Shamir Rai’s research while affiliated with Vancouver General Hospital and other places


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Publications (13)


Approach to Acute Traumatic and Nontraumatic Diaphragmatic Abnormalities
  • Literature Review

June 2024

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35 Reads

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1 Citation

Radiographics

Sarah Keyes

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Rebecca J Spouge

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Padraic Kennedy

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[...]

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Nicolas Murray

Acute diaphragmatic abnormalities encompass a broad variety of relatively uncommon and underdiagnosed pathologic conditions, which can be subdivided into nontraumatic and traumatic entities. Nontraumatic abnormalities range from congenital hernia to spontaneous rupture, endometriosis-related disease, infection, paralysis, eventration, and thoracoabdominal fistula. Traumatic abnormalities comprise both blunt and penetrating injuries. Given the role of the diaphragm as the primary inspiratory muscle and the boundary dividing the thoracic and abdominal cavities, compromise to its integrity can yield devastating consequences. Yet, diagnosis can prove challenging, as symptoms may be vague and findings subtle. Imaging plays an essential role in investigation. Radiography is commonly used in emergency evaluation of a patient with a suspected thoracoabdominal process and may reveal evidence of diaphragmatic compromise, such as abdominal contents herniated into the thoracic cavity. CT is often superior, in particular when evaluating a trauma patient, as it allows rapid and more detailed evaluation and localization of pathologic conditions. Additional modalities including US, MRI, and scintigraphy may be required, depending on the clinical context. Developing a strong understanding of the acute pathologic conditions affecting the diaphragm and their characteristic imaging findings aids in efficient and accurate diagnosis. Additionally, understanding the appearance of diaphragmatic anatomy at imaging helps in differentiating acute pathologic conditions from normal variations. Ultimately, this knowledge guides management, which depends on the underlying cause, location, and severity of the abnormality, as well as patient factors. ©RSNA, 2024 Supplemental material is available for this article.


Dual-Source Computed Tomography of the Chest in Blunt Thoracic Trauma: Reduced Aortic Motion Using a Novel Temporal Resolution Optimization Method

April 2019

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60 Reads

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2 Citations

Journal of Thoracic Imaging

Purpose: The purpose of this study was to evaluate the clinical utility of temporal resolution optimization (TR-Opt), a computed tomography (CT) postprocessing technique, in reducing aortic motion artifacts in blunt thoracic trauma patients. Materials and methods: This was an IRB-approved study of 61 patients with blunt thoracic trauma carried out between February 18 and September 6, 2014; the patients had been imaged using a standardized dual-source high-pitch (DSHP) CT protocol. Image raw data were retrospectively postprocessed using the TR-Opt algorithm (DSHP-TR-Opt) and compared with conventional images (DSHP). Diagnostic ability to confidently identify and exclude potential injuries and qualitative aortic motion artifacts using a 5-point Likert scale (1=absence of motion artifacts; 5=severe motion artifact) was graded by 2 readers at multiple thoracic locations. Signal-to-noise and contrast-to-noise ratios were generated as quantitative indices of image quality. Results: Motion artifacts degrading interpretation and limiting diagnosis of aortic injuries were present in 45% (442/976) of the assessed regions on DSHP. TR-Opt algorithm eliminated motion artifacts in 85% of the motion-degraded areas (375/442), leaving persistent motion artifacts in only 15% (67/442). Motion artifacts were most improved at the interventricular septum (1±1 vs. 3±1), aortic valve (2±1 vs. 4±1.5), and ascending aorta (1±1 vs. 3±2, P<0.005). Mean aorta noise (NAo) was 41.7% higher in the DSHP-TR-Opt images (26.5 vs. 18.7 HU, P<0.0001). Conclusions: Temporal resolution optimized reconstruction is a raw data-based CT postprocessing technique that can be used to remove the majority of thoracic aortic motion artifacts that commonly degrade interpretation when imaging blunt thoracic trauma patients.


Dual Energy and Spectral CT Utilization Rates in Acute Abdominopelvic Imaging
  • Conference Paper
  • Full-text available

November 2017

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78 Reads

PURPOSE The clinical applications of Dual Energy CT (DECT) in the abdomen and pelvis is well established. However, the actual utilization rates of DE/Spectral analysis are less well documented, specifically in the acute setting. Our study aims to assess the utilization rates of DECT in acute abdominopelvic imaging in the emergency department and the clinical value added by DE/spectral interrogation methods. METHOD AND MATERIALS For this retrospective, IRB-approved study, the hospital RIS was queried for all abdominopelvic DECT scans performed in the emergency department between January 1 to December 31, 2016. A total of 1238 studies were performed and were included in our study. The reports were reviewed for mention of DE/spectral interrogation as part of the interpretation of the study. Note was made of the number of times DE/spectral interrogation techniques altered management (by changing the diagnosis or detection of an unexpected, clinically relevant finding), confirmed an observation and increased confidence in the definitive diagnosis, provided additional relevant information or characterized an incidental finding – thus avoiding the need for further investigation. RESULTS DE/spectral analysis was utilized in 243 studies out of 1238 (19.63 %). DE/spectral analysis altered management in a significant way 10.3 % of interrogated cases, confirmed suspected observations and increased diagnostic confidence in 21 % of cases, provided relevant information on an observation in 66.7 % of cases and characterized an incidental finding in 18.1 % of cases. DE/spectral analysis was most commonly utilized in assessment of the genitourinary tract (68.5 %) followed by the gastrointestinal tract (20.6 %), the hepatobiliary system (7 %), the musculoskeletal system (2.25 %) and the vascular system (1.5 %). CONCLUSION There is good utilization of DE/spectral analysis in the acute setting, with nearly 1 out of 5 abdominopelvic DECT studies undergoing DE interrogation, adding clinical value to the examination by providing information that would have otherwise required additional imaging or other investigations. DE interrogation altered clinical management in 10 % cases. CLINICAL RELEVANCE/APPLICATION Routine utilization of DE/spectral techniques can impact management, improve diagnostic confidence and provide definitive clinically relevant diagnostic information only capable by DECT/spectral techniques.

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The Utility of Virtual Non-Contrast Images in Assessment of Acute Intracranial Pathology

PURPOSE The purpose of this study is to evaluate whether virtual non-contrast (VNC) images derived from DE CT angiography (CTA) are as reliable as true non-contrast CT (NCCT) images in detecting brain hemorrhage and infarcts. METHOD AND MATERIALS A total of 56 patients with acute stroke symptoms were retrospectively identified between January and April 2016 from a single institution’s emergency department. All the patients underwent both an NCCT and DE CTA. DE images were acquired at 90 kV and Sn 150 kV. Quantitative analysis of the NCCT and VNC Head images were performed using circular region of interests (ROIs) centered on the basal ganglia, internal capsule and the superior sagittal sinus. Mean Hounsfield Units (HU) ± noise was calculated. Two radiologists were blinded and retrospectively interpreted the VNC CT images in comparison to the routine NCCT, assessing for pathology and diagnostic acceptability. The studies were graded on a 5 point Likert scale with 1 being a non-diagnostic examination and 5 representing a diagnostic study similar to a TNC scan. Sensitivity and specificity of VNC at detecting hyperdense-vessel sign, hemorrhage and infarction. RESULTS There was no significant difference between attenuation values for the basal ganglia, internal capsule and superior sagittal sinus on TNC (38.6 HU ± 0.57, 30.3 HU ± 0.56 and 56.5 HU ± 1.4) and VNC (35.6 HU ± 1.6, 30.5 HU ± 1 and 56.2 HU ± 5.2) ( p > 0.1). Sensitivity and specificity of VNC for detection of hemorrhage, hyperdense-vessel sign and infarct was 100% and 100%, 80% and 77.4% and 38.2% and 100% respectively. CONCLUSION VNC images were as reliable as TNC images for detecting hemorrhage and demosntrated acceptable performance in detecting hyperdense-vessel sign. However, VNC images did not reliably detect infarct as compared to TNC images. CLINICAL RELEVANCE/APPLICATION VNC images can reliably diagnose intracranial hemorrhage, however, are not as of yet reliable to forgo the inclusion of a TNC scan in cases of suspected infarction.


Dual Energy/Spectral CT Utilization Rates in the Emergency Radiology Department: Does DECT Add Clinical Value in the Acute Setting?

November 2017

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222 Reads

PURPOSE Several papers have been published in recent years on the potential of Dual Energy CT (DECT) applications and how they may add clinical value to routine CT studies. Our study assessed the utilization rates of DECT in the emergency radiology department of a tertiary care hospital and level I trauma center and the clinical value added by dual energy interrogation methods. METHOD AND MATERIALS For this retrospective, IRB-approved study, the hospital RIS was queried for all DECT scans performed in the emergency department between January 1, 2016 to December 31, 2016. A total of 3159 DECT were performed and were included in our study. The studies were divided by organ system and the reports were reviewed by Emergency Radiology staff, fellows and residents for mention of DE/spectral interrogation as part of the interpretation of the study. Note was made of the number of times DE/spectral interrogation techniques altered management (by changing the diagnosis or detection of an unexpected, clinically relevant finding), confirmed an observation and increased confidence in the definitive diagnosis, provided additional relevant information or characterized an incidental finding – thus avoiding the need for further investigation. RESULTS DE/spectral analysis was utilized in 1497 studies out of 3159 (47.39 %). Utilization rates were highest for the musculoskeletal system (97.8 %) followed by the spine (26.3 %), abdomen and pelvis (19.6 %), head (13 %) and chest (11.8 %). DE/spectral analysis altered management in a significant way 14.7 % of all cases, confirmed suspected observations and increased diagnostic confidence in 13 % of cases, provided relevant information on an observation in 5.7 % of cases and characterized an incidental finding in 1.4 % of all cases. CONCLUSION There is a high utilization rate of dual energy analysis in the acute setting, with close to half of all DECT studies undergoing DE interrogation. DE/spectral analysis frequently adds value to the examination by providing information that would have otherwise required additional imaging or other investigations. CLINICAL RELEVANCE/APPLICATION Routine utilization of DE/spectral techniques can impact management, improve diagnostic confidence and provide definitive clinically relevant diagnostic information only capable by DECT/spectral techniques.



Chapter 63: A Case-Based Guide to Imaging and Management

January 2016

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7 Reads

This chapter details a case of a patient with tuberous sclerosis. The chapter first gives a brief clinical history and reviews the relevant neuroimaging findings from the case. This is followed by a review of the demographics, histopathology, clinical presentation, imaging workup, and differential diagnosis of this entity. Treatment options are briefly reviewed. Key teaching/learning points are highlighted.


Chapter 51: A Case-Based Guide to Imaging and Management

January 2016

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6 Reads

This chapter details a case of a patient with Hurler syndrome. The chapter first gives a brief clinical history and reviews the relevant neuroimaging findings from the case. This is followed by a review of the demographics, histopathology, clinical presentation, imaging workup, and differential diagnosis of Hurler syndrome. Treatment options are briefly reviewed. Key teaching/learning points are highlighted.


Chapter 89: A Case-Based Guide to Imaging and Management

January 2016

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8 Reads

This chapter details a case of a patient with a naked facet sign. The chapter first gives a brief clinical history and reviews the relevant neuroimaging findings from the case. This is followed by a review of the demographics, histopathology, clinical presentation, imaging workup, and differential diagnosis of this entity. Treatment options are briefly reviewed. Key teaching/learning points are highlighted.


Chapter 31: A Case-Based Guide to Imaging and Management

January 2016

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4 Reads

This chapter details a case of a patient with a lipomyelomeningocele. The chapter first gives a brief clinical history and reviews the relevant neuroimaging findings from the case. This is followed by a review of the demographics, histopathology, clinical presentation, imaging workup, and differential diagnosis of this entity. Treatment options are briefly reviewed. Key teaching/learning points are highlighted.


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Citations (3)


... The third-generation DSCT turbo FLASH mode is equipped with wider detector rows and has a gantry rotation speed of 0.25 s, 737 mm/s feed table, and a temporal resolution up to 66 ms with a pitch of 3.2. The acquisition time of the high-pitch wide-coverage scan is significantly reduced, which helps to eliminate the motion artifacts in the cardiovascular application when dealing with the uncooperative or pediatric patients, [1][2][3][4][5][6][7][8][9][10][11] and to reduce the radiation dose and contrast volume when the high-pitch low-voltage protocols are used. [12][13][14][15][16][17][18][19] The scan field of view (SFOV) of the secondgeneration DSCT FLASH mode is limited to 33 cm in diameter (Ø 33 cm), which is not suitable to use in obese patients. ...

Reference:

The ultrafast, high‐pitch turbo FLASH mode of third‐generation dual‐source CT: Effect of different pitch and corresponding SFOV on image quality in a phantom study
Dual-Source Computed Tomography of the Chest in Blunt Thoracic Trauma: Reduced Aortic Motion Using a Novel Temporal Resolution Optimization Method
  • Citing Article
  • April 2019

Journal of Thoracic Imaging

... VNCa images utilize spectral data to detect calcium, then replacing it with a virtual CT number that approximates the expected CT number without calcium. This approach enhances the definition of bone marrow [6••, 25], aiding in the visualization of skeletal lesions linked to bone marrow edema [26] (Fig. 1). Conversely, water HAP material decomposition maps utilize spectral data of water and hydroxyapatite to identify regions with elevated water concentration while suppressing the bone signal [6••, 27•]. ...

Dual Energy CT in Musculoskeletal Tumors
  • Citing Chapter
  • January 2015