Lucerno Dynamics, LLC, 140 Towerview Ct, Cary, NC, 27513, USA.
Med Phys. 2019 Jun;46(6):2690-2695. doi: 10.1002/mp.13536. Epub 2019 Apr 29.
Each year in the United States, approximately 18.5 million nuclear medicine procedures are performed. Various quality control measures are implemented to reduce image errors and improve quantification of radiotracer distribution. However, there is currently no routine or timely feedback about the quality of the radiotracer injection. One potential solution to evaluate the injection quality is to place a topical scintillation sensor near the injection site to record the presence of residual activity. This work investigates a sensor design for identification of injections where the prescribed radioactive activity is not fully delivered into the patient's circulation (an infiltration).
The sensor consists of a single unshielded bismuth germanate (BGO) crystal (3 mm × 3 mm × 3 mm). Using radioactive sources with gamma energies that span the range commonly used in nuclear medicine, we quantified energy resolution and linearity. Additionally, we computed sensitivity by comparing the calculated incident activity to the activity measured by the sensor. Sensor output linearity was calculated by comparing measured data against the radioactive decay of a source over multiple half-lives. The sensor incorporates internal temperature feedback used to compensate for ambient temperature fluctuations. We investigated the performance of this compensation over the range of 15°C-35°C.
Energy spectra from four sensors were used to calculate the energy resolution: 67% for Tc (141 keV), 67% for Ba (344 keV), 42% for F (511 keV), and 32% for Cs (662 keV). Note that the energy used for Ba is a weighted average of the three photon emissions nearest to the most abundant (356 keV). Sensor energy response was linear with a difference of 1%-2% between measured and predicted values. Energy-dependent detector sensitivity, defined as the ratio of measured photons to incident photons for a given isotope, decreased with increasing photon energy from 55.4% for Tc (141 keV) to 3.3% for Cs (662 keV). Without compensation, error due to temperature change was as high as 53%. Temperature compensation reduced the error to less than 1.4%. Sensor output linearity was tested to as high as 210 kcps and the maximum magnitude error was 4%.
The performance of the sensor was adequate for identification of excessive residual activity at an injection site. Its ability to provide feedback may be useful as a quality control measure for nuclear medicine injections.
在美国，每年大约进行 1850 万次核医学程序。 实施了各种质量控制措施，以减少图像误差并提高示踪剂分布的定量。 但是，目前没有关于示踪剂注射质量的常规或及时反馈。 评估注射质量的一种潜在方法是在注射部位附近放置局部闪烁传感器以记录残留活性的存在。 这项工作研究了一种传感器设计，用于识别未将规定的放射性活度完全输送到患者循环中的注射部位（渗透）。
传感器由单个无屏蔽的锗酸铋（BGO）晶体（3mm×3mm×3mm）组成。 使用伽马能量范围涵盖核医学常用范围的放射性源，我们量化了能量分辨率和线性度。 此外，我们通过将计算出的入射活度与传感器测量的活度进行比较来计算灵敏度。 通过比较多个半衰期内源的放射性衰减，计算出传感器输出的线性度。 传感器采用内部温度反馈来补偿环境温度波动。 我们研究了在 15°C-35°C 范围内的这种补偿性能。
从四个传感器的能谱中计算出能量分辨率： Tc（141keV）为 67％， Ba（344keV）为 67％， F（511keV）为 42％， Cs（662keV）为 32％。 请注意， Ba 所用的能量是最丰富的（356keV）三个光子发射中最接近的三个光子发射的加权平均值。 传感器的能量响应呈线性，实测值与预测值之间的差值为 1％-2％。 与给定同位素的入射光子相比，定义为测量光子与入射光子之比的能量依赖性探测器灵敏度随光子能量的增加而降低， Tc（141keV）为 55.4％， Cs（662keV）为 3.3％。 没有补偿时， 由于温度变化引起的误差高达 53％。 温度补偿将误差降低到小于 1.4％。 传感器的输出线性度测试高达 210kcps， 最大幅度误差为 4％。
传感器的性能足以识别注射部位的过量残留活性。 它提供反馈的能力可能是核医学注射质量控制措施的有用工具。
