PubMed Health⌕ Search

Biomedical subjects

M H Pui

Publications and source records attributed to M H Pui.

17 recordsLinked to original sources
PubMed1998

Imaging of nasopharyngeal carcinoma with Tc-99m MIBI.

PURPOSE: Differentiation of recurrent nasopharyngeal carcinoma (NPC) from radiation fibrosis using conventional diagnostic methods can be difficult. The authors prospectively studied patients with NPC to determine the efficacy of Tc-99m MIBI scintigraphy in detecting the primary, residual, and recurrent tumors. MATERIALS AND METHODS: The authors performed Tc-99m MIBI SPECT studies of the head and neck and whole-body scans on 21 healthy adult volunteers and 43 patients with NPC before (n = 26) or after (n = 17) radiotherapy. The images were qualitatively assessed by comparing the nasopharyngeal uptake to scalp radioactivity. MIBI uptake index was calculated as a ratio of mean counts per pixel in the normal nasopharynx or tumor to mean counts per pixel in the scalp. RESULTS: There was significantly higher uptake of Tc-99m MIBI by NPC than normal nasopharynx and radiation fibrosis (P < .05). The authors determined the optimum cutoff MIBI uptake index value of 1.3 with a sensitivity of 97%, a specificity of 100%, a positive predictive value of 100%, a negative predictive value of 96%, and an accuracy of 98% for diagnosing NPC. CONCLUSION: This study suggests that Tc-99m MIBI SPECT is useful for detecting primary NPC and for differentiating residual or recurrent tumor from radiation fibrosis. The authors propose the cutoff MIBI uptake index value of 1.3 for diagnosing NPC.

Adult↗
PubMed1998

Computed tomography of abdominal neurogenic tumours.

Abdominal and pelvic neurogenic tumours are uncommon neoplasms in adults apart from those tumours found in patients with neurofibromatosis. Malignant degeneration occurs in 2.4-29% of neurofibromatosis. Biopsy of neurofibromas can be complicated by sensorimotor nerve deficit. Distinction of malignancy by imaging may circumvent biopsies of asymptomatic benign neurogenic tumours. Benign neurogenic neoplasm is suspected on CT scan if the tumour is in the region of known nerve ganglia or pathway, and is well demarcated, solid, homogeneous, hypodense relative to muscle, and enhances with contrast material. Malignant neurogenic tumours are often large, irregular, infiltrative, and necrotic with heterogeneous contrast enhancement. Computed tomography is valuable in distinguishing malignant from benign neurogenic neoplasms, predicting resectability, detecting distant metastases, and evaluating response to treatment.

Abdominal Neoplasms↗
PubMed1998

Lymphoscintigraphy in chyluria, chyloperitoneum and chylothorax.

UNLABELLED: Lymphoscintigraphy allows functional assessment of lymphatic transport and depiction of regional lymph nodes, is fast and nontraumatic and has no known side effects. We retrospectively analyzed lymphoscintigraphic studies to determine their efficacy in the investigation of chyluria, chyloperitoneum and chylothorax. METHODS: Twenty-one whole-body lymphoscintigrams using 99mTc-antimony sulfide colloid or dextran were acquired in 18 patients with chyluria, chyloperitoneum and/or chylothorax. The images were reviewed to assess the rate of tracer transport and number, size and distribution of lymph vessels and nodes as well as the presence of collateral, fistula or lymph reflux. RESULTS: Lymphoscintigraphy was normal (5 of 11 patients) or showed lymphatic obstruction (6 of 11 patients) in chyluria associated with filariasis. Lymphatic obstruction was demonstrated in chyloperitoneum and/or chylothorax associated with liver cirrhosis (2 patients), postoperative (1 patient) or congenital (1 patient) lymphatic dysplasia, inferior vena cava obstruction (1 patient) and nephrotic syndrome (1 patient). Enhanced lymph flow was seen in systemic lupus erythematosus (1 patient). Follow-up lymphoscintigrams showed patency of lymphovenous anastomosis (1 patient), improvement (1 patient) or no change (1 patient) in lymphatic drainage after treatment. CONCLUSION: Lymphoscintigraphy can demonstrate abnormal lymphatic drainage in chyluria, chyloperitoneum and chylothorax. It is useful for selecting patients for surgery and assessing the effect of treatment.

Adult↗
PubMed1997

Intestinal lymphangiectasia: value of Tc-99m dextran lymphoscintigraphy.

Intestinal lymphangiectasia is a common cause of protein-losing enteropathy characterized by diarrhea, generalized edema, enteric protein loss, hypoproteinemia, and lymphopenia. Diagnosis is based on demonstration of enteric protein loss and characteristic small bowel mucosal histology. Various imaging modalities including barium studies, computed tomography, and lymphangiography have had limited clinical use. The authors report a case of intestinal lymphangiectasia in which Tc-99m dextran lymphoscintigraphy played a significant role in the patient management.

Adult↗
PubMed1997

Magnetic resonance imaging of musculoskeletal lesions: comparison of three fat-saturation pulse sequences.

Fat-saturation (FS) pulse sequences can improve the detection of musculoskeletal lesions. We prospectively compared contrast-enhanced T1-weighted FS spin-echo (SE) images, T2-weighted FS fast spin-echo (FSE) images and inversion recovery (IR) FSE images to determine if any of these three pulse sequences is superior for depicting bone marrow and soft tissue lesions. T1-weighted FS-SE images (400-680/10-20 [TR/TE]) after intravenous injection of gadolinium-diethylenetriaminepentaacetic acid (DTPA), T2-weighted FS-FSE (2400-4200/96-112) and IR-FSE (3700-6000/12-14/170 [TR/TE/TI]) images were obtained with a 1.5-T magnet system in 35 patients. The visibility, margination and extent of 37 bone marrow and 67 soft tissue lesions, image uniformity, susceptibility and motion artefacts were qualitatively analysed by four radiologists. The number and size of lesions detected, the mean lesion signal-to-noise ration (S/N) and contrast-to-noise ratio (C/N) were also statistically compared. More bone and soft-tissue lesions were detected on the IR-FSE and T2-weighted FS-FSE than the T1-weighted FS-SE images. The IR-FSE images were significantly better than the T2-weighted FS-FSE and T1-weighted FS-SE images for bone marrow lesions conspicuity (P < 0.01). The soft-tissue lesions were also more conspicuous on the IR-FSE and T2-weighted FS-FSE images than on the T1-weighted FS-SE images (P < 0.005). The lesion extent and image quality were similar on all three sequences while motion artefacts were most severe on the IR-FSE and least severe on the T1-weighted FS-SE images (P < 0.001). Fat saturation was maximal on the IR-FSE images, resulting in a significantly higher mean C/N of bone marrow lesions. The mean C/N of soft-tissue lesions was higher on the T2-weighted FS-FSE images although the differences were not significant. The T2-weighted FS-FSE and IR-FSE sequences are superior to the contrast-enhanced T1-weighted FS-SE sequence for depicting musculoskeletal lesions. Bone marrow lesion conspicuity is greater on the IR-FSE images, with comparable scan time and image quality but more motion artifacts.

Adult↗
PubMed1997

Lymphangioma: imaging diagnosis.

Lymphangiomas are congenital malformations of the lymphatics that are curable by extirpation. Accurate delineation of lesion extension is important for pre-operative diagnosis, surgical planning, and assessing recurrence. The radiologic findings were retrospectively evaluated to determine the imaging appearance of these benign tumours. The plain radiographs, barium meal, ultrasound, CT, and MR images of 18 patients with one or more pathologically proved lymphangiomas were reviewed. Plain radiography and barium study showed masses displacing adjacent organs. Ultrasound examination showed uni- or multilocular cystic masses with smooth, thin or irregular, thick walls. Enhancement of the cyst wall was variable on CT and MR studies. The CT density of the fluid ranged from -4 to 34 HU depending on the lipid content and the presence of haemorrhage. The cysts were isointense to muscle on T1-weighted and hyperintense to fat on T2-weighted MR images. The MR imaging delineated the tumour lesion extension more clearly than ultrasound and CT scans. Ultrasound, CT, and MR imaging are valuable for evaluating lymphangiomas. Magnetic resonance imaging allows accurate determination of lesion extension.

Adult↗
PubMed1996

Clinical value of proton magnetic resonance spectroscopy for differentiating recurrent or residual brain tumor from delayed cerebral necrosis.

PURPOSE: Delayed cerebral necrosis (DN) is a significant risk for brain tumor patients treated with high-dose irradiation. Although differentiating DN from tumor progression is an important clinical question, the distinction cannot be made reliably by conventional imaging techniques. We undertook a pilot study to assess the ability of proton magnetic resonance spectroscopy (1H MRS) to differentiate prospectively between DN or recurrent/residual tumor in a series of children treated for primary brain tumors with high-dose irradiation. METHODS AND MATERIALS: Twelve children (ages 3-16 years), who had clinical and MR imaging (MRI) changes that suggested a diagnosis of either DN or progressive/recurrent brain tumor, underwent localized 1H MRS prior to planned biopsy, resection, or other confirmatory histological procedure. Prospective 1H MRS interpretations were based on comparison of spectral peak patterns and quantitative peak area values from normalized spectra: a marked depression of the intracellular metabolite peaks from choline, creatine, and N-acetyl compounds was hypothesized to indicate DN, and median-to-high choline with easily visible creatine metabolite peaks was labeled progressive/recurrent tumor. Subsequent histological studies identified the brain lesion as DN or recurrent/residual tumor. RESULTS: The patient series included five cases of DN and seven recurrent/residual tumor cases, based on histology. The MRS criteria prospectively identified five out of seven patients with active tumor, and four out of five patients with histologically proven DN correctly. Discriminant analysis suggested that the primary diagnostic information for differentiating DN from tumor lay in the normalized MRS peak areas for choline and creatine compounds. CONCLUSIONS: Magnetic resonance spectroscopy shows promising sensitivity and selectivity for differentiating DN from recurrent/progressive brain tumor. A novel diagnostic index based on peak areas for choline and creatine compounds may provide a simple discriminant for differentiating DN from recurrent or residual primary brain tumors.

Adolescent↗
PubMed1996

Comparison of inversion recovery fast spin-echo (FSE) with T2-weighted fat-saturated FSE and T1-weighted MR imaging in bone marrow lesion detection.

OBJECTIVE: To prospectively compare inversion recovery (IR) fast spin-echo (FSE) with T1-weighted spin-echo (SE) and T2-weighted chemical-shift fat-saturated (FS) FSE magnetic resonance sequences in the detection of bone marrow abnormality. DESIGN: Twenty-nine sets of T1-weighted SE [400-640/10-20 (TR/TE)], T2-weighted FS-FSE [2400-3800/91-112/8 (TR/TE/ETL), and IR-FSE [3700-6000/12-14/170/8 (TR/TE/T1/ETL)] images were acquired with a 1.5-T magnet in 27 patients with bone marrow lesions. The visibility, margination, and extent of 41 lesions, image quality, contrast, and artifacts were qualitatively and quantitatively compared. RESULTS: The lesions were more conspicuous on the IR-FSE than on the T1-weighted SE and T2-weighed FS-FSE images. The extent of lesions was similar for all three sequences. Image quality was better and there were fewer motion artifacts on the T1-weighted images. The mean lesion contrasted-to-noise ratio was significantly higher on the T1-weighted images (p < 0.05). CONCLUSION: The IR-FSE sequence is highly sensitive for detecting bone marrow pathology, with scan time comparable to the T1-weighted SE and T2-weighted FS-FSE sequences.

Adult↗
PubMed1996

Bone changes in tuberous sclerosis mimicking metastases.

Sclerotic and lytic bone changes of tuberous sclerosis (TS) can mimic bone metastases. We report a case of bone metastases from bronchogenic carcinoma in a patient with TS bone changes. Bone scintigraphy and magnetic resonance imaging are useful in distinguishing the TS bone lesions from bone metastases.

Adenocarcinoma↗
PubMed1995

Musculoskeletal melioidosis: clinical and imaging features.

OBJECTIVE: Melioidosis is a tropical infection caused by a gram-negative bacillus, Pseudomonas pseudomallei. The disease manifests initially as localized suppurative lesions and can progress to acute disseminated septicemia with 65-90% mortality if inadequately treated. Musculoskeletal involvement is common. The purpose of this study was to describe the clinical features and imaging appearances of musculoskeletal melioidosis. DESIGN: We retrospectively analyzed the clinical profiles and images of 26 patients diagnosed over a 6-year period as suffering from melioidosis. PATIENTS: The study group comprised 11 patients with musculoskeletal melioidosis and 15 patients with nonmusculoskeletal melioidosis. RESULTS AND CONCLUSIONS: We found that musculoskeletal melioidosis mimicks other infections both clinically and radiologically. Clinical awareness is therefore crucial, as diagnosis can only be established by bacteriological and immunological studies. Prompt treatment with long-term combination antibiotics in high dosages and surgical drainage of abscesses improves survival.

Adult↗
PubMed1995

Imaging patterns in melioidosis.

Melioidosis is an infectious disease caused by Pseudomonas pseudomallei. It is seldom diagnosed promptly and, if untreated, can lead to an 80-100% mortality rate. Twenty-eight patients with melioidosis were identified over a 6 year period, and their imaging patterns were analysed. Respiratory infections were the commonest form of presentation, frequently shown as diffuse airspace consolidation, and accounted for the highest mortality. Visceral and musculoskeletal infections were associated with chronicity and a high relapse rate. Multifocal splenic abscesses were a common occurrence. Septic arthritis of the knee was frequently seen. The majority of patients had diabetes mellitus and chronic ill-health. An increased awareness of the disease can contribute to its early detection and appropriate treatment.

Abscess↗
PubMed1995

MR imaging of the brain: comparison of gradient-echo and spin-echo pulse sequences.

OBJECTIVE: Gradient-echo pulse sequences can reduce imaging time and decrease motion artifacts. If gradient-echo pulse sequences are shown to be comparable to spin-echo sequences in MR imaging of the brain, then gradient-echo imaging can be valuable for examining critically ill, anxious, or uncooperative patients and can increase patient throughput. The purpose of this study was to prospectively compare one fast multiplanar spoiled gradient-recalled acquisition in the steady state (GRASS) (FMPSPGR) sequence with one conventional T1-weighted spin-echo sequence to determine the reliability of the FMPSPGR sequence for detecting cerebral lesions. SUBJECTS AND METHODS: Fifty-one patients with 142 cranial lesions, including brain tumors, infarction, infection, and noninflammatory lesions, were examined. Forty-two unenhanced and 39 contrast-enhanced FMPSPGR (113-240/2.6-3.6/90 degrees/4 [TR/TE/flip angle/acquisitions]) and spin-echo T1-weighted (400-579/11-12/90 degrees/2) MR images of the head were obtained with a 1.5-T system. The visibility, margination, and extent of the lesions; image quality; contrast; and artifacts were qualitatively and quantitatively compared. RESULTS: Supratentorial lesions were more conspicuous on the unenhanced FMPSPGR images because of the higher signal-to-noise ratio of the normal brain resulting in higher lesion contrast. The higher contrast-to-noise ratio of neoplasms on the contrast-enhanced spin-echo images was not found to be significant in the independent qualitative analysis. The conspicuity and extent of other lesions evaluated with the two pulse sequences were not significantly different for either the unenhanced or the contrast-enhanced studies. Vascular pulsation artifacts were significantly reduced on the contrast-enhanced FMPSPGR images. Susceptibility and chemical-shift phase-cancellation artifacts were more pronounced on the FMPSPGR images. CONCLUSION: The FMPSPGR sequence provides high-quality images with fewer vascular pulsation artifacts three to four times faster than the spin-echo sequence. The FMPSPGR sequence can reliably show intracranial lesions and can substitute for the T1-weighted spin-echo sequence in routine brain imaging.

Adolescent↗
PubMed1994

Granulocytic sarcoma in childhood leukemia: imaging features.

PURPOSE: To assess imaging features of granulocytic sarcoma (GS) in children with myelogenous leukemia. MATERIALS AND METHODS: Retrospectively analyzed were radiographs, bone scintigrams, ultrasound (US) scans, computed tomography (CT) scans, and magnetic resonance (MR) images obtained in 30 patients with acute and one with chronic myelogenous leukemia. RESULTS: With one exception in which GS antedated leukemia, GS was present concurrently with onset of leukemia or during remission or relapse. Radiographs, nuclear studies, and US findings were nonspecific. One parascapular GS was hyperintense on T2-weighted MR images, but in all eight central nervous system studies, tumors were isointense to gray matter, muscle, or marrow on T1-weighted images and to white matter or muscle, marrow, or both on T2-weighted images. Contrast enhancement of GS was homogenous on cranial CT scans and all MR studies. CONCLUSION: CT and MR imaging features may allow distinction of GS from hematomas and abscesses, which are also complications of leukemia. Thus, biopsy may be avoided in some patients.

Child↗
PubMed1994

Magnetic resonance imaging of splenic hemangiomatosis.

The authors report a case of splenic hemangiomatosis evaluated by magnetic resonance imaging (MRI). Typical areas of hyperintensity were observed in T2-weighted images. Because it is noninvasive and highly sensitive, MRI proved valuable in suggesting the diagnosis in this patient.

Aged↗
PubMed1986

False-normal bone imaging in spinal tuberculosis.

Tc-99m MDP bone imaging in spinal tuberculosis usually shows increased radioactivity at the sites of involvement. Uncommonly, the bone scan can be normal if the infection is low grade, indolent, or severely destructive. Two cases of spinal tuberculosis with normal bone imaging are reported. A normal bone image does not exclude tuberculous spondylitis. If there is clinical suspicion of this disease, further investigations, including tissue specimens, should be obtained.

Aged↗
PubMedDate not supplied

Gd-DTPA enhancement of CSF in meningeal carcinomatosis.

OBJECTIVE: We report four cases of CSF enhancement secondary to meningeal carcinomatosis observed during MRI. Only one case has been reported previously. MATERIALS AND METHODS: Four patients ranging from 4 to 20 years of age, and all having primary or secondary CNS neoplasms, were examined by cranial and/or spinal MRI before and after Gd-DTPA administration. Three of the patients had additional delayed imaging, and subtraction was used in one case. RESULTS: All four patients demonstrated CSF enhancement after Gd-DTPA administration, which increased on delayed imaging and was more apparent following subtraction. Three of the four patients died within 5 months of the MRI examination. CONCLUSION: CSF enhancement is uncommon, but when seen indicates massive tumor that coats the surface of the CNS. Detection of CNS enhancement may alter therapy; however prognosis may be poor when CSF enhancement is present. Delayed imaging and subtraction may improve detection of CSF enhancement.

Adult↗