3-T MRI with Phased-array Coil in Local Staging of Prostatic Cancer

Rationale and Objectives

To evaluate the diagnostic accuracy of a 3-T magnetic resonance imaging (MRI) system with a phased-array coil (3T MRI) in the local staging of prostatic cancer.

Materials and Methods

Between July 2004 and September 2007, 59 patients (mean age 66 years) with a histologic diagnosis of prostatic cancer underwent 3-T MRI with a phased-array coil. A total of 42/59 patients underwent a radical prostatectomy within 3 weeks of the MRI examination. Two radiologists with differing experience in the interpretation of prostatic imaging used a 1–5 scale score to assess extracapsular spread, seminal vesicle and neurovascular bundle infiltration, and prostatic apex involvement. The anatomopathologic examination conducted on histologic macrosections was the reference test used to evaluate the results of 3-T MRI. Interobserver reliability was assessed using the k value.

Results

The sensitivity, specificity, and accuracy values obtained by the expert radiologist were 68%, 92%, and 83%, respectively, compared to 50%, 85%, and 71% for the identification of extracapsular spread and 81%, 62%, and 84% compared to 63%, 50%, and 55% for apex involvement. Interobserver reliability was good (k = 0.71). Seminal vesicle infiltration was correctly identified in four of five cases and neurovascular bundle infiltration was identified in four of four cases.

Conclusions

Despite presenting diagnostic accuracy values lower than those reported in literature using 1.5-T endorectal coil MRI, the use of 3-T MRI with a phased-array coil could constitute a valid alternative to MRI techniques using endorectal coils in selected patients. Direct comparative studies between the two methods on large caseloads are required to confirm this hypothesis.

Although its use has yet to be univocally accepted in the urology sector and it presents artifact-related, technical, and methodologic problems, endorectal coil magnetic resonance imaging (erMRI) using 1.5-T magnets is still considered the most accurate imaging technique in the local staging of prostate cancer ( ). In recent years, MRI appliances with field intensities of 3 T (3-T MRI) or higher that guarantee an outstanding signal-to-noise ratio, on account of the significant increase in the signal that can be obtained compared to 1.5-T appliances, have become commonplace. A number of recently published works have assessed the results that can be obtained using 3-T MRI, both with a phased-array coil and an endorectal coil, in terms of image quality and diagnostic accuracy in evaluating prostate cancer ( ). The results of these evaluations are contrasting; some authors ( ) confirm that erMRI remains the technique of election for prostate cancer staging, whereas others ( ) argue that the performance of 3-T MRI with phased-array coils is comparable to that of erMRI, without the drawbacks, costs, and artifacts connected to the endorectal coil technique.

The aim of our study is to evaluate the diagnostic accuracy of 3-T MRI with phased-array coils in the local staging of prostatic cancer.

Materials and methods

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Results

Extracapsular Extension

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Table 1

Comparative Evaluation of Extraprostatic Spread and Matched Values of Diagnostic Accuracy

Capsule Expert Radiologist Less Expert Radiologist Involved Spared Involved Spared Pathology Involved 11 5 8 8 Spared 2 24 4 22 Sensitivity (%) 68 50 Specificity (%) 92 85 PPV (%) 85 67 NPV (%) 83 73 Accuracy (%) 83 71 K 0.70

NPV: negative predictive value; PPV: positive predictive value.

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Seminal Vesicle Infiltration

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Neurovascular Bundle Infiltration

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Prostatic Apex Involvement

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Table 2

Comparative Evaluation of Involvement of Glandular Apex and Matched Values of Diagnostic Accuracy

Apex Expert Radiologist Less Expert Radiologist Involved Spared Involved Spared Pathology Involved 13 3 10 6 Spared 10 16 13 13 Sensitivity (%) 81 63 Specificity (%) 62 50 PPV (%) 57 44 NPV (%) 84 68 Accuracy (%) 69 55 K .71

NPV: negative predictive value; PPV: positive predictive value.

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Discussion

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3-T MRI with Phased-array Coil in Local Staging of Prostatic Cancer

Rationale and Objectives

Materials and Methods

Results

Conclusions

Materials and methods

Results

Extracapsular Extension

Seminal Vesicle Infiltration

Neurovascular Bundle Infiltration

Prostatic Apex Involvement

Discussion

References

Further Reading

A Comparison of World Wide Web Resources for Identifying Medical Information

Abstracts of Funded National Institutes of Health Grants

American Registry of Radiologic Technology