1. What Component Identifies the Attribute Contained in a DICOM Data Element ?

Question Set: Forthcoming TG Reports, TG201: Quality Assurance of External Beam Treatment Data Transfer– Alf Siochi

1. What component identifies the attribute contained in a DICOM data element ?

1. Tag
2. Value Representation
3. Value Length
4. Value
5. Protocol Data Unit

Answer: 1

The tag uniquely identifies the attribute whose value is contained in the value component, while the VR and VL describe the data type (integer, text, etc) and size. The PDU describes the packets of data involved in the association.

Ref: 1) Pianykh, OS. Digital Imaging and Communications in Medicine – A Practical Introduction and Survival Guide, Springer-Verlag, Berlin, Heidelberg (2008), p. 197.

Ref: 2) DICOM PS 3.5-2007, p. 35-36. (The lists describe the tag, VR, VL, Value ).

Ref: 3) DICOM PS 3.6-2007, p. 6. (Sec. 3.4 describes the tag).

(Category: INF)

2. A concurrency conflict will most likely occur when two users open the same

1. Patient
2. Treatment plan
3. Treatment Machine
4. Database Record
5. Treatment Beam

Answer: 4

There is no way to know how one vendor versus the next structures their DB. Modifying various beams may not cause a concurrency conflict, unless they are part of the same record. The DB makes its changes at the record level, and sometimes makes checks at the table level. For consistency, it might look at changes to a group of records (transactions).

Ref: 1) Silberschatz A, Korth HF, and Sudarshan S. Database System Concepts, 6/e, McGraw-Hill (2011).

(Category: INF)

3. The use of a data transfer matrix allows one to check

1. The TMS to TPS transfer
2. The TPS to SS transfer
3. The SS to TPS transfer
4. The SS to AS transfer
5. All patient specific data transfers

Answer: 5

The matrix allows one to record all transfers between pairs of sub-systems. This is consistent with the recommendation in the TG 201 rapid communication to check all patient specific data transfers.

Ref: 1) Siochi et al. A rapid communication from the AAPM Task Group 201: Recommendations for the QA of external beam radiotherapy data transfer. JACMP(vol 12, no. 1) pp. 170-181.

(Category: INF)

4. Which of the following is a QA test ?

1. Patient’s IMRT chamber reading
2. Match TMS plan to TPS plan
3. Daily Output Check
4. Patient ID check
5. Plan dose satisfies Prescription

Answer: 3

QA is distinct from QC. QC is done for every plan for every patient, which is the case for items 1,2, 4, and 5. QA verifies that the Clinical Operations System or subsystems meet the specifications needed to deliver the required service or product. A daily output check ensures that a linac (subsystem) provides the correct calibration between programmed MUs and radiation dose (specification).

Ref: 1) Greene, J. and Stellman, A. Head First PMP, 2nd ed., O’Reilly, Sebastopol, CA (2009), p.372.

(Category: C07.B)

5. Which of the following items is an example of logical inconsistency ?

1. TPS Energy >TMS Energy
2. MLC missing in IMRT plan in TMS
3. TMS note updated
4. Rx fractions increased
5. TPS gantry angle changed

Answer: 2

IMRT plans typically have control points with variations of MLC shapes. A fully open beam is not a modulated beam and does not meet the definition of IMRT. This logical inconsistency lead to the accident described in the New York Times.

Ref: 1) Siochi et al. A rapid communication from the AAPM Task Group 201: Recommendations for the QA of external beam radiotherapy data transfer. JACMP(vol 12, no. 1) pp. 170-181.

(Category: INF)