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Biomedical subjects

F C Ng

Publications and source records attributed to F C Ng.

At least 19 recordsLinked to original sources
PubMed2005

Computer-assisted navigational surgery enhances safety in dental implantology.

INTRODUCTION: Dental implants are increasingly used to restore missing dentition. These titanium implants are surgically installed in the edentulous alveolar ridge and allowed to osteointegrate with the bone during the healing phase. After osseo-integration, the implant is loaded with a prosthesis to replace the missing tooth. Conventional implant treatment planning uses study models, wax-ups and panoramic x-rays to prefabricate surgical stent to guide the preparation of the implant site. The drilling into the alveolar ridge is invariably a "blind" procedure as the part of the drill in bone is not visible. Stereotactic systems were first introduced into neurosurgery in 1986. Since then, computer-assisted navigational technology has brought major advances to neuro-, midface and orthopaedic surgeries, and more recently, to implant placement. CLINICAL FEATURE: This paper illustrates the use of real-time computer-guided navigational technology in enhancing safety in implant surgical procedures. OUTCOME AND CONCLUSION: Real-time computer-guided navigational technology enhances accuracy and precision of the surgical procedure, minimises complications and facilitates surgery in challenging anatomical locations.

Dental Implantation↗
PubMed2004

Interaction of dense breast patterns with other breast cancer risk factors in a case-control study.

The question of interactions between breast density and other breast cancer risk factors is of interest, since it bears upon the use of density as a marker for changes in breast cancer risk. We studied breast parenchymal patterns and 13 other potential risk factors for breast cancer in 172 breast cancer cases and 338 age-matched controls in Singapore. Dense breast patterns were defined as having Tabar parenchymal pattern IV or V. We found significant interactions between dense patterns and ethnic group (P=0.046), and between dense patterns and number of deliveries (P=0.04). Among women with nondense breast patterns, the non-Chinese had lower risk than the Chinese with an odds ratio (OR) of 0.47 (95% CI 0.24, 0.88), whereas in those with dense patterns, the non-Chinese had considerably higher risks (OR=5.34, 95% CI 0.54, 52.51). Alternatively expressed, the increased risk with dense patterns was only observed in the non-Chinese (OR=13.99, 95% CI 1.33, 146.99). Among parous women, the protective effect of three or more deliveries was only observed in those with dense breast patterns (OR=0.21, 95% CI 0.06, 0.70). Suggestive but nonsignificant interactions with dense patterns were observed for ever having delivered, age at first delivery, breast feeding and body mass index. The results are consistent with dense breast patterns as a marker for hormonal modification of breast cancer risk.

Adolescent↗
PubMed2004

Extracorporeal shockwave lithotripsy and intracorporeal lithotripsy for proximal ureteric calculi--a comparative assessment of efficacy and safety.

INTRODUCTION: Extracorporeal shockwave lithotripsy (ESWL) is the treatment modality of choice of many urologists for proximal ureteric calculi. In this study, we compared the efficacy and safety of ESWL versus ureteroscopy with holmium laser lithotripsy for the treatment of this group of stones. MATERIALS AND METHODS: Between May 1999 and October 2000, 50 patients had ESWL and another 51 patients underwent ureteroscopy with holmium laser lithotripsy for proximal ureteric calculi. The two groups were similar in age, sex ratio and stone size. ESWL was performed with the Dornier Compact lithotriptor whereas holmium laser lithotripsy was performed via retrograde ureteric access with a Wolf 7.5 Fr semirigid ureteroscope. RESULTS: Ureteroscopy with holmium laser lithotripsy was significantly better in terms of the mean procedure time (56 min in ESWL; 25 min in ureteroscopy; P < 0.001) and the 1-month stone free rate (50% in ESWL; 80% in ureteroscopy; P = 0.001). The 3-month stone free rate was also higher for ureteroscopy (78% in ESWL; 90% in ureteroscopy) but this difference was not statistically significant (P = 0.09). Minor complications of steinstrasse (6%) occurred in ESWL and proximal stone migration (8%) occurred during ureteroscopy. CONCLUSION: Ureteroscopy with holmium laser lithotripsy is a viable and safe alternative to ESWL for the management of proximal ureteric calculi.

Adult↗
PubMed2003

Non-consensual double reading in the Singapore Breast Screening Project: benefits and limitations.

INTRODUCTION: The aims of this study were to assess the efficacy of non-consensual double reading (against single reading) in the Singapore Breast Screening Project (SBSP) and to compare the benefits (increase in cancer detection) and limitations (increase in recall and biopsy) with published data. MATERIALS AND METHODS: The data from the SBSP was retrospectively analysed and the recommendations of the first and second readers were evaluated separately with regards to rate of recall, biopsy and cancer detection. The mean second screener contribution (MSSC) was also calculated for double reading. RESULTS: In the SBSP, double reading detected 7 additional cancers (5.2% of cancers detected) compared with single reading and the MSCC was 5.5%. Double reading also resulted in 632 additional recalls, with a decrease in the positive predictive value (PPV) of cancer in the recalled women from 8.2% for single reading to 6.1% for double reading. An additional 30 biopsies were performed with double reading which represented a small decrease in PPV (41% compared to 42.9% for single reading). CONCLUSION: In the SBSP, non-consensual double reading (compared to single reading) resulted in a modest increase in cancer detection (MSSC, 5.5%) with a modest decrease in PPV of recall (2.1%) and biopsy (1.9%). These findings were consistent with that of published data and non-consensual double reading is thus recommended.

Adult↗
PubMed2002

Penile colour duplex ultrasonography as a screening tool for venogenic erectile dysfunction.

INTRODUCTION: Vasculogenic impotence is one of the major causes of erectile dysfunction. Cavernosometry and cavernosography is traditionally the gold standard for evaluation of venogenic impotence. However, it is invasive and there are potentially significant complications. Penile colour flow Doppler imaging (PCDI) is non-invasive and can be used to assess venous incompetence. MATERIALS AND METHODS: One hundred and sixty-eight patients were referred for PCDI assessment from March 1998 to February 2001. Forty-three of these also had cavernosogram and cavernosometry done and were included in the study. RESULTS: The sensitivity was 93.9%, the specificity was 90.0%, the accuracy was 93.0% with a negative predictive value of 81.8% and a positive predictive value of 96.9%. Kappa value of 0.81 was obtained, indicating excellent agreement between PCDI and cavernosogram and cavernometry. CONCLUSIONS: Penile colour flow Doppler imaging is accurate in the assessment of venogenic erectile dysfunction. It can replace cavernometry and cavernosogram as a screening tool. Cavernometry and cavernosogram should only be done in cases when PCDI suggests venogenic impotence, and when surgery is contemplated.

Adult↗
PubMed2002

Adrenal myelolipoma presenting with spontaneous retroperitoneal haemorrhage demonstrated on computed tomography and angiogram--a case report.

INTRODUCTION: A rare case of adrenal myelolipoma presenting with spontaneous rupture and retroperitoneal haemorrhage is described. CLINICAL PICTURE: A 51-year-old Caucasian male presented with acute onset of right loin pain. Preliminary diagnosis of haemorrhagic adrenal tumour was made on computed tomography (CT) and angiography. TREATMENT: Vascular embolisation was performed to stabilise the patient prior to definitive surgery. Tumour resection was subsequently performed. Histology confirmed ruptured adrenal myelolipoma. OUTCOME: The patient made an uneventful recovery. CONCLUSION: Ruptured adrenal myelolipoma should be considered in cases of spontaneous retroperitoneal haemorrhage. Vascular embolisation may be useful in stabilising the patient prior to definitive surgery.

Adrenal Gland Neoplasms↗
PubMed2002

The use of sildenafil in patients with erectile dysfunction in relation to diabetes mellitus--a study of 1,511 patients.

Erectile dysfunction (ED) seriously impairs the quality of life. Patients with diabetes mellitus (DM) are prone to ED due to various factors, including vasculopathy, neuropathy and sex hormone abnormalities. This is a retrospective study involving 1,511 patients taking sildenafil. Patients with DM have significantly more comorbidities like hypertension and ischaemic heart disease. They are also more likely to be on medications which may affect erectile function, including various antihypertensive drugs. 77.9% of patients with DM reported success with sildenafil, as compared to 86.5% of patients without DM. A significant number of patients with DM require a higher dose of sildenafil as compared to those without DM.

Diabetes Complications↗
PubMed2001

Holmium laser lithotripsy in the management of ureteric calculi.

INTRODUCTION: To evaluate the efficacy and safety of the holmium:YAG laser in retrograde ureteroscopic laser lithotripsy of ureteric calculi. METHODS: Three hundred and twenty-five patients (256 males and 69 females) with mean age of 45 years underwent 328 retrograde ureteroscopic laser lithotripsy as the primary therapy for ureteric calculi using semirigid mini-ureteroscopes and the holmium:YAG laser (Coherent, Palo Alto, California, USA). Four consultants and three registrars performed the procedures over a period of 31 months. RESULTS: The mean largest diameter of the calculi was 8.4 mm. The mean hospital stay was 1.8 days and the mean duration for the operation was 25 minutes. One hundred and twenty-two (37%) procedures were done as day surgery cases. Complete stone-free rates after single primary treatment using only the holmium:YAG laser were 75% and 91% at 4 weeks and 12 weeks of follow-up, respectively. Including 22 (7.6%) renal units which required additional procedures, the overall stone-free rate was 97%. Seventeen cases (5.2%) needed additional extracorporeal shock wave lithotripsy (ESWL) and 5 cases (1.5%) needed an additional repeat ureteroscopy and lithotripsy for complete stone clearance. Significant complications include 1 case of ureteric perforation. CONCLUSIONS: The holmium:YAG is a safe and effective intracorporeal lithotripter when deployed in a retrograde manner in conjunction with a mini-ureteroscope.

Female↗
PubMed2000

Pathologic-radiologic correlations in screen-detected ductal carcinoma in situ of the breast: findings of the Singapore breast screening project.

Mammography detected 34 (25%) cases of ductal carcinoma in situ (DCIS) of the breast out of a total of 135 cancers diagnosed in 28, 231 participating women during the Singapore breast screening project. Radiologic findings in these 34 women with DCIS were calcifications only in 25 (74%); mass only in 2 (6%); and mass with calcifications in the remaining 7 (20%) cases. Calcifications were classified mammographically as powderish in 2 (6%), crushed stone-like in 16 (50%) and casting in 14 (44%) cases. Pathologic assessment revealed 11 (32%) cases with pure comedo, 16 (47%) mixed, 3 (9%) cribriform, 2 (6%) papillary, 1 (3%) micropapillary and 1 (3%) solid patterns. Histologic nuclear grade was low in 6 (18%), intermediate in 9 (26%) and high in 19 (56%). Necrosis was observed in 26 (77%) cases and absent in the rest. Pathologic-radiologic correlations yielded a significant association between the mammographic and pathologic lesional size, with the degree of agreement improved when there was histologic necrosis. A trend for radiologic crushed stone-like and casting-type calcifications to be associated with DCIS with necrosis and of higher nuclear grade was noted. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 231-236 (2000).

Aged↗
PubMed2000

Mammographic parenchymal patterns and risk of breast cancer at and after a prevalence screen in Singaporean women.

BACKGROUND: The objective of this study was to assess the effect of mammographic parenchymal patterns on risk of breast cancer detected at first screen or in the period following a negative screen. METHODS: The study utilizes a nested case-control design with 132 breast cancer patients detected at first screen (from a total of 29 193 screened) and 42 breast cancer patients detected in the period following the first screen. These patients were matched to 348 screened-negative controls. The mammograms were classified according to Tabar's classification for parenchymal pattern and statistical analysis was done by conditional logistic regression. RESULTS: The risk of breast cancer for women with Tabar pattern IV was significantly high when compared to the remaining patterns (odds ratio 2.59). Risk factors for Tabar pattern IV coincided largely with established risk factors for breast cancer. CONCLUSION: The study confirms the increased risk of breast cancer associated with Tabar pattern IV (approximately Wolfe pattern P2), in an Asian population. This pattern is associated with nulliparity and high educational status and is strongly associated with grade 3 cancers.

Asian People↗
PubMed2000

Spectrum of abnormal mammographic findings and their predictive value for malignancy in Singaporean women from a population screening trial.

INTRODUCTION: 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. MATERIALS AND METHOD: 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. RESULTS: 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. CONCLUSION: 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.

Asian People↗
PubMed1999

Screen detected breast cancer in an Asian population: pathological findings of the Singapore breast screening project.

We document the pathological characteristics of 135 cancers detected in 132 predominantly Chinese women in the Singapore breast screening project. Thirty-four (25%) screen detected tumours were in situ ductal cancers; 98 (73%) invasive, while three (2%) women with malignant fine needle aspirate smears refused further treatment. The median size of in situ cancers was 10 mm; the majority (56%) demonstrated a comedo pattern. Of the invasive tumours which had a median size of 15 mm, three (3%) were microinvasive, 75 (77%) infiltrative ductal, three (3%) invasive lobular, and the remaining 17 (17%) special types or others. Histologic grading revealed 23 (24%) grade I, 52 (53%) grade II, 19 (19%) grade III and four (4%) ungraded cases. Sixty-three (65%) of the invasive cancers were node negative, while 64% of all screen detected malignancies were Stages 0 (in situ) or I. From the pathological perspective, problems of borderline lesions, microinvasion, grade assessment and histological subtyping have to be addressed.

Journal Article↗
PubMed1998

Results of intermediate measures from a population-based, randomized trial of mammographic screening prevalence and detection of breast carcinoma among Asian women: the Singapore Breast Screening Project.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Aged↗
PubMed1997

Electrohydraulic lithotripsy: an effective and economical modality of endoscopic ureteric lithotripsy.

BACKGROUND: Electrohydraulic lithotripsy (EHL) has been available for endoscopic treatment of urinary calculi since 1960, but the large probe size and concerns regarding safety had previously restricted its use to the treatment of bladder calculi. However, recent refinements have made it particularly suitable for the treatment of ureteric calculi. METHODS: The authors report their initial experience using EHL in conjunction with mini-ureteroscopy in the treatment of 94 ureteric calculi in 89 patients. The size of the calculi ranged from 3 to 19 mm in diameter, with a mean of 8.2 mm. The mean operating time was 29 min, ranging from 10 to 120 min. RESULTS: A complete fragmentation rate of 91.5% of the calculi was achieved. There were no major complications and a low incidence of minor complications: haematuria (2.2%), urinary tract infection (3.4%) and postoperative ureteric colic (2.2%). There were four cases of minor ureteric perforations (4.5%); all were successfully treated using conservative measures. CONCLUSIONS: It is concluded that EHL is a safe and effective method of treating ureteric calculi.

Adult↗
PubMed1995

Laparoscopic varicocelectomy: technique and results.

OBJECTIVE: To determine the safety and efficacy of laparoscopic varicocelectomy in the treatment of symptomatic varicocele. PATIENTS AND METHODS: Indications for surgery were subfertility in 98 patients and pain in nine. All varicoceles were confirmed on Doppler ultrasound. Seventy-two per cent of the patients had left-sided varicoceles and bilateral varicoceles were seen in 27%. A three-puncture technique was used with carbon dioxide insufflation. The spermatic vessels were individually identified and clips were used to ligate the veins. The spermatic artery was preserved in all cases. The operation was performed on a day surgery basis with an average operative time of 61.4 min (56.6 min for unilateral and 75.8 min for bilateral varicocelectomy). RESULTS: Morbidity was low, with pneumoscrotum in two patients and wound infection in two others. Sixty-one patients for whom pre- and post-operative seminal analyses were available showed improvement in sperm count and motility, with a concomitant fall in the percentage of abnormal sperm forms. CONCLUSION: Laparoscopic varicocelectomy is safe and effective, causing minimal discomfort and allowing patients an early return to activity.

Adult↗
PubMed1995

Venous ligation for cavernous leak impotence--a report on 30 cases.

We report our experience with the surgical treatment of 30 patients with venous leak impotence seen at the Division of Urology, Toa Payoh Hospital, over a period from April 1991 to August 1993. The patients were assessed by history, clinical examination, hormonal evaluation and intracavernosal injection of papaverine. Confirmation of venous leak impotence was obtained by pharmaco-cavernosography in all patients; dynamic cavernosometry was performed in the later part of the series. Surgical treatment consisted of ligation and stripping of the deep dorsal vein, ligation of all its emissary and circumflex tributaries for all patients, with crural plication and suspensory ligament re-approximation in selected patients. Peroperative intracavernosal injection of papaverine was used to identify veins and to assess the adequacy of the extent of venous ligation. The mean age of the patients was 40 years. The average operative time was 2 hours. The usual period of hospitalisation was 3 days. Patients were followed up for an average period of 15.6 months. Success was defined as having adequate erections for normal coitus; the success rates at 1, 3, 6, 9 and 12 months were 76.2%, 61.9%, 52.4%, 42.9% and 38.1%, respectively.

Adult↗