Biomedical subjects

P S Christy

Publications and source records attributed to P S Christy.

5 recordsLinked to original sources

PubMed1995

Interleukin-2-induced splenic enlargement.

BACKGROUND: Splenomegaly in patients with cancer raises the suspicion of tumor involvement. Splenic enlargement in the absence of splenic metastases, however, has been reported in patients treated with interleukin-2 (IL-2) immunotherapy. This study characterizes the change in spleen size that occurred in 42 patients treated with IL-2 between 1989 and 1993 for nonhematologic malignancies. METHODS: Computed tomography (CT) scans before and during immunotherapy were available for review on all 42 patients and after immunotherapy on 16 of these patients. The splenic index was measured for each CT by a single reader blinded to the time course of IL-2 therapy. RESULTS: Mean splenic index increased 64.1% from 646 cm3 (standard deviation [SD], 387) pre-IL-2 to 1059 cm3 (SD, 534) during therapy with IL-2 (P < 0.0001). The splenic index remained elevated at 1112 cm3 (SD, 633) after completion of IL-2 therapy. CONCLUSIONS: Splenomegaly, temporally associated with IL-2 therapy for nonhematologic malignancies, is likely to represent a sequela of therapy and not tumor progression.

Adult↗

PubMed1995

Coronary MRI with a respiratory feedback monitor: the 2D imaging case.

The inability to return the heart to the same position for all breath-holds during 2D coronary MR imaging can result in imaging different locations than desired. This can lead to problems such as (i) missing a whole vessel, or a part of it, (ii) misaligning segments of vessels imaged in different breath-holds, and (iii) degrading image quality when a single slice is acquired in multiple breath-holds. To reduce inconsistencies in the breath-hold level, we designed a respiratory feedback monitor (RFM) that uses a bellows to monitor the circumference of the subject's chest. When the circumference of the subject's chest is within preset limits, an audio signal alerts subjects to hold their breath at that position. Use of the RFM significantly reduces the problems caused by inconsistent breath-holds and the number of breath-holds for an examination in 2D coronary MR imaging.

Adult↗

PubMed1995

Respiratory blur in 3D coronary MR imaging.

3D MR imaging of coronary arteries has the potential to provide both high resolution and high signal-to-noise ratio, but it is very susceptible to respiratory artifacts, especially respiratory blurring. Resolution loss caused by respiratory blurring in 3D coronary imaging is analyzed theoretically and verified experimentally. Under normal respiration, the width for any Gaussian point spread function is increased to a new value that is at least several millimeters (about 3-4 mm). In vivo studies were performed to compare respiratory pseudo-gated 3D acquisition with breath-hold 2D acquisition. On average, the overall quality of a pseudo-gated 3D image is worse than that of the corresponding breath-hold 2D image (P = 0.005). In most cases, respiratory blur caused coronary arteries in pseudo-gated 3D data to have lower resolution than in breath-hold 2D data.

Adult↗

PubMed1995

Use of a neural network and a multiple regression model to predict histologic grade of astrocytoma from MRI appearances.

Several MRI features of supratentorial astrocytomas are associated with high histologic grade by statistically significant p values. We sought to apply this information prospectively to a group of astrocytomas in the prediction of tumor grade. We used 10 MRI features of fibrillary astrocytomas from 52 patient studies to develop neural network and multiple linear regression models for practical use in predicting tumor grade. The models were tested prospectively on MR images from 29 patients studies. The performance of the models was compared against that of a radiologist. Neural network accuracy was 61% in distinguishing between low and high grade tumors. Multiple linear regression achieved an accuracy of 59%. Assessment of the images by a radiologist yielded 57% accuracy. We conclude that while certain MRI parameters may be statistically related to astrocytoma histologic grade, neural network and linear regression models cannot reliably use them to predict tumor grade.

Astrocytoma↗

PubMed1992

Recursive RF excitation.

We have investigated the properties of a recursive process in which the output signal from a given RF excitation pulse may be used as the input (excitation) pulse of a subsequent iteration. This recursive excitation technique increases contrast and improves feature segmentation for the purpose of motion tracking.

Agar↗