Avci Recep, Paskaranandavadivel Niranchan, Eichler Chad E, Lam Byron Y C, Angeli Timothy R, Bradshaw Leonard A, Cheng Leo K
Annu Int Conf IEEE Eng Med Biol Soc. 2020 Jul;2020:2376. doi: 10.1109/EMBC44109.2020.9176431.
In this study, we investigated the feasibility of computationally reconstructing the 3D geometry of the stomach by performing source localization of the magnetic field (MF) induced from the stomach surface. Anatomically realistic stomach and torso models of a human participant, reconstructed from the CT images, were used in the computations. First, 128 coils with a radius of 5 mm were positioned on different locations on the stomach model. Next, MF at the sensor positions were computed using Bio-Savart law for the currents of 10 and 100 mA. Then, three noise levels were defined using the biomagnetic data recorded from the same participant and two additional sets of generated white-noise resulting in mean signal to noise ratios (SNR) of 20 and 10 dB. Finally, for each combination of the current and noise level, the magnetic dipole (MDP) approximation was performed to estimate coil positions. The performance of the source localization was assessed by computing the goodness of fit (GOF) values and the distance between the coil and the estimated MDP positions. We obtained GOF values over 98% for all coils and a mean localization error of 0.69±0.08 mm was achieved when 100 mA current was used to induce MF and only biomagnetic data was added. When additional white-noise was added, the GOF values decreased to 95% and the mean localization error increased to around 4 mm. A current of 10 mA was enough to localize the coil positions with a mean error around 8 mm even for the highest noise level we tested but for the few coils furthest from the body surface, the error was around 10 cm. The results indicate that source localization using the MDP approximation can successfully extract spatial information of the stomach.Clinical relevance-Extracting the spatial information of the stomach during the recording of the slow wave activity provides new insights in assessing gastric recordings and relating to disorders.
在本研究中，我们通过对胃表面感应的磁场（MF）进行源定位，研究了通过计算重建胃的三维几何形状的可行性。计算中使用了从CT图像重建的人体参与者的解剖学逼真的胃和躯干模型。首先，将128个半径为5毫米的线圈放置在胃模型的不同位置。接下来，使用毕奥 - 萨伐尔定律计算传感器位置处10和100 mA电流的MF。然后，使用从同一参与者记录的生物磁数据和另外两组生成的白噪声定义了三个噪声水平，导致平均信噪比（SNR）为20和10 dB。最后，对于电流和噪声水平的每种组合，进行磁偶极子（MDP）近似以估计线圈位置。通过计算拟合优度（GOF）值以及线圈与估计的MDP位置之间的距离来评估源定位的性能。当使用100 mA电流感应MF且仅添加生物磁数据时，我们获得了所有线圈超过98％的GOF值，平均定位误差为0.69±0.08毫米。当添加额外的白噪声时，GOF值降至95％，平均定位误差增加到约4毫米。即使对于我们测试的最高噪声水平，10 mA的电流也足以将线圈位置定位在平均误差约8毫米的范围内，但对于离体表最远的少数线圈，误差约为10厘米。结果表明，使用MDP近似的源定位可以成功提取胃的空间信息。临床相关性 - 在慢波活动记录期间提取胃的空间信息为评估胃记录和与疾病的关系提供了新的见解。
