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DOI: 10.1148/radiol.2472070823
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(Radiology 2008;247:458-464.)
© RSNA, 2008

Genitourinary Imaging

Renal Masses: Characterization with Diffusion-weighted MR Imaging—A Preliminary Experience1

Jingbo Zhang, MD, Yousef Mazaheri Tehrani, PhD, Liang Wang, MD, Nicole M. Ishill, MS, Larry H. Schwartz, MD, and Hedvig Hricak, MD, PhD

1 From the Departments of Radiology (J.Z., L.W., L.H.S., H.H.), Medical Physics (Y.M.T.), and Biostatistics and Epidemiology (N.M.I.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, RM C278D, New York, NY 10021. Received May 10, 2007; revision requested July 6; revision received July 19; accepted August 20; final version accepted October 12. Address correspondence to J.Z. (e-mail: zhangj12{at}mskcc.org).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Purpose: To retrospectively assess the usefulness of apparent diffusion coefficients (ADCs) for characterizing renal masses (ie, viable solid tumors, necrotic or cystic tumor areas, and benign cysts).

Materials and Methods: The institutional review board waived the requirement for informed consent for this retrospective HIPAA-compliant study. The data of 25 consecutive patients (15 men, 10 women; age range, 39–75 years) who underwent renal magnetic resonance (MR) imaging, including diffusion-weighted imaging, before nephrectomy were included. Renal MR examinations were performed by using transverse T1-weighted dual-echo in-phase and out-of-phase sequences and transverse and coronal T2-weighted single-shot fast spin-echo sequences. Three-dimensional fat-saturated T1-weighted dynamic gadopentetate dimeglumine–enhanced sequences also were performed. Precontrast single-shot spin-echo echo-planar diffusion-weighted images were obtained with b values of 0, 500, and 1000 sec/mm2 at 1.5 T. Regions of interest were placed on renal lesions to measure the ADC of whole lesions, enhancing viable soft tissue, and nonenhancing necrotic or cystic areas. The T1 signal characteristics of the renal lesions and necrotic or cystic areas were recorded. The Wilcoxon rank sum test was used to compare the median ADC values of the various types of lesions and areas.

Results: Twenty-six renal tumors were found in the 25 patients. Eight patients were found to have 11 benign cysts. Renal tumors had significantly lower ADCs (median, 189.3 x 10–3 mm2/sec; range, [102.0–262.0] x 10–3 mm2/sec) compared with benign cysts (median, 322.8 x 10–3 mm2/sec; range, [217.0–421.0] x 10–3 mm2/sec; P < .001). Solid enhancing tumors had significantly lower ADCs (median, 162.3 x 10–3 mm2/sec; range, [102.0–284.0] x 10–3 mm2/sec) compared with nonenhancing necrotic or cystic regions (median, 247.7 x 10–3 mm2/sec; range, [85.2–310.0] x 10–3 mm2/sec; P = .007). T1 hyperintense lesions had lower ADCs compared with their hypointense counterparts.

Conclusion: The T1 signal characteristics of a renal lesion appear to be related to the ADC of the lesion. ADC may be helpful in characterizing and differentiating renal masses.

© RSNA, 2008


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Contrast material–enhanced computed tomography (CT) and magnetic resonance (MR) imaging are two of the most commonly used modalities for evaluation of renal masses. The presence of enhancing soft tissue in a renal lesion at CT or MR imaging is considered to be diagnostic of a renal neoplasm (1–5). However, an extensively necrotic or cystic renal tumor may demonstrate little or no contrast enhancement, and the appearance of this tumor may overlap with that of complex benign renal cysts on conventional MR images (3).

Diffusion-weighted MR imaging is an established diagnostic technique in neuroimaging. The clinical applications of this procedure include the diagnosis of acute ischemic injury to the brain (6) and the evaluation of brain tumors (7). Diffusion-weighted imaging is used to measure the Brownian motion of water molecules in tissue, which has been shown to be inversely proportional to cellular density (8), presumably because increased cellular density limits water diffusion in the interstitial space. The apparent diffusion coefficient (ADC), a quantitative parameter measured with diffusion-weighted imaging, has been shown to be lower in high-grade brain gliomas than in low-grade brain gliomas (9), although there is some overlap (10). In addition, it has been demonstrated that diffusion-weighted imaging may add incremental value to MR spectroscopy in the differentiation between brain abscesses and necrotic brain tumors (11). This distinction is of substantial clinical importance, as the treatment strategies for benign brain abscesses and necrotic brain tumors are vastly different.

The use of diffusion-weighted sequences in body imaging is technically challenging, as these sequences are generally sensitive to motion and susceptibility artifacts and yield limited signal-to-noise ratio. Thus, their application in abdominal imaging has been limited. However, with recent advances in MR technology and the use of faster, more robust sequences, better image quality can be achieved, and diffusion-weighted imaging has shown great potential for use in abdominal imaging in a number of investigations (12–14). Diffusion-weighted imaging has been found to be useful for differentiating focal hepatic lesions (15–18) and evaluating diffuse hepatic parenchymal abnormalities such as cirrhosis (19). A few studies have been performed to investigate the role of diffusion-weighted imaging in the evaluation of renal function in both native (20–23) and transplanted kidneys (24). In addition, study results have shown that diffusion-weighted imaging may be used to differentiate hydronephrosis from pyonephrosis (25,26).

To our knowledge, experience in using diffusion-weighted imaging to characterize renal lesions—especially renal masses—has been limited. Thus, the purpose of our study was to retrospectively assess the usefulness of ADCs for characterizing renal masses (ie, viable solid tumors, necrotic or cystic tumor areas, and benign cysts).


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Study Group
In our retrospective study, we initially included the data of 28 consecutive patients who underwent renal MR imaging—which included diffusion-weighted imaging—and subsequent nephrectomy between October 2005 and September 2006. Our study was approved by our institutional review board and was compliant with the Health Insurance Portability and Accountability Act. The institutional review board waived the requirement for informed patient consent.

Twenty-five of the 28 diffusion-weighted MR examinations—performed in the 28 patients—yielded adequate image quality, and the images obtained at these 25 tests—in 25 patients—were included in the final data analysis. The images obtained at three MR examinations were excluded owing to excessive artifacts induced by patient motion. Fifteen patients were men, and 10 were women; their median age was 58 years (age range, 39–75 years).

There were 26 renal tumors in the 25 patients (Table 1). The median size of the tumors was 8.2 cm (range, 1.7–18.5 cm). The median time between MR imaging and surgery was 18 days (range, 2–96 days). The 26 tumors found at postsurgical histopathologic analysis were 10 clear cell, five papillary, three chromophobe, and two unclassified renal cell carcinomas; three other malignant renal tumors (angiosarcoma, collecting ductal carcinoma, and primitive neuroectodermal tumor); two oncocytomas; and one angiomyolipoma.


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  		Table 1. Patient and Lesion Characteristics

 
MR Imaging
MR examinations were performed with the patient in a supine position by using a 1.5-T imaging unit (Signa; GE Medical Systems, Milwaukee, Wis) with a body phased-array coil. For morphologic evaluation of the kidneys, transverse T1-weighted dual-echo in-phase and out-of-phase sequences, transverse and coronal T2-weighted single-shot fast spin-echo sequences, and three-dimensional fat-saturated T1-weighted dynamic contrast-enhanced sequences were performed during the patient's suspended respiration. The T1-weighted dual-echo images were acquired with the following parameters: 210/2.1, 4.2 (repetition time msec/echo time msec); field of view, 36–44 cm; section thickness, 7–8 mm; intersection gap, 1 mm; and matrix, 256 x 128. The T2-weighted single-shot fast spin-echo images were acquired with the following parameters: infinite/90–105; field of view, 36–44 cm; section thickness, 4 mm; no intersection gap; and matrix, 256 x 256. For the three-dimensional dynamic contrast-enhanced sequences, the following parameters were used: 3.5–3.9/1.6–1.9; field of view, 34–48 cm; interpolated section thickness, 2.5 mm; and matrix, 256 x (160–192). Gadopentetate dimeglumine (Magnevist; Berlex Laboratories, Wayne, NJ) (0.1 mmol per kilogram of body weight) was injected intravenously at a rate of 2 mL/sec by using a power injector (Spectris; Medrad, Pittsburgh, Pa) and followed by a 20-mL saline flush. Dynamic contrast-enhanced imaging was performed in the transverse plane at baseline (precontrast), during the arterial phase, and 70 and 180 seconds after the arterial phase. Computer software (SmartPrep; GE Medical Systems) was used to synchronize the contrast material administration with the image acquisition. As part of our routine protocol, voxel-by-voxel subtraction of the unenhanced images from the three-dimensional fat-saturated dynamic contrast-enhanced images obtained at all time points was performed at the console.

Transverse breath-hold diffusion-weighted images were obtained by using a single-shot spin-echo echo-planar sequence (1800/74–104; flip angle, 90°; field of view, 36–42 cm; matrix, 128 x 128; section thickness, 7 mm; intersection gap, 1 mm; all directions; one signal acquired) before contrast material was administered, with b values of 0, 500, and 1000 sec/mm2. Pixel-wise ADC maps were generated by using a commercially available software-workstation system (Advanced Workstation; GE Medical Systems).

Image Analysis
Two investigators (J.Z., L.W.; 5 and 8 years experience reading abdominal MR images, respectively) who were blinded to the histopathologic analysis results manually defined multiple regions of interest (ROIs) in consensus at the workstation. First, they placed the largest possible round or elliptical ROIs on renal lesions to measure the ADCs of whole lesions, which included renal tumors and benign cysts. Subsequently, the renal tumors that contained both enhancing viable soft tissue and nonenhancing necrotic or cystic areas were identified on the unenhanced and contrast-enhanced three-dimensional T1-weighted images and on the subtracted images. In addition, the T1 signal characteristics of the renal lesions and necrotic or cystic tumor areas were recorded as hyperintense or hypointense relative to the background renal parenchyma depicted on the fat-saturated T1-weighted images. The investigators placed smaller ROIs on areas of enhancing viable tumor tissue, on nonenhancing T1 hyperintense or hypointense areas in the tumors, and on T1 hyperintense or hypointense cysts and measured the ADCs in these ROIs. If T1 hyperintense and hypointense necrotic or cystic areas coexisted in the same renal mass, then the ADCs for these areas were measured separately. ROI size varied according to lesion size. Depending on the lesion size, ROIs were outlined on up to three sections in each renal mass and in each viable tumor area or necrotic or cystic tumor area. When more than one ROI was placed in a lesion or area, the mean ADC was calculated and represented the ADC value for that lesion or area.

Statistical Analyses
To compare the median ADCs among the various types of lesions and areas, the Wilcoxon rank sum test was used. All P values of less than .05 were considered to indicate statistical significance. The distributions of ADCs were displayed in box plots. All analyses were performed by using Stata 2005, version 9, software for Windows (Stata, College Station, Tex).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Lesion Characteristics
Twenty-five of the 26 tumors had measurable enhancing solid tumor areas. Sixteen of the 26 tumors had areas of necrotic or cystic change, as evidenced by a lack of contrast enhancement on the MR images. Of these 16 lesions, eight demonstrated T1 hyperintense necrotic or cystic areas and 12 demonstrated T1 hypointense necrotic or cystic areas; some tumors had both T1 hyperintense and T1 hypointense areas (Fig 1). Eight patients were found to have 11 benign cysts, four of which were T1 hyperintense and seven of which were T1 hypointense.


Figure 1A
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  		Figure 1a: Transverse MR images of left clear cell renal carcinoma in 41-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.7/1.8, 12° flip angle, 46-cm field of view, 256 x 192 matrix) shows a heterogeneous mass (arrow) with focal T1 hyperintense areas in the left kidney. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows heterogeneous enhancement of the renal lesion. (c) Image generated by subtracting a from b shows a nonenhancing necrotic area (arrow) in the left renal mass, corresponding to the T1 hyperintense area in a. (d) On single-shot fast spin-echo diffusion-weighted image (1800/90, 90° flip angle, 40-cm field of view, b = 500 sec/mm2), three ROIs are drawn: over the entire lesion (1), over the enhancing tumor area (2), and over the T1 hyperintense nonenhancing necrotic area (3).

 

Figure 1B
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  		Figure 1b: Transverse MR images of left clear cell renal carcinoma in 41-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.7/1.8, 12° flip angle, 46-cm field of view, 256 x 192 matrix) shows a heterogeneous mass (arrow) with focal T1 hyperintense areas in the left kidney. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows heterogeneous enhancement of the renal lesion. (c) Image generated by subtracting a from b shows a nonenhancing necrotic area (arrow) in the left renal mass, corresponding to the T1 hyperintense area in a. (d) On single-shot fast spin-echo diffusion-weighted image (1800/90, 90° flip angle, 40-cm field of view, b = 500 sec/mm2), three ROIs are drawn: over the entire lesion (1), over the enhancing tumor area (2), and over the T1 hyperintense nonenhancing necrotic area (3).

 

Figure 1C
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  		Figure 1c: Transverse MR images of left clear cell renal carcinoma in 41-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.7/1.8, 12° flip angle, 46-cm field of view, 256 x 192 matrix) shows a heterogeneous mass (arrow) with focal T1 hyperintense areas in the left kidney. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows heterogeneous enhancement of the renal lesion. (c) Image generated by subtracting a from b shows a nonenhancing necrotic area (arrow) in the left renal mass, corresponding to the T1 hyperintense area in a. (d) On single-shot fast spin-echo diffusion-weighted image (1800/90, 90° flip angle, 40-cm field of view, b = 500 sec/mm2), three ROIs are drawn: over the entire lesion (1), over the enhancing tumor area (2), and over the T1 hyperintense nonenhancing necrotic area (3).

 

Figure 1D
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  		Figure 1d: Transverse MR images of left clear cell renal carcinoma in 41-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.7/1.8, 12° flip angle, 46-cm field of view, 256 x 192 matrix) shows a heterogeneous mass (arrow) with focal T1 hyperintense areas in the left kidney. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows heterogeneous enhancement of the renal lesion. (c) Image generated by subtracting a from b shows a nonenhancing necrotic area (arrow) in the left renal mass, corresponding to the T1 hyperintense area in a. (d) On single-shot fast spin-echo diffusion-weighted image (1800/90, 90° flip angle, 40-cm field of view, b = 500 sec/mm2), three ROIs are drawn: over the entire lesion (1), over the enhancing tumor area (2), and over the T1 hyperintense nonenhancing necrotic area (3).

 
ADC Values
The 26 renal tumors had significantly lower ADCs (median, 189.3 x 10–3 mm2/sec; range, [102.0–262.0] x 10–3 mm2/sec) compared with the benign cysts (median, 322.8 x 10–3 mm2/sec; range, [217.0–421.0] x 10–3 mm2/sec) (P < .001) (Table 2). The areas of solid enhancing tumor tissue within the renal tumors had significantly lower ADCs (median, 162.3 x 10–3 mm2/sec; range, [102.0–284.0] x 10–3 mm2/sec) compared with the nonenhancing necrotic or cystic areas (median, 247.7 x 10–3 mm2/sec; range, [85.2–310.0] x 10–3 mm2/sec) (P = .007). The necrotic or cystic areas within the renal tumors had significantly lower ADCs (median, 247.7 x 10–3 mm2/sec; range, [85.2–310.0] x 10–3 mm2/sec) compared with the benign cysts (median, 322.8 x 10–3 mm2/sec; range, [217.0–421.0] x 10–3 mm2/sec (P = .001) (Fig 2). The ADC values for these renal lesion groups differed significantly, but they also overlapped (Fig 3).


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  		Table 2. ADCs for All Renal Lesions and Lesion Areas

 

Figure 2A
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  		Figure 2a: Transverse MR images of left renal angiosarcoma found to contain large necrotic areas at postsurgical histopathologic analysis in 63-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.6/1.7, 12° flip angle, 36-cm field of view) shows a T1 hyperintense mass (M) in the left kidney (K). A T1 hypointense benign cyst (C) is seen in the anterior region. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows no obvious enhancement in either renal lesion. (c) Findings on the image generated by subtracting a from b confirm the findings in b. (d–f) Single-shot fast spin-echo diffusion-weighted images (1800/75, 86; 90° flip angle; 36-cm field of view) obtained with b values of 0 sec/mm2 (d), 500 sec/mm2 (e), and 1000 sec/mm2 (f) show the high signal intensity of the tumor is maintained at increasing b values, whereas the signal intensity of the cyst decreases, indicating a lower ADC in the necrotic tumor region (85.2 x 10–3 mm2/sec) than in the cyst (290.0 x 10–3 mm2/sec).

 

Figure 2B
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  		Figure 2b: Transverse MR images of left renal angiosarcoma found to contain large necrotic areas at postsurgical histopathologic analysis in 63-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.6/1.7, 12° flip angle, 36-cm field of view) shows a T1 hyperintense mass (M) in the left kidney (K). A T1 hypointense benign cyst (C) is seen in the anterior region. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows no obvious enhancement in either renal lesion. (c) Findings on the image generated by subtracting a from b confirm the findings in b. (d–f) Single-shot fast spin-echo diffusion-weighted images (1800/75, 86; 90° flip angle; 36-cm field of view) obtained with b values of 0 sec/mm2 (d), 500 sec/mm2 (e), and 1000 sec/mm2 (f) show the high signal intensity of the tumor is maintained at increasing b values, whereas the signal intensity of the cyst decreases, indicating a lower ADC in the necrotic tumor region (85.2 x 10–3 mm2/sec) than in the cyst (290.0 x 10–3 mm2/sec).

 

Figure 2C
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  		Figure 2c: Transverse MR images of left renal angiosarcoma found to contain large necrotic areas at postsurgical histopathologic analysis in 63-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.6/1.7, 12° flip angle, 36-cm field of view) shows a T1 hyperintense mass (M) in the left kidney (K). A T1 hypointense benign cyst (C) is seen in the anterior region. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows no obvious enhancement in either renal lesion. (c) Findings on the image generated by subtracting a from b confirm the findings in b. (d–f) Single-shot fast spin-echo diffusion-weighted images (1800/75, 86; 90° flip angle; 36-cm field of view) obtained with b values of 0 sec/mm2 (d), 500 sec/mm2 (e), and 1000 sec/mm2 (f) show the high signal intensity of the tumor is maintained at increasing b values, whereas the signal intensity of the cyst decreases, indicating a lower ADC in the necrotic tumor region (85.2 x 10–3 mm2/sec) than in the cyst (290.0 x 10–3 mm2/sec).

 

Figure 2D
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  		Figure 2d: Transverse MR images of left renal angiosarcoma found to contain large necrotic areas at postsurgical histopathologic analysis in 63-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.6/1.7, 12° flip angle, 36-cm field of view) shows a T1 hyperintense mass (M) in the left kidney (K). A T1 hypointense benign cyst (C) is seen in the anterior region. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows no obvious enhancement in either renal lesion. (c) Findings on the image generated by subtracting a from b confirm the findings in b. (d–f) Single-shot fast spin-echo diffusion-weighted images (1800/75, 86; 90° flip angle; 36-cm field of view) obtained with b values of 0 sec/mm2 (d), 500 sec/mm2 (e), and 1000 sec/mm2 (f) show the high signal intensity of the tumor is maintained at increasing b values, whereas the signal intensity of the cyst decreases, indicating a lower ADC in the necrotic tumor region (85.2 x 10–3 mm2/sec) than in the cyst (290.0 x 10–3 mm2/sec).

 

Figure 2E
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  		Figure 2e: Transverse MR images of left renal angiosarcoma found to contain large necrotic areas at postsurgical histopathologic analysis in 63-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.6/1.7, 12° flip angle, 36-cm field of view) shows a T1 hyperintense mass (M) in the left kidney (K). A T1 hypointense benign cyst (C) is seen in the anterior region. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows no obvious enhancement in either renal lesion. (c) Findings on the image generated by subtracting a from b confirm the findings in b. (d–f) Single-shot fast spin-echo diffusion-weighted images (1800/75, 86; 90° flip angle; 36-cm field of view) obtained with b values of 0 sec/mm2 (d), 500 sec/mm2 (e), and 1000 sec/mm2 (f) show the high signal intensity of the tumor is maintained at increasing b values, whereas the signal intensity of the cyst decreases, indicating a lower ADC in the necrotic tumor region (85.2 x 10–3 mm2/sec) than in the cyst (290.0 x 10–3 mm2/sec).

 

Figure 2F
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  		Figure 2f: Transverse MR images of left renal angiosarcoma found to contain large necrotic areas at postsurgical histopathologic analysis in 63-year-old man. (a) Nonenhanced fat-saturated T1-weighted image (3.6/1.7, 12° flip angle, 36-cm field of view) shows a T1 hyperintense mass (M) in the left kidney (K). A T1 hypointense benign cyst (C) is seen in the anterior region. (b) Corresponding contrast-enhanced fat-saturated T1-weighted image shows no obvious enhancement in either renal lesion. (c) Findings on the image generated by subtracting a from b confirm the findings in b. (d–f) Single-shot fast spin-echo diffusion-weighted images (1800/75, 86; 90° flip angle; 36-cm field of view) obtained with b values of 0 sec/mm2 (d), 500 sec/mm2 (e), and 1000 sec/mm2 (f) show the high signal intensity of the tumor is maintained at increasing b values, whereas the signal intensity of the cyst decreases, indicating a lower ADC in the necrotic tumor region (85.2 x 10–3 mm2/sec) than in the cyst (290.0 x 10–3 mm2/sec).

 

Figure 3
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  		Figure 3: Box plots of ADC values, which differed significantly between benign cysts, necrotic or cystic tumor areas, and solid tumor areas. Boxes represent data from the 25th to the 75th percentile (middle 50% of observations); the horizontal line through each box represents the median value. Lines extend from the box to the minimal and maximal observed values.

 
When the lesion groups were subdivided according to T1 signal characteristics, overlaps in ADC values decreased. The T1 hyperintense lesions had lower ADCs compared with their hypointense counterparts (Fig 4). For example, the T1 hypointense benign cysts had the highest ADCs of all the types of lesion areas assessed; they essentially had no overlap in ADCs with the solid tumor tissues and very little overlap with the necrotic or cystic tumor areas. Although the cysts that were T1 hyperintense, presumably because of hemorrhagic or proteinaceous content, had lower ADCs compared with the cysts that were T1 hypointense, the difference was not significant (P = .15). The ADCs of the T1 hyperintense benign cysts overlapped significantly with the ADCs of the T1 hypointense necrotic or cystic tumor areas but only slightly with the ADCs of the T1 hyperintense necrotic or cystic tumor areas.


Figure 4
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  		Figure 4: Box plots of ADC values for the different types of renal lesions and lesion areas with different T1 signal characteristics. Boxes represent data from the 25th to the 75th percentile (middle 50% of observations); the horizontal line through each box represents the median value. Lines extend from the box to the minimal and maximal observed values.

 
Among the necrotic or cystic tumor areas, the T1 hyperintense regions had significantly lower ADCs compared with the T1 hypointense regions (P = .004). The T1 hyperintense areas had the lowest range of ADC values among the necrotic or cystic tumor areas, with a range of ADCs comparable to that for the solid tumor tissues.

In terms of the ADCs of specific histologic renal tumor subtypes, the numbers of lesions in each histologic subtype category (Table 3) were too small to perform statistical analysis to determine whether ADCs differed significantly between histologic renal tumor subtypes.


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  		Table 3. ADCs for Renal Tumors Categorized according to Histologic Subtype

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
It has been shown that diffusion-weighted MR imaging can yield valuable diagnostic information for the evaluation of diffuse parenchymal abnormalities and focal lesions in abdominal organs. For example, Namimoto et al (15) found that the ADCs of malignant masses were significantly lower than the ADCs of benign masses (ie, hemangiomas and cysts) in the liver, although there was a small degree of overlap. Investigators in another study similarly found that hepatic hemangiomas, metastases, and hepatocellular carcinomas had different ADCs (16). Results of other studies showed that when appropriate techniques and ADC thresholds were used, high sensitivity and specificity in the differentiation between malignant and benign liver lesions could be achieved with diffusion-weighted imaging (17,18). With regard to the kidneys, it has been found that ADCs correlate with renal function (20,22). The feasibility and reproducibility of diffusion-weighted imaging in the assessment of renal function have been shown in a few relatively recent studies (23,24). However, literature on the evaluation of focal renal masses is sparse. Although renal lesions sometimes have been included in studies to investigate the feasibility, technique, and role of diffusion-weighted imaging in abdominal imaging overall (12,13,19), few studies have been dedicated to the assessment of diffusion-weighted imaging for evaluation of focal renal lesions (25).

Our study results demonstrate that renal lesions with different tissue contents may have different diffusion characteristics. Solid tumor tissue has lower ADCs compared with necrotic or cystic tumor tissue, in which the ADCs are lower than those in benign cysts. It also appears that the T1 signal characteristics of a lesion are related to the ADC of the lesion. For example, T1 hyperintense cysts have lower ADCs than do T1 hypointense cysts, and T1 hyperintense necrotic or cystic tumor areas have lower ADC values compared with their T1 hypointense counterparts. The underlying cause of the association between ADC and T1 signal is unknown. We speculate that this association may be related to the blood or proteinaceous contents that contribute to the high T1 signal in renal lesions. For example, both increases and decreases in brain tissue ADCs after hemorrhage have been reported (27,28). This is because in the brain, the hemorrhagic product undergoes a sequential evolution in chemical composition with time. It is conceivable that in a renal lesion, the hemorrhage, if present, would be mainly chronic at the time of imaging and therefore might have a single-direction influence on ADC values. When both ADC values and T1 features are considered, benign cysts can be differentiated from necrotic or cystic tumors, with only a small overlap in ADCs.

We learned two important facts from our study results: First, benign cysts and necrotic or cystic tumor areas have significantly different ADCs, even though they may have a similar appearance on conventional (eg, T1-weighted, T2-weighted, and contrast-enhanced) MR images. This is presumably because although the nonviable soft tissue in necrotic tumors does not enhance, unlike cystic fluid, it is solid and does lead to restricted water diffusion. Therefore, the ADC potentially can be used as an additional parameter for characterizing renal lesions. Second, the finding that the T1 signal is related to the ADC of a lesion may be important when diffusion-weighted imaging is performed to evaluate other lesions in the body. In other words, the T1 signal characteristics of a lesion might need to be taken into account when ADCs are interpreted to evaluate a disease process.

Our study had limitations. A major limitation was the relatively small patient sample, which was due in part to our attempt to limit the study population to patients with histopathologically confirmed findings. However, even though the patient sample was relatively small, we were able to demonstrate significant differences in ADCs among the different types of renal lesions and lesion areas. Another limitation was that because of the small patient sample, we did not include any tumors that were truly cystic—that is, without measurable soft-tissue components—such as multilocular cystic renal cell carcinoma or multicystic nephroma. Therefore, it is difficult to determine whether cystic tumors lined with thin layers of tumor cells demonstrate restricted diffusion to the same extent as necrotic or cystic areas of solid tumors. Further studies with larger patient populations and larger varieties of tumors are needed to confirm our preliminary findings.

In conclusion, the T1 signal characteristics of a renal lesion appear to be related to the ADC of the lesion. The ADC of a renal lesion potentially can be used as an additional parameter to help determine the appropriate clinical management.


   ADVANCES IN KNOWLEDGE
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
IMPLICATION FOR PATIENT CARE
 References
 


   IMPLICATION FOR PATIENT CARE
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
References
 


   ACKNOWLEDGMENTS
 
We thank Ada Muellner, BA, for editorial support.


   FOOTNOTES
 

Abbreviations: ADC = apparent diffusion coefficient • ROI = region of interest

Author contributions: Guarantor of integrity of entire study, J.Z.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, J.Z., Y.M.T.; clinical studies, J.Z., Y.M.T., L.W., L.H.S.; statistical analysis, N.M.I.; and manuscript editing, J.Z., Y.M.T., L.W., N.M.I., H.H.

Authors stated no financial relationship to disclose.


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 

  1. Semelka RC, Shoenut JP, Kroeker MA, MacMahon RG, Greenberg HM. Renal lesions: controlled comparison between CT and 1.5-T MR imaging with nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold FLASH techniques. Radiology 1992;182:425–430.[Abstract/Free Full Text]
  2. Bosniak MA. Problems in the radiologic diagnosis of renal parenchymal tumors. Urol Clin North Am 1993;20:217–230.[Medline]
  3. Hecht EM, Israel GM, Krinsky GA, et al. Renal masses: quantitative analysis of enhancement with signal intensity measurements versus qualitative analysis of enhancement with image subtraction for diagnosing malignancy at MR imaging. Radiology 2004;232:373–378.[Abstract/Free Full Text]
  4. Ho VB, Allen SF, Hood MN, Choyke PL. Renal masses: quantitative assessment of enhancement with dynamic MR imaging. Radiology 2002;224:695–700.[Abstract/Free Full Text]
  5. Rofsky NM, Bosniak MA. MR imaging in the evaluation of small (< or =3.0 cm) renal masses. Magn Reson Imaging Clin N Am 1997;5:67–81.[Medline]
  6. Srinivasan A, Goyal M, Azri FA, Lum C. State-of-the-art imaging of acute stroke. RadioGraphics 2006;26(suppl 1):S75–S95.
  7. Al-Okaili RN, Krejza J, Wang S, Woo JH, Melhem ER. Advanced MR imaging techniques in the diagnosis of intraaxial brain tumors in adults. RadioGraphics 2006;26(suppl 1):S173–S189.
  8. Gupta RK, Sinha U, Cloughesy TF, Alger JR. Inverse correlation between choline magnetic resonance spectroscopy signal intensity and the apparent diffusion coefficient in human glioma. Magn Reson Med 1999;41:2–7.[CrossRef][Medline]
  9. Yang D, Korogi Y, Sugahara T, et al. Cerebral gliomas: prospective comparison of multivoxel 2D chemical-shift imaging proton MR spectroscopy, echoplanar perfusion and diffusion-weighted MRI. Neuroradiology 2002;44:656–666.[CrossRef][Medline]
  10. Lam WW, Poon WS, Metreweli C. Diffusion MR imaging in glioma: does it have any role in the preoperation determination of grading of glioma? Clin Radiol 2002;57:219–225.[CrossRef][Medline]
  11. Lai PH, Ho JT, Chen WL, et al. Brain abscess and necrotic brain tumor: discrimination with proton MR spectroscopy and diffusion-weighted imaging. AJNR Am J Neuroradiol 2002;23:1369–1377.[Abstract/Free Full Text]
  12. Murtz P, Flacke S, Traber F, van den Brink JS, Gieseke J, Schild HH. Abdomen: diffusion-weighted MR imaging with pulse-triggered single-shot sequences. Radiology 2002;224:258–264.[Abstract/Free Full Text]
  13. Yoshikawa T, Kawamitsu H, Mitchell DG, et al. ADC measurement of abdominal organs and lesions using parallel imaging technique. AJR Am J Roentgenol 2006;187:1521–1530.[Abstract/Free Full Text]
  14. Yamada I, Aung W, Himeno Y, Nakagawa T, Shibuya H. Diffusion coefficients in abdominal organs and hepatic lesions: evaluation with intravoxel incoherent motion echo-planar MR imaging. Radiology 1999;210:617–623.[Abstract/Free Full Text]
  15. Namimoto T, Yamashita Y, Sumi S, Tang Y, Takahashi M. Focal liver masses: characterization with diffusion-weighted echo-planar MR imaging. Radiology 1997;204:739–744.[Abstract/Free Full Text]
  16. Ichikawa T, Haradome H, Hachiya J, Nitatori T, Araki T. Diffusion-weighted MR imaging with a single-shot echoplanar sequence: detection and characterization of focal hepatic lesions. AJR Am J Roentgenol 1998;170:397–402.[Abstract/Free Full Text]
  17. Taouli B, Vilgrain V, Dumont E, Daire JL, Fan B, Menu Y. Evaluation of liver diffusion isotropy and characterization of focal hepatic lesions with two single-shot echo-planar MR imaging sequences: prospective study in 66 patients. Radiology 2003;226:71–78.[Abstract/Free Full Text]
  18. Kim T, Murakami T, Takahashi S, Hori M, Tsuda K, Nakamura H. Diffusion-weighted single-shot echoplanar MR imaging for liver disease. AJR Am J Roentgenol 1999;173:393–398.[Abstract/Free Full Text]
  19. Ichikawa T, Haradome H, Hachiya J, Nitatori T, Araki T. Diffusion-weighted MR imaging with single-shot echo-planar imaging in the upper abdomen: preliminary clinical experience in 61 patients. Abdom Imaging 1999;24:456–461.[CrossRef][Medline]
  20. Namimoto T, Yamashita Y, Mitsuzaki K, Nakayama Y, Tang Y, Takahashi M. Measurement of the apparent diffusion coefficient in diffuse renal disease by diffusion-weighted echo-planar MR imaging. J Magn Reson Imaging 1999;9:832–837.[CrossRef][Medline]
  21. Muller MF, Prasad PV, Bimmler D, Kaiser A, Edelman RR. Functional imaging of the kidney by means of measurement of the apparent diffusion coefficient. Radiology 1994;193:711–715.[Abstract/Free Full Text]
  22. Toyoshima S, Noguchi K, Seto H, Shimizu M, Watanabe N. Functional evaluation of hydronephrosis by diffusion-weighted MR imaging: relationship between apparent diffusion coefficient and split glomerular filtration rate. Acta Radiol 2000;41:642–646.[CrossRef][Medline]
  23. Thoeny HC, De Keyzer F, Oyen RH, Peeters RR. Diffusion-weighted MR imaging of kidneys in healthy volunteers and patients with parenchymal diseases: initial experience. Radiology 2005;235:911–917.[Abstract/Free Full Text]
  24. Thoeny HC, Zumstein D, Simon-Zoula S, et al. Functional evaluation of transplanted kidneys with diffusion-weighted and BOLD MR imaging: initial experience. Radiology 2006;241:812–821.[Abstract/Free Full Text]
  25. Cova M, Squillaci E, Stacul F, et al. Diffusion-weighted MRI in the evaluation of renal lesions: preliminary results. Br J Radiol 2004;77:851–857.[Abstract/Free Full Text]
  26. Chan JH, Tsui EY, Luk SH, et al. MR diffusion-weighted imaging of kidney: differentiation between hydronephrosis and pyonephrosis. Clin Imaging 2001;25:110–113.[CrossRef][Medline]
  27. Hiwatashi A, Kinoshita T, Moritani T, et al. Hypointensity on diffusion-weighted MRI of the brain related to T2 shortening and susceptibility effects. AJR Am J Roentgenol 2003;181:1705–1709.[Free Full Text]
  28. Atlas SW, DuBois P, Singer MB, Lu D. Diffusion measurements in intracranial hematomas: implications for MR imaging of acute stroke. AJNR Am J Neuroradiol 2000;21:1190–1194.[Abstract/Free Full Text]



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