Body diffusion-weighted MR imaging of uterine endometrial cancer: Is it helpful in the detection of cancer in nonenhanced MR imaging?

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Abstract

Objective

In this study, the authors discussed the feasibility and value of diffusion-weighted (DW) MR imaging in the detection of uterine endometrial cancer in addition to conventional nonenhanced MR images.

Methods and materials

DW images of endometrial cancer in 23 patients were examined by using a 1.5-T MR scanner. This study investigated whether or not DW images offer additional incremental value to conventional nonenhanced MR imaging in comparison with histopathological results. Moreover, the apparent diffusion coefficient (ADC) values were measured in the regions of interest within the endometrial cancer and compared with those of normal endometrium and myometrium in 31 volunteers, leiomyoma in 14 patients and adenomyosis in 10 patients. The Wilcoxon rank sum test was used, with a p < 0.05 considered statistically significant.

Results

In 19 of 23 patients, endometrial cancers were detected only on T2-weighted images. In the remaining 4 patients, of whom two had coexisting leiomyoma, no cancer was detected on T2-weighted images. This corresponds to an 83% detection sensitivity for the carcinomas. When DW images and fused DW images/T2-weighted images were used in addition to the T2-weighted images, cancers were identified in 3 of the remaining 4 patients in addition to the 19 patients (overall detection sensitivity of 96%). The mean ADC value of endometrial cancer (n = 22) was (0.97 ± 0.19) × 10−3 mm2/s, which was significantly lower than those of the normal endometrium, myometrium, leiomyoma and adenomyosis (p < 0.05).

Conclusion

DW imaging can be helpful in the detection of uterine endometrial cancer in nonenhanced MR imaging.

Introduction

Diffusion-weighted (DW) MR imaging visualizes a random microscopic motion of molecules (Brownian motion) and thereby provides a tissue contrast different from that of conventional T1- and T2-weighted images. Recently, it is attractive in the detection of malignant tumors and the histologic characterization of focal lesions in the abdomen. DW imaging was primarily used in imaging the central nervous system, especially in cases of acute ischemic stroke, which causes a decrease of water diffusion compared with that of normal tissue [1], [2], [3]. Determination of the apparent diffusion coefficient (ADC) values on high b value DW images is currently a good imaging method for quantifying in vivo water diffusion. It was reported that high b value DW images showed high signal intensity for malignant tumors relative to normal tissue or benign lesions, with lower ADC values for the former [4], [5], [6], [7], [8], [9], [10], [11], [12]. However, the application of high b value DW imaging to the abdomen has been hindered by the presence of bulky physiologic motions such as respiration, peristalsis, and blood flow. Thus, to reduce respiratory motion, the patient must hold their breath during the examination. Such an approach limits the acquisition time, and both the signal to noise ratio and the spatial resolution are compromised as a result. To resolve these issues, in 2004, Takahara et al. reported a high b value DW MR imaging technique that tolerated free breathing, and afforded multiple and thin slice excitations with signal averaging over an extended period of time [13].

In the conventional MR imaging of endometrial cancer, T1- and T2-weighted images and contrast-enhanced images were performed, which were useful in detecting malignant lesions and to diagnose the extent of lesions [14], [15], [16], [17], [18]. However, it was difficult to detect malignant lesions in some cases where the endometrium was not thickened or in some cases with myometrial involvement of leiomyoma or adenomyosis [19], [20]. We then considered whether DW imaging in addition to nonenhanced MR imaging could be useful in the detection of endometrial cancer.

In this study, we discussed the feasibility and additional value of body DW imaging and ADC values when coupled with conventional nonenhanced MR images for the detection of uterine endometrial cancer.

Section snippets

Study populations

This was a retrospective study conducted at a single institution over a period of 15 months, and included 23 female patients with histologically proven endometrial cancer of the uterus (mean age: 60.0 years ±8.7 (standard deviation); age range: 43–78 years). MR imaging was performed in order to assess the extent of the cancer and local staging following histopathological confirmation by biopsy under hysteroscopy. All patients obtained a total hysterectomy between 14 and 34 days after the MR

Image analysis

  • (1)

    Two abdominal radiologists (Y.I., M.M.), with 5 and 15 years of individual experience, were blinded to the localization of the cancer but knew the age of the patients and whether patients were pre- or post-menopausal. At first, they read the T2-weighted images to detect the cancer. Endometrial cancer was diagnosed in cases with a thickened endometrium and low signal intensity relative to a normal endometrium. This was more than 10 mm in pre-menopausal patients and more than 4 mm in

Results

  • (1)

    The histopathological results proved adenocarcinoma in all of the 23 patients. In addition to the endometrial cancer, 9 patients had coexisting leiomyoma, 2 had adenomyosis and 2 had both. Based on a 1997 TNM system, the patients were pathologically divided into groups: pT1a (n = 3), pT1b (n = 12), pT1c (n = 2), pT2b (n = 2), pT3a (n = 3) and pT3c (n = 1).

  • (2)

    There was no disagreement between diagnoses of the two readers. In 19 of 23 patients, endometrial cancers were detected only on T2-weighted images and

Discussion

In the detection and evaluation of uterine endometrial cancer, conventional MR imaging, particularly T2-weighted imaging, are very useful. On the T2-weighted images, endometrial cancer shows a thickened endometrium with low signal intensity relative to normal endometrium, the thickness of which is more than 10 mm in pre-menopausal women and more than 4 mm in post-menopausal women [14]. On the contrast-enhanced T1-weighted images, cancer shows lower signal intensity than normal myometrium and in

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