Korean J Radiol.  2013 Feb;14(1):61-69. 10.3348/kjr.2013.14.1.61.

Diffusion-Weighted Magnetic Resonance Imaging for the Evaluation of Prostate Cancer: Optimal B Value at 3T

• Koo JH
• Kim CK
• Choi D
• Park BK
• Kwon GY
• Kim B

• KMID: 1430045
• DOI: http://doi.org/10.3348/kjr.2013.14.1.61

Abstract

OBJECTIVE
To retrospectively determine the optimal b value of diffusion-weighted imaging (DWI) for predicting the presence of localized prostate cancer, and to evaluate the utility of DWI under different b values in differentiating between cancers and benign prostatic tissues.
MATERIALS AND METHODS
Eighty patients with suspected prostate cancer underwent MRI including DWI at 3T, followed by radical prostatectomy. DWI was examined under different b values. Apparent diffusion coefficient (ADC) maps were generated by using b = 0, and other b values of 300, 700, 1000 or 2000 s/mm2. For predicting the presence of cancers, four different ADC maps were analyzed independently by two blinded readers. ADCs were measured in benign and malignant tissues.
RESULTS
For predicting the presence of 110 prostate cancers, the sensitivity and area under the curve (AUC) for an experienced reader was significantly greater at b = 1000 (85% and 0.91) than b = 300, 700 or 2000 s/mm2 (p < 0.01). For a less-experienced reader, the AUC was significantly greater at b = 700, 1000 or 2000 than b = 300 s/mm2 (p < 0.01). Mean ADCs of the cancers in sequence from b = 300 to 2000 s/mm2 were 1.33, 1.03, 0.88 and 0.68 x 10(-3) mm2/s, which were significantly lower than those of benign tissues (p < 0.001).
CONCLUSION
The optimal b value for 3T DWI for predicting the presence of prostate cancer may be 1000 s/mm2.

Keyword

Diffusion-weighted MR imaging; Prostate neoplasm; Apparent diffusion coefficient; Diagnosis

MeSH Terms

Aged
Aged, 80 and over
Area Under Curve
Biopsy
Diagnosis, Differential
Diffusion Magnetic Resonance Imaging/*methods
Humans
Male
Middle Aged
Neoplasm Staging
Predictive Value of Tests
Prostate-Specific Antigen/blood
Prostatectomy
Prostatic Neoplasms/*diagnosis/pathology/surgery
Retrospective Studies
Sensitivity and Specificity

Figure

• 

  Fig. 1 Prostate cancer in left transition zone (TZ) in 72-year-old man. A. Transverse T2-weighted turbo spine echo image shows ill-defined, low-signal lesions in both TZs. B-E. Transverse apparent diffusion coefficient (ADC) maps of b = 300 (B), 700 (C), 1000 (D) and 2000 s/mm2 (E) show focally restricted mass (arrow) in only left TZ (measured ADC of cancer = 1.57, 0.96, 0.88 and 0.69 × 10-3 mm2/s in sequence). Surgical specimen confirmed cancer in corresponding site on ADC maps.

• 

  Fig. 2 Prostate cancer in peripheral zone (PZ) of left mid-gland in 71-year-old man. A. Transverse T2-weighted turbo spin echo image shows ill-defined, low-signal lesions in both PZs. B-E. Transverse apparent diffusion coefficient (ADC) map of b = 1000 s/mm2 (D) shows well-delineated, restricted mass (arrow) in left PZ. However, mass is obscure on transverse ADC maps of b = 300 (B), 700 (C and 2000 (E) s/mm2. Surgical specimen confirmed cancer in left PZ.

• 

  Fig. 3 Results of ROC curve analyses for predicting prostate cancer location for experienced (A) and less-experienced (B) readers. AUC = area under curve, ROC = receiver operating characteristic

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