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  • Academic
    hollett@stanford.edu
    University - Faculty other teaching Department: Rad/Body Imaging Position: Adjunct Clinical Associate Professor

All Publications

  • Meniscal tears of the knee: Accuracy of detection with fast spin-echo MR imaging and arthroscopic correlation in 293 patients RADIOLOGY Cheung, L. P., Li, K. C., HOLLETT, M. D., Bergman, A. G., Herfkens, R. J. 1997; 203 (2): 508-512

    Abstract

    To evaluate the accuracy of a magnetic resonance (MR) imaging strategy that uses primarily fast spin-echo (SE) sequences for the diagnosis of meniscal tears.The original clinical interpretations of MR images in 293 patients who underwent imaging for suspected internal derangement of a knee joint were correlated with results from subsequent arthroscopy. MR examination included a double-echo fast SE sequence as the only imaging in the sagittal plane.The sensitivity and specificity for 143 confirmed tears of the medial meniscus were 89% and 84%, respectively, while the values for 96 confirmed tears of the lateral meniscus were 72% and 93%. These values are within the ranges of values recently reported for imaging strategies relying predominantly on conventional SE sequences.Fast SE imaging of the knee can be an alternative to conventional SE imaging for the detection of meniscal tears.

    View details for Web of Science ID A1997WU53200042

    View details for PubMedID 9114113

  • In vivo magnetic resonance evaluation of blood oxygen saturation in the superior mesenteric vein as a measure of the degree of acute flow reduction in the superior mesenteric artery: Findings in a canine model ACADEMIC RADIOLOGY Li, K. C., Pelc, L. R., Dalman, R. L., Wright, G. A., HOLLETT, M. D., Chen, I., SONG, C. K., Porath, T. S. 1997; 4 (1): 21-25

    Abstract

    The authors tested the hypothesis that changes in oxygen saturation (%HbO2) in the superior mesenteric vein (SMV), as measured with in vivo magnetic resonance (MR) oximetry, correlate with the degree of acute superior mesenteric artery (SMA) flow reduction.Ten mongrel dogs were studied. A catheter was inserted into the SMV, and a perivascular ultrasonic flow probe and an adjustable mechanical occluder were placed around the SMA. MR oximetry was carried out at the resting state and after the SMA was constricted to predetermined levels (0%-75% of initial flow). In seven dogs, SMV blood samples were obtained immediately before and after each MR measurement; %HbO2 was measured simultaneously by using an oximeter. With linear regression analysis, the SMV %HbO2 measurements obtained at MR imaging were compared with those obtained at oximetry. With a logistic model, MR imaging changes in SMV %HbO2 were compared with the degree of SMA flow reduction.SMV %HbO2 measurements obtained with MR imaging correlated well with those obtained with oximetry (r = .97). Changes in SMV %HbO2 measured at MR imaging also correlated well with the degree of SMA flow reduction, as determined with a logistic model (P = .01).Noninvasive in vivo MR measurements of SMV %HbO2 can be used to determine the degree of acute SMA flow reduction with a high degree of accuracy in a canine model.

    View details for Web of Science ID A1997WF65900004

    View details for PubMedID 9040866

  • MRI of pulmonary embolism using Gd-DTPA-polyethylene glycol polymer enhanced 3D fast gradient echo technique in a canine model MAGNETIC RESONANCE IMAGING Li, K. C., Pelc, L. R., NAPEL, S. A., Goris, M. L., Lin, D. T., SONG, C. K., Leung, A. N., Rubin, G. D., HOLLETT, M. D., Harris, D. P. 1997; 15 (5): 543-550

    Abstract

    This study was to evaluate the accuracy of MR angiography (MRA) using a Gd-DTPA-polyethylene glycol polymer (Gd-DTPA-PEG) with a 3D fast gradient echo (3D fgre) technique in diagnosing pulmonary embolism in a canine model. Pulmonary emboli were created in six mongrel dogs (20-30 kg) by injecting tantalum oxide-doped autologous blood clots into the femoral veins via cutdowns. MRI was performed with a 1.5 T GE Signa imager using a 3D fgre sequence (11.9/2.3/15 degrees) following intravenous injection of 0.06 mmol Gd/kg of Gd-DTPA-PEG. The dogs were euthanized and spiral CT of the lungs were then obtained on the deceased dogs. The MRI images were reviewed independently and receiver-operating-characteristic (ROC) curves were used for statistical analysis using spiral CT results as the gold standard. The pulmonary emboli were well visualized on spiral CT. Out of 108 pulmonary segments in the six dogs, 24 contained emboli >2 mm and 27 contained emboli < or = 2 mm. With unblinded review, MRI detected 79% of emboli >2 mm and only 48% of emboli < or = 2 mm. The blinded review results were significantly worse. Gd-DTPA-PEG enhanced 3D fgre MRI is potentially able to demonstrate pulmonary embolism with fairly high degree of accuracy, but specialized training for the interpretations will be required.

    View details for Web of Science ID A1997XM76800004

    View details for PubMedID 9253998

  • QUANTITATIVE-EVALUATION OF PANCREATIC ENHANCEMENT DURING DUAL-PHASE HELICAL CT RADIOLOGY HOLLETT, M. D., Jorgensen, M. J., Jeffrey, R. B. 1995; 195 (2): 359-361

    Abstract

    To determine the improvement in pancreatic enhancement at helical computed tomography (CT) performed with an early delay after administration of contrast material compared with that performed with a standard delay.Dual-phase helical CT of the abdomen was performed in 120 patients with a 150-mL bolus of contrast material infused at 5 mL/sec. Early and standard delayed scanning was performed beginning at 20 seconds and 49-71 seconds, respectively. Regions of interest were measured in the head, body, and tail of the pancreas in 92 patients. The difference in enhancement between early and standard delayed scanning was calculated.Mean pancreatic enhancement was 82 HU +/- 3 (standard error) with an early delay, whereas enhancement on standard delay scans was 62 HU +/- 2 (P < .001). An improvement in enhancement greater than 10 HU was attained in 66 of 92 cases (72%).Pancreatic enhancement at helical CT with an early delay after contrast material administration is often significantly greater than the enhancement seen with a standard delay when a monophasic, rapidly infused bolus of contrast material is used.

    View details for Web of Science ID A1995QU71700013

    View details for PubMedID 7724753

  • Dual-phase helical CT of the liver: value of arterial phase scans in the detection of small (< or = 1.5 cm) malignant hepatic neoplasms. AJR. American journal of roentgenology HOLLETT, M. D., Jeffrey, R. B., Nino-Murcia, M., Jorgensen, M. J., Harris, D. P. 1995; 164 (4): 879-884

    Abstract

    Helical CT scanners now allow sequential arterial phase and portal venous phase scans of the entire liver to be obtained during a single bolus injection of contrast material. The purpose of this study was to determine if arterial phase scans improve detection of small (< or = 1.5 cm) malignant hepatic neoplasms when compared with portal venous scans alone.Dual-phase helical CT of the liver was done in 96 patients referred for known or suspected malignant hepatic lesions. Malignant hepatic neoplasms were detected in 38 patients (27 with at least one small neoplasm), one patient had undetected metastases, one patient had a benign hepatic neoplasm, and 56 patients had no hepatic neoplasm. Proof of individual neoplasms was based on biopsy results, surgical findings, or findings on other imaging studies (primarily follow-up CT). The absence of disease was established by surgical or autopsy findings, findings on subsequent imaging studies, or a combination of clinical and laboratory data. A total of 150 ml of 60% nonionic contrast material was infused at 5 ml/sec followed by sequential arterial phase and portal venous phase helical scans of the liver. Three radiologists retrospectively reviewed the scans. Individual lesions were measured and the conspicuity of each lesion on arterial phase and portal venous phase scans was compared. The percentage of patients in whom some malignant neoplasms were detected better on the arterial phase scan was calculated using categories based on lesion size and typical tumor vascularity.In 10 (37%) of 27 patients who had at least one small malignant neoplasm, lesions 1.5 cm or less in diameter were only visible or were more conspicuous on the arterial phase scan. No malignant neoplasms more than 1.5 cm in diameter were visible only on the arterial phase scan. In four (11%) of 38 cases, malignant neoplasms more than 1.5 cm in diameter were more conspicuous on the arterial phase scan. The arterial phase scans improved lesion conspicuity in nine (39%) of 23 patients who had typically hypervascular neoplasms, whereas lesion conspicuity was improved in three (20%) of 15 patients who had typically hypovascular neoplasms (p = .02). The arterial phase scan resulted in the false-positive detection of lesions in two (2%) of 96 cases.Arterial phase helical CT of the liver improves detection of some small, malignant hepatic neoplasms when performed in addition to portal venous scanning. The value is greatest in those patients who have hypervascular neoplasms.

    View details for PubMedID 7726040

  • DUAL-PHASE HELICAL CT OF THE LIVER - VALUE OF ARTERIAL PHASE SCANS IN THE DETECTION OF SMALL (LESS-THAN-OR-EQUAL-TO-1.5-CM) MALIGNANT HEPATIC NEOPLASMS AMERICAN JOURNAL OF ROENTGENOLOGY HOLLETT, M. D., Jeffrey, R. B., NINOMURCIA, M., Jorgensen, M. J., Harris, D. P. 1995; 164 (4): 879-884

    Abstract

    Helical CT scanners now allow sequential arterial phase and portal venous phase scans of the entire liver to be obtained during a single bolus injection of contrast material. The purpose of this study was to determine if arterial phase scans improve detection of small (< or = 1.5 cm) malignant hepatic neoplasms when compared with portal venous scans alone.Dual-phase helical CT of the liver was done in 96 patients referred for known or suspected malignant hepatic lesions. Malignant hepatic neoplasms were detected in 38 patients (27 with at least one small neoplasm), one patient had undetected metastases, one patient had a benign hepatic neoplasm, and 56 patients had no hepatic neoplasm. Proof of individual neoplasms was based on biopsy results, surgical findings, or findings on other imaging studies (primarily follow-up CT). The absence of disease was established by surgical or autopsy findings, findings on subsequent imaging studies, or a combination of clinical and laboratory data. A total of 150 ml of 60% nonionic contrast material was infused at 5 ml/sec followed by sequential arterial phase and portal venous phase helical scans of the liver. Three radiologists retrospectively reviewed the scans. Individual lesions were measured and the conspicuity of each lesion on arterial phase and portal venous phase scans was compared. The percentage of patients in whom some malignant neoplasms were detected better on the arterial phase scan was calculated using categories based on lesion size and typical tumor vascularity.In 10 (37%) of 27 patients who had at least one small malignant neoplasm, lesions 1.5 cm or less in diameter were only visible or were more conspicuous on the arterial phase scan. No malignant neoplasms more than 1.5 cm in diameter were visible only on the arterial phase scan. In four (11%) of 38 cases, malignant neoplasms more than 1.5 cm in diameter were more conspicuous on the arterial phase scan. The arterial phase scans improved lesion conspicuity in nine (39%) of 23 patients who had typically hypervascular neoplasms, whereas lesion conspicuity was improved in three (20%) of 15 patients who had typically hypovascular neoplasms (p = .02). The arterial phase scan resulted in the false-positive detection of lesions in two (2%) of 96 cases.Arterial phase helical CT of the liver improves detection of some small, malignant hepatic neoplasms when performed in addition to portal venous scanning. The value is greatest in those patients who have hypervascular neoplasms.

    View details for Web of Science ID A1995QN20700015