磁共振扩散峰度成像鉴别诊断前列腺癌与前列腺增生

目的 探讨磁共振扩散峰度成像（DKI）鉴别诊断前列腺癌（PCa）与前列腺增生（BPH）的应用价值。方法 回顾性分析前列腺疾病患者59例,根据病理结果分为PCa组和BPH组。对所有患者均行MR常规扫描和肝脏容积超快速三维成像序列动态增强扫描、DWI及DKI扫描。由2名医师测量两组病灶DKI的各参数值。采用组内相关系数（ICC）分析2名医师测量结果的一致性;对两组各参数值的比较采用两独立样本t检验;绘制各参数的ROC曲线,分析诊断效能。结果 2名观察者测得两组各参数值一致性良好（ICC均>0.75）。PCa组平均扩散峰度值、平行扩散峰度值、垂直扩散峰度值高于BPH组（P均<0.01）;PCa组平均扩散系数、平行扩散系数、垂直扩散系数值低于BPH组（P均<0.01）。ROC分析显示各参数诊断PCa和BPH的曲线下面积均>0.90。结论 DKI各参数可为临床鉴别诊断PCa和BPH提供更多重要的参考信息。     

扩散峰度成像在正常成人脑组织中可重复性的研究

目的对正常成人脑组织进行扩散峰度成像(DKI)的可重复性研究。材料与方法选取年龄在31~66岁的正常成人志愿者26例,采用b值为0、500、1000、1500、2000 s/mm2多参数和多方向的DKI序列进行头部扫描,经2名观察者(放射科医师)分别独立在不同的时间,测量相同区域的扩散系数(MD)和扩散峰度系数(MK)值并记录。运用SPSS 19.0进行统计学分析评估DKI扩散系数(MD)和扩散峰度系数(MK)值观察者内、观察者间一致性。结果经2名观察者在不同的时间点测量得到胼胝体膝部、胼胝体压部、内囊前肢、内囊后肢及丘脑等部位的MD和MK值。同一观察者两次所测得值(观察者内)之间差异无统计学意义(P0.05);2名观察者分别所测得值(观察者间)之间差异无统计学意义(P0.05)。结论脑组织扩散峰度成像(DKI)具有良好的可重复性,可应用于反映脑组织微观结构变化特点。     

缺血性脑卒中早期DKI、DWI预测病灶最终转变的对比研究

目的探究扩散峰度成像(diffusion kurtosis imaging,DKI)与扩散加权成像(diffusion weighted imaging,DWI)预测急性脑梗死病灶最终转变的能力,以便为脑梗死核心区的准确判断提供补充。材料与方法选取急性脑梗死病例18例,分别于发病48 h内、30天后进行2次MRI扫描,绘制急性期DWI图、DKI的平均扩散峰度(mean kurtosis,MK)参数图与随访T2WI图显示的病灶范围,测量并计算3组图像中的病灶体积。不同参数图像中各体积值之间的差异采用Kruskal-Wallis H检验评估;并采用Spearman秩相关分析研究基线DWI、MK图体积与复查T2WI软化灶体积之间的相关性。结果急性期DWI、MK图与复查T2WI异常区域的体积,经Krustal-Wallis H检验,差异无统计学意义(H=5.819,P0.05)。随访T2WI的病灶体积(766.3±1406.4)mm~3与急性期MK图的病灶体积(905.8±1605.4)mm~3呈高度相关(r=0.977,P0.01),与急性期DWI的病灶体积(1642.5±3296.9)mm~3呈中度相关(r=0.548,P0.05)。结论急性期DKI较DWI与病灶的最终坏死灶范围具有更好的相关性,DKI更能准确地预测病灶的最终转变。     

移植肾急性排斥扩散加权成像早期诊断价值

目的探讨移植肾急性排斥扩散加权成像早期诊断价值。材料与方法应用3.0 T MR扩散加权成像序列(b=0、100、800 s/mm~2),分别扫描原位正常肾51例(A组)、移植正常肾22例(B组)、急性排斥反应移植肾15例(C组)志愿者,数据导入自带工作站处理获得3组肾皮质、髓质、肌肉的表观扩散系数(apparent diffusion coefficient,ADC_(0-800))。比较原位肾组皮髓质ADC_(0-800)值双侧差异,两组正常肾皮质与髓质差异,3组年龄、性别间以及肌肉、肾皮质、髓质ADC_(0-800)值差异,以活检病理为"金标准",评价肾皮质ADC_(0-800)值诊断移植肾急性排斥效能。结果 3组间年龄、性别、肌肉ADC_(0-800)值无统计学差异(P0.05);原位肾皮髓质ADC_(0-800)值双侧差异无统计学意义(P0.05);正常肾皮质ADC_(0-800)值高于髓质,差异有统计学意义(P0.05);3组间肾皮质ADC_(0-800)值差异有统计学意义(P0.05),两两比较C组与A、B组间均有统计学差异(P0.05),A组与B组间差异无统计学意义(P0.05);髓质ADC值3组间无统计学差异(P0.05)。以病理为标准,取1.76×10~(-3)mm~2/s为阈值,皮质ADC_(0-800)值诊断急性排斥移植肾受试者工作特征曲线下面积为0.942,敏感度与特异性分别为86.7%和90.4%。结论磁共振扩散加权成像对移植肾急性排斥早期诊断具有较高价值。     

MR扩散峰度成像对非酒精性脂肪性肝病诊断价值

目的探讨扩散峰度成像(DKI)对非酒精性脂肪性肝病(NAFLD)定量分级诊断及早期检出非酒精性脂肪性肝炎(NASH)的价值。方法采用高脂饮食喂养新西兰大白兔,构建不同等级非酒精性脂肪性肝病动物模型。采用3.0 T磁共振、关节表面柔线圈,进行肝脏扩散峰度成像(b=0、400、800 s/mm2)和磁共振扩散加权成像(DWI),分别获取MD值、MK值和ADC值,对所有肝脏标本进行非酒精性脂肪性肝病活动度评分。采用Spearman相关性分析评估不同等级与磁共振参数的相关性。采用ROC明确各磁共振参数诊断不同等级非酒精性脂肪性肝病的效能。采用比较ROC分析不同模型参数在早期诊断非酒精性脂肪性肝炎中的价值。结果ADC值和MD值与非酒精性脂肪性肝病等级程度呈负相关(ρ=-0.52,-0.904;P<0.05)。MK值与疾病等级程度呈正相关(ρ=0.761;P<0.05)。MD值和MK值在临界组和NASH组间差异有统计学意义(MD:1.729±0.114比1.458±0.240μm^2/ms;MK:1.096±0.079比1.237±0.180;P<0.05)。MD值和MK值诊断NASH的ROC曲线下面积分别为0.955和0.905,且均优于ADC值(AUC=0.727)(P<0.05)。结论扩散峰度成像可对非酒精性脂肪性肝病进行分级诊断,且早期诊断非酒精性脂肪性肝炎的价值优于传统磁共振扩散加权成像。     

兔坐骨神经背景信号抑制扩散加权成像

目的 探讨DWIBS周围神经成像扫描参数的优化方案.方法 对5只健康新西兰白兔行坐骨神经冠状位MRN成像,评价不同参数组合DWIBS序列及T2WI/SPIR图像兔坐骨神经的显示效果以及图像信号噪声比(SNR)与对比噪声比(CNR).制作兔坐骨神经组织切片.结果 T2WI/SPIR图像和b值=200 s/mm2、层厚=2 mm的DWIBS序列兔坐骨神经成像效果较好.T2WI/SPIR图像SNR和CNR最高.DWIBS中,以b值:200 s/mm2、层厚=1.5 mm序列SNR、CNR最高.结论 采用适当b值(200 s/mm2)和薄层扫描(1.5mm)能够获得较好的兔坐骨神经DWIBS图像.     

扩散峰度成像在颈髓的应用及与年龄相关性研究

目的探讨正常成人的脊髓扩散峰度成像(diffusion kurtosis imaging,DKI)序列扩散参数值变化规律及其与年龄的相关性,为定量诊断脊髓疾病提供参考。材料与方法选取2015年8月至2016年3月中国医科大学附属盛京医院患者36例,按年龄分组后,采用3.0 T MR进行DKI序列扫描,分别测定颈髓灰质和白质各向异性分数(fractional anisotropy,FA)、平均弥散系数(mean diffusivity,MD)、平均弥散峰度(mean kurtosis,MK)参数值。比较各间盘层面FA、MD及MK参数值差异性、变化趋势及各参数与年龄相关性。结果颈髓头尾方向DKI参数总体趋势为:MD逐渐增高,FA和MK逐渐减低。C2-3层面FA-灰质(gray matter,GW)和MD-白质(white matter,WM)与其他层面存在显著性差异(F=10.01,P0.05;F=16.94,P0.05),C6-7层面MK-GM和MD-GM亦与其他层面存在显著性差异(F=10.11,P0.05;F=10.01,P0.05)。FA-WM年龄呈负相关(r=-0.507,P0.05);MK-GM和MK-WM年龄呈正相关(r=0.436,P0.01;r=0.249,P0.05);FA-WM和MK-GM各年龄组间存在显著性差异(P0.05)。结论 DKI能反映健康成人的脊髓灰、白质微观结构的改变,其参数值变化与年龄存在相关性,MK可能是反映神经系统复杂微观结构和损伤改变的高度敏感指标。     

DKI及DTI在鉴别诊断低级别胶质瘤与脑炎中的价值

目的 评估MR扩散峰度成像(diffusion kurtosis imaging, DKI)及扩散张量成像(diffusion-tensor imaging, DTI)在鉴别低级别胶质瘤与脑炎中的价值。材料与方法 回顾性分析58例低级别胶质瘤或脑炎患者的影像学资料,所有患者在术前或保守治疗前均行MRI常规序列及DKI序列扫描。用NeuDiLab软件处理DKI图像,获得基于DKI模型的平均峰度(mean kurtosis, MK)、轴向扩散峰度(axial kurtosis, AK)和径向扩散峰度(radial kurtosis, RK)以及基于DTI模型的平均扩散系数(mean diffusivity, MD)、轴向扩散系数(axial diffusivity, AD)、径向扩散系数(radial diffusivity, RD)和各向异性分数(fractional anisotropy, FA)参数图及b=0 s/mm²的扩散图像(B0)。用ITK-SNAP软件在B0图像上手动勾画肿瘤的感兴趣容积(volume of interest, VOI),将其配准到其他...     

扩散峰度成像评估孤独症谱系障碍儿童纹状体异常

目的：采用扩散峰度成像（Diffusional kurtosis imaging,DKI）探索孤独症谱系障碍（Autism spectrum disorder,ASD儿童纹状体的结构特点。方法：收集27例ASD儿童（ASD组）以及19例健康儿童（对照组）的资料，两组儿童均进行颅脑MRI平扫及DKI序列扫描，DKI序列经过后处理得到扩散张量参数和扩散峰度参数。比较两组儿童纹状体平均扩散峰度（Mean kurtosis,MK）、平均扩散系数（Mean diffusivity,MD）和各向异性分数（Fractional anisotropy,FA）的差异。分析ASD组DKI参数与Gesell发育量表评分的相关性。探讨DKI参数对ASD的诊断效能。结果：与对照组相比，ASD组左侧苍白球和双侧壳核的FA值均升高（P<0.05）,ASD组双侧壳核的MD值均降低（P<0.05）,ASD组左侧壳核的MK值升高（P<0.05）。ASD组显著改变的结构的DKI参数值与Gesell发育量表均无显著相关性（P均>0.05）。左侧苍白球、右侧和左侧壳核FA值诊断ASD的曲线下面积（AUC...     

扩散峰度成像评价阿尔茨海默病患者脑白质微观结构的改变

目的 采用扩散峰度成像(DKI)探讨阿尔茨海默病(AD)患者脑白质微观结构的改变。方法 对23例AD患者(AD组)和24名健康对照者(HC组)进行常规MR序列及DKI扫描,手动测量额叶、顶叶、枕叶及颞叶皮层下白质、内囊(前、后肢)、外囊、胼胝体(膝、干、压部)的DKI参数,包括扩散峰度(MK)、横向峰度(Ka)、径向峰度(Kr)、平均扩散率(MD)、横向扩散率(Da)、径向扩散率(Dr)及FA值。采用ROC曲线下面积评价各参数值诊断AD的效能。结果 与HC组相比,AD组的顶叶及颞叶皮层下白质、外囊的MK、Ka、Kr值均降低;枕叶皮层下白质的MK、Kr值均降低;内囊前肢、胼胝体膝的MK、Ka值均降低;胼胝体干的MK、Kr值均降低;胼胝体压、内囊后肢的Ka值降低(P均<0.05)。额叶皮层 下白质、内囊前肢、胼胝体干的MD、Da、Dr值均升高;顶叶及颞叶皮层下白质、外囊的MD、 Dr值均升高;胼胝体压部的MD、Da值均升高;内囊后肢、胼胝体膝的MD值均升高;枕叶皮层下白质的Dr值升高(P均<0.05)。额叶、顶叶、枕叶及颞叶皮层下白质、胼胝体干、胼胝体膝、内囊前肢、外囊的FA值减小(P均<0.05)。颞叶皮层下白质Dr值的ROC曲线下面积最大,为0.95。所有部位的MK、Ka、Kr及FA值与MMSE评分均呈正相关;MD、Da及Dr值与MMSE评分呈负相关。结论 DKI参数可反映AD患者脑白质微观结构的改变,颞叶皮层下白质的Dr值是鉴别AD患者与正常人的最佳指标。     

Multimodality Rodent Imaging Chambers for Use Under Barrier Conditions with Gas Anesthesia

Purpose  The ability to reproducibly and repeatedly image rodents in noninvasive imaging systems, such as small-animal positron emission tomography (PET) and computed tomography (CT), requires a reliable method for anesthetizing, positioning, and heating animals in a simple reproducible manner. In this paper, we demonstrate that mice and rats can be reproducibly and repeatedly imaged using an imaging chamber designed to be rigidly mounted on multiple imaging systems. Procedures  Mouse and rat imaging chambers were made of acrylic plastic and aluminum. MicroCT scans were used to evaluate the positioning reproducibility of the chambers in multimodality and longitudinal imaging studies. The ability of the chambers to maintain mouse and rat body temperatures while anesthetized with gas anesthesia was also evaluated. Results  Both the mouse and rat imaging chambers were able to reproducibly position the animals in the imaging systems with a small degree of error. Placement of the mouse in the mouse imaging chamber resulted in a mean distance of 0.23 mm per reference point in multimodality studies, whereas for longitudinal studies the mean difference was 1.11 mm. The rat chamber resulted in a mean difference of 0.46 mm in multimodality studies and a mean difference of 4.31 mm in longitudinal studies per reference point. The chambers maintained rodent body temperatures at the set point temperature of 38°C. Conclusions  The rodent imaging chambers were able to reproducibly position rodents in tomographs with a small degree of variability and were compatible with routine use. The embedded anesthetic line and heating system was capable of maintaining the rodent’s temperature and anesthetic state, thereby enhancing rodent health and improving data collection reliability.     

胃癌磁共振扩散加权成像:并行采集联合分次屏气多信号平均技术的临床研究

目的探索实现胃癌磁共振扩散加权成像(DWI)的技术因素,评价胃癌DWI的临床应用价值.方法扩散加权单次激发平面回波成像(SS-EPI)序列连续检查胃癌患者53例,其中前期17例进行ASSET-DWI成像方法研究,结合分次屏气多信号平均技术,以肿瘤显示、伪影分级、对比噪声比(CNR)为评价标准,比较有无ASSET及不同信号平均次数(NEX)与ASSET搭配所得DWI图像的质量,确定成像参数;利用确定序列对后续36例胃癌进行成像研究,确定胃癌及非癌胃壁的DWI影像学表现及ADC值范围.扩散敏感梯度取b=0、1000 s/mm2.结果ASSET-DWI组较无ASSET组成像速度提高,相关伪影(磁敏感伪影、化学位移伪影及Ghost伪影)轻且图像基本无变形(P＜0.01);分次屏气采集对ADC值计算无影响(P＞0.05);分次屏气多信号平均(4 NEX)采集,可基本消除ASSET相关伪影,具备良好的对比噪声比.胃癌癌肿在DWI图上表现为稳定的高信号,平均ADC值为(1.17±0.22)×10-3 mm2/s,非癌胃壁表现为低信号,平均ADC值为(1.94±0.28)×10-3 mm2/s,二者差异有统计学意义(P＜0.01);以ADC值＜1.46×10-3 mm2/s作为判定胃癌的标准,敏感性97.0%,特异性90.9%.结论8通道体部相控阵线圈联合ASSET技术及分次屏气多信号平均采集,实现了胃癌高b值扩散加权成像;ADC值可作为胃癌诊断的辅助指标.     

In vitro and in vivo mapping of drug release after laser ablation thermal therapy with doxorubicin-loaded hollow gold nanoshells using fluorescence and photoacoustic imaging

Doxorubicin-loaded hollow gold nanoshells (Dox@PEG-HAuNS) increase the efficacy of photothermal ablation (PTA) not only by mediating efficient PTA but also through chemotherapy, and therefore have potential utility for local anticancer therapy. However, in vivo real-time monitoring of Dox release and temperature achieved during the laser ablation technique has not been previously demonstrated before. In this study, we used fluorescence optical imaging to map the release of Dox from Dox@PEG-HAuNS and photoacoustic imaging to monitor the tumor temperature achieved during near-infrared laser-induced photothermal heating in vitro and in vivo. In vitro, treatment with a 3-W laser was sufficient to initiate the release of Dox from Dox@PEG-HAuNS (1:3:1 wt/wt, 1.32 × 10¹² particles/mL). Laser powers of 3 and 6 W achieved ablative temperatures of more than 50 °C. In 4T1 tumor-bearing nude mice that received intratumoral or intravenous injections of Dox@PEG-HAuNS, fluorescence optical imaging (emission wavelength = 600 nm, excitation wavelength = 500 nm) revealed that the fluorescence intensity in surface laser-treated tumors 24 h after treatment was significantly higher than that in untreated tumors (p = 0.015 for intratumoral, p = 0.008 for intravenous). Similar results were obtained using an interstitial laser to irradiate tumors following the intravenous injection of Dox@PEG-HAuNS (p = 0.002 at t = 24 h). Photoacoustic imaging (acquisition wavelength = 800 nm) revealed that laser treatment caused a substantial increase in tumor temperature, from 37 °C to ablative temperatures of more than 50 °C. Ex vivo analysis revealed that the fluorescence intensity of laser-treated tumors was twice as high as that of untreated tumors (p = 0.009). Histological analysis confirmed that intratumoral injection of Dox@PEG-HAuNS and laser treatment caused significantly more tumor necrosis compared to tumors that were not treated with laser (p < 0.001). On the basis of these findings, we conclude that fluorescence optical imaging and photoacoustic imaging are promising approaches to assessing Dox release and monitoring temperature, respectively, after Dox@PEG-HAuNS-mediated thermal ablation therapy.     

磁敏感加权成像在诊断脑微出血中的应用

目的 探讨SWI在诊断脑微出血(CMBs)中的应用价值。方法 回顾性分析15例CMBs患者共257个病灶的影像学资料,观察病灶信号、大小、位置,并分析不同类型图像检出CMBs病灶的差异。结果 257个CMBs病灶中均匀信号病灶165个,混杂信号病灶92个;最大径1.4~8.4 mm,混杂信号病灶最大径明显大于均匀信号病灶(P<0.01);混杂信号主要分布于幕上,少见于幕下。SWI、幅度(Mag)、相位(Phase)及最小密度投影(mIP)图像检出的CMBs病灶总数差异无统计学意义(P>0.05)。Phase图像混杂信号占比明显高于SWI及Mag图像(P均<0.01),mIP图像明显低于SWI及Mag图像(P均<0.01)。结论 CMBs影像表现多样,并受病灶大小和位置影响。SWI可作为诊断CMBs的有效检查方法。     

儿童骨显像操作指南

儿童骨显像操作指南编写的主要内容包括儿童骨显像检查的临床适应证及禁忌证、核医学医务人员岗位要求、检查操作规范（病史采集、患儿准备及注意事项、放射性药物、图像采集、显像模式）、报告处理、质量控制及显像过程中的辐射安全。该指南主要适用于临床应用最多的⁹⁹Tc^m-MDP儿童骨显像检查。该操作指南的目的是为核医学医师在临床工作中处理儿童骨显像检查提供实用而行之有效的操作规范。     

对比99Tcm-DX与99Tcm-HAS显像诊断小肠淋巴管扩张症

目的 比较⁹⁹Tc^m-DX与⁹⁹Tc^m-HSA显像对小肠淋巴管扩张症的诊断效能。方法 收集56例低蛋白血症患者,均在7天内接受⁹⁹Tc^m-DX与⁹⁹Tc^m-HSA显像;以病理检查、胶囊肠镜或临床最终诊断作为“金标准”,评价2种检查方法的诊断效能,应用Kappa检验分析这两种方法的一致性。结果 38例（38/56,67.86%）最终诊断为IL,其中原发性IL34例,继发性IL4例;余18例中,10例诊断为乳糜性单或多浆膜腔积液,1例为肾病综合征,2例为不明原因失蛋白性肠病,5例为不明原因低蛋白血症。⁹⁹Tc^m-DX与⁹⁹Tc^m-HSA显像诊断IL的灵敏度分别60.53%（23/38）、94.73%（36/38）,特异度为88.89%（16/18）、61.11%（11/18）,准确率为69.64%（39/56）、83.93%（47/56）,阳性预测值为92.00%（23/25）、83.72%（36/43）,阴性预测值为51.61%（16/31）、84.62%（11/13）;两者诊断符合率为67.85%（38/56,Kappa=0.392,P<0.05）。结论 ⁹⁹Tc^m-HSA显像诊断IL的灵敏度较高,而⁹⁹Tc^m-DX显像的特异度较高,两者结合可能有助于提高诊断IL的准确性。     

门静脉血流灌注对健康志愿者肝脏MR弹性值的影响

目的 探讨门静脉血流灌注量的改变对磁共振弹性成像(MRE)所测肝弹性值的影响。方法 对32名健康志愿者分别在空腹和进食标准餐后(可有效增加门静脉灌注量)定量测量门静脉灌注量及肝弹性值,并进行比较分析。结果 进食后门静脉灌注量均显著上升,平均幅度123.5%。进食前、后的平均肝弹性值分别为(2.30±0.28)kPa及(2.32±0.24)kPa,差异无统计学意义(t=-0.63,P=0.54);门静脉灌注量与肝弹性值的变化无明显相关性(r=0.15,P=0.42)。结论 正常人餐后肝脏门静脉灌注变化不会引起肝脏弹性值的变化,进食状态不影响MRE测量结果的可重复性。     

胸腺瘤的MRI表现

目的 分析胸腺瘤的MRI表现。方法 收集经病理证实并有完整影像学资料的29例胸腺瘤患者,分析平扫、DWI及增强扫描MRI表现,并根据病理结果分为低危组（n=18）和高危组（n=11）,分析其影像学表现的差异。结果 肿瘤均为单发,28例病灶位于前纵隔,1例位于左锁骨上窝;21例肿瘤形态不规则,21例与邻近结构分界清楚。24例病灶T2WI呈高/稍高信号;20例T1WI呈低—中等信号;9例病变内有囊变坏死,7例可见分隔,1例可见液平;全部病灶DWI呈均匀或混杂信号。9例病灶增强扫描轻度强化,11例中度强化,9例明显强化。低危组与高危组ADC值差异无统计学意义（P=0.42）。结论 胸腺瘤常规MRI及DWI表现有一定特征性,有助于术前诊断胸腺瘤。     

高场MRI诊断周围型肝内胆管细胞癌

目的探讨高场MRI对周围型肝内胆管细胞癌(IHPCC)的诊断和鉴别诊断价值。方法对18例经病理证实的IHPCC的MR资料进行回顾性分析。所有患者均接受MR平扫及多期增强扫描。观察MR平扫和各期强化特点,测量病灶和正常肝实质的ADC值。结果所有病灶T2WI主体均呈不均匀高或稍高信号,其中11例中心可见斑片状或星芒状低或略低信号。12例病灶动脉期呈环状强化,门静脉期及延迟期强化范围向中心扩展;3例动脉期周边及中心均不规则强化,门静脉期及延迟期强化范围扩大;1例动脉期未见强化,门静脉期边缘强化,延迟期中心强化;2例动脉期和门静脉期呈环状强化,延迟期中心未见强化。DWI病灶均呈不均匀高或稍高信号。病变区和正常肝实质ADC值为(1.42±0.13)×10-3mm2/s、(1.26±0.08)×10-3mm2/s(P<0.05)。结论高场MRI的T2WI、DWI、ADC值及多期增强扫描相结合对IHPCC的诊断具有重要价值。     

Optimizing quantitative in vivo fluorescence imaging with near‐infrared quantum dots

Quantum dots (QDs) are fluorescent nanoparticles with broad excitation and narrow, wavelength‐tunable emission spectra. They are used extensively for in vitro fluorescence imaging studies and more recently for in vivo small animal and pre‐clinical studies. To date there has been little concern about the selection of QD size (and thus emission wavelength peak) and excitation wavelengths, as they have little relevance to the results of in vitro studies. In vivo imaging, however, poses additional constraints, such as the scattering and absorption by tissue, which may influence the signal intensity at the body surface. Here, we demonstrate that longer‐wavelength excitation and emission yield less quantization error in measured relative fluorescence intensity, using three near‐infrared QDs (QD655, QD705 and QD800) applied to in vivo lymphatic imaging, and a range of excitation wavelengths from the blue to the red. Statistically significant differences in quantization error were observed between nearly all pairs of excitation wavelengths (445–490, 503–555, 575–605, 615–665 and 671–705 nm). Similarly, quantization error decreased with longer emission wavelengths (655, 705 and 800 nm). Light absorbance and scattering were demonstrated to be more potent factors than absorbance efficiency of QDs in producing quantization error in the measured fluorescence intensity. As a result, while wavelengths can be adjusted for qualitative experiments, the longest possible wavelengths should be used if quantification is desired during QD imaging experiments. Copyright © 2010 John Wiley & Sons, Ltd.