Spontaneous Regression of a Large Vestibular Schwannoma: Is Nonoperative Management Reasonable?

Vestibular schwannomas (VSs) are the most common cerebellopontine tumors. The natural history of smaller-sized VSs (<30 mm) has been well-studied, leading to the recommendation of a "watch and wait" approach. However, large VSs (>30 mm) have not been extensively studied, mainly because of their rarity. As such, most patients are conventionally offered surgery which carries a significant risk of neurological morbidity. Here, we report a case of a giant VS (>40 mm) in a 30-year-old man who regressed spontaneously. He was lost to follow-up for 18 years and, upon re-presentation, the symptomatology drastically improved and repeat imaging demonstrated a marked reduction in tumor size. Referring to similar cases in other studies, we postulate that most large and giant VSs undergo a phase of growth and stasis, followed by regression due to shifts in the balance between tumorigenic and regressive factors. Taken together with emerging molecular data, further studies are required to better understand the history of large and giant VSs to shape more personalized treatment options. This potentially includes non-operative management as a tenable option.

Deep Learning Systems for Pneumothorax Detection on Chest Radiographs: A Multicenter External Validation Study.

PURPOSE: To assess the generalizability of a deep learning pneumothorax detection model on datasets from multiple external institutions and examine patient and acquisition factors that might influence performance. MATERIALS AND METHODS: In this retrospective study, a deep learning model was trained for pneumothorax detection by merging two large open-source chest radiograph datasets: ChestX-ray14 and CheXpert. It was then tested on six external datasets from multiple independent institutions (labeled A-F) in a retrospective case-control design (data acquired between 2016 and 2019 from institutions A-E; institution F consisted of data from the MIMIC-CXR dataset). Performance on each dataset was evaluated by using area under the receiver operating characteristic curve (AUC) analysis, sensitivity, specificity, and positive and negative predictive values, with two radiologists in consensus being used as the reference standard. Patient and acquisition factors that influenced performance were analyzed. RESULTS: The AUCs for pneumothorax detection for external institutions A-F were 0.91 (95% CI: 0.88, 0.94), 0.97 (95% CI: 0.94, 0.99), 0.91 (95% CI: 0.85, 0.97), 0.98 (95% CI: 0.96, 1.0), 0.97 (95% CI: 0.95, 0.99), and 0.92 (95% CI: 0.90, 0.95), respectively, compared with the internal test AUC of 0.93 (95% CI: 0.92, 0.93). The model had lower performance for small compared with large pneumothoraces (AUC, 0.88 [95% CI: 0.85, 0.91] vs AUC, 0.96 [95% CI: 0.95, 0.97]; P = .005). Model performance was not different when a chest tube was present or absent on the radiographs (AUC, 0.95 [95% CI: 0.92, 0.97] vs AUC, 0.94 [95% CI: 0.92, 0.05]; P > .99). CONCLUSION: A deep learning model trained with a large volume of data on the task of pneumothorax detection was able to generalize well to multiple external datasets with patient demographics and technical parameters independent of the training data.Keywords: Thorax, Computer Applications-Detection/DiagnosisSee also commentary by Jacobson and Krupinski in this issue.Supplemental material is available for this article.©RSNA, 2021.

Anaplastic Oligodendroglioma with Transdural Extension.

Oligodendrogliomas, the third most common primary gliomas, have a strict molecular definition, characterized by the combined presence of isocitrate dehydrogenase mutation and 1p19q codeletion. Herein, we describe an extremely unusual case of molecularly defined anaplastic oligodendroglioma with transdural extension into the frontal and ethmoid sinuses, without prior neurosurgical intervention or radiotherapy. The molecular profile of the tumor is also provided. To the best of our knowledge, this has never been reported before. Most of the previously reported glial tumors with transdural extension were cases of histologically proven glioblastomas and gliosarcomas, typically seen in the context of prior neurosurgical intervention and/or radiotherapy. This case adds to the limited literature on oligodendrogliomas with transdural extension. Further studies are necessary to elucidate the relationship between the incidence of transdural extension and molecular subtypes of oligodendrogliomas.

Competency-based Radiology Residency: A Survey of Expectations from Singapore's Perspective.

In response to the demands of an ageing nation, the postgraduate medical education in Singapore is currently in the early stage of transition into the American-styled residency programme. This study assessed the expectations of both radiology trainees and faculty on their ideal clinical learning environment (CLE) which facilitates the programme development. A modified 23-item questionnaire was administered to both trainees and faculty at a local training hospital. All items were scored according to their envisioned level of importance and categorised into 5 main CLE domains-supervision, formal training programme, work-based learning, social atmosphere and workload. 'Supervision' was identified as the most important domain of the CLE by both trainees and faculty, followed by 'formal training programmes', 'work-based learning' and 'social atmosphere'. 'Workload' was rated as the least important domain. For all domains, the reported expectation between both trainees and faculty respondents did not differ significantly. Intragroup comparison also showed no significant difference within each group of respondents. This study has provided valuable insights on both respondents' expectations on their ideal CLE that can best train competency in future radiologists. Various approaches to address these concerns were also discussed. The similarities in findings between ours and previous studies suggest that the 'supervision', 'formal training programmes' and 'work-based learning' domains are crucial for the success of a postgraduate medical training and should be emphasised in future curriculum. 'Workload' remains a challenge in postgraduate medical training, but attempts to address this will have an impact in future radiology training.

Simultaneous measurement of breathing rate and heart rate using a microbend multimode fiber optic sensor.

We propose and demonstrate the feasibility of using a highly sensitive microbend multimode fiber optic sensor for simultaneous measurement of breathing rate (BR) and heart rate (HR). The sensing system consists of a transceiver, microbend multimode fiber, and a computer. The transceiver is comprised of an optical transmitter, an optical receiver, and circuits for data communication with the computer via Bluetooth. Comparative experiments conducted between the sensor and predicate commercial physiologic devices showed an accuracy of ±2 bpm for both BR and HR measurement. Our preliminary study of simultaneous measurement of BR and HR in a clinical trial conducted on 11 healthy subjects during magnetic resonance imaging (MRI) also showed very good agreement with measurements obtained from conventional MR-compatible devices.

Intensity-modulated microbend fiber optic sensor for respiratory monitoring and gating during MRI.

This paper describes a novel microbend fiber optic sensor system for respiratory monitoring and respiratory gating in the MRI environment. The system enables the noninvasive real-time monitoring and measurement of breathing rate and respiratory/body movement pattern of healthy subjects inside the MRI gantry, and has potential application in respiratory-gated image acquisition based on respiratory cues. The working principle behind this sensor is based on the microbending effect of an optical fiber on light transmission. The sensor system comprises of a 1.0-mm-thin graded-index multimode optical fiber-embedded plastic sensor mat, a photoelectronic transceiver, and a computer with a digital signal processing algorithm. In vitro testing showed that our sensor has a typical signal-to-noise ratio better than 28 dB. Clinical MRI trials conducted on 20 healthy human subjects showed good and comparable breathing rate detection (with an accuracy of ±2 bpm) and respiratory-gated image quality produced using the sensor system, with reference to current predicate hospital device/system. The MRI safe, ease of operation characteristics, low fabrication cost, and extra patient comfort offered by this system suggest its good potential in replacing predicate device/system and serve as a dual function in real-time respiratory monitoring and respiratory-gated image acquisition at the same time during MRI.

Clinics in diagnostic imaging (140). Iatrogenic sciatic nerve injury secondary to intramuscular injection.

A 77-year-old Chinese female patient presented with acute onset of left lower limb paraesthesia and weakness after she received an intramuscular injection for pain relief in the gluteal region. Magnetic resonance (MR) imaging of her lumbosacral spine and sacral plexus was performed. The MR imaging findings are reviewed and discussed.

MRI in spinal cord decompression sickness.

INTRODUCTION: Spinal cord decompression sickness (DCS) is a rare condition that can lead to spinal cord infarction. Despite the low incidence of diving-related DCS, we have managed to collect the data and MRI findings of seven patients who have been diagnosed with and treated for DCS in our local hyperbaric facility. This study describes the clinical presentation, MRI spinal cord findings, treatment administered and outcome of these patients. METHODS: The patient medical records, from 1997 to 2007, were retrospectively reviewed. All patients with a final diagnosis of DCS and who underwent examination were included. The images were independently reviewed by two radiologists who recorded the location and number of lesions within the spinal cord. The Frankel grading was used to assess the initial and clinical outcome response. RESULTS: Patchy-increased T2W changes affecting several levels at the same time were found. Contrary to the popular notion that venous infarction is the leading cause of DCS, most of our patients also demonstrated affliction of grey matter, which is typically seen in an arterial pattern of infarction. Initial involvement of multiple (>6) spinal cord levels was associated with a poor outcome. Patients who continued to have multiple neurological sequelae with less than 50% resolution of symptoms despite recompression treatment were also those who had onset of symptoms within 30 min of resurfacing. CONCLUSIONS: DCS is probably a combination of both arterial and venous infarction. Short latency to the onset of neurological symptoms and multilevel cord involvement may be associated with a poorer outcome.

[18F] FDG PET/CT in patients with fever of unknown origin: a local experience.

OBJECTIVE: 2-deoxy-2-[¹8F]fluoro-D-glucose positron emission tomography/computed tomography ([¹8F] FDG PET/CT) has become an established imaging tool in oncology and is now emerging in the field of infectious disease. The aim of this study is to assess the value of fluorine [¹8F] FDG PET/CT in the investigation of patients with fever of unknown origin (FUO). METHODS: [¹8F] FDG PET/CT scans and clinical data of 12 patients were reviewed. These patients met the revised definition criteria of FUO (febrile illness of greater than 3 weeks duration, temperature greater than 38.3°C and no diagnosis after at least 3 days of in-patient investigation or 2 weeks of outpatient investigation). A retrospective analysis of our local database was performed and evaluated for the diagnostic contribution of [¹8F] FDG PET/CT scans. RESULTS: An infective cause of the FUO was found in four (33.3%) patients, a neoplasm in two (16.7%) patients, non-infectious inflammatory disease or autoimmune in one (8.3%) patient. A definitive causative agent could not be found in five (41.7%) patients despite extensive investigations.In all, five (41.6%) patients had a PET/CT scan that was abnormal and was deemed 'helpful' as part of the investigation that pointed to the final diagnosis. Two (16.7%) patients had abnormal scans, which were deemed 'not-helpful' for the final diagnosis. CONCLUSION: [¹8F] FDG PET/CT can be helpful in some patients with FUO. This study adds value to the limited data published so far on this subject.

Incidental finding of focal FDG uptake in the bowel during PET/CT: CT features and correlation with histopathologic results.

OBJECTIVE: The purpose of this study was to identify and characterize the clinically significant lesions associated with incidental detection of focal uptake of (18)F-FDG in the bowel at PET/CT. MATERIALS AND METHODS: Among 2,250 consecutively registered patients with various nongastrointestinal malignant diseases who underwent FDG PET/CT as part of their care, patients with the incidental finding of focal bowel uptake of FDG were included in the study. All patients underwent an endoscopic or surgical procedure for characterization of the lesions. The location, intensity of uptake, and appearance of the lesions on PET/CT images were recorded and compared with the endoscopic and surgical pathologic results. RESULTS: Twenty-one of 25 foci of intense uptake in the bowel were associated with endoscopic or surgical abnormalities (positive predictive value, 84%). Seven lesions were malignant (two primary, five secondary); 13 were premalignant (nine tubovillous adenoma, four tubular adenoma); and one lesion was benign (hyperplastic polyp). Eleven lesions detected with endoscopy were not FDG avid, and all 11 were smaller than 1 cm in diameter. There was no statistically significant difference in the maximum standardized uptake values of the benign and malignant lesions. CONCLUSION: The incidental finding of focal FDG uptake in the bowel justifies further investigation of these foci and should not be dismissed as physiologic uptake. Premalignant lesions, such as adenoma, are often found, and early treatment may prevent the development of carcinoma.

Decompression sickness: MRI of the spinal cord.

Decompression sickness (DCS) typically causes changes in the white matter of the spinal cord on MR imaging. We present a case of DCS in a scuba diver with dorsal white matter lesions typical of venous infarction. In addition, some central gray matter involvement was noted. Characteristic features of venous spinal cord infarction can be recognized on MR imaging in DCS but may be more extensive in severe cases.