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PubMed1988

Lower gastrointestinal hemorrhage in renal transplant recipients.

A review of the literature and our own series revealed 38 patients with lower gastrointestinal (LGI) hemorrhage among 4086 renal transplant recipients (0.9%). These patients represent 30% of 128 patients with major colorectal complications in this group. Of the 32 patients whose treatment and outcome were reported, only 12 (38%) were treated operatively. The overall mortality rate was 72%. The causes of LGI hemorrhage included colitis from opportunistic infections (42%); pseudomembranous, ischemic, or uremic colitis (40%); and idiopathic ulcers of the colon (18%). Colonoscopic, gross, and histopathologic findings of a patient with massive LGI hemorrhage from a fungal ulcer of the colon are the focus of this study, as are the implications of such findings. We propose an algorithm for diagnostic and therapeutic management decisions. We emphasize prompt diagnosis and the importance of colonoscopy. We propose withdrawal of immunosuppression and early operative intervention if the patient survival rate is to improve.

Candidiasis↗
PubMed1999

Accuracy of Pap tests reported as CIN I.

Papanicolaou (Pap) tests reported as CIN I (cervical intraepithelial neoplasia, grade 1) may be subject to laboratory misclassification because of screening and interpretative errors. A peer-groupC consensus review was conducted to measure the misclassification rate of Pap tests reported as CIN I and to analyze the undercalled and overcalled tests for due cause. Four hundred and forty-nine Pap tests originally reported as CIN I were independently reviewed twice by a panel of four pathologists, and disagreements were resolved by consensus review. Results were based on the original screening for the first review and, following the removal of those markings, were based on a second, independent rescreening for the second review. A review result of low-grade squamous intraepithelial lesion (LSIL) and atypical squamous cells of undetermined significance (ASCUS) favoring LSIL was equated with the original CIN I result. Final classification was based on the second consensus review. Misclassified tests were categorized as screening or interpretative errors, based on a comparison of the review classifications. LSIL and ASCUS favoring LSIL were reported in 85.1% and 73.9% of the first and second reviews, respectively. In the final classification there were 362 (80.6%) LSIL and ASCUS-LSIL and 87 (19.4%) misclassifications: 31 (6.9%) undercalls and 56 (12.5%) overcalls. Screening error accounted for 35.5% of undercalled tests, and the remainder were interpretative errors, as were all those overcalled. In this study, Pap tests reported as CIN I were subject to misclassification because of a laboratory error in 19.4% of tests. Reductions in screening and interpretative errors were identified as mechanisms for improving accuracy. Diagn. Cytopathol. 1999;21:129-136.

Algorithms↗
PubMed1992

Recommendations for the investigation of abnormal hepatic function in asymptomatic workers.

Occupational medicine programs use medical surveillance tests to measure physiologic parameters that may be affected by workplace exposures. Surveillance tests can detect early detrimental changes before workers manifest recognizable symptoms. Hepatic function testing is one type of surveillance test used to monitor workers exposed to hepatotoxins. However, a significant proportion of these test reports return showing abnormal hepatic function without a readily apparent etiology. Follow-up investigation of abnormal liver enzyme tests is a commonly encountered problem in occupational medicine clinics. The algorithm proposed in this paper will outline a systematic approach for investigating abnormal hepatic function tests from asymptomatic workers.

Alcohol Drinking↗
PubMed1999

Early repolarization.

Early repolarization (ER) is an enigma. The purpose of this review is to reemphasize the overall electrocardiographic (ECG) pattern of this normal ST variant which continues to challenge the clinician because of its similarity to the current of injury potential to myocardium or an acute pericarditis. The data were provided from the studies identified through computerized searches of Medline, Toxline, Oxford, Agricola, and Bios Afterdark, Cumulative index, and a review of bibliographies of relevant articles on the related subjects. Early repolarization has elevated, upward, concave ST segments, located commonly in precordial leads, with reciprocal depression in a VR, tall, peaked and slightly asymmetrical T waves with notch, and slur on the R wave. The other accompanying features in the ECG are vertical axis, shorter and depressed P-R interval, abrupt transition, counterclockwise rotation, presence of U waves, and sinus bradycardia. Males dominate and patients are often younger than 50 years of age. The incidence of 1 to 2% is found equally common in all races. Degree and incidence of ST elevation decrease as age advances. Exercise or isoproterenol administration may normalize the ST segment. Early repolarization is a benign condition. If the ECG conforms to a classical pattern of ER on serial ECGs, it would exclude the unnecessary hazards of present day revascularization therapy for myocardial infarction such as primary angioplasty or thrombolytic therapy, or aggressive management of acute pericarditis, and so forth. This review concludes with a discussion of comparative ECG features of ER, pericarditis, and myocardial infarction, and provides an algorithm for diagnostic management of patients suffering from these conditions.

Acute Disease↗
PubMed2006

Spectral mapping tools from the earth sciences applied to spectral microscopy data.

BACKGROUND: Spectral imaging, originating from the field of earth remote sensing, is a powerful tool that is being increasingly used in a wide variety of applications for material identification. Several workers have used techniques like linear spectral unmixing (LSU) to discriminate materials in images derived from spectral microscopy. However, many spectral analysis algorithms rely on assumptions that are often violated in microscopy applications. This study explores algorithms originally developed as improvements on early earth imaging techniques that can be easily translated for use with spectral microscopy. METHODS: To best demonstrate the application of earth remote sensing spectral analysis tools to spectral microscopy data, earth imaging software was used to analyze data acquired with a Leica confocal microscope with mechanical spectral scanning. For this study, spectral training signatures (often referred to as endmembers) were selected with the ENVI (ITT Visual Information Solutions, Boulder, CO) "spectral hourglass" processing flow, a series of tools that use the spectrally over-determined nature of hyperspectral data to find the most spectrally pure (or spectrally unique) pixels within the data set. This set of endmember signatures was then used in the full range of mapping algorithms available in ENVI to determine locations, and in some cases subpixel abundances of endmembers. RESULTS: Mapping and abundance images showed a broad agreement between the spectral analysis algorithms, supported through visual assessment of output classification images and through statistical analysis of the distribution of pixels within each endmember class. CONCLUSIONS: The powerful spectral analysis algorithms available in COTS software, the result of decades of research in earth imaging, are easily translated to new sources of spectral data. Although the scale between earth imagery and spectral microscopy is radically different, the problem is the same: mapping material locations and abundances based on unique spectral signatures.

Algorithms↗
PubMed2003

Bladder filling by autologous urine production during cystometry: a urodynamic pitfall!

AIMS: The rate of autologous urine production should not have a major disturbing influence on cystometric urodynamic parameters such as first filling sensation, normal desire to void, strong desire to void, and cystometric bladder capacity. Instructions to patients and drinking behavior can have considerable impact, especially if filling cystometry is preceded by free uroflowmetry. We studied the influence of autologous urine production during filling cystometry on total bladder volume. METHODS: Urodynamic investigations performed between September of 2000 and February of 2001 were analyzed. Only those urodynamic investigations for which total bladder capacity could be calculated were taken into account (i.e., catheterization before and after cystometry and no urine loss during the investigations). RESULTS: After screening, 186 investigations were used for further analysis. Mean filled volume (external infusion plus autologous urine production) was 346 +/- 152 mL, but mean real bladder capacity (i.e., voided volume + residual urine) was 391 +/- 170 mL. In all patients, 14% extra urine was produced due to autologous urine production (mean filling rate, 6.1 mL/min). In 42% of the investigations, the real bladder capacity was more than 110% of the infused volume. In 18% of the patients, the contribution of natural bladder filling was more than 25% of the infused volume. CONCLUSIONS: Natural bladder filling plays a substantial role during filling cystometry and has a disturbing influence on calculated urodynamic parameters. Attention should be paid to patient instructions before the urodynamic investigation. The combination of free uroflowmetry followed by filling cystometry should be avoided. This avoidance is especially important if interventional studies are performed. Careful interpretation of studies depending on bladder capacity parameters is mandatory, and such parameters should be corrected for autologous bladder filling.

Algorithms↗
PubMed1990

Effect of the thermodynamics of an infant plethysmograph on the measurement of thoracic gas volume.

Adult plethysmographs have frequency responses that are essentially flat over the range of frequencies encountered in the measurement of thoracic gas volume (TGV). An infant plethysmograph is necessarily much smaller than an adult model. This means that there is a smaller mean distance over which heat diffusion must occur between the air in the plethysmograph and its walls. This in turn leads to a much reduced thermal time constant. We examined the effects of thermal time constant of a 60 L infant plethysmograph on measurements of TGV in infants. The thermal time constant was measured by rapidly injecting 20 mL of air into the plethysmograph, and found to be 0.16 +/- 0.09s when the box was empty. We calculated from this time constant that measurements of TGV should be quite dependent on the frequency at which the associated panting maneuvers are performed. TGV was measured in 5 infants less than 6 months old in the recovery phase following acute viral bronchiolitis. When we performed a digital correction of the measurements, to compensate for the thermal time constant of the plethysmograph, the TGV values decreased by a mean of 12%. Agitating the air in the plethysmograph with a fan decreased the thermal time constant of the box and reduced measured TGV by a mean of 8.4%. These results indicate that thermodynamics of infant plethysmographs can be an important source of error in TGV measurements.

Algorithms↗
PubMed1991

Sonographic imaging of the thyroid in children.

High-resolution sonographic imaging of thyroid disorders in paediatrics has become an extremely accurate method and is being more frequently used. The need for scintigraphy has therefore dramatically decreased. The anatomy and sonographic morphology of the thyroid gland (normal findings, variants) in infants and children are presented, as are patterns of thyroid disorders and respective algorithms of diagnostic imaging.

Adolescent↗
PubMedDate not supplied

Are the increasing clinical demands for osmolality measurements and their associated electrolytes appropriate?

An audit of urine and plasma osmolalities and their associated urea and electrolytes over a 4 week period found that there were 124 plasma and 96 urine osmolality requests from 67 patients. In 21 patients (31.3 per cent), the osmolality results were useful in reaching a more precise diagnosis. In a further 11 cases, urine osmolality rather than plasma would have been appropriate. Seventy-one per cent originated from the Intensive Therapy Unit and were largely requested reflexly by the hospital computer order communication system. Plasma osmolal gaps could be calculated on 80 occasions (65 per cent). The formula 1.89 Na + 1.38 K + 1.03 urea + 1.08 glucose + 7.45 proved to be more accurate than the formula [Na+K] x 2 + urea+glucose (in mmol/L) with the latter showing a positive bias when compared to measured values. The osmolal gap was > 10 mOsm/Kg using the more complex formula on 23 occasions in 16 patients but only twice using the simpler calculation. These 16 patients usually had organ failure and were very ill. Urine sodium and potassium were measured on 72 occasions in 27 of these patients but urine chloride was never requested. Urine sodium < 20 mmol/L was found in 7 patients all of whom had relative or absolute hypovolaemia. Urine sodium was measured in 73 per cent of patients investigated for SIADH in general wards. Data was available to calculate the urine osmolal gap on 52 occasions. The value was > 100 mmol/L in 10 cases and this may be used as an index of the renal ammonium response to acidosis. Much potential derived information from simple indices is unused. As a result of this study, there was an approximate halving of the subsequent request volume.

Algorithms↗
PubMed1998

Elastic image registration using correlations.

We have developed a multiscale algorithm for elastic registration of images. Rigid registration has many applications but it is often limited by distortions in the images. For example, different views of the same object produce distortions. Common examples of slightly different views producing a distortion can be found in medical imaging, such as matching a current mammogram or chest radiograph with one from a previous year, and in remote sensing, such as matching images taken from different satellite positions. We have developed two methods of elastic registration. Both are multiscale but one used an iterative minimization of the local error and the other uses a windowed correlation. We present preliminary results of the elastic registration method used on windowed correlations.

Algorithms↗
PubMed1997

Image data compression.

The tutorial will expand on all of the topics outlined above and will provide additional information on other compression techniques. The practical implications of data compression and the important considerations in choosing a compression scheme will also be discussed. Development of new compression algorithms remains an active area of investigation and will continue to increase the degree of compression possible.

Algorithms↗
PubMed1999

A comparison of wavelet and Joint Photographic Experts Group lossy compression methods applied to medical images.

This presentation focuses on the quantitative comparison of three lossy compression methods applied to a variety of 12-bit medical images. One Joint Photographic Exports Group (JPEG) and two wavelet algorithms were used on a population of 60 images. The medical images were obtained in Digital Imaging and Communications in Medicine (DICOM) file format and ranged in matrix size from 256 x 256 (magnetic resonance [MR]) to 2,560 x 2,048 (computed radiography [CR], digital radiography [DR], etc). The algorithms were applied to each image at multiple levels of compression such that comparable compressed file sizes were obtained at each level. Each compressed image was then decompressed and quantitative analysis was performed to compare each compressed-then-decompressed image with its corresponding original image. The statistical measures computed were sum of absolute differences, sum of squared differences, and peak signal-to-noise ratio (PSNR). Our results verify other research studies which show that wavelet compression yields better compression quality at constant compressed file sizes compared with JPEG. The DICOM standard does not yet include wavelet as a recognized lossy compression standard. For implementers and users to adopt wavelet technology as part of their image management and communication installations, there has to be significant differences in quality and compressibility compared with JPEG to justify expensive software licenses and the introduction of proprietary elements in the standard. Our study shows that different wavelet implementations vary in their capacity to differentiate themselves from the old, established lossy JPEG.

Algorithms↗
PubMed2001

[Metastatic epidural spinal compression: prognostic factors and results of radiotherapy].

BACKGROUND: The metastatic epidural spinal cord compression is an oncologic emergency. Presently, there is no agreement on a standard diagnostic or therapeutic algorithm. In spite of improvement in diagnostic imaging, a great proportion of patients are plegic at the time of the first presentation. PATIENTS AND METHODS: Therapy charts of 53 consecutive patients--31 male and 22 female--with metastatic epidural spinal cord compression treated with radiation therapy only have been analyzed. Median age was 60 years. The most frequent primary tumors were bronchogenic carcinoma (13 patients), breast cancer (ten patients) and prostate cancer (ten patients). RESULTS: MRI was the most sensitive diagnostic tool in detecting spinal cord compression. Plain X-ray films were not useful. Pain symptoms were improved in 66% of the patients. The most important prognostic factor was the pretreatment mobility status. 94% of the ambulatory patients kept their walking ability, but only one plegic patient could walk again after radiation therapy (p < 0.001). Patients whose back pain was presented to an oncologist were more likely to keep their walking ability by the end of the therapy. Patients with bronchogenic cancer and plegic patients had a significantly worse survival. CONCLUSION: Patients with a known malignant tumor and progressive or axial back pain should undergo MRI scan to rule out spinal cord compression. For patients without severe neurologic deficit and MRI proven epidural compression, radiation therapy is able to preserve walking ability and reduce pain. For patients with neurologic symptoms radiation therapy should start within 24 hours.

Adenocarcinoma↗
PubMed1998

[Radiologic emergency management in multiple trauma cases].

The management of multiple trauma patients has improved recently. Surgeons' education, preclinical rescue structures, initial clinical survey and therapeutic strategies, as well as diagnostic imaging, have progressed. Plain film imaging is increasingly being abandoned in favor of CT. Fast imaging techniques (spiral CT) have led to the inclusion of CT in the primary survey. To minimize the risk to the patient during prolonged diagnostic time, algorithms have to be defined concerning structures, emergency room equipment and quality. Basics, state of the art and suggestions concerning management of multiple trauma patients are presented and discussed from the radiologist's point of view.

Emergencies↗
PubMed2004

Pediatric MRU--its potential and its role in the diagnostic work-up of upper urinary tract dilatation in infants and children.

Knowledge of the manifestation, physiology and the natural course of pediatric upper urinary tract dilatation has grown with the ongoing discussion on adequate imaging. Furthermore, MR-urography techniques (MRU) have matured and have become applicable to infants and children. Modern MRU offers not only increased spatial and temporal resolution, thus enabling an investigation throughout the entire childhood, but also provides (semi-)quantitative functional information on renal perfusion, excretion and drainage. Thus MRU is increasingly considered the ideal non-ionizing "one stop shop" for the assessment of significant upper urinary tract dilatation in children. The goal of this review is to briefly comment on MRU techniques as applicable in childhood, discuss MRU indications, and summarize their potential in children with upper urinary tract dilatation. Additionally, diagnostic imaging algorithms for typical clinical conditions and queries that try to define the role MRU in pediatric upper urinary tract dilatation are suggested and discussed.

Algorithms↗
PubMed2006

A blurring index for medical images.

This study was undertaken to investigate a useful image blurring index. This work is based on our previously developed method, the Moran peak ratio. Medical images are often deteriorated by noise or blurring. Image processing techniques are used to eliminate these two factors. The denoising process may improve image visibility with a trade-off of edge blurring and may introduce undesirable effects in an image. These effects also exist in images reconstructed using the lossy image compression technique. Blurring and degradation in image quality increases with an increase in the lossy image compression ratio. Objective image quality metrics [e.g., normalized mean square error (NMSE)] currently do not provide spatial information about image blurring. In this article, the Moran peak ratio is proposed for quantitative measurement of blurring in medical images. We show that the quantity of image blurring is dependent upon the ratio between the processed peak of Moran's Z histogram and the original image. The peak ratio of Moran's Z histogram can be used to quantify the degree of image blurring. This method produces better results than the standard gray level distribution deviation. The proposed method can also be used to discern blurriness in an image using different image compression algorithms.

Algorithms↗