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Biomedical subjects

P R Morrison

Publications and source records attributed to P R Morrison.

At least 19 recordsLinked to original sources
PubMed2000

MR-based temperature monitoring for hot saline injection therapy.

We applied magnetic resonance (MR) phase mapping methods to monitor the thermal frequency shift of water in order to study temperature changes from percutaneous hot saline injection therapy (PSIT) using in vitro swine livers and in vivo rabbit livers. The thermal coefficients calculated from the shifts of the water frequency with thermocouple based temperature measurements were -0.0085 +/- 0.0019 ppm/ degrees C for the in vitro studies and -0.0089 ppm/ degrees C for the in vivo studies. The error range was estimated to be +/- 3 degrees C and +/- 4.5 degrees C, respectively. Color-coded temperature maps were compared with macroscopic lesion sizes of the specimen. Regions defined using a 20 degrees C elevation in the initial images following hot saline injection (around 55 degrees C in absolute temperature) closely correlated with visible coagulation in size. We conclude that MR temperature monitoring of PSIT is quite feasible and may be helpful in expanding the clinical use of this thermal therapeutic tool for liver tumors.

Animals↗
PubMed2000

MR imaging-guided percutaneous cryotherapy of liver tumors: initial experience.

PURPOSE: To describe the cryoablation of liver tumors by using a percutaneous approach and intraprocedural magnetic resonance (MR) imaging monitoring and to assess the feasibility and safety of the procedure. MATERIALS AND METHODS: Fifteen hepatic tumors (mean diameter, 2.9 cm) in 12 patients were treated (18 total cryoablations). Fourteen were metastases and one was a hemangioma; all were proved at biopsy. By using a 0.5-T open MR imaging system, cryoneedles were placed and lesions ablated by using real-time monitoring. Clinical signs and symptoms were assessed and laboratory tests performed. Intraprocedural depictions of iceballs were compared with contrast material-enhanced MR imaging-based estimates of cryonecrosis that were obtained 24 hours after cryoablation. RESULTS: MR imaging-guided percutaneous cryotherapy resulted in no serious complications and no clinically important changes in serum liver enzymes or creatinine or myoglobin levels. Intraprocedural MR imaging demonstrated iceballs as sharply marginated regions of signal loss that expanded and engulfed tumors. The maximal iceball size was 4.9 x 2.2 x 2.2 cm with the use of one cryoneedle and 6.0 x 5.6 x 4.9 cm with three cryoneedles. Intraprocedural iceball depictions correlated well with postprocedural cryonecrosis estimates. CONCLUSION: MR imaging-guided percutaneous cryotherapy of liver tumors is feasible and safe. MR imaging can be used to estimate cryotherapy effects and guide therapy intraprocedurally.

Adult↗
PubMed1998

Computer-augmented endoscopic sinus surgery.

Review of current literature on computer-augmented endoscopic sinus surgery reflects a sustained interest in developing a role for available frameless stereotactic technologies to provide image guidance for the surgeon. The interest is motivated by the prospect of increased intraoperative patient safety in that image guidance assists the surgeon in navigating through diseased or surgically revised complex anatomy. The authors feel that in time the technique will enable a new level of efficiency in endoscopic sinus surgery.

Endoscopy↗
PubMed1998

Endoscopic sinus surgery with magnetic resonance imaging guidance: initial patient experience.

We report the first endoscopic surgeries performed with patients under general anesthesia using intraoperative guidance with MRI. The procedures were experimental and intended to test (1) the unusual working environment of a unique new "open-configuration" MRI unit for head and neck surgery, and (2) real-time image guidance. Twelve patients underwent endoscopic sinus surgery while under general anesthesia in a new open MRI unit that provides the surgeon with access to the patient while imaging is performed. Eleven patients had chronic sinusitis (eight of them had bilateral disease), and one had a right nasoethmoid and antral tumor. All 12 surgeries were performed without complications. Both the endoscopic view and the MRI scans were available at the surgical field. The image plane was surgeon controlled, and the MRI updated images in as little as 14 seconds. MRI provided adequate visualization of both the disease and the related anatomy and allowed the surgeon to navigate during the procedure. The intraoperative data reflect the tissue changes during surgery and provide optimum feedback for surgical guidance. Although the operating environment poses some limitations, it has become apparent that intraoperative MRI has a role in the treatment of head and neck disorders and warrants further study.

Adult↗
PubMed1996

Dynamic T1-weighted magnetic resonance imaging of interstitial laser photocoagulation in the liver: observations on in vivo temperature sensitivity.

BACKGROUND AND OBJECTIVE: Magnetic resonance imaging's (MRI) potential to monitor interstitial laser photocoagulation (ILP) has been previously demonstrated and is further tested here with improved spatial and temporal resolution. STUDY DESIGN/MATERIALS AND METHODS: In vivo experiments employed fiber-delivered 1,064 nm light (3.0 W, 150 sec) in six rabbit livers monitored under T1-weighted FSE MRI as 1 image/10 sec and a 3 mm thick 8 cm FOV. Image signal intensities (SI) were compared with temperatures (T) at 7, 10, and 15 mm from the fiber. RESULTS: Data showed 33 degrees C < T < 60 degrees C. SI did not vary inverselinearly with T; changes in the tissue altered the MRI signal interfering with the SI changes due to temperature. CONCLUSION: MRI cannot map SI-derived temperatures over the entire treatment site. The role of MRI's temperature sensitivity must be coordinated with organ- and dose-specific tissue changes.

Animals↗
PubMed1996

Image guidance with laser applications.

Image-guided laser surgery is defined, and an outline of its development is provided. Recent advances in radiologic imaging provide added visualization of laser-induced tissue effects. Current research around the world illustrates the power and potential of this technique in both laser and nonlaser applications. Future studies will reveal the actual contribution to laser surgery in otolaryngology.

Animals↗
PubMed1994

Comparative cell targeting in vitro using the CO2 laser.

In keeping with current interest in bactericidal effects of lasers to treat localized infection, we examined the effect of CO2 laser light on three bacterial species. Cell monolayers were placed atop filters minimizing the presence of extracellular water. Samples were exposed to irradiance values between 0 and 520 W/cm2 for 0.1 s. Cell survival was determined by colony counts. There was logarithmic killing of the bacteria with increasing irradiance; 90% kill was effected at 180 W/cm2 for Escherichia coli, 350 W/cm2 for Streptococcus mutans, and 250 W/cm2 for Bacillus stearothermophilus. However, standard deviations suggest no significant difference between cell types. Our results show the bactericidal effect of the CO2 laser with no remarkable difference between Gram types. However, substantial cell kill was achieved at relatively low irradiance. Whereas selectivity of damage may not be afforded by the CO2 laser, it may minimize collateral damage.

Carbon Dioxide↗
PubMed1992

Pulse duration effects on cutaneous pigment.

Melanin, an endogenous chromophore in pigment containing cells in skin, is being specifically altered by lasers using the principle of selective photothermolysis (SPT). This implies that a combination of specific laser parameters of wavelength, pulse duration, spotsize, and energy density are required to confine the delivered laser energy to the targeted cells alone. Because the bulk of cutaneous pigment is localized to epidermal basal cells, pigmentary incontinence has been found to occur in skin exposed to laser irradiation. This study demonstrates that pulse duration or exposure time of the laser affect the severity of pigmentary incontinence induced. Pigment granules are more abundant, aggregated, and located deeper in the dermis following exposure to 500 nsec pulse duration than 100 nsec at a wavelength of 504 nm. This relationship appears to be independent of the laser energy density used.

Animals↗
PubMed1992

Altered actin and myosin expression in muscle during exposure to microgravity.

The mechanism for cardiovascular deconditioning and skeletal muscle atrophy during microgravity is not known. The purpose of the present study was to determine whether a decrease in contractile protein gene expression in the muscle of rats occurred after 14 days of microgravity. No differences existed in the profile of myosin protein isoforms or beta-myosin heavy chain mRNA in hearts between the flight and synchronous control groups. On the other hand, differences in the expression of beta-myosin heavy chain mRNA relative to the 18S and 28S rRNA in the heart between flight and synchronous control groups were noted with a covariance mapping analysis. Both the vastus intermedius and lateral gastrocnemius muscles exhibited significant (P less than 0.05) decreases in skeletal alpha-actin mRNA per unit of extractable RNA in the flight group compared with the synchronous control group. However, no significant difference for skeletal alpha-actin mRNA occurred in the triceps brachii muscle between these groups. Cytochrome c mRNA per unit of extractable RNA decreased (P less than 0.05) only in the vastus intermedius but not in the lateral gastrocnemius or triceps brachii muscles. In summary, changes in the pretranslational regulation of contractile protein gene expression occur in both heart and skeletal muscle after 14 days of microgravity.

Actins↗
PubMed1991

Cytochrome c mRNA levels decrease in senescent rat heart.

The concentration of mitochondria decreases in the heart as rodents age from maturity to senescence. The reason for this change is not known. One purpose of the present study was to determine if cytochrome c mRNA, representative of proteins of the inner mitochondrial membrane, decreased in the hearts of Fischer 344 rats as they aged from 12 to 24 months. Twenty-two percent less cytochrome c mRNA existed per given quantity of extracted RNA from the heart in 24-month-old rats as compared with the 12-month-old group. No change in the quantities of cardiac alpha-actin mRNA, Ca2+/calmodulin protein kinase II mRNA or 18S rRNA was noted between 12- and 24-month-old hearts. Thus, the decrease in cytochrome c mRNA suggests that decreases in mRNAs for proteins of the inner mitochondrial membrane could play some role in the diminished concentration of mitochondria that exists in the senescent heart.

Actins↗
PubMed1989

Daily running for 2 wk and mRNAs for cytochrome c and alpha-actin in rat skeletal muscle.

The purpose of the study was to determine whether daily running durations that were 7-14% of the durations employed in the chronic stimulation protocols (consisting of 24 h of daily indirect electrical stimulation of skeletal muscles) still resulted in increases in a mitochondrial protein mRNA. Adult female rats were run 100 min/day on motor-driven treadmills for 2 wk. Documentation that rats underwent the stated training program was obtained by a 30-41% increase in citrate synthase activity in hindlimb muscles after 2 wk of the training. Cytochrome c mRNA was increased 17-56% in hindlimb muscles after the 2-wk training program. Thus shorter durations of exercise (100 min/day rather than 24 h/day) can increase cytochrome c mRNA. alpha-Actin mRNA increased 61-62% in fast-twitch muscles in the hindlimbs of the same rats that underwent the 2 wk of run training but did not increase in the predominantly slow-twitch soleus muscle. The increase in alpha-actin mRNA was unexpected, since it is well known that this type of physical exercise does not increase the size of fast-twitch skeletal muscle.

Actins↗
PubMed1988

Nd:YAG laser-induced hyperthermia in a mouse tumor model.

Hyperthermic tumor response induced by 1,064-nm radiation from an Nd:YAG laser was investigated in DBA/2J female mice bearing the SMT-F mammary carcinoma. The measured temperature-depth profiles indicate that hyperthermic temperatures can be achieved in tumors ranging from 3 to 8 mm thick at power inputs on the order of 1 W. For small tumors, a 5-week complete response rate exceeding 50% required 45 minutes at 45.0 degrees C. Control of large tumors (6-8 mm thick) was not achieved. The observed tumor response rates are consistent with semiempirical time-temperature relations based on other heating modalities.

Animals↗
PubMed1988

Assessment of a microcomputer-based version of the Austin maze.

The Austin (or Milner) Maze consists of a 10 x 10 array of electrical contacts through which the subject must discover a hidden pathway by touching successive points in the matrix. Trials needed to reach 3 consecutive errorless performances, errors committed, and time taken to reach this criterion are commonly regarded as indicators of frontal lobe function. This study evaluated the equivalence of a computer-based version of this task. Thirty-two male computer science students completed both forms of the maze in counterbalanced order, separated by an interval of 4 weeks. In a 2-year follow-up, 25 remaining subjects completed the tasks in reverse order, again separated by a 4-week interval. Correlational data and analysis of variance supported the proposition that the computer-based version could act as a substitute for the more tediously administered traditional form. Although the sample characteristics may limit the generalizability of this conclusion, the application and development of the software by independent investigators may facilitate its clinical application and allow a more efficient resolution of relevant theoretical issues.

Adolescent↗
PubMed1987

Cytochrome c protein-synthesis rates and mRNA contents during atrophy and recovery in skeletal muscle.

It is known that immobilization of the rat hindlimb by plaster casting leads to muscle atrophy and loss of muscle protein. In the present study, immobilization of the rat hindlimb for 6 h resulted in a significant 27% decrease in the absolute rate of cytochrome c synthesis in the red quadriceps muscle, without any change in the relative amount of cytochrome c mRNA. Cytochrome c mRNA in normal red quadriceps muscle was observed to be of four different lengths (1400, 1050, 650 and 580 bases). After 7 days of immobilization, the absolute rate of cytochrome c synthesis remained depressed and cytochrome c mRNA decreased by 40%; each of the cytochrome c mRNAs decreased, with a preferential disappearance of the 1050- and 1400-base lengths. Immobilization was ended on day 7, and the atrophied muscle was allowed to recover. At day 4 of recovery, the absolute rate of cytochrome c synthesis was 92% higher and the amount of cytochrome c mRNA had returned to control values. The abundances of the 1050- and 1400-base cytochrome c mRNAs had increased more than the shorter cytochrome c mRNAs, so that they were higher than control values. It appears that acute decreases in contractile activity of the red quadriceps muscle alter cytochrome c synthesis rates via translational or post-translational mechanisms, whereas chronic periods of modified contractile activity alter its synthesis rate via pre-translational mechanisms.

Animals↗
PubMed1987

Actin synthesis rate and mRNA level increase during early recovery of atrophied muscle.

The purpose of this study was to correlate actin synthesis rate and alpha-actin mRNA level in the gastrocnemius-plantaris muscles of limbs during their recovery from 7 days of immobilization in 200- to 280-g female rats. The fractional synthesis rate of actin in control muscle was 1%/day. Actin synthesis rate was 33% of control level at the 7th day of hindlimb immobilization, returned to control value at the 2nd recovery day, and was three times higher than control on the 4th day of recovery. The alpha-actin mRNA was 53% of control at the 7th day of immobilization, and its increase during the 1st 2 recovery days paralleled the increase in actin synthesis rate; this suggests that pretranslational mechanisms caused the initial increase in actin synthesis. Further increases in actin synthesis from the 2nd to the 4th day appear to be under translational control, since actin synthesis was 300% of control on the 4th recovery day and alpha-actin mRNA was only 128% of control.

Actins↗