Pawar Shreeniket, Arepally Nageshwar, Carlton Hayden, Vanname Joshua, Ivkov Robert, Attaluri Anilchandra
Department of Mechanical Engineering, School of Science, Engineering, and Technology, The Pennsylvania State University Harrisburg, Harrisburg, PA, United States.
Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, United States.
Front Therm Eng. 2025;5. doi: 10.3389/fther.2025.1520951. Epub 2025 Feb 16.
Magnetic particle imaging (MPI) is a nascent tracer imaging modality that generates images from magnetic iron oxide nanoparticles (MIONs) in tissue. MPI resolution is a critical input parameter for defining the reliability of simulations-based temperature predictions for magnetic nanoparticle hyperthermia (MNPH). The objective of this study was to ascertain how spatial resolution provided by MPI data affects the reliability of predicted temperatures and thermal dose in simulations using MPI data as inputs.
Computed tomography (CT) and MPI scans obtained from a tumor injected with MIONs were co-registered to align their coordinates. Co-registered data were used to obtain geometry and volumetric heat sources for computational simulations of MNPH in phantom tumors. In addition to using the MPI-derived MION distribution (D1) we analyzed two mathematical MION distributions: uniform (D2) and Gaussian (D3). All distributions were discretized into cubic voxels and the data were imported into a commercial finite element bioheat transfer (FEBHT) software for thermal simulations. FEBHT simulations were conducted using the Pennes' bioheat equation using four different MION specific loss power (SLP) values in the range 300-600 [W/g Fe]. The impact on predicted temperature resolution and thermal dose of spatial resolution were assessed by varying the linear voxel density (LVD) from 0.36 to 4.06 [voxel/mm]. Results were compared against the simulation with the highest LVD [4.06(voxel/mm)], where deviations in temperature of ≤ ±1 [°C] and thermal dose coverage ≤ ±5 [%] were deemed acceptable.
The D3 distribution resulted in the highest predicted temperatures, followed by D1 and D2; however, in terms of thermal dose, D1 showed lowest tumor coverage, requiring higher heat output from MIONs than was required for the other distributions studied. The results of the sensitivity analysis revealed that the predicted tumor temperature increased with LVD across all tested SLP values. Additionally, we observed that the minimum acceptable LVD increased with SLP.
Current (preclinical small animal) MPI scanners provide sufficient spatial resolution to predict temperature to within ±1 [°C], and thermal dose coverage to within ±5 [%] for MION formulations having heat output SLP = <370 [W/g Fe]. Higher spatial resolution is needed to achieve a similar precision when MION SLP exceeds 370 [W/g Fe]. We also conclude from the results that assuming a uniform MION distribution in tissue, which has been a common practice in MNPH simulations, overestimates the SLP needed to deposit meaningful thermal dose.
磁粒子成像（MPI）是一种新兴的示踪剂成像模态，可从组织中的磁性氧化铁纳米颗粒（MION）生成图像。MPI分辨率是定义基于模拟的磁纳米颗粒热疗（MNPH）温度预测可靠性的关键输入参数。本研究的目的是确定MPI数据提供的空间分辨率如何影响以MPI数据为输入的模拟中预测温度和热剂量的可靠性。
从注射了MION的肿瘤获得的计算机断层扫描（CT）和MPI扫描进行配准以对齐其坐标。配准后的数据用于获取几何形状和体积热源，以对体模肿瘤中的MNPH进行计算模拟。除了使用MPI衍生的MION分布（D1）外，我们还分析了两种数学上的MION分布：均匀分布（D2）和高斯分布（D3）。所有分布都离散化为立方体素，并将数据导入商业有限元生物热传递（FEBHT）软件进行热模拟。使用Pennes生物热方程进行FEBHT模拟，使用300 - 600 [W/g Fe]范围内的四个不同的MION比吸收率（SLP）值。通过将线性体素密度（LVD）从0.36改变到4.06 [体素/mm]来评估对预测温度分辨率和空间分辨率热剂量的影响。将结果与具有最高LVD [4.06（体素/mm）]的模拟进行比较，其中温度偏差≤±1 [°C]和热剂量覆盖≤±5 [%]被认为是可接受的。
D3分布导致预测温度最高，其次是D1和D2；然而，就热剂量而言，D1显示出最低的肿瘤覆盖范围，与其他研究的分布相比，需要MION产生更高的热输出。敏感性分析结果表明，在所有测试的SLP值下，预测的肿瘤温度随LVD增加而升高。此外，我们观察到最小可接受LVD随SLP增加而增加。
对于热输出SLP = <370 [W/g Fe]的MION制剂，当前（临床前小动物）MPI扫描仪提供了足够的空间分辨率来将温度预测在±1 [°C]以内，热剂量覆盖在±5 [%]以内。当MION SLP超过370 [W/g Fe]时，需要更高的空间分辨率才能达到类似的精度。我们还从结果中得出结论，在组织中假设MION分布均匀（这在MNPH模拟中是常见做法）会高估沉积有意义热剂量所需的SLP。
