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M K O'Connor

Publications and source records attributed to M K O'Connor.

At least 19 recordsLinked to original sources
PubMed1999

Comparative study of 99mTc-ECD and 99mTc-HMPAO for peri-ictal SPECT: qualitative and quantitative analysis.

OBJECTIVES: Most studies that clinically validated peri-ictal SPECT in intractable partial epilepsy had used technetium-99m-hexamethylpropylene amine oxime (99mTc-HMPAO or 99mTc-exametazime) as the radiopharmaceutical. Because of some theoretical advantages, technetium-99m-ethyl cysteinate diethylester (99mTc-ECD or 99mTc-bicisate) is increasingly being used instead. This study compares unstabilised 99Tc-HMPAO and 99mTc-ECD in the performance of peri-ictal SPECT in partial epilepsy. METHODS: The injection timing and localisation rates in 49 consecutive patients with partial epilepsy who had peri-ictal injections with unstabilised 99mTc-HMPAO were compared with 49 consecutive patients who had peri-ictal injections with 99mTc-ECD. Quantitative cortical/subcortical and cortical/extracerebral uptake ratios were also compared. Subtraction SPECT coregistered to MRI (SISCOM) was performed in patients whose interictal SPECTS were available. RESULTS: In the 99mTc-ECD patients, the latency from seizure commencement to injection was shorter (median 34 v 80 seconds, p<0.0001) and there was a lower rate of postictal injections (16.3% v 57.1%, p<0.0001). The cortical/extracerebral and cortical/subcortical uptake ratios were greater in the 99mTc-ECD images (median 5.0 v 3.6, and 2.5 v 2.2 respectively; both p<0.005), but the relative peri-ictal increase in uptake in the cortical focus did not differ significantly (median 37.0% v 37.0%; p>0.05). Blinded review of the SISCOM images were localising in a higher proportion of the 99mTc-ECD patients (40/45 (88.9%) v 25/37 (67.6%), p<0.05), and had a better concordance with EEG, MRI, and with the discharge diagnosis. CONCLUSION: 99mTc-ECD compares favourably with unstabilised 99mTc-HMPAO as a radiopharmaceutical for peri-ictal SPECT studies. Its use results in earlier injections and less frequent postictal injections than unstabilised 99mTc-HMPAO, thereby enhancing the sensitivity and the specificity of peri-ictal SPECT for the localisation of intractable partial epilepsy.

Adolescent↗
PubMed1998

The practical utility of performing peri-ictal SPECT in the evaluation of children with partial epilepsy.

Peri-ictal brain single-photon emission computed tomography (SPECT) is increasingly being established as a useful test in localizing partial epilepsy in adults. However, obtaining an ictal injection and acquiring the SPECT images poses a greater challenge in pediatric patients, and few reports have specifically addressed the practical use of this technique in children. The Mayo Clinic experience of peri-ictal SPECT in the evaluation of children with partial epilepsy is reported here. Peri-ictal SPECT was attempted during 71 admissions involving 59 patients (median age 12 years, range 1 year 6 months-17 years). A peri-ictal SPECT injection was performed on 48 (67.6%) of these admissions in 43 (72.9%) patients, and only two patients could not be scanned. Of the 46 peri-ictal images successfully obtained, 30 (65.2%) were from ictal injection and 16 (34.8%) from post-ictal injections. Forty-two (91.3%) of the successfully obtained SPECT images, in 38 patients (92.3%), were classified as localizing (15 temporal, 24 extratemporal). We conclude that, with the appropriate unit setup and well-trained staff, peri-ictal SPECT scans can be obtained in most pediatric partial epilepsy patients. Moreover, the procedure provides specific localizing information in a high proportion of these patients.

Adolescent↗
PubMed1998

Subtraction ictal SPET co-registered to MRI in partial epilepsy: description and technical validation of the method with phantom and patient studies.

Computer-aided subtraction of the co-registered and normalized interictal from the ictal single photon emission tomography (SPET) scan, followed by co-registration to the magnetic resonance image, may improve the utility of ictal SPET in the localization of partial epilepsy. This paper describes and technically validates our method. The SPET to SPET co-registration was tested using six sequential 99Tc(m) brain phantom SPET images of different known positions (15 matches). The registration error was determined by multiplying the calculated match transformation matrix by the inverse of the known transformation matrix. The 'worst case' co-registration error was less that one voxel diameter in all cases (median 3.2 mm, range 1.2-4.8 mm). For interictal to ictal SPET registrations in 10 consecutive intractable partial epilepsy patients, a similar root mean square distance (RMSD) between corresponding points on the matched scans was found as for the phantom studies (median 2.2 vs 2.6 mm). The appropriateness of our normalization was studied by comparing the pixel intensity distributions between the matched scans, and by analysing the subtraction pixel intensity distribution. The pixel intensity distribution for both the normalized phantom, and paired normalized patient studies, were closely matched to each other except for the extreme values, which in clinical situations likely represent regions of ictal activation or depression. The subtraction image intensity distributions were symmetrically centred on zero for all values up to at least within the 5th to 95th centile range, confirming good normalization for the 'non-activated' pixels. Also, a linear relationship was demonstrated between the measured pixel intensity on the phantom scans and the true changes in 99Tc(m) activity based on its decay constant. The results of this study demonstrate that our method produces accurate SPET to SPET co-registration, and appropriate SPET normalization, thereby allowing a valid ictal subtraction image to be derived.

Brain↗
PubMed1998

Effectiveness of ECT in patients with parkinsonism.

Electroconvulsive therapy (ECT) has been used to treat the psychiatric complications of Parkinson's disease. Concurrent improvement of parkinsonian motor symptoms has been noted. This retrospective study compared the outcomes of 25 patients with parkinsonism receiving ECT for psychiatric indications with outcomes of 25 patients (matched for age and gender) without neurological disease also receiving ECT for psychiatric indications. Significant improvement in psychiatric symptoms was noted following ECT for both groups. No differences in efficacy of ECT were found between the two groups. Fourteen of the 25 patients with Parkinson's symptoms were noted to have at least transient improvement in motor function at discharge. ECT is an effective treatment for patients with parkinsonism and psychiatric comorbidity.

Aged↗
PubMed1998

Bone density and fracture risk in men.

We evaluated different definitions of osteoporosis in a population-based sample of 348 men (age 22-90 years) compared with 351 women (age 21-93 years). Thirty-six men (10%) and 46 women (13%) had a history of osteoporotic fracture (hip, spine, or distal forearm due to moderate trauma at >/= age 35). In logistic regression analysis, osteoporotic fracture risk was associated with bone mineral density (BMD) at all sites (neck, trochanter, total hip, lumbar spine, and total wrist) in both genders (p < 0.001) except spinal BMD in men. After adjusting for age, total hip BMD was the strongest predictor of fracture risk in women (odds ratio [OR] per 1 SD decline, 2.4; 95% confidence interval [CI], 1.6-3.7), while wrist BMD was best in men (OR, 1.5; 95% CI, 1.1-2.0). Among men but not women, bone mineral apparent density (BMAD) was a better predictor of fracture than BMD (wrist BMAD OR, 1.7; 95% CI, 1.3-2.3). Hip BMD/BMAD decreased linearly from age 20 years onward in both genders, while spinal BMD/BMAD declined after age 40 in women but not in men. In both genders, total wrist BMD/BMAD decreased after age 50. By World Health Organization criteria, the age-adjusted prevalence of osteoporosis at the hip, spine, or wrist was 35% among women >/=50 years of age. A similar approach (BMD > 2.5 SD below the young male mean) produced an osteoporosis prevalence rate in men >/=50 years of age of 19%. Thus, bone density predicts fracture risk in men as it does in women, and the prevalence of osteoporosis in men, using sex-specific normal values, is substantial. These observations indicate a need for better prevention and treatment strategies for men.

Adult↗
PubMed1998

Long-term effects of calcium supplementation on serum parathyroid hormone level, bone turnover, and bone loss in elderly women.

We report a 4-year randomized, double-blind, placebo-controlled clinical trial in 236 normal postmenopausal women (mean age +/- SE, 66.3+/-0.2 years) who were randomized to a calcium (1600 mg/day as the citrate) or placebo group. The women were seen every 6 months; 177 completed the trial. Net percentage changes in each group are given relative to baseline. The differences in net percentage changes (calcium group minus placebo group) in medians were: for lumbar spine bone density, 2.0% (p < 0.001) at year 1 and 0.3% (not significant) at year 4; for proximal femur bone density, 1.3% (p = 0.003) at year 1 and 1.3% (p = 0.015) at year 4; and for total body bone mineral, 0.4% (p = 0.002) at year 1 and 0.9% (p = 0.017) at year 4. Similar differences at year 4 were: -18.9% (p = 0.002) for parathyroid hormone (PTH), -11.9% (p = 0.026) for serum osteocalcin, and -32.2% (p = 0.003) for urine free pyridinoline. We conclude that long-term administration of calcium supplements to elderly women partially reverses age-related increases in serum PTH level and bone resorption and decreases bone loss. However, the effects on bone loss were weaker than those reported for estrogen, bisphosphonates, or calcitonin therapy, indicating that calcium supplements alone cannot substitute for these in treating established osteoporosis. Nonetheless, because of their safety, high tolerance, and low expense, calcium supplements may be a useful preventive measure for elderly postmenopausal women whose bone mineral density values are normal for their age.

Aged↗
PubMed1998

Major depression in medically ill patients.

Major depression is one of the most common psychiatric problems complicating the treatment and prognosis of patients with active medical illness. Recognizing and treating major depressive conditions in this population can often be challenging, even for the most seasoned clinicians. This article reviews the medical and neurologic conditions that have been associated with the high prevalence rates of major depression. Highlights of the evaluation process that help confirm this suspected diagnosis are addressed, and management issues are discussed. Brief reviews of supportive psychotherapeutic tools that the clinician may find helpful are included, as well as current advances in pharmacologic interventions.

Antidepressive Agents↗
PubMed1998

Comparison of four motion correction techniques in SPECT imaging of the heart: a cardiac phantom study.

UNLABELLED: The aim of this study was to evaluate the accuracy of four different motion correction techniques in SPECT imaging of the heart. METHODS: We evaluated three automated techniques: the cross-correlation (CC) method, diverging squares (DS) method and two-dimensional fit method and one manual shift technique (MS) using a cardiac phantom. The phantom was filled with organ concentrations of 99mTc closely matching those seen in patient studies. The phantom was placed on a small sliding platform connected to a computer-controlled stepping motor. Linear, random, sinusoidal and bounce motions of magnitude up to 2 cm in the axial direction were simulated. Both single- and dual-detector 90 degrees acquisitions were acquired using a dual 90 degrees detector system. Data were acquired over 180 degrees with 30 or 15 frames/detector (single-/dual-head) at 30 sec/frame in a 64x64 matrix. RESULTS: The simulated single-detector system, CC method, failed to accurately correct for any of the simulated motions. The DS technique overestimated the magnitude of phantom motion, particularly for images acquired between 45 degrees left anterior oblique and 45 degrees left posterior oblique. The two-dimensional and MS techniques accurately corrected for motion. The simulated dual 90 degrees detector system, CC method, only partially tracked random or bounce cardiac motion and failed to detect sinusoidal motion. The DS technique overestimated motion in the latter half of the study. Both the two-dimensional and MS techniques provided superior tracking, although no technique was able to accurately track the rapid changes in cardiac location simulated in the random motion study. Average absolute differences between true and calculated position of the heart on single- and dual 90 degrees -detectors were 1.7 mm and 1.5 mm for the two-dimensional and MS techniques, respectively. The corresponding values for the DS and CC techniques were 5.7 and 8.9 mm, respectively. CONCLUSION: Of the four techniques evaluated, manual correction by an experienced technologist proved to be the most accurate, although results were not significantly different from those observed with the two-dimensional method. Both techniques accurately determined cardiac location and permitted artifact-free reconstruction of the simulated cardiac studies.

Heart↗
PubMed1997

Noninvasive prediction of residual blood flow within the risk area during acute myocardial infarction: a multicenter validation study of patients undergoing direct coronary angioplasty.

BACKGROUND: In a previous study from a single center, radionuclide measures of collateral flow with technetium 99m sestamibi have been shown to be significantly associated with angiographic residual (antegrade and collateral) flow and independent predictors of final infarct size in acute myocardial infarction. This study examined whether the previously described radionuclide measures of blood flow to the infarct zone were reproducible with different laboratories and imaging systems. METHODS AND RESULTS: Residual flow to the infarct zone was assessed by both invasive and noninvasive methods in 77 patients with first-time myocardial infarction (32 anterior, 45 nonanterior). All patients underwent acute coronary angiography before any intervention within 8 hours of the onset of chest pain (4.0 +/- 1.5 hours; range 1.2 to 7.9 hours). 99mTc sestamibi was injected intravenously before reperfusion therapy, and tomographic imaging was performed 1 to 6 hours after injection. A central core laboratory processed the acquired images from three centers, each with a unique camera and computer system. Three previously published methods based on the severity of the acute perfusion defect were used to measure residual flow to the infarct zone (nadir, severity index, area). Antegrade (Thrombolysis in Myocardial Infarction flow) and collateral flow before direct angioplasty were blindly graded on a four-point scale (0 to 3) from the acute angiogram. The simple sum of the two grades was defined as the angiographic flow index, representing residual flow to the jeopardized zone. All three noninvasive measures of residual flow were highly associated with the angiographic flow index in a linear fashion: severity index (p = 0.0006), area (p = 0.003), and nadir (minimum/maximum counts; p = 0.004). This association was independent of the laboratory where the data were acquired. CONCLUSIONS: Despite different laboratories and camera systems, radionuclide measures of residual flow were highly associated with the angiographic flow index before reperfusion therapy. These results suggest that these measures are applicable on a broader scale for the noninvasive determination of collateral and antegrade flow in acute myocardial infarction.

Coronary Angiography↗
PubMed1997

Hypokalemia leading to torsades de pointes. Munchausen's disorder or bulimia nervosa?

A 45-year-old woman traveled over 1000 miles from a major metropolitan area to obtain another opinion for medically refractory diarrhea. She had an extremely complicated medical history with no outside records or family members accompanying her to give collateral history. She had multiple previous diagnostic evaluations including 13 surgical procedures and many therapeutic trials of various medications. She acknowledged a preoccupation with weight and appearance, described previous attempts to diet, and repetitively denied purging, including laxative abuse. During her hospitalization she had two episodes of torsades de pointes requiring cardiac defibrillation. Laboratory testing revealed hypokalemia at the time of these events, and a toxicology screen was positive for bisacodyl, confirming laxative abuse. When confronted by a combined team of cardiology, gastroenterology, and psychiatry specialist, she admitted her laxative abuse and surrendered her supply of Dulcolax tablets. The discussion addresses the procedures employed to detect her surreptitious medication use, the near lethal cardiac complications, and the appropriate psychiatric diagnosis.

Bulimia↗
PubMed1997

Assessing sleep in psychiatric inpatients: nurse and patient reports versus wrist actigraphy.

This study was designed to evaluate the conventional techniques of assessing sleep, nursing and patient report, of inpatients on a clinical psychiatric unit. Nurses assessed sleep/wake status at hourly checks and patients completed a sleep diary. For three nights patients wore a wrist actigraph, a portable instrument which provides objective data about sleep/wake activity. The nursing and patient data obtained were compared with actigraphy data. Nursing staff evaluated sleep with satisfactory agreement (76.5% night 1 and 81.6% night 3) that improved over the first three nights of hospitalization (p < 0.03). When the nurses' report did not agree with the actigraph, they tended to overestimate sleep. Patients tended to underestimate their total sleep time and total time awake after sleep onset. Time in bed and initial sleep latency were overestimated. There was great intersubject variability, making determination of agreement impossible. This data suggest that treatment teams on psychiatric units should in general consider nursing reports of sleep more accurate than patient self-report. However, since nursing staff and patients observe different aspects of sleep, both sources of data are important to inpatient treatment teams on clinical units.

Adult↗
PubMed1997

Technetium-99m MIBI to assess coronary collateral flow during acute myocardial infarction in two closed-chest animal models.

UNLABELLED: Collateral flow is an independent determinant of infarct size in both animal and clinical studies of myocardial infarction. The purpose of this study was to quantitatively evaluate, in a closed-chest animal model, a noninvasive method of measuring coronary collateral flow over a wide spectrum of collateral flow rates from a tracer that can be injected during occlusion but measured after reperfusion. METHODS: Fourteen animals underwent 40 min of coronary occlusion using a closed-chest technique. Two closed-chest models representing different rates of collateral flow were used: canine and porcine. Coronary blood flow was measured by radiolabeled microspheres. Collateral blood within the risk zone was estimated from the severity of 99mTc-sestamibi tomographic perfusion defect. RESULTS: Collateral blood flow was significantly higher in the canine model than it was in the porcine model. There was close agreement (r = 0.90) between absolute collateral flow by microspheres and the severity of the tomographic perfusion defect. CONCLUSION: These results suggest that an accurate noninvasive estimate of collateral blood flow can be provided by an intravenous injection of 99mTc-sestamibi.

Animals↗
PubMed1996

Instrument- and computer-related problems and artifacts in nuclear medicine.

Advances in gamma-camera design over the last 5 to 10 years have improved all aspects of image quality, particularly for tomographic imaging. As system complexity increases, it becomes more important that both the technologist and physician be able to recognize the various types of artifacts that can occur in gamma-camera systems and their potential impact on clinical studies. A thorough evaluation of the system at installation and a comprehensive quality control program will detect most problems that can occur. The most sensitive indicator of gamma-camera performance is uniformity. Because this measurement is performed on a daily basis, it is the principle tool in evaluating the status of the gamma-camera. Most artifacts related to the integrity of the detector head, computer system, and hard copy device can be detected on the uniformity image. For tomographic imaging, a quantitative determination of uniformity is needed to ensure that the system will not introduce ring artifacts into the patient data. Unlike planar imaging, the complex nature of tomographic imaging requires additional checks on system performance to ensure that other components of the system, such as the collimator, gantry, and imaging table, are not a source of artifact in the reconstructed image data. Failure of a system component can occur at any time and may be subtle and difficult to recognize in modern systems. In such an environment it becomes imperative that any unexpected finding in a clinical study be questioned with respect to a possible malfunction of some aspect of data acquisition and analysis.

Artifacts↗
PubMed1996

Technical pitfalls in image acquisition, processing, and display.

Optimal image quality is an ideal in nuclear medicine that is not always realized, being subject to a variety of conditions that can act, either singly or in combination, to undermine its accomplishment. These conditions include potential defects and limitations in both the hardware and software used for the acquisition and reconstruction of nuclear medicine images. Factors relating to individual patients can contribute to these obstacles, including limitations in mobility and compliance. Importantly, suboptimal or erroneous technique is a common source of poor imaging results, with loss of diagnostic efficacy. Appropriate test selection and careful attention to patient preparation and procedural details are essential elements in avoiding image flaws and artifacts in nuclear medicine.

Artifacts↗
PubMed1996

Patient-related pitfalls and artifacts in nuclear medicine imaging.

Quality control in nuclear medicine is all important. This applies not only to preparation of the patient and acquisition of the image, but also to interpretation of the study. Although it may seem self-evident, it is important to remain aware of artifacts that are directly related to the patient and need special consideration. Furthermore, at times the distinction between normal variants and artifacts can be difficult. Commonly encountered patient-related artifacts include artifacts caused by attenuation, contamination artifacts, and artifacts caused by intravenous lines, tubes, and catheters. Less commonly, artifacts arise because of the use of multiple isotopes, the presence of fistulas or surgically altered anatomy, and pharmaceuticals and other substances interfering with expected radiopharmaceutical uptake and distribution. The diagnostic accuracy of nuclear medicine reporting can be improved by awareness of these patient-related artifacts. Both awareness and experience are also important when it comes to detecting and identifying normal (and abnormal) variants.

Artifacts↗
PubMed1996

Hyperventilation alters colonic motor and sensory function: effects and mechanisms in humans.

UNLABELLED: BACKGROUND & AIMS. Hyperventilation-induced hypocapnia affects hemodynamic function and enhances colonic motility. The aims of this study were to determine the effects of hypocapnic hyperventilation on colonic motility and sensation in health and to explore the putative neurohumoral mechanisms. METHODS: In experiment 1, colonic tone, sensation, plasma levels of cortisol, beta-endorphin, selected gut neuropeptides, norepinephrine, epinephrine, and splanchnic blood volume were measured during two sequences of hypocapnic hyperventilation. In experiment 2, colonic tone and sensation were assessed during eucapnic hyperventilation and abdominal compression. RESULTS: Hypocapnic hyperventilation, but not eucapnic hyperventilation or abdominal compression, significantly increased colonic tone and sensitivity to balloon distention (P = 0.017) without altering humoral mediators or splanchnic blood volume. Plasma norepinephrine level increased (P = 0.017) and splanchnic blood volume decreased (P = 0.028) during 5 minutes after hyperventilation, consistent with homeostatic responses. CONCLUSIONS: Increased colonic tone and sensation during hypocapnic hyperventilation are not caused by colonic compression. These effects of hyperventilation are not mediated humorally but may result from direct metabolic effects of hypocapnia on colonic muscle or from changes in central autonomic control of colonic smooth muscle.

Adult↗
PubMed1996

Single photon emission computed tomography brain imaging.

SPECT brain perfusion imaging has definite value in the evaluation of cerebrovascular disease (particularly acute stroke), dementia, epilepsy, and may have a role in the diagnosis of brain death and head trauma. SPECT with tumor tracers T1-201 and Tc-99m sestamibi shows promise for detecting tumor recurrence.

Brain↗