Quantitative diffusion imaging of adipose tissue in the human lower leg at 1.5 T

Diffusion‐weighted spin‐echo echo‐planar imaging was developed and applied for assessment of diffusion coefficients of adipose tissue in human lower leg on a 1.5‐T whole‐body MR scanner. Because of the higher molecular weight of triglycerides, apparent diffusion coefficients (ADCs) of adipose tissue are approximately two orders of magnitude smaller compared with water, leading to the necessity of using high b‐values up to 50,000 sec/mm² and an echo time of 240 msec for sufficient diffusion‐related signal attenuation. ADC maps of adipose tissue in the human lower leg were derived for diffusion encoding along orthogonal spatial directions in six healthy volunteers. Mean diffusion coefficients in the tibial bone marrow amounted to (1.81 ± 0.10) × 10^?5 mm²/sec (left–right), (1.96 ± 0.10) × 10^?5 mm²/sec (anterior–posterior), and (1.96 ± 0.20) × 10^?5 mm²/sec (head–feet), respectively. Pixel‐wise calculated ADC values of subcutaneous adipose tissue showed a distinctly higher variation with the smallest ADC values similar to those measured for tibial bone marrow. Some subcutaneous adipose tissue regions showed increased signal attenuation at higher b‐values resulting in ADC coefficients up to 4.2 × 10^?5 mm²/sec. It must be noted that diffusion measurements with extremely high b‐values in vivo are extremely sensitive to incoherent motion effects in tissue. Nonetheless, it could be shown that in vivo diffusion imaging of adipose tissue in human lower leg is possible at 1.5 T in acceptable measurement time of a few minutes. Potential future applications of fat diffusion imaging are seen in temperature measurements in adipose tissue, detection of free fatty acids in white or brown adipose tissue in case of high lipolysis, differentiation of macro‐ and microvesicular steatosis, or assessment of the mobility of intramyocellular lipids. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Validity of apparent diffusion coefficient (ADC) value in diagnosis and follow-up of multiple sclerosis patients in different clinical subtypes

Background

Multiple sclerosis (MS) is a chronic disease with a wide range of pathologic changes that modify the apparent diffusion coefficient (ADC) value.

MRI characterization of diffusion coefficients in a rat spinal cord injury model

Apparent diffusion coefficients (ADC) were measured in a rat spinal cord weight-drop injury model. After sacrifice, the spinal cords were fixed in situ and excised for MR imaging and ADC measurement. Diffusion is anisotropic in normal gray and white matter. There were significant decreases in ADCs measured along the longitudinal axis of the injured cord and increases in ADCs measured transverse to the cord. Injured segments demonstrated reductions in diffusion anisotropy in the white matter. Diffusion was completely isotropic at the epicenter of the weight-drop injury. Significant decreases in longitudinal ADC and increases in transverse ADC were observed in portions of the cord which appeared normal on conventional spin-echo and calculated T₂ images. Thus ADC measurement may complement routine imaging for evaluation of spinal cord injury.     

van der Knaap syndrome: MR imaging findings including FLAIR, diffusion imaging, and proton MR spectroscopy

A patient is reported with diffuse leukoencephalopathy associated with cystic degeneration of the white matter of the brain (van der Knaap syndrome). The changes were studied by fluid attenuated inversion recovery (FLAIR), and diffusion-weighted MR imaging. The FLAIR sequence revealed suppressed signal of the cysts, and widespread high-signal white matter changes associated with thinned cortices. On diffusion-weighted MR imaging, apparent diffusion coefficient (ADC) values ranged from 3.0 × 10^–3 to 2.7 × 10^–3 mm²/s in the temporal cysts, similar to that of CSF. The ADC values within the parenchyma ranged between 2 × 10^–3 and 2.1 × 10^–3 mm²/s, a value falling between normal parenchyma and cerebrospinal fluid, compared with a control group of three healthy subjects. The changes were also evaluated by proton MR spectroscopy, and were compared with a control group of 12 cases. Magnetic resonance spectroscopy revealed apparently increased NAA/Cr ratios in most parts of the brain. The NAA/Cho ratios were either high or low, and the Cho/Cr ratios were increased or normal in different regions. Received: 27 October 1999; Revised: 9 December 1999; Accepted: 20 December 1999     

Increased brain water self-diffusion in patients with idiopathic intracranial hypertension.

PURPOSETo investigate changes in brain water diffusion in patients with idiopathic intracranial hypertension.METHODSA motion-compensated MR pulse sequence was used to create diffusion maps of the apparent diffusion coefficient (ADC) in 12 patients fulfilling conventional diagnostic criteria for idiopathic intracranial hypertension and in 12 healthy volunteers.RESULTSA significantly larger ADC was found within subcortical white matter in the patient group (mean, 1.16 x 10(-9) m2/s) than in the control group (mean, 0.75 x 10(-9) m2/s), whereas no significant differences were found within cortical gray matter, the basal nuclei, the internal capsule, or the corpus callosum. Four of 7 patients with increased ADC in subcortical white matter also had increased ADC within gray matter.CONCLUSIONMeasurement of diffusion coefficients in vivo demonstrated increased local water mobility within subcortical white matter in 7 patients with idiopathic intracranial hypertension that otherwise appeared normal on conventional MR imaging. Further studies are necessary to assess the clinical significance of these observations.     

Feasibility of MR Diffusion Studies in the Kidney

Renal apparent diffusion coefficients (ADCs) were anisotropic within and significantly different between cortex and medulla using a relatively motion-insensitive one-dimensional technique in 20 volunteers. ADC values ranged from 1.79 ±.39 to 2.95 ±.58(× 10^-3mm²/sec), relatively high but similar to other reports. Further investigation may help clarify this data, and determine whether the findings result from diffusion properties (and/or radially oriented parenchymal architecture), or artifacts due to factors such as bulk motion.     

Diffusion-weighted MR imaging in the brain in children: findings in the normal brain and in the brain with white matter diseases

PURPOSE: To establish quantitative standards for age-related changes in diffusion restriction of cerebral white matter in healthy children and to compare data with results in children with white matter diseases. MATERIALS AND METHODS: Diffusion-weighted magnetic resonance (MR) imaging was performed in 44 children (age range, 7 days to 7.5 years) without brain abnormalities and in 13 children with proved leukodystrophy. Apparent diffusion coefficient (ADC) and apparent anisotropy (AA) were measured in 11 regions of interest within white matter. Age-related changes were analyzed with regression analysis. RESULTS: During normal brain myelination, ADCs in different anatomic regions were high at birth (range, 1.04 x 10(-9) m(2)/sec +/- 0.05 [SD] to 1.64 x 10(-9) m(2)/sec +/- 0.09) and low after brain maturation (range, 0.75 x 10(-9) m(2)/sec +/- 0.02 to 0.92 x 10(-9) m(2)/sec +/- 0.02). AA was low at birth (range, 0.05 +/- 0.01 to 0.52 +/- 0.04) and high after brain maturation (range, 0.25 +/- 0.02 to 0.85 +/- 0.03). Age relationship could be expressed with monoexponential functions for all anatomic regions. Anisotropy preceded the myelination-related changes at MR imaging. ADC and AA in four children with Pelizaeus-Merzbacher disease were identical with results in healthy newborn children and showed no age dependency. In peroxisomal disorders, Krabbe disease, and mitochondriopathy, demyelination on T1- and T2-weighted MR images led to expected findings at diffusion-weighted MR imaging, with high ADC and low AA, whereas in Canavan disease and metachromatic leukodystrophy, the opposite findings were revealed, with low ADC within the demyelinated white matter. CONCLUSION: During early brain myelination, diffusion restriction in normal white matter increases. Anisotropy precedes myelination changes that are visible at MR imaging. Compared with T1- and T2-weighted MR imaging, diffusion-weighted MR imaging in white matter diseases reveals additional information.     

Validation of functional diffusion maps (fDMs) as a biomarker for human glioma cellularity

Purpose:

To present comprehensive examinations of the assumptions made in functional diffusion map (fDM) analyses and provide a biological basis for fDM classification.

Materials and Methods:

Sixty‐nine patients with gliomas were enrolled in this study. To determine the sensitivity of apparent diffusion coefficients (ADCs) to cellularity, cell density from stereotactic biopsy specimens was correlated with preoperative ADC maps. For definition of ADC thresholds used for fDMs, the 95% confidence intervals (CI) for changes in voxel‐wise ADC measurements in normal appearing tissue was analyzed. The sensitivity and specificity to progressing disease was examined using both radiographic and neurological criteria.

Results:

Results support the hypothesis that ADC is inversely proportional to cell density with a sensitivity of 1.01 × 10^?7 [mm²/s]/[nuclei/mm²]. The 95% CI for white matter = 0.25 × 10^?3 mm²/s, gray matter = 0.31 × 10^?3 mm²/s, a mixture of white and gray matter = 0.40 × 10^?3 mm²/s, and a mixture of white matter, gray matter, and cerebrospinal fluid = 0.75 × 10^?3 mm²/s. Application of these measurements as ADC thresholds produce varying levels of sensitivity and specificity to disease progression, which were all significantly better than chance.

Conclusion:

This study suggests fDMs are valid biomarkers for brain tumor cellularity. J. Magn. Reson. Imaging 2010;31:538–548. ©2010 Wiley‐Liss, Inc.

     

Diffusion-weighted MR imaging of the normal human spinal cord in vivo

BACKGROUND AND PURPOSE: Diffusion-weighted imaging is a robust technique for evaluation of a variety of neurologic diseases affecting the brain, and might also have applications in the spinal cord. The purpose of this study was to determine the feasibility of obtaining in vivo diffusion-weighted images of the human spinal cord, to calculate normal apparent diffusion coefficient (ADC) values, and to assess cord anisotropy. METHODS: Fifteen healthy volunteers were imaged using a multi-shot, navigator-corrected, spin-echo, echo-planar pulse sequence. Axial images of the cervical spinal cord were obtained with diffusion gradients applied along three orthogonal axes (6 b values each), and ADC values were calculated for white and gray matter. RESULTS: With the diffusion gradients perpendicular to the orientation of the white matter tracts, spinal cord white matter was hyperintense to central gray matter at all b values. This was also the case at low b values with the diffusion gradients parallel to the white matter tracts; however, at higher b values, the relative signal intensity of gray and white matter reversed. With the diffusion gradients perpendicular to spinal cord, mean ADC values ranged from 0.40 to 0.57 x 10(-3) mm2/s for white and gray matter. With the diffusion gradients parallel to the white matter tracts, calculated ADC values were significantly higher. There was a statistically significant difference between the ADCs of white versus gray matter with all three gradient directions. Strong diffusional anisotropy was observed in spinal cord white matter. CONCLUSION: Small field-of-view diffusion-weighted images of the human spinal cord can be acquired in vivo with reasonable scan times. Diffusion within spinal cord white matter is highly anisotropic.     

Subarachnoid hemorrhage in the subacute stage: elevated apparent diffusion coefficient in normal-appearing brain tissue after treatment

PURPOSE: To prospectively evaluate whether subarachnoid hemorrhage (SAH) is associated with a change in the apparent diffusion coefficient (ADC) in normal-appearing brain parenchyma. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained for all patient and volunteer studies. One hundred patients (48 men, 52 women; mean age, 52 years +/- 12 [standard deviation]) with aneurysmal SAH underwent conventional and diffusion-weighted magnetic resonance (MR) imaging at a mean of 9 days +/- 3 after SAH to evaluate possible lesions caused by SAH, treatment of SAH, and vasospasm. Aneurysms were treated surgically (n = 70) or endovascularly (n = 30) before MR imaging. Diffusion-weighted MR imaging was performed at 1-year follow-up in 30 patients (10 men, 20 women; mean age, 51 years +/- 11). Thirty healthy age-matched volunteers (11 men, 19 women; mean age, 54 years +/- 16) underwent MR imaging with an identical protocol. ADC values were measured bilaterally in the gray and white matter (parietal, frontal, temporal, occipital lobes; cerebellum; caudate nucleus; lentiform nucleus; thalamus; and pons) that appeared normal on T2-weighted and diffusion-weighted MR images. Linear mixed model was used for comparison of ADC values of supratentorial gray matter and white matter; general linear regression analysis was used for comparison of ADC values of cerebellum and pons. RESULTS: In patients with SAH, the ADC values in normal-appearing white matter, with a single exception in the frontal lobe (P = .091), were significantly higher than they were in healthy volunteers (P /= .121). CONCLUSION: SAH and its treatment may cause global mild vasogenic edema in white matter and deep gray matter that is undetectable on T2-weighted and diffusion-weighted MR images but is detectable by measuring the ADC value in the subacute stage of SAH.     

Characterization of chondroblastic osteosarcoma: Gadolinium‐enhanced versus diffusion‐weighted MR imaging

Purpose

To detect differences in magnetic resonance imaging (MRI) between chondroblastic osteosarcoma and the other types of osteosarcomas or chondrosarcomas using gadolinium‐enhanced versus diffusion‐weighted sequences.

Materials and Methods

Contrast‐enhanced MRI and diffusion‐weighted imaging (DWI) were performed in five chondroblastic osteosarcoma (CO) cases, 17 other types of osteosarcomas (OS), and 18 chondrosarcomas (CS). DWI was obtained with a single‐shot echo‐planar imaging (EPI) sequence using a 1.5T MR imager. The apparent diffusion coefficients (ADCs) of the minimum and maximum values were also obtained. The contrast‐enhancement pattern was evaluated and minimum‐maximum ADC value of CO was compared with other types of OS and CS.

Results

Both CO and CS showed a similar enhancement pattern; both showed septonodular and peripheral rim enhancement. The minimum ADC value of CO (1.24 ± 0.10 × 10^?3mm²/sec) was significantly higher than that of other types of OS (0.84 ± 0.15 × 10^?3mm²/sec) and was significantly lower than that of CS (1.64 ± 0.20 × 10^?3mm²/sec). In addition, the maximum ADC value of CO (2.28 ± 0.20 × 10^?3mm²/sec) was significantly higher than that of other types of OS (1.33 ± 0.26 × 10^?3mm²/sec).

Conclusion

DWI appears to be more useful for differentiating between chondroblastic osteosarcoma and chondrosarcoma or other types of osteosarcoma than Gd‐enhanced MRI. J. Magn. Reson. Imaging 2009;29:895–900. © 2009 Wiley‐Liss, Inc.

     

Temporal and anatomical variations of brain water apparent diffusion coefficient in perinatal cerebral hypoxic-ischemic injury: Relationships to cerebral energy metabolism

Cerebral apparent diffusion coefficients {ADCs) were determined in nine newborn piglets before and for 48 h after transient hypoxia-ischemia. Phosphorus MRS revealed severely reduced cerebral energy metabolism during the insult and an apparently complete recovery 2 h after resuscitation commenced. At this time, mean ADC over the imaging slice (ADC_global) was 0.88 (0.04) × 10^{? 9} m² · s^{? 1} (mean (SD}), which was close to the baseline value of 0.92 (0.4) × 10^{? 9} m² · s^{? 1}. In seven of the animals, a “secondary” failure of energy metabolism then evolved, accompanied by a decline in ADC_global to 0.64 (0.17) × 10^{? 9} m² · s^{? 1} at 46 h postresuscitation (P < 0.001 versus baseline). For these seven animals, ADC_global correlated linearly with the concentration ratio [phosphocreatine (PCr)][inorganic phosphate (Pi)] (0.94 r < 0.99; P > 0.001). A nonlinear relationship was demonstrated between ADC_global, and the concentration ratio [nucleotide triphosphate (NTP)]/ [Pi + PCr + 3 NTP]. The ADC reduction commenced in the parasagittal cortex before spreading in a characteristic pattern throughout the brain. ADC seems to be closely related to cerebral energy status and shows considerable potential for the assessment of hypoxic-ischemic injury in the newborn brain.     

In vivo measurement of water diffusion in the human heart

Existing magnetic resonance methods for diffusion imaging, including echo planar, are ineffective in the beating heart due to motion-induced signal attenuation. To overcome this problem, we used a diffusion-weighted stimulated echo-echo planar magnetic resonance imaging sequence. The two lobes of the diffusion-sensitizing gradient were synchronized to the same point in successive cardiac cycles in order to fix the cardiac position and avoid bulk motion effects. The apparent diffusion coefficients (ADCs) of the interventricular septum in 12 healthy subjects for diffusion gradients along the x-, y-, and z-directions were 1.40 ± 0.27, 1.48 ± 0.35, and 1.78 ± 0.27 × 10^?3 mm²/s. The ADCs of the interventricular septum in a second group of 15 healthy subjects for diffusion gradients along the short axis, horizontal and vertical long axes were 0.92 ± 0.15. 1.50 ± 0.15, and 1.10 ± 0.24 × mm²/s. Because the ADCs were less than the measured values for skeletal muscle and their standard deviations were low, it seems unlikely that bulk motion effects made the dominant contribution to the measured myocardial ADC for the interventricular septum, although motion and/or susceptibility artifacts frequently degraded measurements in the free wall of the left ventricle. Additional evidence that ADC was not predominantly determined by wall motion was obtained in a third group of patients with various cardiac abnormalities, in whom there was only a weak correlation between ADC and ejection fraction. Although further study is needed to better understand the factors contributing to the myocardial ADC, we hypothesize that the measured diffusional anisotropy in the septum might be explained largely on the basis of myofiber orientation.     

Diffusion-weighted imaging of the human optic nerve: A New approach to evaluate optic neuritis in multiple sclerosis

The apparent diffusion coefficient (ADC) in the optic nerve was measured from diffusion-weighted magnetic resonance imaging using an intravoxel incoherent motion (IVIM) sequence. The subjects were seven normal volunteers and eight patients with multiple sclerosis (MS) with a total of four optic nerves with acute neuritis and nine nerves with chronic neuritis. The mean ADC (4.18 ± 1.13 × 10^?3 mm²/s, n = 9) in the optic nerves with chronic neuritis was significantly higher than that in normal volunteers (1.56 ± 0.675 × 10^?3 mm²/s, n = 14) and that in the nerves with acute neuritis (0.94 ± 0.43 × 10^?3 mm²/s n = 4) (P < 0.001). The ADC is useful in assessing MS foci in the optic nerves.     

Navigator respiratory‐triggered diffusion‐weighted imaging in the follow‐up after hepatic radiofrequency ablation—initial results

Purpose

To evaluate diffusion alterations after hepatic radiofrequency (RF) ablation using a navigator respiratory‐triggered diffusion‐weighted imaging (NRT‐DWI) sequence with regard to potential diagnostic information for detection of local tumor progression (LTP).

Materials and Methods

One hundred forty‐eight consecutive follow‐up magnetic resonance (MR) examinations of 54 patients after hepatic RF ablation were reviewed. Apparent diffusion coefficient (ADC) values of ablation zones and liver parenchyma were assessed using a single‐shot echoplanar imaging sequence with the NRT technique. ADC values of ablation zones and adjacent signal alterations identified in NRT‐DWI were analyzed with regard to LTP.

Results

Mean ADC values of ablation zones (119.9 ± 30.5 × 10^?5 mm²/sec) and liver (106.3 ± 21.2 × 10^?5 mm²/sec) differed significantly (P = 0.0003). No evident changes in ablations' ADC values over time could be identified. ADC values obtained from the entire ablation zone did not significantly differ regarding the presence of LTP. In 58 examinations, hyperintense areas in the periphery of the ablation zone were detected on the NRT‐DWI. Corresponding ADC values were significantly lower in patients with LTP (102.1 ± 22.4 versus 130.8 ± 47.6 × 10^?5 mm²/sec; P = 0.0124).

Conclusion

NRT‐DWI is useful in the follow‐up imaging after RF ablation. ADC‐based evaluation of signal alterations adjacent to the ablation zone may contribute to the identification of LTP and nontumoral posttreatment tissue changes. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.

     

脑结节性硬化的MR DWI分析

目的:使用磁共振扩散加权成像(DWI)研究结节性硬化(TS)患者脑灰质和白质内病灶的扩散特点,并观察表观扩散系数(ADC)的变化。方法:对18例临床影像学诊断的TS患儿使用1.5TMR系统行DWI检查,测量大脑皮质和皮质下61个结节的ADC值和对照组15例正常儿童的正常白质的ADC值。结果:TS患儿大脑皮质和白质病灶的ADC值明显高于健康儿童正常脑白质的ADC值,两者存在统计学差异(P<0.001)。其中4例TS伴发的室管膜下巨细胞星形细胞瘤ADC值与正常脑实质的相似,两者无统计学差异(P>0.05)。结论:DWI可提供TS患儿脑皮质和白质病灶的病理信息,TS脑白质内结节灶的高ADC值可区别常规MRI检查T1WI和T2WI信号与TS相似的其他疾病结节状病灶。     

Discrimination between different types of white matter edema with diffusion-weighted MR imaging

Brain edema can be classified into three categories: vasogenic, cytotoxic, and interstitial. The mechanism of edema is thought to be different in each type. The authors studied the movement of water molecules in each type of white matter edema in a rat model by using diffusion-weighted magnetic resonance imaging. Conventional T2-weighted imaging did not allow distinction between the three types of white matter edema; the three types of edema were, however, distinguished by using diffusion-weighted imaging. The apparent diffusion coefficient (ADC) of water was different in each type of edema. Water molecules in cytotoxic edema induced by triethyl-tin intoxication showed a smaller and less anisotropic ADC than in normal white matter. In contrast, water in vasogenic edema induced by cold injury had a larger and more anisotropic ADC than in normal white matter. Water in interstitial edema due to kaolin-induced hydrocephalus had an anisotropic and very large ADC.     

Diffusional kurtosis imaging of normal-appearing white matter in multiple sclerosis: preliminary clinical experience

Purpose

We evaluated diffusional changes in normal-appearing white matter (NAWM) regions remote from multiple sclerosis (MS) plaques by using diffusional kurtosis imaging (DKI) to investigate the non-Gaussian behavior of water diffusion.

Materials and methods

Participants were 11 MS patients and 6 age-matched healthy volunteers. DKI was performed on a 3-T MR imager. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), and diffusional kurtosis (DK) maps were computed. Regions of interest (ROIs) were compared in 24 cerebral regions, including the frontal, parietal, and temporal lobe white matter (WM) in controls and NAWM in MS patients.

Results

The mean FA of all ROIs was 0.468 ± 0.014 (SD) (controls) or 0.431 ± 0.029 (MS group) (P = 0.016). Mean ADC was 0.785 ± 0.034 × 10^?3 mm²/s (controls) or 0.805 ± 0.041 × 10^?3 mm²/s (MS group). The mean DK of all ROIs was 0.878 ± 0.020 (controls) or 0.823 ± 0.032 (MS group) (P = 0.002). Analysis of individual ROIs revealed significant differences in DK in 3 ROIs between normal WM and NAWM, but significant differences in ADC and FA in only one ROI each.

Conclusion

DKI may be a new sensitive indicator for detecting tissue damage in MS patients in addition to conventional diffusional evaluations, for example diffusion tensor imaging.     

Detection of invasive components in cases of breast ductal carcinoma in situ on biopsy by using apparent diffusion coefficient MR parameters

Objectives

To evaluate whether apparent diffusion coefficient (ADC) parameters could identify invasive components in cases with ductal carcinoma in situ (DCIS) diagnosed by biopsy.

Methods

This retrospective study was approved by the institutional review board and the requirement to obtain informed consent was waived. Sixty-nine consecutive women with 70 lesions diagnosed with DCIS by biopsy underwent breast magnetic resonance (MR) imaging. Multiple regions of interest were placed (as many as possible) within the lesion on ADC maps. The minimum ADC values and the ADC difference values obtained as the difference between minimum and maximum ADCs were evaluated.

Results

Surgical specimens revealed 51 lesions with pure DCIS and the remaining 19 lesions with DCIS with invasive components (DCIS-IC). The minimum ADC value for DCIS-IC (0.99?±?0.04?×?10^?3 mm²/s) was significantly lower than that of pure DCIS (1.15?±?0.03?×?10^?3 mm²/s) (P??=??0.0037). The ADC difference value for DCIS-IC (0.38?±?0.05?×?10^?3 mm²/s) was significantly higher than that of pure DCIS (0.17?±?0.03?×?10^?3 mm²/s). ROC curve analysis for differentiating DCIS-IC from pure DCIS revealed that the area under the curve was 0.71 for minimum ADC value and 0.77 for ADC difference value.

Conclusions

The minimum ADC values and ADC difference values could suggest the presence of invasive components.

Key Points

? Identification of invasive components in DCIS before treatment is clinically important. ? Diffusion-weighted MR imaging can help lesion assessment in breast cancer. ? The minimum ADC value may suggest the presence of an invasive component in DCIS. ? The ADC difference value also suggests the presence of an invasive component in DCIS. ? Preoperative evaluation of diffusion-weighted MR imaging may help surgical planning for DCIS.     

Quantitative analysis of diffusion-weighted magnetic resonance imaging in malignant breast lesions using different b value combinations

Objectives

To explore how apparent diffusion coefficients (ADCs) in malignant breast lesions are affected by selection of b values in the monoexponential model and to compare ADCs with diffusion coefficients (Ds) obtained from the biexponential model.

Methods

Twenty-four women (mean age 51.3 years) with locally advanced breast cancer were included in this study. Pre-treatment diffusion-weighted magnetic resonance imaging was performed using a 1.5-T system with b values of 0, 50, 100, 250 and 800 s/mm². Thirteen different b value combinations were used to derive individual monoexponential ADC maps. All b values were used in the biexponential model.

Results

Median ADC (including all b values) and D were 1.04?×?10^-3?mm²/s (range 0.82–1.61?×?10^-3?mm²/s) and 0.84?×?10^-3?mm²/s (range 0.17–1.56?×?10^-3?mm²/s), respectively. There was a strong positive correlation between ADCs and Ds. For clinically relevant b value combinations, maximum deviation between ADCs including and excluding low b values (<100 s/mm²) was 11.8 %.

Conclusion

Selection of b values strongly affects ADCs of malignant breast lesions. However, by excluding low b values, ADCs approach biexponential Ds, demonstrating that microperfusion influences the diffusion signal. Thus, care should be taken when ADC calculation includes low b values.

Key Points

? Diffusion-weighted sequences are increasingly used in breast magnetic resonance imaging ? Diffusion-weighting (b) values strongly influence apparent diffusion coefficients of malignant lesions ? Exclusion of low b values reduces the apparent diffusion coefficient ? Flow-insensitive monoexponential apparent diffusion coefficients approach biexponential diffusion coefficients