CT图像中金属伪影的快速校正

CT系统由于检测对象含有金属夹杂而使得重建图像中出现金属伪影,影响图像的质量。针对金属伪影,提出一种快速而稳定的校正方法。首先判断金属投影区域,然后对金属投影进行插值,然后重建图像。最后,在重建的图像中插入金属部分,得到完整的重建图像。数值模拟和实际CT系统的实验表明,该方法能有效的消除金属伪影,并能保留金属信息,恢复图像的完整。该算法计算复杂度很小,计算快速,具有较高的实用价值。     

PET/CT在甲状腺癌中的应用

目的:探讨正电子发射型计算机断层成像(PET/CT)在甲状腺癌原发灶、转移灶的诊断,复发检测中的应用价值。方法:回顾性分析应用PET/CT检查的40例甲状腺癌患者的临床资料,将其显像结果与病理,部分与Bus、CT比较。结果:PET/CT显像结果与病理结果符合率极高,对原发灶的诊断灵敏度100%,特异度87.5%,对转移灶的诊断灵敏度92.1%,特异度92.0%,优于CT和彩超。结论:PET/CT对甲状腺癌原发灶、转移灶的诊断,临床分期,甲状腺癌术后观测疗效、监测复发具有明显的优势。     

18F-FDG PET/CT对宫颈癌预后的相关研究

因为PET/CT在宫颈癌诊断、分期及指导治疗方面的巨大价值,许多学者开始探索PET/CT在宫颈癌预后方面的价值,尤其是最大标准摄取值(maximum standardized uptake value,SUVmax)在宫颈癌预后方面的作用,研究发现随着治疗前宫颈癌原发病灶或转移淋巴结SUVmax值的升高,患者生存率相应下降,复发率相应升高;并且通过比较宫颈癌原发病灶治疗前后18F-FDG(脱氧葡萄糖)异常浓聚缓解程度来判断预后,完全缓解的患者预后较好,缓解不完全或出现新的18F-FDG异常浓聚的患者预后较差.     

PET/CT在胰腺癌的应用进展

PET/CT将PET的功能显像与CT的解剖成像有机融合,它不仅能有效显示肿瘤的代谢、增生、乏氧和细胞凋亡状态,而且能精确显示肿瘤与其周围脏器组织的解剖结构。PET/CT在胰腺癌患者的诊疗指导、肿瘤分期、疗效监控和预后评价等方面,都具有重要的临床应用价值。     

PET/CT在腋窝肿物诊断中的应用价值的研究

 目的 研究PET／CT在腋窝肿物诊断中的应用价值。方法 对以腋窝肿物为主诉的患者行PET／CT、B超、双乳腺钼靶检查，通过术后常规病理进行验证，分析比较PET／CT的优劣势。结果 三者在诊断乳腺病变中PET／CT的特异性、准确性均高于B超及钼靶，P＞0.05；诊断淋巴结病变时PET／CT敏感性大于B超、钼靶，P＜0.05。结论 PET／CT在诊断以腋窝肿物为主诉的病例中显示出较常规检查更多的优势，尤其表现在寻找原发病灶和排除全身其他部位病变方面。     

PET/MR与PET/CT对18F-FDG PET阳性肝转移瘤病灶检出能力的比较

目的 比较一体化PET/MR和PET/CT对18F-FDG PET阳性肝转移瘤病灶的检出能力.方法 回顾性分析54例经病理及影像随访证实为肝转移瘤的患者.所有患者同一天先后行全身18F-FDG PET/CT显像及上腹部18F-FDG PET/MR局部显像.比较2种检查方法对PET阳性肝转移瘤患者及病灶的检出数量.并根据...     

PET/CT分子影像新技术在肿瘤中的应用

分子影像学的迅速发展使得对疾病的诊断由传统的解剖形态学阶段,向前推进到功能、代谢,甚至是受体和基因的分子水平阶段成为可能。18F-FDGPET/CT显像在肿瘤早期诊断、临床分期、鉴别肿瘤的复发与坏死、指导制定治疗方案、疗效评价以及肿瘤放疗的精确定位等方面均有重要的临床应用价值。     

PET/CT在甲状腺癌的临床应用进展

摘 要：甲状腺癌是最常见的内分泌肿瘤,虽死亡率不高,但发病率逐年上升。PET/CT在协助甲状腺癌诊断、分期、治疗后疗效评价及预后评估等方面具有重要临床应用价值。近年,18F-FDG及多种新型显像剂的出现,在各种病理分型的甲状腺癌治疗方案选择及患者预后评估中起到重要作用。     

PET/CT在乳腺癌临床治疗决策中的应用

PET是利用肿瘤组织与正常组织的生物学特点的差异而成像的功能显像方法.目前,临床上应用最广泛的放射性示踪剂是葡萄糖结构类似物2-18F-脱氧葡萄糖(18F-FDG),PET与CT的结合使肿瘤复杂的分子代谢变化与解剖结构的准确定位相结合,从而为肿瘤的准确诊断和明确分期提供了更精确的影像资料.     

PET/CT在肿瘤放射治疗中的作用

随着计算机技术和医学影像技术的飞速发展,先后出现了CT、MRI,尤其是近年来,出现了PET(正电子发射型计算机断层显像)以及PET/CT,并成功地应用于肿瘤的早期诊断、寻找转移性肿瘤的原发病灶,确定肿瘤的分期,选择最佳治疗方案、指导肿瘤治疗等等。由于放射肿瘤治疗学的不断进步,PE     

PET用于勾画生物靶区的呼吸运动体模研究

目的测量不同运动频率和不同运动幅度下,用PET影像勾画GTV的大小,探讨不同运动状态对PET影像中病灶体积的影响。方法使用自行研制的二维运动平台系统及体模,模拟不同频率及幅度的呼吸运动,在不同运动状态下对体模进行PET-CT扫描,利用PET图像勾画GTV并计算其大小。结果静止状态下GTV(GTV0)为(7.90±0.21)cm3,运动频率为16次/min、18次/min及20次/min状态下GTV分别为(11.56±2.62)cm3(GTV16)、(12.51±3.57)cm3(GTV18)及(11.86±3.27)cm3(GTV20)。GTV0、GTV16、GTV18及GTV20之间差异有统计学意义,P均<0.01。z轴方向运动幅度为1.0、1.5及2.0cm状态下GTV分别为(11.44±3.68)cm3(GTVz-1.0)、(11.64±3.47)cm3(GTVz-1.5)、(12.83±2.02)cm3(GTVz-2.0)。x轴方向运动幅度为0.5、1.0及1.5cm状态下GTV分别为(9.68±2.32)cm3(GTVx-0.5)、(14.41±3.19)cm3(GTVx-1.0)、(11.83±1.92)cm3(GTVx-1.5)。在z轴和x轴运动方向上,各GTV差异有统计学意义。结论不同呼吸频率和运动幅度对PET图像勾画靶区均会产生较大影响,在采用PET影像制定放疗计划时建议采取门控技术等有效措施尽量减少这种影响,使得到的生物靶区尽可能地接近靶区的实际情况。     

Dual energy CT attenuation correction methods for quantitative assessment of response to cancer therapy with PET/CT imaging

We hypothesize that improved quantification for PET imaging of high atomic number materials can be achieved by combining low-dose x-ray imaging with dual energy CT for PET attenuation correction. Improved quantification of tracer uptake will lead to improved patient outcomes by providing more accurate information for therapeutic choices. Accurate PET/CT measurements of early response will be critical in determining the best cancer therapy option for each patient in a timely manner and in sparing patients the morbidity and cost of ineffective treatments. We first evaluate the potential errors in PET images arising from CT-based attenuation correction when iodine-based contrast is incorrectly classified as bone when forming the linear attenuation coefficient image. We then investigate two methods of reducing errors in the linear attenuation image: an approximate, but fast, hybrid classification/scaling algorithm and a model-based dual-energy CT method that incorporates the polyenergetic spectrum and a noise model in an iterative reconstruction method. Both methods are shown to reduce errors in the estimated linear attenuation coefficient image, but require further study to determine the effects of noise propagation if low-dose CT scans are used for the estimation of the linear attenuation image.     

Retrospective attenuation correction of PET data for radiotherapy planning using a free breathing CT.

PURPOSE: To evaluate the image quality of retrospectively attenuation corrected Positron Emission Tomography (PET) scans used for gross tumor volume (GTV) delineation in lung cancer patients. MATERIALS AND METHODS: Data of 13 lymph node positive lung cancer patients were acquired on separate CT and PET scanners under free breathing conditions (for radiotherapy planning). First we determined a protocol for CT/PET registration. Second, we compared the image quality of attenuation-corrected PET images using positron transmission images and CT images, in terms of signal-to-noise ratio (SNR) and lesion-to-background ratio (contrast). RESULTS: The largest differences between manual and automatic CT/PET registration were found in the anterior-posterior direction with a mean of 1.8 mm (SD 1.0 mm). Differences in rotations were always smaller than 1.0 degrees . The attenuation-corrected images using CT showed a larger SNR (mean 30%, SD 17%) and larger contrast (mean 14.0%, SD 8.5%) compared to attenuation-corrected images using positron transmission. For lymph nodes, the mean contrast was 16% (SD 6.4%) larger. CONCLUSIONS: This study demonstrated that attenuation correction based on CT provides a better image quality for GTV delineation than when using positron transmission for attenuation correction. Retrospective attenuation correction of PET scans based on registered CT is a good alternative for a dedicated PET/CT scanner if a free-breathing CT is available, e.g., for radiotherapy planning, and allows the use of CT with diagnostic quality for attenuation correction.     

Deep inspiration breath hold and respiratory gating strategies for reducing organ motion in radiation treatment

We examine 2 strategies for reducing respiration-induced organ motion in radiation treatment: deep inspiration breath hold (DIBH) and respiratory gating. DIBH is a controlled breathing technique in which the patient performs a supervised breath hold during treatment. The technique offers 2 benefits: reduced respiratory motion from the breath hold and increased normal tissue sparing from the increased lung volume. In respiratory-gated treatment, a device external to the patient monitors breathing and allows delivery of radiation only during certain time intervals, synchronous with the patient's respiratory cycle. Gated treatment offers reduced respiratory motion with less patient effort than DIBH. We briefly survey the development of these 2 strategies, describe their clinical implementation for treatment of thoracic and liver tumors at the Memorial Sloan-Kettering Cancer Center, and discuss their advantages and limitations.     

KVX线锥形束CT呼吸运动目标成像的体模研究

目的:研究呼吸运动对安装于Varian23EX加速器的KV X线锥形束CT(cone beamCT,CBCT)成像结果的影响.方法:利用自行研制的运动体模系统,模体直径分别为1、2和3 cm,设定横轴方向运动幅度分别为0.5、1.0和1.5 cm,纵轴方向分别为0.5、10.和2.0 cm,体模往返运动频率分别为12、20和25次/min,模拟呼吸运动并行CBCT扫描.结果:1)实际直径分别为10、20和30 mm的静止体模CBCT图像清晰,无变形,测量的直径分别为9.8±0.66[95% CI(9.1～10.5)mm]、19.9±0.75C95%CI(19.1～20.7)mm]和(29.7±0.69)mm [95%CI(29.0～30.4)mm],横轴方向和纵轴方向的大小与体模实际大小相符合,误差均<1 mm.2)横轴和纵轴方向的呼吸运动对体模CBCT成像都有明显的影响.与静止体模CBCT图像相比,横轴和纵轴方向的体模运动都使CBCT图像清晰度下降、变形以及体积增大.在设定的运动幅度和运动频率范围内,3种大小的运动体模CBCT图像在横轴方向和纵轴方向的大小都与设定的体模实际运动范围(模体直径加运动幅度)相符合.差值均<3 mm.结论:呼吸运动对CBCT成像影响明显,成像结果反应规律性呼吸运动物体的实际运动范围.     

PET/CT用于肿瘤放疗计划靶区勾画的相关问题

PET/CT用于精确放疗靶区勾画时,目前存在诸多不确定因素。主要包括以下几个方面：PET/CT扫描条件和影像融合方式;谁来勾画靶区以及采取的勾画方式;靶区勾画阈值的选择;针对PET和CT靶区范围差异的靶区确立原则。正因为在许多方面尚无法达成统一的共识,所以,各研究机构和治疗中心更应有谨慎和严格的质量控制程序和标准。     

Impact of scatter and attenuation corrections for iodine-131 two-dimensional quantitative imaging in patients

This study assessed the impact of scatter and attenuation corrections on the estimated activity delivered to whole body and liver in five patients included in a radioimmunotherapy clinical trial. Before injection of the radiopharmaceutical, transmission images were acquired with the Transmission Attenuation Correction - Whole-body (SMVi-GEMS) prototype. Emission images were obtained in energy-indexed list mode at least four times after injection. 20% window and scatter-corrected images (Dual Energy Window-DEW and Triple Energy Window-TEW) were generated. Whole-body activity was calculated 1-h after injection (and compared with injected activity). Cumulated activities in whole body and liver were determined according to the geometric mean approach. The mean relative error made in estimations of whole-body activity at 1-h was 6.9+/-10.3% without corrections. Taking scatter into account led to underestimation, but reduced the influence of patient morphotype (-40.0+/-7.6% and -43.3+/-6.2% for DEW and TEW). Attenuation correction led to a large overestimation, whether used alone (155.2+/-39.0%) or associated with scatter correction (39.6+/-10.4% and 35.9+/-10.2% for DEW and TEW). Compared to the geometric mean alone, scatter correction led to a reduction of cumulated activities of around 45% for whole body and less than 30% for liver. Attenuation correction had a more marked impact, particularly for liver where estimated cumulated activity increased from 150 to 300%. Preliminary scatter correction limited the increase to 100% for DEW and 150% for TEW in liver and to 25% for both DEW and TEW in whole body. Although this would probably be different at the organ level, the calculation of whole-body activity without scatter and attenuation correction gave the lowest biases. But from a scientific point of view, this cannot be a satisfactory method. Attenuation correction has a greater impact than scatter correction. The association of both corrections is not sufficient to obtain accurate absolute quantification. Other factors limit planar quantification with iodine-131, notably auto-absorption of sources, septal penetration of high-energy photons through the collimator and superimposition of sources.     

PET and PET/CT in radiation treatment planning for prostate cancer

Molecular imaging by means of PET provides a method to study the metabolic activity of tumors in vivo. ¹⁸F- or ¹¹C-choline and occasionally ¹⁸F- or ¹¹C-acetate, are used as tracers for prostate cancer, reflecting the phospholipid metabolism. The hybrid technology PET/computed tomography significantly reduces image fusion mismatch. The role of molecular imaging is increasing in radiation treatment planning for prostate cancer. Local prostate cancer recurrence after primary radiation treatment usually originates at the location of the primary tumor. Focusing the dose escalation on the actual tumor is an option to increase tumor control without increasing toxicity. Image-guided radiotherapy and intensity-modulated radiotherapy are prerequisite technologies for applying the simultaneous boost concept. Clinical results are needed in the near future to support the effectiveness of the concept.     

PET and PET/CT in radiation treatment planning for prostate cancer

Molecular imaging by means of PET provides a method to study the metabolic activity of tumors in vivo. (18)F- or (11)C-choline and occasionally (18)F- or (11)C-acetate, are used as tracers for prostate cancer, reflecting the phospholipid metabolism. The hybrid technology PET/computed tomography significantly reduces image fusion mismatch. The role of molecular imaging is increasing in radiation treatment planning for prostate cancer. Local prostate cancer recurrence after primary radiation treatment usually originates at the location of the primary tumor. Focusing the dose escalation on the actual tumor is an option to increase tumor control without increasing toxicity. Image-guided radiotherapy and intensity-modulated radiotherapy are prerequisite technologies for applying the simultaneous boost concept. Clinical results are needed in the near future to support the effectiveness of the concept.