放置在空气中和放置在模型上。照射后 24 小时，使用平板扫描仪（ES-G11000，精工爱普生公司，长野，日本）以 RGB（48 位）模式以 72 dpi 对 LD-V1 进行五次扫描。

结果与讨论

当光束质量改变时，相对于PPIC测量值的响应比从0.8变化到1.2；然而，观察到了一些异常情况。在低剂量范围内，反应率变化很大；然而，随着空气比释动能的增加，该比率接近 1。因此，LD-V1 不需要对乳腺 X 线摄影中使用的每种光束质量进行校准。LD-V1 通过在乳房 X 线摄影中使用的某些 X 射线条件下创建空气比释动响应曲线来实现空气比释动评估。

结论

我们建议将剂量范围限制在 12 mGy 或更高，以将光束质量的响应变化保持在 ±20% 以下。如果需要进一步测量以减少响应变化，则应将剂量范围转移到更高的剂量范围。