Dose Length Product Estimate Calculator

Dose Length Product (DLP) is estimated using:

DLP = CTDIvol × L

For multiple series:

DLP_total = (CTDIvol × L) × N

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A common effective dose estimate uses a region conversion factor k:

E ≈ DLP_total × k

This effective dose is a population-average approximation, not a patient-specific dose.

1. Select a computation method.
2. Enter CTDIvol and scan length, or measured DLP.
3. Set the number of series for multi-phase protocols.
4. Choose a body region or enter a custom k factor.
5. Press Calculate to view results above.
6. Use CSV or PDF buttons to export your results.

Values are illustrative for learning and protocol comparisons.

1) Why Dose Length Product matters

Dose Length Product (DLP) summarizes scanner output across a scanned distance. It multiplies dose intensity by length, giving a single value that helps compare protocols, series counts, and coverage changes. DLP is commonly reported by CT systems and used in audits and dose-tracking dashboards.

2) Core inputs: CTDIvol and scan length

This calculator can derive DLP from CTDIvol and scan length. CTDIvol is typically shown in mGy and reflects output for a standardized phantom, while scan length is entered in cm. The basic relationship is linear: doubling the length doubles the estimated DLP when CTDIvol stays constant.

3) Multi-series protocols and totals

Many exams include multiple series such as non-contrast, arterial, and venous phases. If each series uses similar settings, total DLP can be approximated by multiplying the single-series estimate by the number of series. If series settings differ, compute each series separately and add the values for the most accurate total.

4) Effective dose estimation with k factors

To convert DLP into an approximate effective dose, a region-specific factor k (mSv per mGy·cm) is applied. Typical adult reference factors vary by body region and age group. The built-in presets provide convenient starting points, while the custom k option supports your local coefficients.

5) Units, rounding, and data quality

Keep units consistent: CTDIvol in mGy, length in cm, DLP in mGy·cm, and effective dose in mSv. Small entry errors can propagate, especially for long scan ranges. Use realistic rounding: one decimal for CTDIvol and length is usually adequate, while totals can be shown to the nearest whole mGy·cm.

6) Interpreting results for protocol review

Use derived DLP to compare versions of a protocol, evaluate the impact of extending coverage, or track dose changes across scanners. For example, increasing length from 30 cm to 45 cm at the same CTDIvol raises DLP by 50%. This type of sensitivity check is useful during protocol optimization.

7) Practical checks before exporting

Before exporting CSV or PDF, confirm that the selected mode matches your data source. If you have a measured DLP, choose the measured option to avoid double-counting. For derived estimates, verify the series count and region selection. These checks keep your exports consistent for reporting and comparisons.

8) Limitations and responsible use

DLP and effective dose are population-based metrics and do not represent patient-specific absorbed dose. Factors like patient size, tube current modulation, scan range overlap, and reconstruction choices can change risk-relevant dose distributions. Treat outputs as estimates for quality management, not clinical decision-making.

1) What is the difference between CTDIvol and DLP?

CTDIvol describes scanner output intensity for a standardized phantom. DLP multiplies that intensity by scan length, giving a protocol-level total that grows with longer coverage and additional series.

2) When should I use “Measured DLP” mode?

Use it when the scanner already reports DLP for the series or exam. This avoids re-deriving the value and reduces the chance of unit or length entry mistakes.

3) How do I handle protocols with different phases?

If phases use different CTDIvol or lengths, calculate each phase separately and add DLPs. If phases are similar, using the series count can provide a quick estimate.

4) What does the k factor represent?

It is a conversion coefficient that estimates effective dose from DLP for a body region. It is derived from reference models and is intended for population-average comparisons, not individual dose.

5) Why does effective dose change when I switch regions?

Different organs have different radiation sensitivities and typical scan geometries. Region-specific k factors reflect these differences, so the same DLP can map to different effective dose estimates.

6) Are these results suitable for patient counseling?

No. These values are estimates for protocol management and reporting. Patient-specific dose and risk depend on anatomy, size, and exam details. Follow your clinical and physics guidance for communication.

7) What is a reasonable way to validate my inputs?

Compare your derived DLP with the scanner’s reported DLP for a similar exam. Large differences usually indicate a unit mismatch, incorrect length, or an incorrect number of series.