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M W Hedgcock

Publications and source records attributed to M W Hedgcock.

At least 19 recordsLinked to original sources
PubMed1993

Bayesian inference for model-based segmentation of computed radiographs of the hand.

We present a method for medical image understanding by computer that uses model-based, hierarchical Bayesian inference to accurately segment imaged anatomy. A first application is a prototype system that automatically segments and measures symptoms of arthridities in hand radiographs. This is potentially useful in radiological diagnosis and tracking of arthridities. Key steps of the model-based, Bayesian inference approach are: (1) prediction of imagery features from 3D models of anatomy, parameterized by population statistics, (2) local image feature extraction in predicted sub-regions, and (3) the use of a probabilistic calculus to accrue results of image processing and image feature matching procedures in support or denial of hypotheses about the imaged anatomy. The prototype system for hand radiograph analysis accurately segments normal and somewhat degenerated hand anatomy. Results are shown of the ability of the automated system to 'fail soft', recognizing when segmentation is inadequate for accurate measurement. This self evaluation capability improves reliability of measurements for potential clinical use.

Arthritis↗
PubMed1989

Transrectal probe for 1H MRI and 31P MR spectroscopy of the prostate gland.

A transrectal probe for 1H imaging and 31P MR spectroscopy of the prostate gland is described. The probe is covered with plastic and consists of an insectional portion containing an rf coil and a handle containing a tuning and matching circuit. Using this transrectal probe, 1H MR images and the first 31P MR spectra of the in situ canine prostate were obtained. Serial alterations in prostate size and changes in the ratio of phosphomonoesters to ATP ratio following orchiectomy were observed. Transrectal images of the prostate appear to be superior to conventional whole body coil images in the canine. For the first time a device to obtain high signal-to-noise 1H images and 31P spectra of the in situ prostate has been constructed. This will allow the assessment of transrectal imaging and spectroscopy as tools for medical studies of prostate pathophysiology.

Administration, Rectal↗
PubMed1987

Complex and simple renal cysts: comparative evaluation with MR imaging.

Magnetic resonance (MR) imaging was performed in two groups of patients to determine its usefulness in evaluating fluid-containing renal masses deemed complex with computed tomography (CT). Twenty-two patients in group 1 had indeterminate renal masses by CT, five of which were also indeterminate by ultrasound (US). The results in this group were compared with histologic findings. Group 2 consisted of 20 patients with simple renal cysts diagnosed according to rigid CT criteria. On MR imaging, 11 of the 23 masses in group 1 and 19 of the 20 in group 2 were diagnosed as benign cysts. Fluid within the cyst had long T1 and T2, resulting in a low signal intensity on T1-weighted images. In the 12 remaining lesions in group 1 and in one lesion in group 2, the fluid content was indeterminate and MR did not permit differentiation of cystic renal carcinoma from old hemorrhage or adenoma. When fluid within the cystic mass did not have the MR characteristics of simple fluid, MR was not helpful in characterizing the mass, but when the fluid intensity was similar to normal urine, the cyst was benign.

Adenoma↗
PubMed1985

Magnetic resonance imaging in the diagnosis and staging of renal and perirenal neoplasms.

Thirty-one adult patients underwent magnetic resonance (MR) imaging after CT scans had demonstrated findings consistent with renal cell carcinoma. MR images were interpreted prospectively and independently of the CT findings. Because the CT scanning was performed at multiple institutions by many examiners, this study was not a direct comparison of CT versus MR. The preoperative diagnoses and staging of the neoplasms, as judged by MR, were compared with those obtained at laparotomy (n = 28), autopsy (n = 1), or biopsy (n = 2). Correct preoperative diagnoses were rendered in 31 patients (100%) on the basis of MR findings. The anatomic staging of 27 renal cell carcinomas was correctly performed by MR in 26 patients (86%). When compared with results of previous studies of the value of CT in the diagnosis and staging of renal neoplasms, MR appears to have several advantages in determination of the origin of the mass; the evaluation of vascular patency; the detection of perihilar lymph node metastases; and the evaluation of direct tumor invasion of adjacent organs. MR is sensitive in determining the extent of tumor thrombus and in evaluating invasion of the inferior vena caval wall. MR should assume an important role in the diagnosis and staging of renal neoplasms.

Adult↗
PubMed1983

Evaluation of plain abdominal radiographs in the diagnosis of abdominal pain.

In an effort to develop referral criteria for the ordering of abdominal radiographs for patients presenting with abdominal symptoms, we prospectively studied the relation between clinical data and radiographic abnormalities. Of 1780 examinations, 179 (10.0%) showed some radiographic abnormality. If abdominal radiographs would have been limited to those patients who had moderate or severe abdominal tenderness, or to patients with a high clinical suspicion of bowel obstruction, renal or ureteral calculi, trauma, ischemia, or gallbladder disease, regardless of the degree of tenderness, 956 (53.7%) examinations would not have been done. All radiographic abnormalities reflecting a serious pathologic process would have been identified. Only 33 (3.5%) abnormalities of limited significance, almost all localized or generalized ileus, would have been undetected. The adoption of these referral criteria would result in minimal loss of clinically useful information, large financial savings, and a reduction in radiation exposure.

Abdomen, Acute↗
PubMed1983

Anatomy and pathology of the male pelvis by magnetic resonance imaging.

Magnetic resonance imaging (MRI) of the male pelvis was performed in 25 subjects: five normal volunteers; six patients with carcinoma of the bladder; nine with benign nodular hyperplasia (including five with concomitant bladder carcinoma); nine with prostatic carcinoma; and one with a lymphocele after radical prostatectomy. The display of normal anatomy is enhanced by the ability of the MRI device to provide images in direct transverse, sagittal, and coronal planes. Sessile and pedunculated types of bladder carcinoma are readily shown due to the superior ability of MRI for soft-tissue characterization. Direct sagittal scans are advantageous for evaluation of tumors at the bladder base, and by combining two different planes of images, the extent of the neoplasm is better delineated. In the analysis of the prostate, MRI displays the gland in three dimensions and therefore allows accurate volumetric measurements. The greatest potential of MRI seems to be its ability to detect pathology confined to the gland. However, it is not yet known if a neoplastic nodule can be differentiated from chronic prostatitis. Unlike x-ray CT, metallic clips produce no streaking artifacts, giving MRI a definite advantage in the evaluation of patients after radical surgery. These observations were made on a small number of patients. If the results are confirmed with a larger number of patients, MRI will assume a prominent role in the clinical evaluation of bladder and prostate cancer.

Adult↗
PubMed1982

Evaluation of plain abdominal radiographs in the diagnosis of abdominal pain.

In an effort to develop referral criteria for the ordering of abdominal radiographs for patients presenting with abdominal symptoms, we prospectively studied the relation between clinical data and radiographic abnormalities. Of 1780 examinations, 179 (10.0%) showed some radiographic abnormality. If abdominal radiographs would have been limited to those patients who had moderate or severe abdominal tenderness, or to patients with a high clinical suspicion of bowel obstruction, renal or ureteral calculi, trauma, ischemia, or gallbladder disease, regardless of the degree of tenderness, 956 (53.7%) examinations would not have been done. All radiographic abnormalities reflecting a serious pathologic process would have been identified. Only 33 (3.5) abnormalities of limited significance, almost all localized or generalized ileus, would have been undetected. The adoption of these referral criteria would result in minimal loss of clinicall useful information, large financial savings, and a reduction in radiation exposure.

Adult↗
PubMed1981

Preliminary radiograph for barium enema examination: is it necessary?

In a study of 200 barium enema examinations, the value of the preliminary radiograph, both in demonstrating abnormalities not detectable on the contrast radiographs and in showing the amount of residual fecal material in the colon, was assessed. No clinically significant abnormalities were seen on the preliminary film alone. Estimation of residual fecal material from the preliminary radiograph was frequently faulty and could have resulted in needless additional preparation of patients. This study suggests that inclusion of the preliminary radiograph does not affect the overall diagnostic accuracy of the barium enema examination. Its elimination would yield large savings in health care costs and radiation exposure.

Barium Sulfate↗
PubMed1980

Renal failure after major angiography.

A recently reported 12 per cent incidence of renal failure following angiography prompted our prospective study to substantiate or repudiate this seemingly excessive rate. In 100 consecutive patients, there was no instance of renal failure following angiography. The results of our study indicate that when adequate hydration is maintained angiography does not pose a "significant hazard" of renal failure as previously reported, even in patients with underlying medical problems.

Acute Kidney Injury↗
PubMed1980

Neurologic complications of angiography in patients with critical stenosis of the carotid artery.

We retrospectively studied 85 patients with angiographically demonstrable critical carotid stenosis. None suffered either immediate or delayed complications after angiography. In patients with critical stenosis of the carotid artery, the benefits of cerebral angiography clearly outweigh the small potential risk when the procedure is performed with meticulous attention to technical detail.

Carotid Artery Diseases↗
PubMed1980

Neurologic complications of angiography for cerebrovascular disease.

A recent study reported a 12.2% incidence of cerebral complications (5.2% permanent) after cerebral angiography in 147 patients. Because this was markedly different from our experience, we initiated a retrospective study of 301 patients who had undergone cerebral angiography for hemisphere transient ischemia or amaurosis fugax. There was only a 1.3% rate of transient complications (none permanent) in our patients. The benefits of cerebral angiography in patients with suspected cerebrovascular occlusive disease overwhelm the small potential risk of the procedure.

Cerebral Angiography↗
PubMed1980

Compensation examination of the cervical and lumbar spines: critical disagreement in radiographic interpretation.

Radiographic interpretation is often the major factor in the decision to award compensation for job-related complaints, especially in the Veterans Administration system. Three board-certified radiologists reviewed 200 consecutive lumbar and cervical spine examinations and assigned each case to one of three categories: normal, normal for age (not compensable), or degenerative disease (compensable). A critical disagreement, in which at least one radiologist considered the examination compensable and another not compensable, occurred in interpretation of 31% of the cervical and 46% of the lumbar spine examinations. Although the overall detection of radiographic findings was similar among all three radiologists, diagnostic interpretation of the findings varied greatly. Although most radiologists and orthopedists agree that the use of plain radiography of the spine as a deciding factor in awarding compensation is unjustified and inappropriate, until the regulations are changed there is a pressing need for strict, objective, radiographic criteria for determining "normal aging" of the cervical and lumbar spines so that interpreatations can be more uniform.

Adult↗
PubMed1980

Optimal use of portable and stat examination.

Using previously published criteria for "justification" of requests for portable and stat radiographs, a prospective study was instituted in a 300-bed teaching hospital. The rates of "unjustified" portable and stat examinations were 5% and 10%, respectively, significantly lower than in a previous study. The results indicate that close cooperation between radiologists and referring clinicians and proper education of house staff can result in more optimal use of these valuable, though often overused, techniques.

California↗
PubMed1980

Optimum radiographic examination for consideration of compensation awards: I. General methodology and application to chest examination.

A major goal of the radiologist is to devise methods to decrease health care costs and radiation exposure without sacrificing diagnostic accuracy. In a large Veterans Administration (VA) hospital, a prospective study was undertaken to determine the optimum number of radiographic projections needed to assess applicants for VA compensation for chest disease or injury claimed to be service-related. Three separate readings of every chest radiographic assessment could have been made from a single posteroanterior view. In eight cases, granulomas or mild hyperexpansion of the lungs were only appreciated using the lateral projection, but these findings were not clinically significant and did not affect decisions as to whether compensation sould be awarded. The only potentially serious lesion missed (a possible pulmonary nodule) using the posteroanterior view alone was also missed using the lateral and only suggested by the oblique views. Extrapolating these results to data on compensation examinations performed in the entire VA system (fiscal year 1978), it was concluded that limiting the radiographic examination of the chest to a single posteroanterior view would eliminate 150,000 radiographs in the evaluation of 190,000 applicants and yield an annual savings of almost $900,000.

Accidents, Occupational↗
PubMed1980

Optimum radiographic examination for consideration of compensation awards: II. Cervical and lumbar spines.

In a large Veterans Administration (VA) hospital, a prospective study was undertaken to determine the optimum number of radiographic projections needed to assess applicants for VA compensation for cervical and lumbar spine disease or injury claimed to be service-related. Results show that the final radiographic assessment could be made in 100% (245) of cervical spine examinations using two views (anteroposterior and lateral) and in 99.3% (699/704) of lumbar spine examinations using two views (anteroposterior and a single well centered lateral). Extrapolating these results to data on compensation examinations performed in the entire VA system (fiscal year 1978), it was concluded that limiting the radiographic examinations of the cervical and lumbar spines to these views would eliminate 193,000 radiographs in the evaluation of 100,000 applicants and yield an annual savings of about $1,000,000.

Accidents, Occupational↗