Search PubMed⌕ Search

Biomedical subjects

P Y Poon

Publications and source records attributed to P Y Poon.

At least 19 recordsLinked to original sources
PubMed2000

Tumour extent and T stage of nasopharyngeal carcinoma: a comparison of magnetic resonance imaging and computed tomographic findings.

PURPOSE: To compare magnetic resonance imaging (MRI) and computed tomography (CT) in defining the T stage and full tumour extent of nasopharyngeal carcinoma. PATIENTS AND METHODS: Forty-eight patients with pathologically proven nasopharyngeal carcinoma underwent MRI and CT examinations within 2 weeks of each other. Contrast medium was used in both examinations. The T stage and full tumour extent according to MRI and CT were compared. RESULTS: In 32 patients MRI and CT findings agreed completely. MRI findings resulted in assignment of a higher stage than CT findings in another 8 patients. In the remaining 8 patients MRI showed wider tumour spread than CT, although there was no discordance in the T stage assigned. CONCLUSION: When compared with CT in defining the full tumour extent and assigning the T stage in 48 patients with nasopharyngeal carcinoma, MRI showed more extensive disease in 16 patients, including 8 in whom the T stage was revised upward. Therapy was altered as a result of the MRI findings.

Adult↗
PubMed1999

MR imaging of brachial plexopathy in breast cancer patients without palpable recurrence.

OBJECTIVE: To investigate the role of MR imaging in detecting brachial plexus (BP) abnormalities in breast cancer patients with plexopathy but without palpable masses. DESIGN: MR imaging of the BP was performed on 26 breast cancer patients with brachial plexopathy without palpable regional masses, using 0.5 T and 1.5 T imaging systems. Findings were correlated with the clinical diagnoses. PATIENTS: Twenty-six patients with brachial plexopathy and history of breast cancer were enrolled in the study. All patients presented with plexopathy symptoms. Fourteen patients were positive and 12 patients were indeterminate for BP metastasis according to clinical criteria. RESULTS AND CONCLUSION: MR imaging demonstrated masses involving the BP representing metastases in two patients. Nine patients had other regional abnormalities with a normal brachial plexus. It is concluded that MR imaging is useful in the assessment and direction of therapy of brachial plexopathy in breast cancer patients by detecting both metastases to the BP as well as other abnormalities, unrelated to the BP, which may explain the patient's symptoms.

Adult↗
PubMed1999

Increased sialylation of polymeric immunoglobulin A1: mechanism of selective glomerular deposition in immunoglobulin A nephropathy?

Immunoglobulin A nephropathy (IgAN) is characterized by raised serum IgA and predominant mesangial IgA deposits of polymeric nature. The abnormal glycosylation of the carbohydrate moieties in the hinge region of the IgA molecule has recently attracted much attention. In this study we investigated the galactosylation and sialylation of monomeric and polymeric IgA1 isolated from patients with IgAN. Total IgA1 in serum samples from patients with IgAN or from healthy controls was isolated with a jacalin-agarose column as jacalin-bound protein (JBP). Monomeric and polymeric IgA1 were distinctly separated by fast protein liquid chromatography. Lectin binding assays were designed to examine the sialylation and the expression of terminal galactose and N-acetyl galactosamine of the O-linked carbohydrate in the hinge region of the IgA molecule. Reduced terminal galactosylation was demonstrated in serum IgA and monomeric IgA1 isolated from patients with IgAN as compared with results in healthy control subjects. However, a reduction in terminal galactosylation was not found in polymeric IgA1 isolated from patients with IgAN. Instead, increased sialylation of IgA1 (alpha2-3 linked to galactose) was demonstrated in polymeric IgA1. This abnormality of IgA1 could bear considerable implication on the pathogenesis of IgAN, because the masking effect of sialic acid may hinder the clearance of polymeric IgA1 by the asialoglycoprotein receptor (ASGP-R) of the liver cells. An increase in the sialylated content would also render the polymeric IgA from patients with IgAN more anionic. These immunochemical properties may contribute to the selective glomerular deposition of polymeric IgA1 in IgAN.

Adult↗
PubMed1998

Gadolinium-enhanced dynamic MRI of the fractured carpal scaphoid: preliminary results.

The aim of the present report was to evaluate the vascularity of fracture fragments of the fractured carpal scaphoid in the acute (< 4 weeks) and chronic (> 3 months) phases using a gadolinium-enhanced dynamic MRI sequence. Eight patients with acute scaphoid fractures, six patients with chronic scaphoid fractures, and three control patients without fractures were evaluated using a T1-weighted fast spoiled gradient recalled acquisition (fSPGR) sequence with gadolinium-DTPA enhancement (0.1 mmol/kg bodyweight). Signal intensity over time plots were obtained using region of interest measurements from both fracture fragments. Enhancement factors (EF) were then calculated from the plots. No enhancement of the scaphoid was seen in control subjects (EF: distal scaphoid pole 1.04 +/- 0.01, proximal pole 1.07 +/- 0.08). In acute fracture patients, enhancement of the distal pole was greater than that of the proximal in all cases but one in which the two poles enhanced in a similar fashion (EF: distal 1.99 +/- 0.77, proximal 1.43 +/- 0.99). In chronic fracture patients the enhancement pattern was reversed, as the proximal pole enhanced to a greater degree than the distal with the exception of one case where both poles enhanced equally (EF: distal 1.74 +/- 0.52, proximal 2.64 +/- 0.50). Using a two-tailed non-parametric Mann-Whitney U-test, the difference in enhancement of the proximal poles between the acute and chronic groups was found to be highly significant (P < 0.003). Dynamic contrast-enhanced (fSPGR) MRI demonstrates significant differences in the enhancement patterns of the scaphoid when chronic and acute fractures are compared.

Adult↗
PubMed1997

Candida osteomyelitis and disc space infection of the lumbar spine.

Candida osteomyelitis is an uncommon complication of immunosuppressive therapy. Its radiographic manifestations are similar to those of other relatively indolent infectious agents. We report the CT and MR findings in a patient who developed this condition following treatment for acute myelogenous leukemia, and review the imaging literature covering similar cases.

Aged↗
PubMed1997

Osteoblastic metastases from breast carcinoma with false-negative bone scan.

The authors report a case of metastatic breast carcinoma that on investigation was shown to have a negative bone scan in spite of multiple densely sclerotic metastases on radiography and CT and a positive bone biopsy. The literature is reviewed with regard to the subject of negative bone scans in this situation.

Biopsy↗
PubMed1997

Percutaneous gastrostomy in radiologic practice.

Long-term gastrostomy tubes have a well-accepted role in providing nutritional support. Traditionally they have been placed by surgeons and by endoscopists. In the last decade, radiologists have come to play a major role in the placement of gastrostomy and gastrojejunostomy devices, and can usually do so as effectively and at lesser expense. A technique for placement is outlined, with a discussion of patient selection and complications. A review of the literature is provided.

Contraindications↗
PubMed1996

Congenital-infantile fibrosarcoma: magnetic resonance imaging findings.

Congenital-infantile, fibrosarcoma is a rare tumour presenting at birth or in the neonatal period. Few such tumours have been reported, and imaging details in particular are scant. The authors describe two neonates with congenital-infantile fibrosarcoma, the first case involving the right thigh and extending into the pelvis, and the second involving the calf and the ankle. In both cases magnetic resonance imaging (MRI) demonstrated well-demarcated, low-signal-intensity soft-tissue masses with t1-weighting and inhomogeneous, high-signal-intensity masses with T2-weighting. MRI was superior to other imaging modalities in the assessment of soft-tissue involvement and proved especially useful in planning therapy and monitoring chemotherapeutic response.

Biopsy↗
PubMed1996

Computed tomography of retroperitoneal and mesenteric sarcomas: a pictorial essay.

Retroperitoneal and mesenteric sarcomas are rare tumours that often do not present until they are very large. Computed tomography (CT) is helpful for diagnosis and for planning therapy. This pictorial essay illustrates the spectrum of CT manifestations of these tumours that the authors have encountered and includes a review of the various aspects of clinical presentation and treatment.

Fibrosarcoma↗
PubMed1995

Pituitary and intradural spinal metastases: an unusual initial presentation of lung cancer.

The authors report the clinical and imaging findings for a 47-year-old woman who presented with the classic symptoms of a sellar or suprasellar mass; the lesion was initially diagnosed as germinoma and was treated accordingly. The patient also had intradural, extramedullary spinal metastases. Radiotherapy failed, and the patient died. Autopsy revealed that the lesions were metastatic from previously unrecognized large-cell carcinoma of the lung. This distribution of metastases from a primary lesion not located within the central nervous system is unusual but should be considered in any patient presenting with masses at these sites, particularly if the response to therapy is less than expected.

Carcinoma, Large Cell↗
PubMed1994

Quantitative effect of combined chemotherapy and fractionated radiotherapy on the incidence of radiation-induced lung damage: a prospective clinical study.

PURPOSE: The objective of this work was to assess the incidence of radiological changes compatible with radiation-induced lung damage as determined by computed tomography (CT), and subsequently calculate the dose effect factors (DEF) for specified chemotherapeutic regimens. METHODS AND MATERIALS: A prospective, clinical study was conducted to determine the response of normal lung tissue to combined chemotherapy and radiotherapy. Radiation treatments were administered once daily, 5 days-per-week. Six clinical protocols were evaluated: ABVD (adriamycin, bleomycin, vincristine, and DTIC) followed by 35 Gy in 20 fractions; MOPP (nitrogen mustard, vincristine, procarbazine, and prednisone) followed by 35 Gy in 20; MOPP/ABVD followed by 35 Gy in 20; CAV (cyclophosphamide, adriamycin, and vincristine) followed by 25 Gy in 10; and 5-FU (5-fluorouracil) concurrent with either 50-52 Gy in 20-21 or 30-36 Gy in 10-15 fractions. CT examinations were taken before and at predetermined intervals following radiotherapy. CT evidence for the development of radiation-induced damage was defined as an increase in lung density within the irradiated volume. The radiation dose to lung was calculated using a CT-based algorithm to account for tissue inhomogeneities. Different fractionation schedules were converted using two isoeffect models, the estimated single dose (ED) and the normalized total dose (NTD). RESULTS: A total of 102 patients were entered and 70 completed the study. Forty-two patients developed CT changes compatible with lung damage. The actuarial incidence of radiological pneumonitis was 71% for the ABVD, 49% for MOPP, 52% for MOPP/ABVD, 67% for CAV, 73% for 5-FU radical, and 58% for 5-FU palliative protocols. Depending on the isoeffect model selected and the method of analysis, the DEF was 1.11-1.14 for the ABVD, 0.96-0.97 for the MOPP, 0.96-1.02 for the MOPP/ABVD, 1.03-1.10 for the CAV, 0.74-0.79 for the 5-FU radical, and 0.94 for the 5-FU palliative protocols. CONCLUSION: Quantitative dose effect factors (DEF) were measured by comparing the incidences of CT-observed lung damage in patients receiving chemotherapy and radiotherapy to those receiving radiotherapy alone. The addition of ABVD or CAV appeared to reduce the tolerance of lung to radiation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Musculoskeletal infection: findings on magnetic resonance imaging.

Magnetic resonance imaging (MRI) can provide considerable useful information in cases of musculoskeletal infection, in particular demonstrating the extent of involvement of soft tissues and medullary bone. Differentiation between infected tissue and abscess is also possible with MRI, especially if contrast agent is administered. MRI therefore serves as an adjunct to other imaging modalities, especially in complex cases. This review covers various manifestations of musculoskeletal infection as depicted with MRI.

Abscess↗
PubMed1994

Imaging of soft-tissue sarcomas.

Soft-tissue sarcomas are encountered only infrequently, but their diagnosis is important because the long-term prognosis is usually good if the tumour is properly managed. The role of various imaging modalities in the evaluation of these neoplasms is discussed, with special emphasis on magnetic resonance imaging. The authors review the importance of imaging in tumour detection, characterization, staging and surveillance after therapy, and they emphasize the critical subject of proper biopsy technique.

Humans↗
PubMed1994

Tumour of a peripheral nerve sheath with invasion of the lumbar spine.

Tumours of peripheral nerve sheaths are rarely malignant, and even when malignant they are only infrequently associated with extensive destruction of bone. The authors report the computed tomography and magnetic resonance imaging findings for an unusually large sheath tumour that presented with extensive destruction in the lumbar spine.

Aged↗