CT-Based Radiation Dose Map Overlays Improve Radiologists' Interpretation of Surveillance Imaging in Thoracic Malignancies

Purpose: Interpretation of surveillance imaging for oncology patients treated with radiation therapy can be challenging since (1) the indication for imaging may not adequately describe the radiation fields and (2) radiation treatment effect and progression can appear similar. The volumetric visualization of the radiation dose is often inaccessible to radiologists. A semi-automated workflow can create an image series of the dose information overlaid on CT images and transfer images to PACS to aid radiologists’ interpretations.

Methods/Materials: Pre- & post-treatment CT imaging of 32 patients who received thoracic radiation to 1-5 lesion(s) for a primary or metastatic thoracic malignancy were reviewed by a board certified thoracic radiologist and a diagnostic radiology resident. A brief clinical history was provided for each case. The readers interpreted images first without, and then with access to radiation dose information (Figure). One month separated interpretation of imaging without and with radiation dose information. Readers were asked to identify the treated lesion(s) and radiation treatment effect(s), and record their confidence using a Likert scale of 1-5.

Results: There were 19 patients with 1 lesion and 13 patients with >1 lesion. Correct identification of all treated lesions significantly increased with the addition of dose visualization (62% to 81%; p=0.001), with the largest increase noted for cases with >1 lesion (15% to 57%; p=0.004). Without dose information, 12.5% of labeled lesions did not receive radiation, and 13% of labeled radiation effects fell outside of the irradiated areas. Both values fell to less than 2% with the addition of dose information. The readers’ confidence that they had identified treated lesion(s) increased from a rating of 4.1 to 4.8 (p=0.000005).

Conclusions: When radiation dose information is shown, correct identification rate of irradiated lesions and treatment effects, as well as confidence in irradiated lesion identification significantly increased. Our results demonstrate that adding volumetric visualization of the radiation dose to imaging within PACS can improve quality of surveillance care for patients with irradiated thoracic malignancies.