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ABSTRACT: Catheter angiography is an established imaging modality of evaluating cerebral and head and neck vascular diseases. It is, however, an invasive procedure with a small risk of complications. The aim of our study was to evaluate the prevalence of peri-procedural complications in a local hospital setting.
A total of 88 patients underwent diagnostic and interventional craniocervical procedures over 6 months in our department. The casenotes of 83 patients were retrospectively reviewed for complications arising from a total of 99 procedures carried out.
A new focal neurological deficit developed in 3 different patients after a procedure, giving a prevalence of 3.0%. All these occurred in diagnostic procedures and were permanent deficits with correlative computed tomography (CT) or magnetic resonance (MR) imaging findings of acute cerebral infarction. All these occurred in high-risk patients who had severe underlying cerebrocarotid vascular compromise. There was 1 case of contrast medium-induced nephropathy (1.0%), occurring in a patient with pre-existing renal impairment. Local complications included 1 case of iatrogenic external iliac artery dissection (1.0%) and 5 cases (5.1%) of small and uncomplicated puncture site groin haematomas.
The most significant complication associated with a craniocervical angiographic procedure was the development of post-procedural stroke in patients with significant preexisting cerebrocarotid vascular compromise. In the absence of this risk factor, craniocervical catheter angiography is a relatively safe procedure.
Annals of the Academy of Medicine, Singapore 10/2004; 33(5):607-13. · 1.25 Impact Factor
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ABSTRACT: Cerebrovascular accident (CVA) is a leading cause of death and disability in many countries. Diffusion-weighted (DW) magnetic resonance (MR) imaging has been reported to be useful in the detection of acute strokes and as an investigative tool evaluating the therapeutic effects of neuroprotective and thrombolytic agents. The objectives of this study are to share our experience using the commercially available isotropic DW scan in imaging of acute stroke, assess its usefulness over conventional T2-weighted (T2W) scans in a busy clinical radiology unit and highlight it pitfalls. We found the rapid sub-minute DW technique well suited for ill and restless stroke patients and superior to T2W scans in many ways. It was highly sensitive to acute ischaemic lesions, made lesions easily identifiable and readily differentiated the acute lesion from a background of multiple chronic infarcts. However, there are potential pitfalls in the evaluation of small hyperacute posterior fossa strokes and venous infarcts. The major strength of this MR technique lies in its ability to diagnose hyperacute strokes and thence the potential for therapeutic thrombolysis, but unfortunately patients qualifying for the "therapeutic window" were a minority. More efforts need to be focused on public education in order for this powerful imaging modality to find its true value and contribute to viability of an effective thrombolytic programme.
Singapore medical journal 04/2002; 43(3):118-23. · 0.73 Impact Factor
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ABSTRACT: It has been reported that reduction of the apparent diffusion coefficient (ADC) after stroke can persist for several days, after which the ADC increases gradually to an abnormally high level. We evaluated ADC values of stroke lesions and compared the results to the cellular density of the lesion by means of the creatine (Cre) level. This two-parameter estimation is of particular relevance in ascertaining the underlying cellular status. Lesion-to-contralateral ADC ratios (ADCn) were obtained based on diffusion-weighted echo-planar and fast spin-echo imaging. Single-voxel localized spectroscopy was used for quantification of cerebral metabolites in infarcted regions. Their levels were also compared to that in homotopic contralateral regions. Fifteen patients with ischemic stroke were examined at times ranging from 18-88 hours following the onset of symptoms. In the stroke lesion, there was a significant correlation between the ADC and the Cre level showing that the higher the cell density the lower the ADC value. For ADCn vs. the lesion Cre concentration and the lesion-to-contralateral Cre ratio (Cre(n)), the strengths of relationship were R2 = 0.70 and 0.58, respectively. It is concluded that ADC is a good reflection of cell density. Greatly lowered ADC values occur within the context of a stable cellularity. ADC and the Cre level have complementary roles in the characterization of stroke lesion with regard to the sequential stage.
Journal of Magnetic Resonance Imaging 04/2001; 13(3):335-43. · 2.70 Impact Factor
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ABSTRACT: To evaluate the roles and effectiveness of US and CT in a clinical algorithm for the evaluation of children with suspected appendicitis.
Patients with suspected appendicitis were prospectively evaluated with ultrasound (US), and in some cases with CT, after they were graded to have high, intermediate or low clinical likelihood for appendicitis. Imaging findings were made known to clinicians who then decided on a line of management. Patho-histological examination and clinical follow-up established the final diagnoses, which were correlated with the imaging findings. The effect of imaging on the management of patients was examined.
Overall, the sensitivity of US was 92.9%, specificity 96.9%, accuracy 96.0%, positive predictive value 89.7% and negative predictive value 97.9%. Imaging did not affect the decision to operate in 13/14 (92.9%) patients in the high likelihood subgroup. Imaging guided the clinicians to the right management pathway in 26/30 (86.7%) patients in the intermediate group. 77/82 (93.9%) of US was truly negative in the low likelihood group. CT was performed in 12 patients because of unsatisfactory US scans or incompatibility between the US and the clinical findings. CT correctly diagnosed the presence or absence of appendicitis in all 12 patients.
US and CT are accurate modalities in the diagnosis of acute appendicitis in children. US is most useful in patients with equivocal clinical findings. US should be the first modality used to evaluate children with suspected appendicitis. CT should be reserved for cases where US is sub-optimal or where the findings are inconsistent with the clinical findings.
Singapore medical journal 09/2000; 41(8):387-92. · 0.73 Impact Factor
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ABSTRACT: The ability to categorise mammographic features according to their likelihood of malignancy would be valuable in the management of women with abnormal mammograms. The aim of our study was to correlate abnormal mammographic features in a screened population with their histology to identify those features which are predictive of malignancy. The study also examined the spectrum of mammographic features in an Asian population.
This prospective study involved 28,231 women who were randomly selected from a population registry and underwent two-view screening mammography without physical examination. Women with suspicious lesions were recalled for further mammographic views or to a joint assessment clinic prior to biopsy. Mammographic abnormalities and their corresponding histology were assessed.
The spectrum of mammographic abnormalities was similar to that in Caucasian populations. The positive predictive value for malignancy was 44.1% of all biopsied cases. Mammographic features could be broadly classified into low-, moderate- and high-risk categories for malignancy. Those features which correspond to high malignancy rates (9.8% to 16.0%) include multiple abnormalities or parenchymal lesions with microcalcifications. The presence of microcalcifications was a good predictor of ductal carcinoma-in-situ (DCIS): 46% of lesions in which the microcalcifications were the sole abnormality were DCIS only. Further, 71% of cancers with any microcalcification on the mammogram had a focus of DCIS on histology.
Mammographic abnormalities can be segregated into three risk groups for malignancy, and this in turn can improve the selection criteria for breast biopsy, hence reducing unnecessary intervention. Furthermore, the presence of microcalcifications denotes the presence of DCIS, and would be an important determinant of the extent of surgical excision.
Annals of the Academy of Medicine, Singapore 08/2000; 29(4):457-62. · 1.25 Impact Factor
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ABSTRACT: Magnetic resonance (MR) imaging of brain metastases relies on the neovascularity of metastases and the associated breach of blood-brain barrier manifesting as enhancement on T1-weighted images. There are 2 main strategies to improve the detection of brain metastases. One may increase the dose of gadolinium and increase the signal of the lesion. Alternatively, one may also lower the signal of the background (by magnetisation transfer suppression), in which case the enhancing lesion is rendered more conspicuous without increasing the dose of gadolinium. We aim to compare the efficacy of single-dose conventional spin-echo T1 scans with magnetisation transfer (MT) suppression with triple-dose conventional spin-echo T1 scans in the detection of brain metastases in 18 patients undergoing imaging for brain metastases. An incremental dose technique was employed. After administration of a single dose of gadolinium, MT suppressed T1-weighted scans were obtained, followed by a conventional T1 scan. Two doses of gadolinium were subsequently given, achieving a cumulative triple-dose, and a conventional T1-weighted scan was then performed. We found single-dose MT suppressed and triple-dose scans performed equally well and detected 26 metastatic lesions. They detected 5 (5/26, 19%) more lesions than the conventional single-dose T1 scans. Five (5/21, 24%) questionable lesions on single-dose conventional scans were confidently diagnosed on the single-dose MT suppressed and the triple-dose conventional scan. We conclude that single-dose MT suppressed scans are a cost-effective technique of detecting brain metastases.
Annals of the Academy of Medicine, Singapore 08/1999; 28(4):529-33. · 1.25 Impact Factor
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ABSTRACT: The phenotypic variability in X-linked adrenoleukodystrophy (X-ALD) can be wide and varied. Rarely, it can present with clinical signs of spinocerebellar degeneration. There are very few reported cases of selective predominant white matter disease of the cerebellum in these patients. We report a patient with a rare variant of adult onset ALD who was previously diagnosed as spinocerebellar ataxia. He was a 24-year-old male who had delayed developmental milestones, developed signs of spinocerebellar degeneration (SCD) after 10 years of Addison's disease. Serial Magnetic Resonance Imaging (MRI), revealed cerebellar and pontine white matter disease but sparing the cerebral cortex and supratentorial white matter. His diagnosis of X-ALD was subsequently confirmed by the elevated serum very long chain fatty acids. This patient illustrates the unusual clinical presentation and imaging features of X-ALD and the importance of considering X-ALD in the clinical context of spinocerebellar degeneration. Early recognition of this rare variant would allow proper genetic counselling and institution of dietary therapy and/or bone marrow transplantation.
Clinical Neurology and Neurosurgery 07/1999; 101(2):137-40. · 1.58 Impact Factor
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ABSTRACT: Vascular compression of the facial nerve is a well recognized cause of hemifacial spasm (HFS). In this study, we described the magnetic resonance imaging (MRI) and three-dimensional magnetic resonance angiography (MRA) techniques used and findings in 34 patients with hemifacial spasm. A vascular abnormality, defined as a vessel seen in close proximity, touching or compressing the facial nerve, was identified in 22 of the 25 patients (88%) who had both MRI and MRA studies. Vessels identified were anterior inferior cerebellar artery (59.2%), posterior inferior cerebellar artery (13.6%), vertebral artery (18.2%) and basilar artery (4.5%). All vascular abnormalities were ipsilateral to the side of the HFS. Only 3 of the 12 controls (25%) had a vascular abnormality in both MRI and MRA studies. One of the 9 HFS patients (11.1%) who had MRI only had an ipsilateral vascular abnormality. There is a role for combined MRI and MRA studies in the non-invasive evaluation of patients with HFS.
Annals of the Academy of Medicine, Singapore 04/1999; 28(2):169-73. · 1.25 Impact Factor
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ABSTRACT: The availability of computed radiography has opened the possibility of using reduced dosage for radiographs in clinical settings and reducing the retake rate. A prospective controlled study was carried out over a period of four months comparing conventional X-rays and computed radiography. The aim was to assess if computed radiography at 50% normal dosage would result in films of adequate quality and a reduced retake rate compared to conventional radiography. The number and reason for retakes in each group were recorded. Film quality comparison using only chest X-rays (CXR) in one of three positions; erect posterior-anterior (PA), anterior-posterior (AP) sitting and supine was done by a panel of radiologists. A total of 6373 conventional and 4127 digital films were analysed. The overall retake rate was lower in the computed radiography group (4.6 vs 8.2% P < 0.001) as was the retake rate due to exposure factors (0.6% vs 3.2% P < 0.01). There was a higher proportion of optimal films in the computed radiography group for erect PA and sitting AP CXR (71% vs 61% P = 0.0015 and 64% vs 9% P = 0.0009 respectively) but no difference for supine films. Computed radiography resulted in a reduced retake rate due to exposure factors leading to a reduction in the overall retake rate. Despite 50% dosage reduction, films were of better or equal quality when compared to conventional radiography.
Annals of the Academy of Medicine, Singapore 12/1998; 27(6):805-7. · 1.25 Impact Factor
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Clinical Radiology 09/1998; 53(8):619-22. · 1.95 Impact Factor
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E H Ng,
F C Ng,
P H Tan,
S C Low,
G Chiang, K P Tan,
A Seow,
S Emmanuel,
C H Tan,
G H Ho,
L T Ng,
C C Wilde
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ABSTRACT: Although increasing rates of breast carcinoma incidence have been observed in Asian countries, appropriate strategies for detecting early stage breast carcinoma in such communities have been difficult to formulate, particularly because no large population screening trial specifically involving Asian women has been reported. The objective of this study was to evaluate the effectiveness and quality of mammography as a screening technique for Singaporean women, who are predominantly Chinese.
In this prospective study, 166,600 women in Singapore ages 50-64 years were randomized to either 2-view mammography without physical examination (67,656) or observation (97,294, controls) over 2 years.
Of these women, 28,231 (41.7%) responded and were screened; they were more likely to be married, have more formal education, be working, be Chinese, and be in a higher socioeconomic group (P < 0.001 for all variables). To assess for response bias that could affect outcome, results were also evaluated for nonrespondents (n = 39,425). The incidence rate of cancers among nonrespondents (1 per 1000 woman-years) was less than the 1.3 in women not invited to have screening (P = 0.03, relative risk [RR], 1.3; 95% confidence interval [CI], 1.0-1.7). However, cancers arising from nonrespondents did not differ significantly in stage distribution when compared with cancers within the control group. For every 1000 women screened, 4.8 cancers were detected. The prevalence ratio (the number of cancers detected per 1000 women at first screening divided by the corresponding incidence rate in controls per year) was 3.6 for screened women and 2.4 for women invited to have screening. The majority of cancers detected through screening were early stage, with 64% as either ductal carcinoma in situ (26%) or Stage I disease (38%) and was significantly more than the corresponding 26% in women not invited to have screening (P < 0.001). When only invasive cancers were considered, screened women still had more early cancers, with 65% having no lymph node involvement, compared with 47% in the group not invited to have screening (P = 0.001; RR, 1.4; 95% CI, 1.2-1.7). Women who were screened had half the risk of having Stage II or later cancers (P < 0.0001; RR, 0.5; 95% CI, 0.4-0.7) when compared with women not invited to have screening. This higher detection rate of early cancers through screening was accomplished with acceptable recall rates of 8% for further mammographic films or physical examination and a biopsy rate of 1.0% (10 per 1000 women screened). The interval cancer rate was 2.1 per 10,000 women screened in the first year of follow-up.
These positive results of intermediate measures suggest that, in Asian communities, screening mammography could be an important modality for detecting early stage breast carcinoma. However, the low compliance rates suggest that health education efforts must focus on issues related to acceptability if such programs are to succeed.
Cancer 05/1998; 82(8):1521-8. · 4.77 Impact Factor
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ABSTRACT: Computed radiology is a radiographic imaging technology that generates a conventional radiographic image in digital form. The image can be recorded on a laser sensitive film or archived to a digital storage device and displayed on a video monitor. This study was performed to evaluate the adequacy of reporting digitised images directly from the workstation. The test set consisted of portable chest images of 55 patients from the cardiothoracic intensive care unit. Normal structures and nine abnormalities were pre-selected for analysis. The radiographs and images on the video display were reviewed on two separate occasions, six months apart by two independent readers. No clinical details were supplied and the intraobserver and interobserver agreement were assessed using Kappa statistics. The overall results indicated that direct reporting from the workstation was as reliable as reporting from the laser printed copies.
Annals of the Academy of Medicine, Singapore 04/1998; 27(2):178-81. · 1.25 Impact Factor
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ABSTRACT: Kimura's disease is an immune mediated inflammatory disorder that usually involves the head and neck region, primarily affecting the salivary glands, adjacent muscle and regional lymph nodes. Peripheral blood eosinophilia is the norm. Clinically and radiologically, it is difficult to differentiate Kimura's disease from salivary gland malignancy, lymphoma or haemangioma. The radiological findings of a patient who presented with a left facial mass involving the left parotid gland and the adjacent muscles are discussed. We also propose that the difference in the degree of enhancement between the initial and subsequent computed tomography study done two and a half years later may be due to the development of increased fibrosis and sclerosis as the disease progresses.
Singapore medical journal 04/1997; 38(3):125-8. · 0.73 Impact Factor
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ABSTRACT: A teleradiology link was established between Singapore General Hospital in Singapore and Stanford University in California, USA. Over eight months, a total of 28 cases (involving 27 magnetic resonance investigations and three computerized tomography scans) were transmitted by ISDN to California. Our initial experience with teleradiology for remote consultation was encouraging, although the data transmission cost was higher than we anticipated. however, costs could be reduced by using data compression. Long-distance telecommunication charges continue to fall, so intercontinental teleradiology of this type may be financially viable in future.
Journal of Telemedicine and Telecare 02/1997; 3 Suppl 1:54-5. · 1.21 Impact Factor
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ABSTRACT: Central pontine and extrapontine myelinolysis is a distinctive clinical syndrome and has characteristic CT and MR features. We describe two patients who presented with nasopharyngeal carcinoma, severe hyponatremia, and had quick correction of hyponatremia. Low T1 and high T2 signal alterations were seen in the basal ganglia and caudate nuclei in both patients whilst one of them had concommitant ventrolateral thalami and central pontine region involvement. Neurologic recovery was good in one case, and initially seen in the other patient before death resulted from septicaemia. Peripheral enhancement of the basal ganglia and caudate nuclei was seen in one patient, which we believe is a new feature.
Singapore medical journal 01/1997; 37(6):622-6. · 0.73 Impact Factor
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ABSTRACT: In computed tomography of young children, the frontal subarachnoid spaces were sometimes noted to be prominent in scans which were otherwise normal. These apparently enlarged spaces raise the suspicion of possible subdural hygromas. The objective of this study is to show the trend and variability of the intracranial subarachnoid spaces, especially the frontal subarachnoid spaces with age in children. Computed tomographic scans of 39 children up to five years of age with normal head scans were assessed for sizes of the subarachnoid spaces which were subjectively graded from I to V. Grade I is not visible while grade V is borderline enlargement. The sizes of the subarachnoid spaces were found to be more variable in those below the age of two years, with a tendency to be larger compared to older children. Based on these observations, prominent subarachnoid spaces in those below the age of two years should be considered a normal variant. A diagnosis of subdural hygroma must, therefore, be made with caution.
Annals of the Academy of Medicine, Singapore 10/1993; 22(5):732-5. · 1.25 Impact Factor
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ABSTRACT: To investigate the accuracy of magnetic resonance angiography (MRA), compared to conventional cerebral and carotid angiography (CA), 45 patients underwent MRA within one week after CA. The MRA involves a FISP (fast imaging steady precession) pulse sequence base on three-dimensional time-of-flight phenomena at 1.0 Tesla. Repetition time of 35-40 msec, echo time of 7-11 msec and a flip angle of 15-25 degrees were used to optimise the depiction of blood flow as high intensity. Volume data were then submitted to a maximum intensity projection programme and viewed at multiple arbitrary projection angles rotating through the three orthogonal planes. Venous structures were suppressed with a presaturation slab superior to the area of interest. All significant stenoses and occlusions at the carotid bifurcation and circle of Willis were detected. Other than the carotid siphon (61.4%), the rest of the arteries have above 70% complete agreement between MRA and CA. The carotid bifurcation and basilar artery show complete agreement of 75.4% and 76.2% respectively, making MRA a simple sensitive screening procedure. This report shows that MR angiography has an important role in the evaluation of blood flow in the head and neck regions.
Annals of the Academy of Medicine, Singapore 10/1993; 22(5):742-8. · 1.25 Impact Factor
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ABSTRACT: Cerebral venous angioma (CVA) is an embryonic venous malformation. Its incidence was thought to be radiologically rare previously but with greater clinical awareness, the routine use of contrast enhanced computerised tomography (CECT) and the increasing availability of magnetic resonance imaging (MRI), it is no longer perceived to be a rare lesion. In fact, it is the commonest intracranial vascular malformation seen at autopsy. We report our experience of 15 patients with cerebral venous angiomas, 14 of whom had their lesions confirmed by cerebral angiography. Presentation was variable and non-specific. The commonest presenting symptom was headache (n = 7). Other clinical presentations included epilepsy (n = 5), intracerebral bleed (n = 4, two were thought to be due to an associated cerebral cavernous angioma and one was due to a ruptured arteriovenous malformation) and non-specific giddiness (n = 3). Six were diagnosed incidentally. Based on the angiographic findings and the relatively benign clinical course in the majority of our patients, we believe that CVA is a developmental anomaly and should not be excised routinely.
Annals of the Academy of Medicine, Singapore 10/1993; 22(5):736-41. · 1.25 Impact Factor
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The Annals of otology, rhinology, and laryngology 10/1993; 102(9):735-7. · 1.05 Impact Factor
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ABSTRACT: In the assessment of radiologic manifestations of joint diseases, rheumatoid arthritis (RA) is the disease to which all others are compared. Knowledge of its characteristics form the basis of the other conditions. To understand the changes seen on the plain radiograph, it is essential to understand its pathophysiology first so that the manifestations of each disease can be appreciated more fully. Due to space constraint, I shall only discuss the main forms of rheumatic joint disease. Other examples of erosive arthropathies, although not rheumatic in origin, will also be included as they form part of the differential diagnosis of an erosive arthropathy, eg gout and psoriasis.
Singapore medical journal 09/1992; 33(4):395-9. · 0.73 Impact Factor
