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Biomedical subjects

K K Yu

Publications and source records attributed to K K Yu.

At least 19 recordsLinked to original sources
PubMed2001

Shared patient analysis: a method to assess the clinical benefits of patient referrals.

BACKGROUND: Referral to specialized physicians or institutions often is deemed necessary in clinical medicine, but no method exists to assess the clinical benefit of such referrals. OBJECTIVES: To describe a method, which is shared patient analysis, to measure the expected improvement in clinical management associated with referrals and to apply that method in the field of abdominal and pelvic oncological radiology. SUBJECTS: All patients referred, during a 4-year period, to surgical oncologists at four academic centers (the referral providers, or RPs) with radiographs performed before referral at a community site (the initial providers, or IPs). Patients (n = 396) for whom both the IP interpretation and a final diagnosis was available were eligible. All IP and RP readings were placed in random order and presented to surgical oncologists, who then recommended a treatment course. MEASUREMENTS: Diagnostic accuracy of the IP and RP readings and the proportion of patients who were assigned to an appropriate treatment by the oncologist were determined. RESULTS: When the indication for imaging was primary diagnosis or staging, the kappa for presence of cancer was 0.70. When the indication was cancer follow-up, the kappa for presence of recurrent/progressing cancer was 0.66. There were disagreements between the IP and RP radiologists over the interpretation of 162 films, with the RP radiologists being correct in 153 (94%). Had the patients been treated using IP readings, there would have been 19 more inappropriate surgeries and 19 more admissions (both P <0.05) than if the oncologists had based their recommendations on RP readings. CONCLUSIONS: The technique of shared patient analysis permits assessment of the clinical benefits associated with referrals.

Academic Medical Centers↗
PubMed2000

Imaging prostate cancer.

In the detection of prostate cancer, the most important role of imaging is ultrasound-guided prostatic biopsy. In the staging evaluation of prostate cancer, each presently used modality--transrectal US (TRUS), MR imaging, CT, nuclear medicine, and positron emission tomography--has advantages and disadvantages. Evidence-based guidelines on the use of CT and nuclear medicine bone scan, in assessing the risk of distant spread of prostate cancer, are available. There is no consensus and there are no guidelines, however, for the use of imaging in the evaluation of prostate cancer local tumor extent. Results on the value of TRUS vary widely, and prospective multicenter studies suggest that TRUS is no better than digital rectal examination in predicting extracapsular extension. MR imaging offers the most promise for local staging of prostate cancer, but it must resolve problems of reproducible image quality and interobserver variability, and it should prove its efficacy in multicenter trials before it can be recommended for general clinical use. The introduction of MR spectroscopic imaging further expands the value of MR imaging, offering anatomic and metabolic evaluation of prostate cancer.

Biopsy↗
PubMed2000

The prostate: MR imaging and spectroscopy. Present and future.

The applications of combined MR imaging and MR spectroscopic imaging of prostate cancer have expanded significantly over the past 10 years and have reached the point of clinical trial results to test robustness and clinical significance. MR spectroscopic imaging extends the diagnostic evaluation of prostate cancer beyond the morphologic information provided by MR imaging throughout the detection of cellular metabolites. The combined metabolic and anatomic information provided by MR imaging and MR spectroscopic imaging has allowed a more accurate assessment of the presence, location, extent, and aggressiveness of prostate cancer both before and after treatment. This information has already demonstrated the ability to improve therapeutic planning for individual prostate cancer patients and shows great promise in the assessment of therapeutic response and the evaluation of new treatment regimes.

Clinical Protocols↗
PubMed2000

The prostate: diagnostic evaluation of metastatic disease.

One of the single most important considerations in clinical management of the patient with prostate cancer is whether or not metastatic disease is present. The identification of metastatic disease in a patient with newly diagnosed prostate cancer represents an absolute contraindication to definitive local therapies such as radial prostatectomy or radiation therapy. Similarly, the identification of metastatic disease in a patient with disease recurrence after definitive local therapy represents an absolute contraindication to salvage radiotherapy or cryosurgery. Patients with metastatic disease do not benefit from definitive therapy, and the cost and morbidity associated with such treatment should therefore be avoided in these patients. Because of the significance of metastatic disease to clinical management, it is important for the diagnostic radiologist to be aware of important considerations in the metastatic work-up of patients with newly diagnosed prostate cancer and patients with suspected cancer recurrence after definitive local therapy.

Bone Neoplasms↗
PubMed2000

Complex adnexal masses: detection and characterization with MR imaging--multivariate analysis.

PURPOSE: To evaluate the accuracy of magnetic resonance (MR) imaging in the detection and characterization of complex adnexal masses, with particular reference to the findings predictive of malignancy, role of gadolinium-enhanced contrast material, and observer variability. MATERIALS AND METHODS: Preoperative MR imaging of the pelvis was performed in 128 consecutive patients with clinically or ultrasonographically detected complex adnexal masses. Histopathologic examination demonstrated 187 masses, 96 of which were malignant. MR imaging studies were prospectively and independently reviewed by two radiologists, one of whom reevaluated the studies after a 6-month interval. The predictive value of MR imaging findings was determined with multivariate logistic regression analysis. The value of gadolinium enhancement was assessed by using receiver operating characteristic analysis. Inter- and intraobserver variabilities were assessed by using weighted K statistics. RESULTS: Gadolinium-enhanced MR imaging depicted 176 (94%) of 187 adnexal masses, with an overall accuracy for the diagnosis of malignancy of 93%. The MR imaging findings that were most predictive of malignancy were necrosis in a solid lesion (odds ratio, 107) and vegetations in a cystic lesion (odds ratio, 40). Use of gadolinium-based contrast material contributed significantly to lesion characterization. Interobserver (K, 0.79-0.85) and intraobserver (K, 0.84-0.86) agreement were excellent. CONCLUSION: Gadolinium-enhanced MR imaging is highly accurate in the detection and characterization of complex adnexal masses, with excellent inter- and intraobserver agreement.

Adolescent↗
PubMed1999

Radiologic staging in patients with endometrial cancer: a meta-analysis.

PURPOSE: To apply a meta-analysis to compare the utility of computed tomography (CT), ultrasonography (US), and magnetic resonance (MR) imaging in staging endometrial cancer. MATERIALS AND METHODS: Data were obtained from a MEDLINE literature search and from manual reviews of article bibliographies. Articles were selected that included results in patients with proved endometrial cancer and imaging-histopathologic correlation and that presented data that allowed calculation of contingency tables. Data for the imaging evaluation of myometrial and cervical invasion were abstracted independently by two authors. Data on year of publication, International Federation of Gynecology and Obstetrics (FIGO) stage distribution, and methodologic quality were also collected. A subgroup analysis was performed to compare contrast medium-enhanced MR imaging with nonenhanced MR imaging, US, and CT. RESULTS: Six studies met the inclusion criteria for CT; 16, for US; and 25, for MR imaging. Summary receiver operating characteristic analysis showed no significant differences in the overall performance of CT, US, and MR imaging. In the assessment of myometrial invasion, however, contrast-enhanced MR imaging performed significantly better than did nonenhanced MR imaging or US (P < .002) and demonstrated a trend toward better results, as compared with CT. The lack of data on the assessment of cervical invasion at CT or US prevented meta-analytic comparison with data obtained at MR imaging. Results were not influenced by year of publication, FIGO stage distribution, or methodologic quality. CONCLUSION: Although US, CT, or MR imaging can be used in the pretreatment evaluation of endometrial cancer, contrast-enhanced MR imaging offers "one-stop" examination with the highest efficacy.

Endometrial Neoplasms↗
PubMed1999

Prostate cancer: localization with three-dimensional proton MR spectroscopic imaging--clinicopathologic study.

PURPOSE: To assess the efficacy of combined magnetic resonance (MR) imaging and three-dimensional (3D) proton MR spectroscopic imaging in the detection and localization of prostate cancer. MATERIALS AND METHODS: MR imaging and 3D MR spectroscopic imaging examinations were performed in 53 patients with biopsy-proved prostate cancer and subsequent radical prostatectomy with step-section histopathologic examination. The prostate was divided into sextants. At MR imaging, the presence or absence of cancer in the peripheral zone of each sextant was assessed independently by two readers (readers 1 and 2) unaware of the findings at 3D MR spectroscopic imaging and histopathologic examination. At 3D MR spectroscopic imaging, cancer was diagnosed as possible if the ratio of choline plus creatine to citrate exceeded 2 SD above population norms or as definite if that ratio exceeded 3 SDs above the norm. RESULTS: On the basis of sextants, sensitivity and specificity, respectively, for MR imaging were 77% and 61% (reader 1) and 81% and 46% (reader 2) with moderate interreader agreement (kappa = 0.43). The 3D MR spectroscopic imaging diagnosis of definite cancer had significantly higher specificity (75%, P < .05) but lower sensitivity (63%, P < .05). Receiver operating characteristic analysis showed significantly (P < .001) improved tumor localization for both readers when 3D MR spectroscopic imaging was added to MR imaging. High specificity (up to 91%) was obtained when combined MR imaging and 3D MR spectroscopic imaging indicated cancer, whereas high sensitivity (up to 95%) was obtained when either test alone indicated a positive result. CONCLUSION: The addition of 3D MR spectroscopic imaging to MR imaging provides better detection and localization of prostate cancer in a sextant of the prostate than does use of MR imaging alone.

Cross-Sectional Studies↗
PubMed1999

Prostate cancer: prediction of extracapsular extension with endorectal MR imaging and three-dimensional proton MR spectroscopic imaging.

PURPOSE: To determine if the addition of three-dimensional (3D) proton magnetic resonance (MR) spectroscopic imaging to endorectal MR imaging helps diagnose extracapsular extension (ECE) of prostate cancer. MATERIALS AND METHODS: Endorectal MR imaging and 3D MR spectroscopic imaging were performed in 53 patients with prostate cancer before radical prostatectomy. MR imaging studies were evaluated by two independent readers unaware of histopathologic findings. The presence of ECE was graded on a five-point scale. At 3D MR spectroscopic imaging, cancer was diagnosed if the ratio of choline plus creatine to citrate was 2 or more SDs above normal. The accuracy of MR imaging alone was compared with that of combined MR imaging and 3D MR spectroscopic imaging, with use of the step-section histopathologic results as the standard of reference. RESULTS: For the less experienced reader, the addition of 3D MR spectroscopic imaging to MR imaging significantly improved accuracy (area under the receiver operating characteristic curve [Az] = 0.75 vs Az = 0.62, P < .05). For the more experienced reader, the addition improved accuracy but not significantly (Az = 0.86 vs Az = 0.78). The addition also reduced interobserver variability (Az = 0.86 vs Az = 0.75). CONCLUSION: The addition of 3D MR spectroscopic imaging to MR imaging improves accuracy for less experienced readers and reduces interobserver variability in the diagnosis of ECE of prostate cancer.

Cross-Sectional Studies↗
PubMed1998

An epidemiological profile of elderly suicides in Hong Kong.

Suicide rates in Hong Kong increased with age, and the highest suicide rate occurred among the oldest age groups. Hong Kong has one of the highest elderly suicide rates in the world. The elderly suicide rate was four to five times above the average. Furthermore, gender differences were observed among different marital status groups. For example, single males had a much higher rate than single females and married males had a higher rate than their widowed counterparts. The suicide rate for an economically inactive person was six times higher than for an active one. Jumping has become increasingly common and seems to substitute for other methods of suicide. Winter months and the Chinese New Year period had the lowest suicide occurrence. Some explanations are given.

Adult↗
PubMed1998

Preoperative staging of cervical carcinoma: phased array coil fast spin-echo versus body coil spin-echo T2-weighted MR imaging.

OBJECTIVE: This study was performed to compare the diagnostic efficacy of MR imaging in the preoperative evaluation of invasive cervical cancer using the pelvic phased array coil in combination with fast spin-echo T2-weighted imaging and the body coil in combination with conventional spin-echo T2-weighted imaging. MATERIALS AND METHODS: Ninety-four women (22-68 years old) with invasive cervical cancer underwent MR imaging (at 1.5 T) using a body coil conventional spin-echo protocol (n = 62) or a phased array coil fast spin-echo protocol (n = 32). Imaging preceded surgery by no more than 5 weeks. MR images were evaluated for tumor size, local stage, and nodal metastasis using surgical pathology as the standard of reference. RESULTS: Overall staging accuracy for the body coil conventional spin-echo protocol (89%) was not significantly different from that of the phased array coil fast spin-echo protocol (91%). Both techniques also achieved similar accuracy in diagnosing parametrial invasion (95% versus 94%) and lymph node metastases (85% versus 91%) and in tumor sizing (correlation coefficient, .93 versus .94). CONCLUSION: In the preoperative staging of cervical carcinoma by MR imaging, both the newer (phased array coil fast spin-echo protocol) and the older (body coil conventional spin-echo protocol) techniques achieved similarly high accuracies in local staging, assessment of parametrial invasion, and evaluation of tumor size. Decreased imaging time and increased image resolution are advantages of the newer technique, although in our series they did not increase staging accuracy.

Adult↗
PubMed1997

Radiological evaluation of lymph node metastases in patients with cervical cancer. A meta-analysis.

OBJECTIVE: To apply meta-analysis to compare the utility of lymphangiography (LAG), computed tomography (CT), and magnetic resonance (MR) imaging for the diagnosis of lymph node metastasis in patients with cervical cancer. DATA SOURCES: MEDLINE literature search and manual reviews of article bibliographies. STUDY SELECTION: Studies selected included at least 20 patients with imaging-histologic correlation, described diagnostic criteria for lymph node metastasis, and presented data to allow calculation of contingency tables. DATA EXTRACTION: Independently by 2 investigators, stratified for stage of disease (early vs late) and for lymph node location (pelvic vs para-aortic). DATA SYNTHESIS: Seventeen studies met the inclusion criteria for LAG, 17 for CT, and 10 for MR imaging. Summary receiver operator characteristic analysis showed no significant differences in the overall performance of LAG, CT, and MR imaging. There was, however, a trend toward better performance for MR imaging than for LAG or CT, both globally and when stratified for stage of disease or for lymph node location. Bayesian analysis of clinical utility showed only moderate increases in positive posttest probability of lymph node metastasis for all methods. Negative test results had a greater impact and, depending on the clinical setting, decreased the probability of lymph node metastasis from 15% to 44% (pretest) to 3% to 18% (posttest). CONCLUSIONS: The LAG, CT, and MR imaging perform similarly in the detection of lymph node metastasis from cervical cancer. As CT and MR imaging are less invasive than LAG and also assess local tumor extent, they should be considered the preferred adjuncts to clinical evaluation of invasive cervical cancer.

Female↗
PubMed1997

Detection of extracapsular extension of prostate carcinoma with endorectal and phased-array coil MR imaging: multivariate feature analysis.

PURPOSE: To determine which magnetic resonance (MR) imaging features are most predictive of extracapsular extension of prostate carcinoma. MATERIALS AND METHODS: In 77 patients who had stage pT2 or pT3 prostate carcinoma, MR images were retrospectively reviewed by three readers with varying experience in interpretation of endorectal coil images of the prostate gland. MR imaging features assessed were broad tumor contact, smooth capsular bulge, irregular bulge, obliteration of the rectoprostatic angle, and asymmetry of the neurovascular bundle. Multivariate logistic regression analysis was performed to determine the relative value of each MR imaging feature. RESULTS: At multivariate analysis, obliteration of the rectoprostatic angle and asymmetry of the neurovascular bundle were most predictive of extracapsular extension, with a specificity of up to 95% and sensitivity of 38%. Poor-quality images reduced accuracy for all readers. The most experienced reader demonstrated overall accuracy of 77% in determination of extracapsular extension. CONCLUSION: Obliteration of the rectoprostatic angle and asymmetry of the neurovascular bundle were most indicative of extracapsular extension. Reader experience plays an important role in the ability to interpret prostate MR images and is an important contributor to interobserver variability.

Aged↗
PubMed1996

Verapamil reduces the size of reperfused ischemically injured myocardium in hypertrophied rat hearts as assessed by magnetic resonance imaging.

Contrast-enhanced magnetic resonance (MR) imaging was used to detect and quantify the extent of myocardial injury after a brief coronary occlusion and reperfusion in response to verapamil treatment in a rat model of left ventricular hypertrophy (LVH). Two groups of rats were prepared by banding the abdominal aorta for 7 to 8 weeks to produce LVH. Group 1 (n = 13) received oral verapamil for 3 days, whereas group 2 (n = 13) received no therapy. Before MR examination was performed, each rat was subjected to 25 min of coronary artery occlusion followed by 1 hour of reperfusion. T1-weighted spin echo images were acquired before and after 0.3 mmol/kg gadoteridol was injected. Three images were acquired at contiguous levels of the LV and used to estimate the size of the myocardial injury. The size of the infarcted region was demarcated at postmortem examination by using triphenyltetrazolium chloride dye (TTC). Before contrast medium was administered, no significant difference in signal intensity was seen between nonischemic and reperfused ischemically injured myocardium. After gadoteridol was injected, a hyperintense zone indicative of myocardial injury was observed in 8 of 13 rats treated with verapamil and in all untreated animals. The size of the injury was significantly larger in untreated hearts than in hearts treated with verapamil as defined on MR images (25% +/- 5% vs 18% +/- 5%, p < 0.05) and TTC staining (12% +/- 4% and 4% +/- 1%, p < 0.05). Good correlation (r = 0.91) was found between the two measurements. No significant difference in the size of jeopardy area was seen between the two groups as (defined by blue dye infusion). In conclusion, contrast-enhanced MR imaging is a suitable technique to evaluate the effects of therapies applied to reduce myocardial injury. Verapamil can cause reduction in the extent of ischemic injury after reperfusion of hypertrophied myocardium.

Animals↗
PubMed1996

Comparison of diagnostic studies in the pretreatment evaluation of stage Ib carcinoma of the cervix.

The results of our study highlight the need for change in the pretreatment workup of clinical stage Ib cervical cancer. The routine use of excretory urography, barium enema, cystoscopy,and sigmoidoscopy is not justified. MR evaluation is recommended in patients with lesions larger than 2 cm (the group with the greatest increase in predictive value). Although CT scanning is not recommended for the evaluation of parametrial invasion, both CT scanning and MR imaging provide similar positive and negative posttest probabilities for the evaluation of nodal disease.

Bayes Theorem↗
PubMed1996

Invasive cervical carcinoma: role of MR imaging in pretreatment work-up--cost minimization and diagnostic efficacy analysis.

PURPOSE: To examine the cost and efficacy of diagnostic work-up in patients with invasive cervical cancer. MATERIALS AND METHODS: In 246 patients with invasive cervical cancer, all diagnostic tests performed before treatment were recorded. Patients were divided into two groups: those who underwent magnetic resonance (MR) imaging as the initial study (n = 105) and those who did not (n = 141). A list of 1995 Medicare global payments was used to measure cost. Bayesian analysis (likelihood ratios derived from a literature search) was performed for bladder, rectal, parameterial, and nodal involvement in stage Ib disease. RESULTS: Significantly fewer procedures and fewer invasive studies were performed in the MR imaging group. Net cost savings for the MR imaging group was $401 for all patients and $449 for patients with stage Ib disease. For stage Ib disease, the 0% pretest probability of bladder or rectal invasion does not justify the routine use of barium enema examination, cystoscopy, or proctoscopy. The increase in predictive values for parameterial and nodal disease was highest for MR imaging when tumor size was at least 2 cm. CONCLUSION: Guidelines for the pretreatment work-up of clinical stage Ib cervical cancer need revision. MR imaging should be used as an adjunct to clinical evaluation.

Adenocarcinoma↗