Missed lung cancers on the scout view: do we look every time?

The CT scout view: complementary value added to abdominal CT interpretation

Computed tomography (CT) scout images, also known as CT localizer radiographs, topograms, or scanograms, are an important, albeit often overlooked part of the CT examination. Scout images may contain important findings outside of the scanned field of view on CT examinations of the abdomen and pelvis, such as unsuspected lung cancer at the lung bases. Alternatively, scout images can provide complementary information to findings within the scanned field of view, such as characterization of retained surgical foreign bodies. Assessment of scout images adds value and provides a complementary "opportunistic" review for interpretation of abdominopelvic CT examinations. Scout image review is a useful modern application of conventional abdominal radiograph interpretation that can help establish a diagnosis or narrow a differential diagnosis. This review discusses the primary purpose and intent of the CT scout images, addresses standard of care and bias related to scout image review, and presents a general systematic approach to assessing scout images with multiple illustrative examples, including potential pitfalls in interpreting scout images.

Detection of missed fractures of hand and forearm in whole-body CT in a blinded reassessment

BACKGROUND

We examined the visibility of fractures of hand and forearm in whole-body CT and its influence on delayed diagnosis. This study is based on a prior study on delayed diagnosis of fractures of hand and forearm in patients with suspected polytrauma.

METHODS

Two blinded radiologists examined CT-scans of patients with fractures of hand or forearm that were diagnosed later than 24 h after admission and control cases with unremarkable imaging of those areas. They were provided with clinical information that was documented in the admission report and were asked to examine forearm and hands. After unblinding, the visibility of fractures was determined. We examined if time of admission or slice thickness was a factor for late or missed diagnoses.

RESULTS

We included 72 known fractures in 36 cases. Of those 65 were visible. Sixteen visible fractures were diagnosed late during hospital stay. Eight more fractures were detected on revision by the radiologists. Both radiologists missed known fractures and found new fractures that were not reported by the other. Missed and late diagnoses of fractures occurred more often around 5 pm and 1 am. Slice thickness was not significantly different between fractures and cases with fractures found within 24 h and those found later.

CONCLUSIONS

The number of late diagnosis or completely missed fractures of the hand and forearm may be reduced by a repeated survey of WBCT with focus on the extremities in patients with suspected polytrauma who are not conscious.

LEVEL OF EVIDENCE

III.

Computed tomography follow-up identifies radically treatable new primaries after resection for lung cancer

OBJECTIVES

The optimal imaging programme for the follow-up of patients who have undergone resection of primary lung cancer is yet to be determined. We investigated the incidence and patterns of new and recurrent malignancy after resection for early-stage lung cancer in patients enrolled into a computed tomography (CT) follow-up programme.

METHODS

We reviewed the outcomes of consecutive patients who underwent CT follow-up after resection of early-stage primary lung cancer at the Oxford University Hospitals NHS Foundation Trust, between 2013 and 2017.

RESULTS

Four hundred and sixty-six consecutive patients underwent resection of primary lung cancer between 1 January 2013 and 31 March 2017. Three hundred and thirty-one patients (71.0%) were enrolled in CT follow-up. The median follow-up was 98 weeks (range 26-262). Sixty patients (18.2%) were diagnosed with programme-detected malignancy. Recurrence was diagnosed in 36 patients (10.9%), new primary lung cancer in 16 patients (4.8%) and non-lung primary tumours in 8 patients (2.4%). A routine CT scan identified the majority of new primary lung cancers (84.2%) and those with disease recurrence (85.7%). The majority of programme-detected malignancies were radically treatable (55%). The median survival of programme-detected cancers was 92.4 versus 23.0 weeks for patients with clinically detected tumours (P < 0.0001). Utilizing the CT scout image as a surrogate for chest X-ray, the sensitivity of this modality was 16.95% (8.44-28.97%) and specificity was 89.83% (79.17-96.18%). Negative likelihood ratio was 0.92 (0.8-1.07).

CONCLUSIONS

CT follow-up of surgically treated primary lung cancer patients identifies malignancy at a stage where radical treatment is possible in the majority of patients. Chest X-ray follow-up may not be of benefit following lung cancer resection.

Precision and Accuracy of Measurements on CT Scout View

OBJECTIVES

The purposes of this study were to (1) investigate the limits of measurements on scout view in three computed tomography axes, x, y and z and (2) develop a model to provide better understanding of measurement accuracy.

METHODS

For the first objective, anteroposterior and lateral scout views of a Catphan phantom 200 mm in diameter and length were acquired with a GE scanner at 21 different table heights. Phantom measurements on scout view were performed by two experienced readers. The comparison of their measures provided estimation of precision. The accuracy was assessed by determining the bias, calculated as the difference between the values measured on scout view and the real phantom size. Second, a model was developed investigating the relationship between the dimensions of the object, its image, and the table height. This relationship was tested on our data.

RESULTS

Scout view measurements were precise, with less than 0.53% difference between readers. In addition, small biases of about 1 mm were detected in the z-axis, whatever the table height. In the other axes, serious biases from -13 to +73 mm were measured. Furthermore, at isocentre, overestimations up to 7 mm were shown. The results also indicated that biases in scout view measurements are because of the geometrical projection related to the object-detector distance.

CONCLUSIONS

Measurements in the table movement axis are precise and accurate, conferring to scout views an added value for preoperative planning in orthopedic surgery.