Least squares parameter estimation methods for material decomposition with energy discriminating detectors
Least squares parameter estimation methods for material decomposition with energy discriminating detectors
复制标题
DOI：
10.1118/1.3525840
复制
发表时间：
2011-01-01
期刊：
影响因子：
3.8
通讯作者：
Molloi, Sabee
中科院分区：
文献类型：
--
作者：
Le, Huy Q.;Molloi, Sabee
目的：能量分辨探测器在一次图像采集中提供多个光谱测量。本研究的目的是调查，模拟，分解四种材料，使用能量鉴别探测器和最小二乘minimization techniques.Methods：三个最小二乘参数估计分解技术进行了研究，在图像域的四种材料的乳房成像任务的能力。第一种技术将体素视为由所有材料的分数组成。第二种方法假设体素主要包含一种材料，并将分解过程分为分割和量化任务。第三种方法类似于第二种方法，但使用了校准。模拟计算机断层扫描（CT）系统由80 kVp光谱和CdZnTe（CZT）探测器组成，该探测器可以将X射线光谱分解为五个能量仓。用平板CT对死后乳房标本进行成像，以提供用于数字模型的模型。将羟基磷灰石（HA）（50、150、250、350、450和550 mg/ml）和碘（4、12、20、28、36和44 mg/ml）造影剂嵌入体模的腺体区域。校准模型由30/70腺体/脂肪组织比例组成，包埋HA（100、200、300、400和500 mg/ml）和碘（5、15、25、35和45 mg/ml）。模拟了X射线传输过程，其中应用了Beer-Lambert定律、泊松过程和CZT吸收效率。对分解技术进行了定性和定量评价并进行了比较。乳房大小的影响也investigated.Results：第一种技术分解碘充分，但其他材料失败。第二种方法分离了材料，但无法对材料进行定量。通过添加校准，第三种技术提供了羟基磷灰石、碘、腺体和脂肪组织的良好分离和定量。该技术定量准确，HA和碘的误差分别为9.83%和6.61%。随着校准和测量之间乳房直径的不匹配增加，一个点（一个乳房尺寸）的校准显示误差增加。四点校准成功地分解了跨越整个范围从8到20厘米的乳房直径。对于一个14厘米的乳房，误差分别从5.44%减少到1.75%和6.17%到3.27%与HA和碘的多点校准，foreign.Conclusions：模拟研究的结果表明，基于CZT探测器结合最小二乘最小化技术的CT系统可以用来分解四种材料。校准的最小二乘参数估计分解技术表现最好，分离和准确定量羟基磷灰石和碘的浓度。c 2011年美国医学物理学家协会。[DOI：10.1118/1.3525840]
Purpose: Energy resolving detectors provide more than one spectral measurement in one image acquisition. The purpose of this study is to investigate, with simulation, the ability to decompose four materials using energy discriminating detectors and least squares minimization techniques.Methods: Three least squares parameter estimation decomposition techniques were investigated for four-material breast imaging tasks in the image domain. The first technique treats the voxel as if it consisted of fractions of all the materials. The second method assumes that a voxel primarily contains one material and divides the decomposition process into segmentation and quantification tasks. The third is similar to the second method but a calibration was used. The simulated computed tomography (CT) system consisted of an 80 kVp spectrum and a CdZnTe (CZT) detector that could resolve the x-ray spectrum into five energy bins. A postmortem breast specimen was imaged with flat panel CT to provide a model for the digital phantoms. Hydroxyapatite (HA) (50, 150, 250, 350, 450, and 550 mg/ml) and iodine (4, 12, 20, 28, 36, and 44 mg/ml contrast elements were embedded into the glandular region of the phantoms. Calibration phantoms consisted of a 30/70 glandular-to-adipose tissue ratio with embedded HA (100, 200, 300, 400, and 500 mg/ml) and iodine (5, 15, 25, 35, and 45 mg/ml). The x-ray transport process was simulated where the Beer-Lambert law, Poisson process, and CZT absorption efficiency were applied. Qualitative and quantitative evaluations of the decomposition techniques were performed and compared. The effect of breast size was also investigated.Results: The first technique decomposed iodine adequately but failed for other materials. The second method separated the materials but was unable to quantify the materials. With the addition of a calibration, the third technique provided good separation and quantification of hydroxyapatite, iodine, glandular, and adipose tissues. Quantification with this technique was accurate with errors of 9.83% and 6.61% for HA and iodine, respectively. Calibration at one point (one breast size) showed increased errors as the mismatch in breast diameters between calibration and measurement increased. A four-point calibration successfully decomposed breast diameter spanning the entire range from 8 to 20 cm. For a 14 cm breast, errors were reduced from 5.44% to 1.75% and from 6.17% to 3.27% with the multipoint calibration for HA and iodine, respectively.Conclusions: The results of the simulation study showed that a CT system based on CZT detectors in conjunction with least squares minimization technique can be used to decompose four materials. The calibrated least squares parameter estimation decomposition technique performed the best, separating and accurately quantifying the concentrations of hydroxyapatite and iodine. c 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3525840]