DwellTimeValidator

Dwell Time Validator

activity brachytherapy dosimetry source calibration TG-43
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Dwell Time Validator — Brachytherapy Dwell Time Validation (AAPM TG-59)

ℹ️ The utility checks correctness of dwell time distribution across source positions in a channel.
ℹ️ Controlled parameters: time sum vs plan, anomalous peaks (hot spots), index integrity.
ℹ️ Processing: only the FIRST record in input.csv file.
⚠️ Critical for HDR brachytherapy! Dwell time errors can lead to local overdosing (necrosis) or target underdosing.

Usage:
DwellTimeValidator.exe → demo mode
DwellTimeValidator.exe input.csv output.json → validate data (first record only)

Input format:
PatientID,ChannelID,TotalPositions,TotalDwellTimeSec,MaxSingleDwellSec,MaxDwellPositionIndex,PlannedTotalTimeSec,MaxAllowedSingleSec

Example (time in seconds, safety limits):
PT-2026-CERVIX-05,CH-03,12,185.5,42.0,7,184.0,30.0

— WHY IS THIS NEEDED?
In brachytherapy, source stops at multiple positions. Planning or transfer errors can create a "hot spot".
• Total time must match TPS plan (~2% tolerance).
• Single position time must not exceed protocol limit (typically 20–30 sec to prevent applicator movement).
• Position index must be within channel length.
• Automated check eliminates human factor in routine QA.
⚠️ CRITICAL:
• Hot Spot (exceeding position limit) — risk of mucosal or healthy tissue necrosis.
• Sum mismatch >5% — possible plan export error or source change issue.
• Invalid index — sign of corrupted plan file.
Critical parameters:
• Time sum tolerance: ±2% (Warning), ±5% (Fail)
• Single position limit: typically 20–30 sec (depends on protocol)
• Index integrity: 1 ≤ Index ≤ TotalPositions
⚠️ Note: Utility automatically marks channel as FAIL if hot spot or critical sum mismatch detected. Result includes status (PASS/WARNING/FAIL) and bilingual recommendation (RU/EN).

input.csv

PatientID,ChannelID,TotalPositions,TotalDwellTimeSec,MaxSingleDwellSec,MaxDwellPositionIndex,PlannedTotalTimeSec,MaxAllowedSingleSec
PT-2026-CERVIX-05,CH-03,12,185.5,42.0,7,184.0,30.0

URS & FS — user requirements and functional specification

This document defines user requirements and functional specification for the quality-control utility. It supports deployment discussion, IQ/OQ preparation and QC workflow integration.

Utility: DwellTimeValidatorAPI / object: Dwell Time ValidatorCategory: Radiation physics

1. Scope

The Dwell Time Validator utility is used for Dwell Time Validator. The actual input.csv is the source of truth for the input structure; control criteria are defined by the executable and the domain description.

The utility does not use machine learning; decisions are produced by deterministic rules.

Categories: Radiation physics

Tags: activity, brachytherapy, dosimetry, source calibration, TG-43

2. Execution modes

DwellTimeValidator.exe                            → demo mode
DwellTimeValidator.exe input.csv output.json      → validate data (first record only)

3. Key controlled areas

  • activity, decay and radiochemical purity

4. Domain limits and critical parameters

  • ⚠️ Critical for HDR brachytherapy! Dwell time errors can lead to local overdosing (necrosis) or target underdosing.
  • ⚠️ CRITICAL:
  • Hot Spot (exceeding position limit) — risk of mucosal or healthy tissue necrosis.
  • Sum mismatch >5% — possible plan export error or source change issue.
  • Invalid index — sign of corrupted plan file.
  • Critical parameters:
  • Time sum tolerance: ±2% (Warning), ±5% (Fail)
  • Single position limit: typically 20–30 sec (depends on protocol)
  • Index integrity: 1 ≤ Index ≤ TotalPositions
  • ⚠️ Note: Utility automatically marks channel as FAIL if hot spot or critical sum mismatch detected. Result includes status (PASS/WARNING/FAIL) and bilingual recommendation (RU/EN).
Limits stated in the description must be verified against the current approved specification, pharmacopoeial monograph and registration dossier before production use.

5. URS — user requirements

IDRequirementCriticalityAcceptance criterion
URS-001The system shall accept an input.csv file for Dwell Time Validator with the exact columns listed in the “Input data contract” section.HighA file with the correct header is processed without manual editing; missing mandatory columns produce FAIL/import error.
URS-002The system shall support execution without arguments in demo mode and execution with input.csv output.json for user data.MediumBoth execution scenarios produce a predictable result or clear diagnostic error.
URS-003The system shall perform rule-based controls for: activity, decay and radiochemical purity.HighEach controlled parameter receives a status and message; the result does not depend on hidden Excel formulas or ML.
URS-004The system shall preserve traceability between batch/lot, source values, applied rules and final verdict.HighOutput includes batch identifier, source values, parameter statuses and critical findings.
URS-005The system shall generate machine-readable output.json for LIMS/ELN/MES, batch record and QA/QC review.HighJSON contains overall status, check array, warnings, failures and source-file reference.
URS-006The system shall support use in the client validation package: URS/FS, IQ/OQ preparation, installation and operational scenario checks.HighThe document, test scenarios and reproducible CSV/JSON flow are suitable for audit and internal approval.
URS-007The system shall clearly separate technical data errors from specification nonconformities.MediumSchema/type errors are not mixed with pharmacopoeial deviations and are reported separately.

6. input.csv data contract

The source of truth for the input schema is the actual input.csv header. Column names are technical identifiers and are not translated.

#ColumnTypeUnitDescriptionSampleControl rule
1PatientIDtextas specifiedPatient IDPT-2026-CERVIX-05mandatory value; format and acceptability are checked by the utility
2ChannelIDtextas specifiedChannel IDCH-03mandatory value; format and acceptability are checked by the utility
3TotalPositionsdecimalas specifiedTotal Positions12mandatory numeric value; rule comparison is performed by the utility
4TotalDwellTimeSecdecimalminTotal Dwell Time Sec185.5mandatory numeric value; rule comparison is performed by the utility
5MaxSingleDwellSecdecimalas specifiedMax Single Dwell Sec42.0mandatory numeric value; rule comparison is performed by the utility
6MaxDwellPositionIndexdecimalas specifiedMax Dwell Position Index7mandatory numeric value; rule comparison is performed by the utility
7PlannedTotalTimeSecdecimalas specifiedPlanned Total Time Sec184.0mandatory numeric value; rule comparison is performed by the utility
8MaxAllowedSingleSecdecimalas specifiedMax Allowed Single Sec30.0mandatory numeric value; rule comparison is performed by the utility

CSV example

PatientID,ChannelID,TotalPositions,TotalDwellTimeSec,MaxSingleDwellSec,MaxDwellPositionIndex,PlannedTotalTimeSec,MaxAllowedSingleSec
PT-2026-CERVIX-05,CH-03,12,185.5,42.0,7,184.0,30.0

7. FS — functional specification

IDFunctionImplementation description
FS-001CLI entry pointThe executable DwellTimeValidator.exe supports demo mode and input.csv output.json processing mode.
FS-002CSV parserThe import module reads CSV, validates header, column presence/order, value count and encoding. Decimal values are expected with a dot separator.
FS-003Field conversionEach column is converted to the expected type: identifier, text, decimal number, date/time or boolean flag.
FS-004Domain rule engineFor Dwell Time Validator, explicit rules are applied: range, minimum, maximum, absence of prohibited flag, data completeness or calculation-based check.
FS-005Criticality handlingCritical violations produce FAIL; non-critical deviations and incomplete data produce WARNING; full conformance produces PASS.
FS-006JSON writeroutput.json stores overall status, per-parameter results, source values, warnings, failures and diagnostic messages.
FS-007Integration contractThe CSV → JSON format is stable for invocation from LIMS/ELN/MES, scheduled task or wrapper service.
FS-008Error handlingSchema error, missing file, non-numeric value or JSON write failure returns diagnosable error without silent PASS.

8. output.json contract

The output file must be suitable for automated processing, audit review and correlation with the source input.csv row.

{
  "utility": "DwellTimeValidator",
  "api": "Dwell Time Validator",
  "batchNumber": "",
  "overallStatus": "PASS|WARNING|FAIL",
  "checkedAtUtc": "2026-05-18T00:00:00Z",
  "checks": [
    {
      "parameter": "PatientID",
      "value": "PT-2026-CERVIX-05",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "ChannelID",
      "value": "CH-03",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "TotalPositions",
      "value": "12",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "TotalDwellTimeSec",
      "value": "185.5",
      "unit": "min",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "MaxSingleDwellSec",
      "value": "42.0",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "MaxDwellPositionIndex",
      "value": "7",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "PlannedTotalTimeSec",
      "value": "184.0",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "MaxAllowedSingleSec",
      "value": "30.0",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    }
  ],
  "criticalFindings": [],
  "sourceFile": "input.csv"
}

9. OQ/PQ test scenarios

IDScenarioExpected result
TC-001Valid CSV with expected header and sample rowAll rows are processed; output contains PASS/WARNING/FAIL and parameter-level detail.
TC-002A mandatory input.csv column is missingImport is rejected or the row receives FAIL with schema reference.
TC-003A numeric field contains text or a blank valueType conversion error is recorded; the result is not hidden as PASS.
TC-004A parameter is outside specification or critical limitCritical parameters produce FAIL; non-critical deviations produce WARNING according to the rule.

10. QA/QC, CSV and change control

  • Before production use, the client records executable version, checksum, specification/monograph version, test CSV, expected JSON and IQ/OQ results.
  • Column names must not be changed without updating the validator and test scenarios.
  • The source CSV, output.json and utility version should be stored together as an evidence package.
  • Any change in control rules must go through change control and repeated OQ scenario verification.

Included in packages

Radiation Physics QC Suite

Utilities for activity, dosimetry, brachytherapy sources, small-field corrections and TG-43 parameters.

Open

RPH use case: PET scanner state, gamma camera and radiation physics

The linked medical-device/radiation-physics layer: PET detector QC, normalization, AC map, cross-calibration, TOF, gamma-camera uniformity, source strength and staff dose.

Open

RPH workflow: dosimetry and therapy planning

Activity planning, absorbed dose, organ dose, lung shunt, preplanning and therapy verification.

Open

RPH workflow: instruments, devices and radiation safety

PET/gamma-camera state, calibration, detector QC, energy window, TOF, shielding and radiation safety.

Open