Artificial intelligence for detection of intracranial haemorrhage on head computed tomography scans: diagnostic accuracy in Hong Kong.

INTRODUCTION: The use of artificial intelligence (AI) to identify acute intracranial haemorrhage (ICH) on computed tomography (CT) scans may facilitate initial imaging interpretation in the accident and emergency department. However, AI model construction requires a large amount of annotated data for training, and validation with real-world data has been limited. We developed an algorithm using an open-access dataset of CT slices, then assessed its utility in clinical practice by validating its performance on CT scans from our institution. METHODS: Using a publicly available international dataset of >750 000 expert-labelled CT slices, we developed an AI model which determines ICH probability for each CT scan and nominates five potential ICH-positive CT slices for review. We validated the model using retrospective data from 1372 non-contrast head CT scans (84 [6.1%] with ICH) collected at our institution. RESULTS: The model achieved an area under the curve of 0.842 (95% confidence interval=0.791-0.894; P<0.001) for scan-based detection of ICH. A pre-specified probability threshold of ≥50% for the presence of ICH yielded 78.6% accuracy, 73% sensitivity, 79% specificity, 18.6% positive predictive value, and 97.8% negative predictive value. There were 62 true-positive scans and 22 false-negative scans, which could be reduced to six false-negative scans by manual review of model-nominated CT slices. CONCLUSION: Our model exhibited good accuracy in the CT scan-based detection of ICH, considering the low prevalence of ICH in Hong Kong. Model refinement to allow direct localisation of ICH will facilitate the use of AI solutions in clinical practice.

Chest computed tomography analysis of lung sparing morphology: differentiation of COVID-19 pneumonia from influenza pneumonia and bacterial pneumonia using the arched bridge and vacuole signs.

INTRODUCTION: This study evaluated the arched bridge and vacuole signs, which constitute morphological patterns of lung sparing in coronavirus disease 2019 (COVID-19), then examined whether these signs could be used to differentiate COVID-19 pneumonia from influenza pneumonia or bacterial pneumonia. METHODS: In total, 187 patients were included: 66 patients with COVID-19 pneumonia, 50 patients with influenza pneumonia and positive computed tomography findings, and 71 patients with bacterial pneumonia and positive computed tomography findings. Images were independently reviewed by two radiologists. The incidences of the arched bridge sign and/or vacuole sign were compared among the COVID-19 pneumonia, influenza pneumonia, and bacterial pneumonia groups. RESULTS: The arched bridge sign was much more common among patients with COVID-19 pneumonia (42/66, 63.6%) than among patients with influenza pneumonia (4/50, 8.0%; P<0.001) or bacterial pneumonia (4/71, 5.6%; P<0.001). The vacuole sign was also much more common among patients with COVID-19 pneumonia (14/66, 21.2%) than among patients with influenza pneumonia (1/50, 2.0%; P=0.005) or bacterial pneumonia (1/71, 1.4%; P<0.001). The signs occurred together in 11 (16.7%) patients with COVID-19 pneumonia, but they did not occur together in patients with influenza pneumonia or bacterial pneumonia. The arched bridge and vacuole signs predicted COVID-19 pneumonia with respective specificities of 93.4% and 98.4%. CONCLUSION: The arched bridge and vacuole signs are much more common in patients with COVID-19 pneumonia and can help differentiate COVID-19 pneumonia from influenza and bacterial pneumonia.

Intravenous C-Arm Conebeam CT Angiography following Long-Term Flow-Diverter Implantation: Technologic Evaluation and Preliminary Results.

BACKGROUND AND PURPOSE: A noninvasive investigation with high spatial resolution and without metal artifacts is necessary for long-term imaging follow-up after flow-diverter implantation. We aimed to evaluate the diagnostic value of conebeam CT angiography with intravenous contrast enhancement in the assessment of vascular status following implantation of the Pipeline Embolization Device and to analyze the preliminary results of vascular status following long-term Pipeline Embolization Device implantation. MATERIALS AND METHODS: This was an ongoing prospective study of consecutive patients with intracranial aneurysms treated with the Pipeline Embolization Device. Patients with a modified Rankin Scale score of 4-5 were excluded. The median and interquartile range of the time interval of Pipeline Embolization Device implantation to conebeam CT angiography with intravenous contrast enhancement were 56.6 and 42.9-62.4 months, respectively. Conebeam CT angiography with intravenous contrast enhancement was performed with the patient fully conscious, by using a C-arm CT with a flat panel detector. RESULTS: There were 34 patients and 34 vascular segments. In all 34 cases, contrast effect and image quality were good and not substantially different from those of intra-arterial conebeam CTA. Metal artifacts occurred in all 14 cases with coil masses; the Pipeline Embolization Device was obscured in 3 cases. In all 34 cases, there was no residual aneurysm, no vascular occlusion, 1 vascular stenosis (50%), good Pipeline Embolization Device apposition to the vessel, and no Pipeline Embolization Device-induced calcification. All 28 Pipeline Embolization Device-covered side branches were patent. CONCLUSIONS: Conebeam CT angiography with intravenous contrast enhancement is potentially promising and useful for effective evaluation of the vascular status following intracranial flow diverters. The Pipeline Embolization Device for intracranial aneurysms is probably safe and promising for long-term placement, with favorable morphologic outcome and without delayed complications.

Angioplasty and stenting of atherosclerotic middle cerebral arteries with Wingspan: evaluation of clinical outcome, restenosis, and procedure outcome.

BACKGROUND AND PURPOSE: MCA is a common location of intracranial stenosis. It is relatively more peripherally located and of a smaller caliber, and could therefore be a site technically more challenging and risky for angioplasty and stenting. The study aimed to evaluate the clinical outcome, restenosis rate, and procedural safety of Wingspan stent placement for atherosclerosis in the MCA compared with stenosis in other arteries. MATERIALS AND METHODS: Patients who underwent Wingspan stent placement for symptomatic intracranial stenosis of ≥70% (or stenosis of ≥50% for recurrent ischemia despite medical therapy) were recruited prospectively and allocated into a study group (MCA stenosis, n=35) and a control group (other stenosis, n=25). Primary end points were the following: 1) all stroke or death rate at 1 year, and 2) significant in-stent restenosis rate at 1 year. Secondary end points were the following: 1) periprocedural complications within 24 hours, rate of TIA during the procedure, all stroke or death rate within 30 days; and 2) the inability to complete the procedure due to technical problems. RESULTS: Results of study group versus the control group were the following: degree of stenosis, 78.4 ± 10.9% versus 72.5 ± 11.2% (P value=.0456); diameter of stenosis, 0.6 ± 0.3 versus 1.0 ± 0.5 mm (P=.0017); all stroke or death rate at 1 year, 14.3% versus 12% (OR=1.22); in-stent restenosis rate at 1 year, 10% versus 10.5% (OR=1.05); periprocedural complication rate at 24 hours, 2.9% versus 4% (OR=0.70); TIA rate during the procedure, 8.6% versus 4% (OR=2.25); all stroke or death rate at 30 days, 5.7% versus 12% (OR=0.44); and technical failure rate, 2.9% versus 0%. CONCLUSIONS: In this study, there were no significant differences in procedural safety, patient outcome, and restenosis rates of stent placement between the group with MCA stenosis and the group with stenoses located at other sites.

An expedited stroke triage pathway: the key to shortening the door-to-needle time in delivery of thrombolysis.

OBJECTIVES: To assess time management of stroke thrombolysis triage and functional outcomes in patients receiving recombinant tissue plasminogen activator for hyperacute stroke, and identify bottlenecks in delivery of the treatment. DESIGN: Prospective study. SETTING: A university teaching hospital in Hong Kong. PATIENTS: Patients with suspected hyperacute stroke referred to the stroke thrombolysis team during October 2008 to September 2009. MAIN OUTCOME MEASURES: Time performance records including door-to-stroke team, door-to-needle, and onset-to-thrombolysis times. Functional outcomes by modified Rankin Scale score at 3 months, and thrombolysis-related complications including haemorrhagic transformations and mortality. RESULTS: During the 12-month period, 95 thrombolysis calls were received; recombinant tissue plasminogen activator was given intravenously to 17 (18%) of the patients and intra-arterially to 11 (12%). The mean (standard deviation) door-to-stroke team and the door-to-needle times for intravenous recombinant tissue plasminogen activator patients were 33 (25) and 80 (25) minutes, respectively; both were about 20 minutes longer than that recommended by the National Institute of Neurological Disorders and Stroke. The mean National Institute of Health Stroke Scale score for patients received intravenous recombinant tissue plasminogen activator was 16 (standard deviation, 7). The mean (standard deviation) onset-to-treatment time was 144 (42) minutes. Nine (53%) patients who received intravenous recombinant tissue plasminogen activator achieved favourable outcomes at 3 months, with a modified Rankin Scale score of 0 to 1. Symptomatic haemorrhage and mortality occurred in one (6%) patient. CONCLUSION: A dedicated stroke triage pathway is essential to ensure efficient and safe delivery of thrombolysis therapy. Improvements in door-to-stroke team time through integration with emergency medicine staff and neuroradiologists may improve thrombolysis eligibility.

Triple coaxial catheter technique for transfacial superior ophthalmic vein approach for embolization of dural carotid-cavernous fistula.

We report a triple coaxial catheter technique to facilitate the venous access to the superior ophthalmic vein during transvenous embolization of dural carotid-cavernous fistula (DCCF) via the transfacial venous route. Two patients with transvenous embolization of DCCFs by coils were treated with transfacial superior ophthalmic vein (SOV) approach by the triple coaxial catheter technique. The triple coaxial catheter system consisted of a 6F guiding catheter as the outer catheter and a 4F guiding catheter as the middle catheter and a microcatheter as the inner catheter to help navigation and manipulation. The DCCFs were completely obliterated in both cases. There were no complications associated with the procedure. The ophthalmic symptoms of the patients had totally resolved at two-month follow-up. The triple coaxial catheter technique can be used with the transfacial SOV approach in embolization of DCCF. This technique has two advantages over the double coaxial catheter technique because it offers additional length and support for the distal navigation of microcatheter into the SOV.

Radiofrequency ablation for 110 malignant liver tumours: preliminary results on percutaneous and surgical approaches.

BACKGROUND: Radiofrequency ablation (RFA) has been widely applied for the treatment of hepatocellular carcinoma and liver metastases. The reported mortality and morbidity rates are low. The aim of this study is to evaluate the safety and efficacy of RFA, and compare the results performed percutaneously versus surgically. PATIENTS AND METHODS: From 2003 to 2006, 79 patients with hepatic malignancies (59 hepatocellular carcinoma, 20 liver metastases) with a total of 110 lesions underwent RFA in our centre. Postablation assessment by CT scan was performed in all patients at 1-, 3- and 6-month intervals. Post-procedural complications, recurrence and survival were analysed. RESULTS: The patients' mean age was 60.0 years. In 46.8% of cases, we used a percutaneous approach; in 53.2% of cases, a surgical approach (8.9% laparoscopic; 44.3% open) was used if percutaneous approach was not feasible. The mean tumour size was 2.4 cm. Within the surgical group, 69% of patients received concomitant operative procedures such as cholecystectomy and hepatectomy. No treatment-related mortality was observed. Immediate complications occurred in five patients (6.3%), including gastric serosal burn (n = 1), ground pad superficial skin burn (n = 1), intra-abdominal bleeding (n = 2) and pleural effusion (n = 1). All patients except one attended subsequent follow-up, with a mean period of 16 months. Ablation was considered complete in 82.3% of patients (percutaneous approach 81.1%, surgical approach 83.3%, p = 0.72). Intrahepatic recurrence was observed in 52.3%, the majority of them located away from the RFA site. Extrahepatic recurrences were observed in 16.9% (percutaneous approach 16.7%, surgical approach 17.1%, p = 0.76). The overall one- and two-year survival rate was 93.7% and 74.4% respectively, and no statistically significant difference was observed between the two approaches. CONCLUSION: RFA is a safe and effective procedure for treating patients with malignant liver tumours. No difference in short term outcomes was observed between percutaneous and surgical approaches. A more prolonged follow-up study is required to assess longer-term outcomes.

Carbon dioxide wedged arterial splenoportography: a new technique--a case report and an experimental study.

BACKGROUND: Patients with splenic vein occlusion may present a diagnostic problem when the location, morphology, and cause of the obstructive lesion and the associated collateral veins cannot be clearly defined by standard diagnostic imaging modalities such as computed tomography, magnetic resonance venography, or indirect splenoportography (arterial portography). PURPOSE: To evaluate the safety and effectiveness of carbon dioxide (CO(2)) wedged arterial splenoportography for definitive investigation of splenic vein occlusion. MATERIAL AND METHODS: Following unsuccessful diagnosis with computed tomography and standard contrast arterial portography in a patient with recurrent gastric variceal bleeding, CO(2) was injected into a wedged splenic arterial catheter and successfully outlined splenic vein occlusion and gastric varices. Our experience with this patient prompted us to perform an experimental study in swine to evaluate the safety and effectiveness of CO(2) wedged arterial splenoportography for visualization of the splenic and portal veins. A microcatheter was advanced coaxially and wedged into the splenic arteries of three pigs. After checking the wedged positioning with contrast medium injection, CO(2) was injected manually and the splenic region imaged. The spleens were then removed for gross and microscopic examinations. RESULTS: In the patient, CO(2) wedged arterial splenoportography demonstrated gastric varices associated with splenic vein occlusion. In all animals, CO(2) wedged arterial splenoportography visualized the splenic and portal veins. No CO(2) extravasations occurred in the spleen. Gross and microscopic examinations revealed no evidence of splenic rupture or intrasplenic hematoma. CONCLUSION: CO(2) wedged arterial splenoportography may be a useful method for visualizing gastric varices associated with splenic vein occlusion. This new technique has the potential to replace the standard splenic arterial portography for visualization of splenic and portal veins, thus eliminating the need for injection of a large volume of iodinated contrast material. Further clinical studies are justified to evaluate this technique.

Transvenous embolization for dural transverse sinus fistulas with occluded sigmoid sinus.

Dural transverse sinus arteriovenous fistulas with cortical venous drainage were associated with a high hemorrhagic risk. Dural transverse sinus arteriovenous dural fistulas could be treated by embolization (transarterial or transvenous), surgery or a combination of both. Transvenous packing of the diseased sinus was considered to be a less invasive and effective method of treatment. Occluded sigmoid sinus proximally, especially cases with isolated transverse sinus, could make the transvenous approach difficult. Craniotomy for sinus packing or surgical excision remained the treatment of choice when the percutaneous transvenous approach was not feasible. We reviewed the techniques of transvenous embolization described in the literature and illustrated our techniques in two consecutive cases of transvenous embolization of the dural arteriovenous fistulas through the occluded sigmoid sinus. We concluded that transvenous embolization remains a safe and feasible technique other than surgery for patients with transverse sinus dural fistula, achieving a long-term occlusion of the pathology.

Delayed complications of radiotherapy treatment for nasopharyngeal carcinoma: imaging findings.

Radiotherapy is used to treat a wide variety of head and neck tumours that arise in and around the skull base. The delayed effects of radiation damages a range of structures, including the nervous system, bone, major vessels, mucus membranes, pituitary and salivary glands, as well as increasing the risk of radiation-induced neoplasms. In this review the complications resulting from radiation treatment for nasopharyngeal carcinoma (NPC), a cancer treated with a high dose of radiation to a fairly large region, are illustrated. Many patients with NPC have a long-term survival, so are at risk of developing delayed radiation effects, and hence may demonstrate a wide range of complications on imaging. Other tumours around the skull base treated with radiotherapy include meningiomas, chordomas, chondrosarcomas, pituitary adenomas, paranasal sinus and nasal cavity tumours. In these cases similar complications may be encountered on imaging, although the severity, incidence and location will vary.

A rare anatomic variant of a solitary internal carotid artery associated with moyamoya phenomenon of the middle cerebral artery.

A case of a congenital solitary internal carotid artery with complicated anastomosis is presented. This rare anomaly was an incidental finding at cerebral angiography in a patient with a poor-grade subarachnoid hemorrhage and a ruptured anterior communicating artery aneurysm.

Preoperative evaluation of resectability of Klatskin tumor with 16-MDCT angiography and cholangiography.

OBJECTIVE: The objective of our study was to evaluate prospectively the preoperative use of 16-MDCT angiography and cholangiography in determining the resectability of Klatskin tumors. CONCLUSION: Preoperative MDCT angiography and cholangiography gave a good assessment of the degree of vascular and biliary involvement of the Klatskin tumor.

Aneurysm recurrence after treatment of paraclinoid/ophthalmic segment aneurysms--a treatment-modality assessment.

OBJECT: The treatment of 21 paraclinoid/ophthalmic segment internal carotid artery aneurysms (PCOSAs) over a seven year period in a regional neurosurgical center was reviewed to assess the degree of obliteration and recurrence rate of these aneurysms after treatment by surgical and endovascular methods. METHOD AND RESULT: An assessment of the clinical notes, operation records and cerebral angiograms was made to evaluate the rate of residual and recurrent aneurysms after treatment and at follow-up. In the coiling group, the aneurysm recurrence rate was eight out of fifteen aneurysms (53%). Four recurrences were from previously totally occluded aneurysms. Out of the six surgical cases, five had follow-up angiography performed. All had stable occlusions of their aneurysms including one with subtotal occlusion. Two clipping procedures after previous coiling achieved total occlusion of aneurysm on follow-up angiography. CONCLUSION: Based on our case series we conclude that PCOSAs frequently recur after primary treatment. GDC coiling was associated with a higher rate of recurrent aneurysms when compared with surgical treatment. A review of the literature on the surgical and endovascular treatment of PCOSAs support this observation.

Case report: lumbar artery bleeding as a complication of percutaneous nephrostomy in a patient with coagulopathy.

A case of severe lumbar artery bleeding as a complication of percutaneous nephrostomy (PCN) is presented. A 70-year-old man with coagulation disorder (factor VIII deficiency) underwent left PCN because of left hydronephrosis and abnormal renal function. The procedure was complicated by a major haemorrhage from the left first lumbar artery into the left posterior pararenal space. This case illustrates bleeding from the lumbar artery in a patient with coagulation disorder resulting in a fatal outcome. CT can provide the diagnosis, while angiography with embolisation is an effective means to control the bleeding. These examinations should be performed as soon as possible.

Vascular lesions of parotid gland in adult patients: diagnosis with high-resolution ultrasound and MRI.

Three adult patients with rare vascular lesions in the parotid gland including pseudoaneurysm, arteriovenous fistula and haemangioma are discussed. All patients presented with non-specific unilateral parotid mass. In all cases high-resolution ultrasound and MRI allowed accurate diagnosis and delineation of the extent of lesion. Conventional angiogram was utilized for planning definitive surgical or endovascular treatment.

Prediction of differential creatinine clearance in chronically obstructed kidneys by non-contrast helical computerized tomography

PURPOSE: We investigate the use of non-contrast helical computerized tomography (NCHCT) in the measurement of differential renal parenchymal volume as a surrogate for differential creatinine clearance (CrCl) for unilateral chronically obstructed kidney. MATERIALS AND METHODS: Patients with unilateral chronically obstructed kidneys with normal contralateral kidneys were enrolled. Ultrasonography (USG) of the kidneys was first done with the cortical thickness of the site with the most renal substance in the upper pole, mid-kidney, and lower pole of both kidneys were measured, and the mean cortical thickness of each kidney was calculated. NCHCT was subsequently performed for each patient. The CT images were individually reviewed with the area of renal parenchyma measured for each kidney. Then the volume of the slices was summated to give the renal parenchymal volume of both the obstructed and normal kidneys. Finally, a percutaneous nephrostomy (PCN) was inserted to the obstructed kidney, and CrCl of both the obstructed kidney (PCN urine) and the normal side (voided urine) were measured two 2 after the relief of obstruction. RESULTS: From March 1999 to February 2001, thirty patients were enrolled into the study. Ninety percent of them had ureteral calculi. The differential CrCl of the obstructed kidney ( percentCrCl) was defined as the percentage of CrCl of the obstructed kidney as of the total CrCl, measured 2 weeks after relief of obstruction. The differential renal parenchymal volume of the obstructed kidney ( percentCTvol) was the percentage of renal parenchymal volume as of the total parenchymal volume. The differential USG cortical thickness of the obstructed kidney ( percentUSGcort) was the percentage of mean cortical thickness as of the total mean cortical thickness. The Pearson's correlation coefficient (r) between percentCTvol and percentCrCl and that between percentUSGcort and percentCrCl were 0.756 and 0.543 respectively. The regression line was percentCrCl = (1.00) x percentCTvol - 14.27. The percentCTvol overestimated the differential creatinine clearance by about 14 percent, but the correlation is good. CONCLUSION: The differential renal parenchymal volume measured by NCHCT provided a reasonable prediction of differential creatinine clearance in chronically obstructed kidneys.