Interval Change in Diffusion and Perfusion MRI Parameters for the Assessment of Pseudoprogression in Cerebral Metastases Treated With Stereotactic Radiation.

OBJECTIVE: Apparent increases in the size of cerebral metastases after stereotactic radiosurgery (SRS) can be caused by pseudoprogression or true disease progression, which poses a diagnostic challenge at conventional MRI. The purpose of this study was to assess whether interval change in DWI and perfusion MRI parameters can differentiate pseudoprogression from progressive disease after treatment with SRS. MATERIALS AND METHODS: Patients with apparent growth of cerebral metastases after SRS treatment who underwent pre- and post-SRS DWI, dynamic susceptibility contrast (DSC)-MRI, and perfusion dynamic contrast-enhanced (DCE)-MRI were retrospectively evaluated. Final assignment of pseudoprogression or progressive disease was determined at 6-month follow-up imaging using the Response Assessment in Neuro-Oncology Brain Metastases criteria. Mean values of apparent diffusion coefficient (ADC), DCE-MRI-derived volume transfer constant (Ktrans), and DSC-MRI-derived relative cerebral blood volume (CBV) from pre- and post-SRS MRI scans were compared between groups using univariate and regression analysis. Fisher exact test was used to compare interval change of imaging biomarkers. RESULTS: Of 102 cerebral metastases evaluated, 32 lesions in 29 patients met our inclusion criteria. The mean duration of follow-up was 7.2 months (range, 6-14 months). Twenty-two lesions were determined as pseudoprogression, and 10 lesions were determined as progressive disease using the Response Assessment in Neuro-Oncology Brain Metastases criteria at 6-month follow-up MRI. The interval change pattern of our imaging parameters matched the expected patterns of treatment response for ADC (23/32 lesions; 72%; p = 0.055; odds ratio, 5.1), Ktrans (24/32 lesions; 75%; p = 0.006; odds ratio, 19.2), and relative CBV (27/32 lesions; 84%; p = 0.001; odds ratio, 25.3). CONCLUSION: Pseudoprogression can be distinguished from disease progression in cerebral metastases treated with SRS via an interval decrease in relative CBV and Ktrans values.

Fractures of the posterolateral maxillary sinus: a masticator space blowout injury?

BACKGROUND AND PURPOSE: Segmental, depressed fractures of the posterolateral maxillary sinus may occur as a result of trauma to the masticator space, previously described in association with mandibular fractures. The authors hypothesize that the fracture is due to a transient increase in pressure in the masticator space (blow out) and therefore should be seen in association with other regional fractures. MATERIALS AND METHODS: Injuries of the masticator space were retrospectively identified by searching the imaging database from January 2014 to November 2014 for keywords that would identify regional trauma. The images were reviewed for segmental depressed fractures in the posterolateral aspect of the maxillary sinus accompanied by herniation of a variable amount of masticator space fat and/or muscle into the adjacent sinus. Three neuroradiologists reviewed the images and agreed by consensus on the presence or absence of a masticator space blowout fracture. RESULTS: Forty-three zygomaticomaxillary complex (ZMC) fractures, 89 mandibular fractures, and 49 isolated zygomatic arch fractures were identified. While all of the ZMC fractures had a maxillary component, 3 of 43 (7.0 %) additional fractures met our fracture definition. Five of 89 (5.6 %) of the mandibular fractures and 6 of 49 (12.2 %) zygomatic arch fractures had an associated posterolateral maxillary fracture. CONCLUSIONS: Segmental depressed fracture of the posterolateral maxillary sinus is relatively common, occurring in conjunction with other regional injuries. The authors hypothesize that it is due to a transient increase in pressure in the masticator space and is a separate entity from other fractures of the region that may occur concurrently.

Migrating bullet: A case of a bullet embolism to the pulmonary artery with secondary pulmonary infarction after gunshot wound to the left globe.

Bullet embolism is a rare phenomenon following gunshot injuries. We present a case of a 25-year-old male who sustained a gunshot wound to his left globe with the bullet initially lodged in his right transverse sinus. The bullet ultimately embolized to a left lower lobe pulmonary artery resulting in a pulmonary infarct. A discussion of select prior cases, pathophysiology, and management strategies follows.

Impact of hindsight bias on interpretation of nonenhanced computed tomographic head scans for acute stroke.

OBJECTIVE: To determine whether knowledge of the presence or the absence of acute stroke from review of follow-up studies, including diffusion-weighted magnetic resonance imaging (DW-MRI) head scans, biases the retrospective review of a radiologist's detection of acute stroke on nonenhanced computed tomographic (CT) scans of the head. METHODS: Forty-four consecutive patients with acute cerebral infarction as defined by positive DW-MRI and a CT scan within 48 hours before the MRI were identified. In addition, 30 control patients with negative DW-MRI results and a head CT scan within 48 hours before the MRI were chosen. Medical records were examined, and the time from onset of symptoms was recorded when this was available. The CT examinations were shown to 6 board-certified radiologists (of which 4 were certificate of added qualification neuroradiologists). The radiologists were asked to provide a probability estimate on whether an acute stroke is present or absent, the location of the stroke if present, and the presence of early ischemic signs including parenchymal hypoattenuation, sulcal effacement, and loss of gray-white matter differentiation. The radiologists had access to the patients' age, sex, and date of study but were not provided with the presenting history. After a minimum 10-day washout period and after reshuffling the cases, the radiologists were asked to reinterpret the examination results after first being shown the DW-MRI of the study in question and allowed access to reports and other follow-up studies. Receiver operating characteristic analysis was performed. RESULTS: For infarctions in the middle cerebral artery, the posterior fossa, and anterior cerebral artery territories, there was a significant increase in performance with knowledge of DW-MRI results than without prior knowledge of the DW-MRI findings. When the basal nuclei and the posterior cerebral artery were included, the difference in performance of the readers without and those with DW-MRI approached significance (t = 2.35, P = 0.0571). CONCLUSIONS: Knowledge of the presence or the absence of an acute infarct influences a radiologist's ability to detect the lesion on CT. The presence of hindsight bias may influence the testimony of expert witnesses in legal cases and have an impact on quality assurance procedures on a hospital level.

On-call radiology: community standards and current trends.

The issues regarding on-call radiology are complex and contentious. Both academic and private practice radiology centers have encountered increasing workloads in recent years. Some academic centers are utilizing night float systems or other models of call to address the increasing complexity and volume of after-hours cases. Many private practice groups are outsourcing after-hours work to commercial nighthawk radiology services. Emergency medicine department and ACR guidelines place additional expectations on the on-call radiologist.

Can MRI signal characteristics of lumbar disk herniations predict disk regression?

PURPOSE: To assess whether or not MRI signal characteristics of lumbar disk herniations can predict subsequent disk regression. MATERIALS AND METHODS: Medical and radiology records from 1999-2003 were reviewed, and 123 patients who had more than one lumbar MRI during the study interval were identified. Of these, 42 patients had a disk herniation (protrusion, extrusion, or free fragment) identified on their first examination. Six of the 42 patients were not included because of prior lumbar surgery, or inadequate examinations. The remaining 36 patients had a total of 77 examinations to evaluate 44 disk herniations. The herniated disks were evaluated by two CAQ neuroradiologists for size, morphology and a qualitative assessment of the T2 signal. RESULTS: Between the first and last examination, 25 of 44 (57%) herniated disks decreased, 17 (39%) were unchanged, and two increased in size. 9 of 11 (82%) of disk extrusions improved. The mean size of the disks that regressed was significantly larger than those that were unchanged (8.6 mm vs. 6 mm, p=.001). On average, the disks decreased 3.2 mm (37%). Of the disks that decreased in size, 15 (63%) had an area of increased signal on T2-weighted images (T2WI) compared to the parent disk on the initial study. Of the disks that were unchanged, 6 (35%) had increased signal on the T2WI's. CONCLUSION: 57% of herniated disks in this study group decreased in size over time. Larger herniations and extrusions were more likely to regress than smaller herniations. Disks that regressed were more likely to have high signal on T2WI's than those that were stable.

Location, size, and distribution of mediastinal lymph node enlargement in chronic congestive heart failure.

PURPOSE: The purpose of this study is to identify the prevalence, location, and size of enlarged mediastinal lymph nodes in patients with chronic congestive heart failure and to correlate the presence of lymph node enlargement with cardiac ejection fraction. METHODS: Sixty-six consecutive, retrospectively identified patients underwent computer tomography (CT) imaging of the thorax as part of a routine work-up prior to cardiac transplantation from 1993 to 1996. CT images of 44 of these patients were independently examined by 3 radiologists for evidence of pulmonary edema, pleural effusions, and the presence, size, and location of lymph nodes >1 cm in short axis. Multigated acquisition (MUGA) scans were available for cardiac ejection fraction assessment in 38 of the 44 patients. RESULTS: Twenty-nine (66%) patients had at least 1 mediastinal lymph node >1 cm. The mean ejection fraction was significantly less for patients with lymph node enlargement when compared with patients without lymph node enlargement (20% versus 35%; P < 0.01). Adenopathy was observed in 81% of patients with a calculated ejection fraction of <35%. No patient with an ejection fraction of >35% had lymph node enlargement. There was no correlation between pulmonary edema and the frequency of lymph node appearance. Sixty-three percent of the enlarged nodes were pretracheal, with a mean short axis diameter for all the enlarged nodes of 1.3 cm. CONCLUSIONS: Enlarged mediastinal lymph nodes were observed in 81% of patients with a calculated ejection fraction of <35%, most commonly in the pretracheal group. The presence of the lymph nodes did not correlate with CT evidence of pulmonary edema.

Evaluation of emergency CT scans of the head: is there a community standard?

OBJECTIVE: This study was designed to assess the accuracy of general radiologists in the interpretation via teleradiology of emergency CT scans of the head. MATERIALS AND METHODS: We studied the interpretations of 716 consecutive emergency CT scans of the head by a group of 15 board-certified general radiologists practicing in the community (as opposed to an academic setting). The scans were sent via teleradiology, and the preliminary interpretations were made. Three of the general radiologists were functioning as nighthawks, and the remaining 12 were acting as on-call radiologists in addition to their normal daytime duties. Each CT examination was interpreted by one of five neuroradiologists the day after the initial interpretation had been performed. The findings of the final interpretation and the preliminary interpretation were categorized as showing agreement, insignificant disagreement, or significant disagreement. The reports in the two categories indicating disagreement were reviewed and reclassified by a consensus of three university-based neuroradiologists. RESULTS: Agreement between the initial interpretation by the general radiologist and the final interpretation by the neuroradiologist was found in 95% of the CT scans. The interpretations were judged to show insignificant disagreement in 3% (23/716) of the scans and to show significant disagreement in 2% (16/716). Of the 16 significant errors, five were false-positive findings and 11 were false-negative findings. Forty-seven CT scans depicted significant or active disease, and in 11 (23%) of these scans, the final report differed significantly from the preliminary interpretation. Three patients had pituitary masses, none of which had been described on the preliminary interpretation. CONCLUSION: The rate of significant discordance between board-certified on-call general radiologists and neuroradiologists in the interpretation of emergency CT scans was 2%, which was comparable to previously published reports of residents' performance. The pituitary gland may be a blind spot, and additional attention should be focused on this area.

Oblique reformation in cervical spine computed tomography: a new look at an old friend.

STUDY DESIGN: Cervical spine computed tomograms were evaluated for neural foraminal stenosis in both the standard axial plane and the oblique reformatted plane. OBJECTIVE: To assess whether oblique reformation of cervical spine computed tomograms reduces interobserver variability in the evaluation of neural foraminal stenosis. SUMMARY OF BACKGROUND DATA: Radiographic assessment of neural foraminal stenosis is subjective, may vary among observers, and can affect surgical planning. METHODS: The cervical spine images from 19 patients with various degrees of neural foraminal stenosis were reformatted in an oblique plane perpendicular to the long axis of the right and left neural foramens. Seven independent observers graded the degree of foraminal stenosis (none, mild [1-25%], moderate [26-75%], or severe [>75%]) and their confidence level (definite, probable, possible) on both the axial images and the oblique reformations. RESULTS: The ages of the 12 male (mean, 67.5 +/- 13.24 years) and 7 female (mean, 62.7 +/- 14.79 years) patients ranged from 39 to 83 years. Interobserver variability was assessed with chi2 analysis. Rates of agreement on degree of stenosis (chi2 = 19.94; df= 9; P< 0.02) were significantly higher for oblique reformations. Confidence ratings also were significantly higher for oblique reformations (chi2 = 18.19; df= 7; P< 0.02). CONCLUSIONS: Oblique reformation of cervical spine images significantly reduces the degree of interobserver variability and increases observer confidence in the assessment of neural foraminal stenosis. Oblique reformations should be considered in the routine evaluation of neural foraminal stenosis.

Radiology resident evaluation of head CT scan orders in the emergency department.

BACKGROUND AND PURPOSE: Prior studies have revealed little difference in residents' abilities to interpret cranial CT scans. The purpose of this study was to assess the performance of radiology residents at different levels of training in the interpretation of emergency head CT images. METHODS: Radiology residents prospectively interpreted 1324 consecutive head CT scans ordered in the emergency department at the University of Arizona Health Science Center. The residents completed a preliminary interpretation form that included their interpretation and confidence in that interpretation. One of five neuroradiologists with a Certificate of Added Qualification subsequently interpreted the images and classified their assessment of the residents' interpretations as follows: "agree," "disagree-insignificant," or "disagree-significant." The data were analyzed by using analysis-of-variance or chi-squared methods. RESULTS: Overall, the agreement rate was 91%; the insignificant disagreement rate, 7%; and the significant disagreement rate, 2%. The level of training had a significant (P =.032) effect on the rate of agreement; upper-level residents had higher rates of agreement than those of more junior residents. There were 62 false-negative findings. The most commonly missed findings were fractures (n = 18) and chronic ischemic foci (n = 12). The most common false-positive interpretations involved 10 suspected intracranial hemorrhages and suspected fractures. CONCLUSION: The level of resident training has a significant effect on the rate of disagreement between the preliminary interpretations of emergency cranial CT scans by residents and the final interpretations by neuroradiologists. Efforts to reduce residents' errors should focus on the identification of fractures and signs of chronic ischemic change.