4.1 Pre-Treatment Chart Check & Plan Verification Protocols

4.1 Pre-Treatment Chart Check & Plan Verification Protocols

Pre-treatment chart verification represents the primary quality assurance defense against misadministrations and catastrophic delivery errors in radiation therapy. Prior to initiating treatment for any oncology patient, a systematic review of the radiation oncology medical chart, treatment plan parameters, and electronic Record and Verify (R&V) data must be conducted by both radiation therapists and a qualified medical physicist. This multi-layered audit ensures that the prescribed radiation dose is delivered accurately to the anatomical target volume while maintaining strict adherence to tissue tolerance constraints.

Overview of Initial Pre-Treatment Chart Audit

The initial chart check is an exhaustive, mandatory verification process performed before the patient receives their first treatment fraction. The primary objective is to verify that all clinical, anatomical, dosimetric, and technical parameters align across the radiation oncologist's written prescription, the treatment planning system (TPS) output, and the linear accelerator control system. According to professional consensus recommendations from the American Association of Physicists in Medicine (AAPM) and the American Society for Radiation Oncology (ASTRO), no radiation treatment may be delivered without a fully executed pre-treatment physics sign-off and therapist chart audit.

The audit begins with verifying patient identification using at least two unique identifiers (e.g., full legal name, date of birth, and medical record number). Radiation therapists must cross-reference these identifiers against the electronic health record (EHR) and the R&V system interface. Following identity verification, the therapist and physicist verify that informed consent has been obtained, documented, and signed by the patient or legal guardian prior to plan authorization.

Components of a Comprehensive Radiation Therapy Prescription

A radiation therapy prescription is a legally binding medical order issued by an authorized radiation oncologist. Treatment delivery cannot proceed if any element of the prescription is incomplete, ambiguous, or discordant with the treatment plan. The essential components of a complete radiation therapy prescription include:

1. Anatomical Target Volume: Explicit definition of the treatment site (e.g., left breast, prostate bed, T6-T8 vertebral bodies, right upper lobe lung).
2. Total Prescribed Dose: The cumulative absorbed radiation dose to be delivered over the entire treatment course, specified in Gray (Gy) or centiGray (cGy).
3. Fractionation Schedule: The individual dose per fraction (e.g., 200 cGy/fraction, 180 cGy/fraction, or 800 cGy for SBRT) and the frequency of treatment (e.g., once daily, five days per week, or twice daily hyperfractionation).
4. Total Number of Fractions: The planned number of treatment sessions (e.g., 30 fractions for 60 Gy total dose).
5. Treatment Delivery Modality & Energy: Radiation type and beam energy (e.g., 6 MV photons, 10 MV FFF photons, 9 MeV electrons).
6. Treatment Technique: Specified delivery methodology (e.g., 3D Conformal Radiation Therapy [3D-CRT], Intensity-Modulated Radiation Therapy [IMRT], Volumetric Modulated Arc Therapy [VMAT], or Stereotactic Body Radiation Therapy [SBRT]).
7. Treatment Unit: Identification of the specific linear accelerator assigned to the patient.
8. Physician Signature & Date: Timely electronic signature by the attending radiation oncologist prior to fraction one.

Dosimetric and Plan Parameter Verification Protocols

Once the written prescription is verified, the detailed parameters of the treatment plan must be audited. Radiation therapists and physicists inspect every beam setting generated by the TPS. Key plan parameters requiring verification include:

• Gantry, Collimator, and Couch Angles: Verification of planned gantry rotation arcs, collimator rotations (especially critical for MLC leakage reduction and arc therapy), and couch angles (isocentric vs. non-coplanar beams).
• Field Size and Jaw Positions: Conformation of symmetric or asymmetric X and Y jaw settings against the planned beam portal sizes.
• Multi-Leaf Collimator (MLC) Configuration: Verification of static or dynamic leaf positions, avoiding potential leaf collision errors or leaf sequencing mismatches.
• Source-to-Surface Distance (SSD) vs. Source-to-Axis Distance (SAD): Confirming whether the plan is set up for SSD (isodose normalized at depth or skin surface, typically 100 cm SSD) or SAD (isocenter placed within target tissue at 100 cm SAD).
• Physical and Enhanced Dynamic Wedges (EDW): Checking wedge angle (15°, 30°, 45°, 60°), orientation (toe vs. heel direction), and field limit constraints.
• Bolus Specifications: Confirming bolus material type, thickness (e.g., 0.5 cm or 1.0 cm synthetic gel), anatomical location, and frequency of application (e.g., daily vs. alternate days).

Independent Secondary Monitor Unit (MU) Calculations

Per AAPM Task Group 114 (TG-114) guidelines, an independent secondary MU calculation must be performed for every treatment beam prior to clinical delivery. This calculation uses an independent algorithm (such as point-dose analytical models or secondary Monte Carlo software) distinct from the primary TPS algorithm. The secondary MU calculation verifies that the Monitor Units assigned to deliver the prescribed dose are free from software bugs, erroneous tissue density overrides, or incorrect beam data tables.

The tolerance for agreement between the primary TPS calculation and the secondary MU calculation is typically ±3% for 3D-CRT plans and ±5% for complex IMRT/VMAT plans in homogeneous tissue regions. Any deviation exceeding these action limits requires immediate investigation by a medical physicist before beam delivery.

Anatomical Contour, Bolus, and Accessory Checks

Plan verification also demands a detailed spatial review of CT simulation imaging and anatomical contouring. The medical physicist and therapist confirm that the target contours (GTV, CTV, PTV) and Organs at Risk (OAR) correctly reflect the patient's current anatomy. Additionally, the CT density calibration table (Hounsfield Unit to electron density conversion) used for heterogeneous tissue corrections must be verified.

Physical accessories—such as custom thermoplastic head masks, vacuum immobilization cushions, foot blocks, abdominal compression belts, and electron applicators/cutouts—must be physically inspected for structural integrity, correct labeling, and alignment with the plan documentation.

Electronic Treatment Record & Verification (R&V) Data Transfer Audit

Modern radiation oncology relies on digital data transfer from the TPS to the R&V platform (e.g., ARIA, MOSAIQ). During data transfer, corrupted parameters or transpositions can occur. AAPM TG-275 emphasizes that automated electronic transfer does not eliminate human error or software transfer bugs.

High-Risk Failure Modes Identified by AAPM TG-275

1. Inverted MLC Leaf Sequencing or Orientation: Dynamic MLC files transferred with reversed orientation relative to patient anatomy.
2. Physical Wedge Orientation Reversal: Transposition of wedge heel and toe, leading to severe dose hot spots in normal tissue.
3. Incorrect Reference Point Placement: Misalignment of the dose prescription point or iso-center coordinates.
4. Unmatched SSD/SAD Setup Parameters: Transferring an SAD plan as an SSD setup, causing incorrect table vertical placement and significant dosimetric errors.
5. Omission of Bolus Rules: Failure of the R&V system to enforce daily bolus interlocks prior to beam activation.

Summary Checklist for Pre-Treatment Chart Audit

The following table summarizes the essential verification steps required during the pre-treatment chart check workflow:

Strict adherence to this pre-treatment chart check protocol guarantees that every radiation therapy treatment is executed with maximum precision, complete documentation, and zero tolerance for preventable delivery errors.