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Body Diffusion-Weighted MR Imaging Using High b -Value for Malignant Tumor Screening Usefulness and Necessity of Referring to T2-Weighted Images and Creating Fusion Images

Posted May 31, 2007 Updated Apr 7, 2023
By Yoshito Tsushima MD , Akie Takano MD , Ayako Taketomi-Takahashi MD , Keigo Endo MD
5 min read

Rationale and Objectives

To evaluate the potential usefulness of high b -value body diffusion-weighted images (DWIs) as a screening tool in the depiction of abdominal malignant tumors.

Materials and Methods

We selected 110 abdominal magnetic resonance examinations (1.5 T; 60 men; age range, 25–90 years) with and without malignant tumors ( n = 37 and n = 73, respectively). Axial DWIs were obtained by single-shot spin-echo (SE) type echo planar imaging (EPI) sequence with inversion pulse (repetition time, 6,800 msec; echo time, 100 msec; T1, 150 msec; b value, 1,000 sec/mm 2 ) without breath-holding. Two radiologists independently interpreted the DWIs, T2-weighted images (T2-WI), all three types of images including DWIs, T2-WIs, and fusion images at the same time (DWIs + T2-WIs + fusion) with 7–14 days’ interval, and the diagnostic confidence for each patient was scored.

Results

The area under the curve (AUC) of the composite receiver operating characteristic (ROC) curve of DWIs + T2-WIs + fusion (0.904) was significantly higher than those of DWIs (0.720; P < .001) and T2-WIs (0.822; P < .05). Both sensitivity and specificity were higher in DWIs + T2-WIs + fusion (89.5% and 81.9%, respectively) compared with those of DWIs (72.4% and 59.0%; P < .01 and P < .001, respectively).

Conclusions

Abdominal high b -value DWIs have a high sensitivity and specificity for malignant tumors when T2-WIs are referred and image fusion technique is employed, suggesting that it may potentially be a new screening tool.

Recent advances in magnetic resonance (MR) technology allow us to obtain diffusion-weighted images (DWIs) with high b -factor not only in the brain but in the body, and the image quality of body DWIs has improved even under a free breathing using a short TI inversion recovery echo planar imaging sequence that allows potent fat suppression ( ).

There have been several reports that showed the high ability of body DWIs to detect various malignant tumors ( ). For instance, Ichikawa et al ( ) reported that the high b -value DWIs allow detection of colorectal adenocarcinoma with a high sensitivity and specificity, and Nasu et al ( ) reported that combined reading of DWIs, and T1- and T2-weighted images had the higher accuracy in the detection of hepatic metastases than did reading of superparamagnetic iron oxide particles (SPIO)-enhanced MR images. These reports let us suggest the potential capability of body DWIs as a screening tool for malignant tumors.

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Materials and methods

Patients

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MR Imaging

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CT Imaging

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Image Fusion Between DWIs and T2-WIs

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Image Analyses

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Statistical Analysis

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Results

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Table 1

Results of Receiver Operating Characteristic Analyses of Two Readers

Reader 1 Reader 2 Composite AUC Sens. Spec. AUC Sens. Spec. AUC Sens. Spec. DWIs 0.667 73.7% 45.8% 0.763 71.1% 72.2% 0.720 72.4% 59.0% *2 *1 *1 T2-WIs 0.856 *2 89.5% *1 51.4% *3 0.810 71.1% 86.1% *1 0.822 *3 80.3% *2 68.8% *3 *2 *1 *2 DWIs+T2-WIs+Fusion 0.931 94.7% 76.4% 0.883 84.2% 87.5% 0.904 89.5% 81.9%

AUC = area under curve; Sens. = sensitivity; Spec. = specificity.

*1 P < 0.05; *2 P < 0.01; *3 P < 0.001; Bonferroni’s method was applied.

Figure 1, Receiver operating characteristic (ROC) curves from the composite data. Area under the curve of the composite ROC curve of diffusion-weighted images (DWIs) + T2-WIs + fusion (0.904) was significantly higher that those of DWIs (0.720; P < .001) and T2-WIs (0.822; P < .05).

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Figure 2, (a) Diffusion-weighted image (DWI). (b) T2-weighted first spin echo image. (c) Fusion image. A 79-year-old man with pancreatic head carcinoma. There is a faint high signal at the pancreatic head on DWI, but this signal may be due to normal duodenum (The intestinal content sometimes show faint signal on DWIs). However, T2-WIs shows biliary tract dilatation (not seen on the presented image) and the fusion image clarify that the abnormal signal on DWI is located in the pancreatic head. Reader 1 changed her category 3 on DWI to category 4 on the fusion image. Reader 2 also changed category 1 to category 5.

Figure 3, (a) Diffusion-weighted image (DWI). (b) T2-weighted first spin echo image. (c) Fusion image. A 56-year-old woman with advanced gastric carcinoma. The gastric wall is diffusely high signal on DWI, and both readers categorized this patient as 4. On T2-WIs, the gastric wall thickening may be recognized, but both readers overlooked this abnormality and categorized it as 1. On the fusion images, both readers categorized as 5.

Figure 4, (a) Diffusion-weighted image (DWI). (b) T2-weighted first spin echo image. (c) Fusion image. A 37-year-old woman with uterine leiomyoma. The high signal intensity in the pelvic cavity was recognized as a possible rectal carcinoma by reader 1 and ovarian carcinoma by reader 2, but the T2-weighted image and fusion image clarified that this mass lesion originates from the uterus, and leiomyoma was the most likely diagnosis. Reader 1 changed her category 4 on DWI to category 2 on the fusion image. Reader 2 also changed her category 4 to category 1

Figure 5, (a) Diffusion-weighted image (DWI). (b) T2-weighted first spin echo image. (c) Fusion image. A 47-year-old man without malignant tumor. There is a spotty high signal in the left upper abdomen on DWI suggestive of colon carcinoma. However, on T2-weighted image, the colon was collapsed and no tumorous lesion was recognized. Enhanced computed tomography failed to demonstrate any colonic tumors. Reader 1 changed her category 4 on DWI to category 2 on the fusion image. Reader 2 also changed category 3 to category 2.

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Discussion

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References

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Academic Radiology, Volume 14, Issue 6
Journals General Radiology
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