Prostate Density Calculator Cheng

Prostate Volume and Density Formulas:

\[ V = \frac{\pi}{6} \times L \times W \times H \] \[ \rho = \frac{PSA}{V} \]

Length (L):

Width (W):

Height (H):

PSA:

ng/ml

Volume (V): cm³

Density (ρ): ng/ml/cm³

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1. What is the Prostate Density Calculator (Cheng method)?

Definition: This calculator estimates prostate volume using ellipsoid formula and calculates PSA density from PSA value and volume.

Purpose: It helps urologists assess prostate cancer risk by calculating PSA density, which is PSA level normalized by prostate volume.

2. How Does the Calculator Work?

The calculator uses the formulas:

\[ V = \frac{\pi}{6} \times L \times W \times H \] \[ \rho = \frac{PSA}{V} \]

Where:

\( V \) — Prostate volume (cm³)
\( L \) — Length (cm)
\( W \) — Width (cm)
\( H \) — Height (cm)
\( \rho \) — PSA density (ng/ml/cm³)
\( PSA \) — Prostate-specific antigen (ng/ml)

Explanation: The prostate is modeled as an ellipsoid, and volume is calculated using the ellipsoid formula. PSA density is then derived by dividing PSA value by this volume.

3. Importance of PSA Density

Details: PSA density helps differentiate between benign prostatic hyperplasia and prostate cancer. Higher density (>0.15 ng/ml/cm³) may indicate increased cancer risk.

4. Using the Calculator

Tips: Enter prostate dimensions (L, W, H) from TRUS or MRI in cm, and PSA value in ng/ml. All dimension values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the Cheng method?
A: It's a standard ellipsoid formula for prostate volume calculation using length, width, and height measurements.

Q2: What's a normal PSA density?
A: Typically <0.15 ng/ml/cm³ is considered normal, but interpretation should be done by a urologist.

Q3: How accurate is this calculation?
A: It provides a good estimate but may differ from actual volume by ±10-15% compared to more precise methods.

Q4: What imaging is used for measurements?
A: Transrectal ultrasound (TRUS) or MRI are most commonly used to obtain prostate dimensions.

Q5: Why is PSA density important?
A: It helps adjust PSA values for prostate size, as larger prostates naturally produce more PSA.