BrachySourceDecayCorrector

Brachy Source Decay

activity biologics brachytherapy dosimetry radiopharma source calibration TG-43

BrachySourceDecayCorrector — Brachytherapy Source Decay Correction (AAPM TG-43)

ℹ️ The utility calculates current source activity and corrected dwell time considering physical decay.
ℹ️ Supported nuclides: Ir-192 (HDR/PDR), I-125 (LDR seeds), Cs-137.
ℹ️ Processing: only the FIRST record in input.csv file.
⚠️ Critical for brachytherapy! Errors in calibration date or ignoring decay lead to tumor under/overdosing and OAR toxicity.

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

Input format:
SourceID,Radionuclide,CalibrationActivity,CalibrationDate,ProcedureDate,PlannedDwellTimeSec

Example (time in seconds, dates ISO 8601):
IR192-SRC-045,Ir192,370.0,2026-01-10T10:00:00Z,2026-02-25T14:00:00Z,15.5

— WHY IS THIS NEEDED?
In brachytherapy, dose is delivered via source decay inside or near the tumor.
• Source activity constantly decreases (Ir-192 half-life ~74 days).
• To deliver the same biological dose, dwell time must increase over time.
• Medical physicist must independently verify TPS calculations.
⚠️ CRITICAL:
• Exact calibration date is the basis of all calculations.
• Half-life must match source certificate (TG-43).
• Old sources (>120 days) require replacement due to excessive procedure time and patient movement risk.
• Time sign errors (past/future) are unacceptable.
Critical parameters:
• Half-life: Ir-192 (73.83 days), I-125 (59.4 days), Cs-137 (~11000 days)
• Max source age: replacement recommended after 3–4 months for Ir-192
• Minimum activity: typically at least 10–20% of initial for efficient operation
⚠️ Note: Utility automatically warns if source is too old or dates are invalid. Result includes status (APPROVED/WARNING/REJECTED), calculated activity, and bilingual recommendation (RU/EN).

input.csv

SourceID,Radionuclide,CalibrationActivity,CalibrationDate,ProcedureDate,PlannedDwellTimeSec
IR192-SRC-045,Ir192,370.0,2026-01-10T10:00:00Z,2026-02-25T14:00:00Z,15.5

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: BrachySourceDecayCorrectorAPI / object: Brachy Source DecayCategory: Radiation physics

1. Scope

The Brachy Source Decay Corrector utility is used for Brachy Source Decay. 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, biologics, brachytherapy, dosimetry, radiopharma, source calibration, TG-43

2. Execution modes

BrachySourceDecayCorrector.exe                            → demo mode
BrachySourceDecayCorrector.exe input.csv output.json      → evaluate data (first record only)

3. Key controlled areas

pH and physicochemical parameters
activity, decay and radiochemical purity

4. Domain limits and critical parameters

⚠️ Critical for brachytherapy! Errors in calibration date or ignoring decay lead to tumor under/overdosing and OAR toxicity.
⚠️ CRITICAL:
Exact calibration date is the basis of all calculations.
Half-life must match source certificate (TG-43).
Old sources (>120 days) require replacement due to excessive procedure time and patient movement risk.
Time sign errors (past/future) are unacceptable.
Critical parameters:
Half-life: Ir-192 (73.83 days), I-125 (59.4 days), Cs-137 (~11000 days)
Max source age: replacement recommended after 3–4 months for Ir-192
Minimum activity: typically at least 10–20% of initial for efficient operation
⚠️ Note: Utility automatically warns if source is too old or dates are invalid. Result includes status (APPROVED/WARNING/REJECTED), calculated activity, 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

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

#	Column	Type	Unit	Description	Sample	Control rule
1	`SourceID`	text	as specified	Source ID	`IR192-SRC-045`	mandatory value; format and acceptability are checked by the utility
2	`Radionuclide`	text	as specified	Radionuclide	`Ir192`	mandatory value; format and acceptability are checked by the utility
3	`CalibrationActivity`	decimal	as specified	Calibration Activity	`370.0`	mandatory numeric value; rule comparison is performed by the utility
4	`CalibrationDate`	date/time	as specified	Calibration Date	`2026-01-10T10:00:00Z`	mandatory value; format and acceptability are checked by the utility
5	`ProcedureDate`	date/time	as specified	Procedure Date	`2026-02-25T14:00:00Z`	mandatory value; format and acceptability are checked by the utility
6	`PlannedDwellTimeSec`	decimal	min	Planned Dwell Time Sec	`15.5`	mandatory numeric value; rule comparison is performed by the utility

CSV example

SourceID,Radionuclide,CalibrationActivity,CalibrationDate,ProcedureDate,PlannedDwellTimeSec
IR192-SRC-045,Ir192,370.0,2026-01-10T10:00:00Z,2026-02-25T14:00:00Z,15.5

7. FS — functional specification

ID	Function	Implementation description
FS-001	CLI entry point	The executable `BrachySourceDecayCorrector.exe` supports demo mode and `input.csv output.json` processing mode.
FS-002	CSV parser	The import module reads CSV, validates header, column presence/order, value count and encoding. Decimal values are expected with a dot separator.
FS-003	Field conversion	Each column is converted to the expected type: identifier, text, decimal number, date/time or boolean flag.
FS-004	Domain rule engine	For Brachy Source Decay, explicit rules are applied: range, minimum, maximum, absence of prohibited flag, data completeness or calculation-based check.
FS-005	Criticality handling	Critical violations produce FAIL; non-critical deviations and incomplete data produce WARNING; full conformance produces PASS.
FS-006	JSON writer	`output.json` stores overall status, per-parameter results, source values, warnings, failures and diagnostic messages.
FS-007	Integration contract	The CSV → JSON format is stable for invocation from LIMS/ELN/MES, scheduled task or wrapper service.
FS-008	Error handling	Schema 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": "BrachySourceDecayCorrector",
  "api": "Brachy Source Decay",
  "batchNumber": "",
  "overallStatus": "PASS|WARNING|FAIL",
  "checkedAtUtc": "2026-05-18T00:00:00Z",
  "checks": [
    {
      "parameter": "SourceID",
      "value": "IR192-SRC-045",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "Radionuclide",
      "value": "Ir192",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "CalibrationActivity",
      "value": "370.0",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "CalibrationDate",
      "value": "2026-01-10T10:00:00Z",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "ProcedureDate",
      "value": "2026-02-25T14:00:00Z",
      "unit": "as specified",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    },
    {
      "parameter": "PlannedDwellTimeSec",
      "value": "15.5",
      "unit": "min",
      "status": "PASS|WARNING|FAIL",
      "message": "Rule-based check result"
    }
  ],
  "criticalFindings": [],
  "sourceFile": "input.csv"
}

9. OQ/PQ test scenarios

ID	Scenario	Expected result
TC-001	Valid CSV with expected header and sample row	All rows are processed; output contains PASS/WARNING/FAIL and parameter-level detail.
TC-002	A mandatory input.csv column is missing	Import is rejected or the row receives FAIL with schema reference.
TC-003	A numeric field contains text or a blank value	Type conversion error is recorded; the result is not hidden as PASS.
TC-004	A parameter is outside specification or critical limit	Critical parameters produce FAIL; non-critical deviations produce WARNING according to the rule.
TC-008	Incorrect activity, reference time or radiochemical purity	FAIL/WARNING is produced with calculation traceability.

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

Radiology QC Suite

QC package for radiology and diagnostic imaging: radiopharmaceuticals, PET/SPECT, contrast media, iodinated and gadolinium products, plus particle, sterility and endotoxin checks.

Open

RPH isotope family: radioiodine

I-123, I-124, I-125 and I-131 for diagnostics, therapy, labelling and purity control.

Open

RPH organ/system: hepatobiliary and GI

HIDA, mebrofenin, gallbladder, gastric emptying, GI transit, bleeding and liver/spleen imaging.

Open

RPH organ/system: oncology and theranostics

Tumour imaging, PSMA/FAPI/receptor tracers, immuno-PET, targeted radionuclide therapy and radioembolization.

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

RPH workflow: stability, storage, decay and waste

Kinetic stability, shelf life, decay correction, expiry, storage, trend and radioactive waste.

Open