Spin-polarized hot electron transport versus spin pumping mediated by local heating.

A 'toy model'-aimed at capturing the essential physics-is presented that jointly describes spin-polarized hot electron transport and spin pumping driven by local heating. These two processes both contribute to spin-current generation in laser-excited magnetic heterostructures. The model is used to compare the two contributions directly. The spin-polarized hot electron current is modeled as one generation of hot electrons with a spin-dependent excitation and relaxation scheme. Upon decay, the excess energy of the hot electrons is transferred to a thermalized electron bath. The elevated electron temperature leads to an increased rate of electron-magnon scattering processes and yields a local accumulation of spin. This process is dubbed as spin pumping by local heating. The built-up spin accumulation is effectively driven out of the ferromagnetic system by (interfacial) electron transport. Within our model, the injected spin current is dominated by the contribution resulting from spin pumping, while the hot electron spin current remains relatively small. We derive that this observation is related to the ratio between the Fermi temperature and Curie temperature, and we show what other fundamental parameters play a role.

No volume effect on retrograde colonic spread of rectally-administered ropivacaine gel.

BACKGROUND: Rectal administration of enemas, foams and suppositories is the most efficient way to deliver locally acting drugs to the distal colon. Ropivacaine, a long-acting local anaesthetic, was chosen as a candidate for a new rectal treatment of ulcerative colitis. AIM: To determine the colonic spread of a rectal ropivacaine formulation. METHODS: In this randomized, incomplete cross-over study, 12 male volunteers were given 200 mg ropivacaine HCl rectally in 20, 40, 60 and 80 mL hydroxypropyl methylcellulose gel. The viscosity of the gel was 1.1 Pa s. The spread of the radiolabelled (99mTc-labelled diethylenetriaminepenta-acetic acid) formulations was assessed by gamma-scintigraphy. Plasma was collected and analysed for ropivacaine base. RESULTS: The retrograde spread was limited to the descending colon and the difference between the studied volumes was not statistically significant. Only the 80-mL volume tended to have a larger distribution, although the 20-mL volume showed the same maximal distribution in two subjects. No distinct relationship between volume, retrograde colonic spread and plasma concentrations could be found. Ropivacaine was well tolerated. CONCLUSIONS: Rectal ropivacaine gel in all volumes between 20 and 80 mL can spread up to the descending colon. There was no relationship between either retrograde colonic spread or the administered volume and the ropivacaine plasma concentrations.

Value of structured clinical and scintigraphic protocols in acute pulmonary embolism.

PURPOSE: To study the use of a combination of a clinical and scintigraphic protocol in relation to the final outcome diagnosis in patients with clinical suspicion of acute pulmonary embolism (PE). MATERIAL AND METHODS: A total of 170 patients with clinical suspicion of acute PE were all examined with ECG, blood chemistry, chest X-ray, pulmonary scintigraphy and selective pulmonary arteriography. The scintigraphic and clinical probabilities of PE were estimated on visual analogue scales (VASs) by different readers unaware of each others' results. The follow-up time was 6 months. In order to establish the final diagnosis a final outcome committee was created. They analysed in retrospect all the clinical and laboratory data and established whether the patient had had PE or not. RESULTS: The final outcome committee concluded that 53 patients had PE. When the scintigraphic and clinical probability judgements were congruent, a combined probability of 1-25% (i.e low probability) had a negative predictive value of 98%. When the combined probability was 26-75% (i.e. intermediate) half of the cases had PE. With a combined probability of 76-100% (i.e. high) the positive predictive value was 100%. CONCLUSION: By applying a model of combined clinical and scintigraphic probabilities for PE, the diagnosis is ruled in when the combined probability is high, and ruled out when the combined probability is low. However, nearly half of the patients will still have an uncertain diagnosis for which further diagnostic procedures may be allocated.

[Continuing should be a part of the clinical reality. Courage is required to see both the strong and the weak sides of the professional situation]. / Fortbildning skall utgå från den kliniska verkligheten. Det krävs mod att se både de starka och de svaga sidoma i yrkessituationen.

Continuing professional development (CPD) is a joint responsibility of the individual physician and the employer. CPD should focus on identification and documentation of the learning needs of the individual, based on professional demands. Reflection, feedback and evaluation of the results are central elements of the process. Efficient learning demands active participation; modern information technology is now becoming more widely available.

An independent evaluation of a new method for automated interpretation of lung scintigrams using artificial neural networks.

The purpose of this study was to evaluate a new automated method for the interpretation of lung perfusion scintigrams using patients from a hospital other than that where the method was developed, and then to compare the performance of the technique against that of experienced physicians. A total of 1,087 scintigrams from patients with suspected pulmonary embolism comprised the training group. The test group consisted of scintigrams from 140 patients collected in a hospital different to that from which the training group had been drawn. An artificial neural network was trained using 18 automatically obtained features from each set of perfusion scintigrams. The image processing techniques included alignment to templates, construction of quotient images based on the perfusion/template images, and finally calculation of features describing segmental perfusion defects in the quotient images. The templates represented lungs of normal size and shape without any pathological changes. The performance of the neural network was compared with that of three experienced physicians who read the same test scintigrams according to the modified PIOPED criteria using, in addition to perfusion images, ventilation images when available and chest radiographs for all patients. Performances were measured as area under the receiver operating characteristic curve. The performance of the neural network evaluated in the test group was 0.88 (95% confidence limits 0.81-0.94). The performance of the three experienced experts was in the range 0.87-0.93 when using the perfusion images, chest radiographs and ventilation images when available. Perfusion scintigrams can be interpreted regarding the diagnosis of pulmonary embolism by the use of an automated method also in a hospital other than that where it was developed. The performance of this method is similar to that of experienced physicians even though the physicians, in addition to perfusion images, also had access to ventilation images for most patients and chest radiographs for all patients. These results show the high potential for the method as a clinical decision support system.

Pre-operative simultaneous stereotactic core biopsy and fine-needle aspiration biopsy in the diagnosis of invasive lobular breast carcinoma.

PURPOSE: To determine the diagnostic value of stereotactic core needle biopsy (SCNB) in comparison to stereotactic fine-needle aspiration biopsy (SFNAB) in patients with invasive lobular carcinoma (ILC). MATERIAL AND METHODS: Twenty-two patients with clinical or mammographic findings suspicious of malignancy underwent surgery where postoperative histopathology showed ILC. Pre-operative attempts of diagnosis were made using SFNAB and SCNB. SFNAB was done with a spinal needle 0.7- or 0.9-mm and SCNB was simultaneously performed with an automated 2.1-mm biopsy gun in all patients. RESULTS: SFNAB was diagnostic of carcinoma in 9 women, showed "probable carcinoma" in 5 and "atypia" in 3. In the remaining 5 women, SFNAB showed no atypia. SCNB diagnosed ILC in 20 patients and showed ILC as well as invasive ductal carcinoma (IDC) in 1. Ductal carcinoma in situ was suggested in the remaining patient. CONCLUSION: SCNB was superior to SFNAB in diagnosing ILC and did not miss any carcinoma, whereas SFNAB was non-diagnostic in 8 cases. SCNB is thus recommended in patients with suspicion of ILC of the breast.

Validity of pulmonary cine arteriography for the diagnosis of pulmonary embolism.

The aim of this study was to assess the interobserver variations in diagnosis of pulmonary embolism (PE) with cine technique and to compare the diagnostic accuracy of pulmonary arteriograms to final-outcome diagnosis. One hundred and seventy patients with clinical suspicion of acute PE were examined with ECG, laboratory tests, chest X-ray, pulmonary scintigraphy and selective pulmonary cine arteriography. The follow-up time was 6 months. Fifty-one arteriograms were interpreted as positive for PE. Two pulmonary emboli were missed when compared with the diagnosis as stated by the final-outcome committee. No arteriograms were considered as not of diagnostic quality. Mean interobserver agreement in lobar vessels was 100%, in segmental vessels 93% and in subsegmental vessels 63%. The mean interobserver agreement was 89%. Pulmonary cine arteriography produces high diagnostic accuracy and few inconclusive results in patients with suspected PE.

Pulmonary angiography: a safe procedure with modern contrast media and technique.

Pulmonary angiography (PA) for decades has been accepted as the gold standard for the diagnosis of pulmonary embolism (PE). Apprehensions that the procedure is expensive, invasive and thus associated with both fatal and non-fatal complications has more or less limited its use to patients presenting a non-diagnostic lung scan. However, this opinion originates from earlier studies. Increasing clinical demands for faster and safer diagnostics, together with improved techniques and safer contrast media, has led to an increased use of PA. In order to evaluate the complication rate, we retrospectively studied the case records of 707 consecutive patients who had undergone PA. During 1990-1994, 728 patients underwent PA at Danderyd and Huddinge University Hospital. Selective pulmonary angiography (cine or digital subtraction angiography), non-ionic, low-osmolar contrast media and modern pigtail catheters were used. Standard volumes were 40 ml at 2 s for each injection. Pressure measurements were made in 376 patients. A test injection was made in all patients in order to assess the flow rate. Experienced radiologists as well as residents performed the examinations and a total of 707 angiography protocols and clinical records were available for review in search of complications associated with the procedure. No deaths occurred. One major non-fatal complication (bleeding in the groin requiring surgery) was reported in one case. Moderate/minor complications (i. e. transient angina and cardiac failure, minor haematomas, urticaria) occurred in 10 patients (1.4 %). With modern contrast media and technique, pulmonary angiography is a safe procedure.

Air enema used in the evaluation of acute colitis. A comparison between instant radiography and endoscopy.

PURPOSE: The purpose of this study was to evaluate air enema as a method of assessing acute colitis. MATERIAL AND METHODS: Twenty-seven patients with symptoms of acute colitis underwent plain abdominal radiography, air enema, and colonoscopy within 48 h. The films were evaluated by 3 observers with different levels of experience, both independently and together, and the results were then compared to the findings at endoscopy. RESULTS: Air enema visualized a greater part of the colon than plain abdominal radiography. When air enema was compared to endoscopy as the reference, it showed good correlation, with a positive predictive value of 92% (sensitivity 62%, specificity 85%). Evaluation of the rectum was less accurate, a finding that emphasized the importance of rigid sigmoidoscopy. CONCLUSION: Air enema is a useful diagnostic method in acute colitis, it is easily performed and tolerated well with no observed complications. It is also easy to interpret, as shown by a high level of agreement (kappa = 0.67) among the 3 independent observers with very different levels of experience.

Interval cancers and cancers in non-attenders in the Ostergötland Mammographic Screening Programme. Duration between screening and diagnosis, S-phase fraction and distant recurrence.

The study was based on a population mammographic screening programme for women aged 40-74 years. Metastatic potential was analysed in 843 invasive breast cancers with regard to mode of detection and a number of prognostic factors. There was a higher metastatic capacity in clinically detected cases, but multivariate analyses showed that neither the mode of detection (hazard rate ratio of distant recurrence RR = 1.39, 95% CI 0.78-2.46 interval cancers and RR = 1.6, 95% CI 0.76-3.36 non-attenders) nor the duration between screening and diagnosis for true interval cancers (RR = 0.47, 95% CI 0.16-1.35 in tumours detected later than one year after screening) were independent prognostic factors. A correlation was found between metastatic potential and the SPF (RR = 2.94, 95% CI 1.57-5.50 in tumours with a high SPF), the oestrogen receptor status and the tumour stage. In conclusion, interval cancers intrinsically are not different from other breast cancers with equivalent characteristics; the duration between screening and diagnosis in interval cancers was not clearly correlated to the prognosis, but the S-phase fraction was a powerful predictor of prognosis.

Adding a visual linear scale probability to the PIOPED probability of pulmonary embolism.

PURPOSE: Reporting a lung scintigraphy diagnosis as a PIOPED categorical probability of pulmonary embolism offers the clinician a wide range of interpretation. Therefore the purpose of this study was to analyze the impact on lung scintigraphy reporting of adding a visual linear scale (VLS) probability assessment to the ordinary PIOPED categorical probability. MATERIAL AND METHODS: The study material was a re-evaluation of lung scintigrams from a prospective study of 170 patients. All patients had been examined by lung scintigraphy and pulmonary angiography. The scintigrams were re-evaluated by 3 raters, and the probability of pulmonary embolism was estimated by the PIOPED categorization and by a VLS probability. The test was repeated after 6 months. RESULTS: There was no significant difference (p > 0.05) in the area under the ROC curve between the PIOPED categorization and the VLS for any of the 3 raters. Analysis of agreement among raters and for repeatability demonstrated low agreement in the mid-range of probabilities. CONCLUSION: A VLS probability estimate did not significantly improve the overall accuracy of the diagnosis compared to the categorical PIOPED probability assessment alone. From the data of our present study we cannot recommend the addition of a VLS score to the PIOPED categorization.

Leukocyte migration in acute colonic inflammatory bowel disease: comparison of histological assessment and Tc-99m-HMPAO labeled leukocyte scan.

UNLABELLED: Noninvasive leukocyte scintigraphy for assessment of localization, extent, and degree of active inflammation in acute colonic inflammatory bowel disease have been shown to correlate well with endoscopy. This study compared findings of mucosal leukocyte migration assessed histologically with those of technetium 99m hexamethylpropylene-amineoxime-labeled leukocyte scintigraphy. PATIENTS AND METHODS: Twenty-one patients hospitalized because of a first attack or a relapse of known inflammatory bowel disease were investigated using leukocyte scintigraphy followed by total colonoscopy with multiple biopsies within 24 h. Histological interpretation focused on the degree of segmental mucosal leukocyte infiltration. RESULTS: Fourteen patients with ulcerative colitis (UC) and seven with colonic Crohn's disease (CD) were included. With the use of histology as the reference method, maximal proximal disease extent was correctly assessed by the leukocyte scan in 11 patients (8 with UC, 3 with CD), although the rectal involvement was not visualized in 5. In seven patients, the extent assessments almost matched (+/- one segment), and in the remaining three patients (two UC, one CD) the scan grossly misinterpreted active histological inflammation (> or = +/- two segments). In patients with UC, the sensitivity, specificity, and diagnostic accuracy concerning the extent of inflammation were 0.84, 0.79, and 0.83, respectively. In patients with CD, the sensitivity was 0.79, and the diagnostic accuracy was 0.78. The relative leukocyte scan activity score was less concordant with the degree of mucosal leukocyte infiltration but still significantly correlated (r = 0.616, p < 0.0001 in UC patients and r = 0.441, p < 0.003 in CD patients). CONCLUSION: Images created by the technetium 99m hexamethylpropylene-amineoxime-labeled leukocyte scan in acute colonic inflammatory bowel disease correlate to mucosal leukocyte migration in terms of proximal disease extent and, to a lesser degree, also to the intensity of mucosal inflammatory infiltration.

Observer agreement and accuracy for lung scintigraphy: a comparison with pulmonary angiography.

This study investigated whether the moderate observer agreement rate for lung scintigraphy, when using the PIOPED criteria, reflects significant variations in accuracy. In a prospective study, 170 patients were investigated with lung scintigraphy and pulmonary angiography. The lung scintigrams were read according to the PIOPED criteria by three skilled observers from different hospitals who had no experience of consensus interpretation. The scintigrams were reinterpreted 6 months later. The inter-observer agreement rates were moderate and fair, with kappa values of 0.49 (0.44-0.54) for the first reading and 0.36 (0.31-0.41) for the second reading. The intra-observer agreement rates were good and moderate, with kappa values of 0.62 (0.51-0.73), 0.52 (0.42-0.62) and 0.54 (0.44-0.64). There were no significant differences between the observers in the areas under the ROC curves. However, one observer showed a significant difference between his first and second reading (P = 0.02). All three observers showed good accuracy. Although there were substantial variations in the inter- and intra-observer agreement rates, this was only reflected to a minor degree in the accuracy.

Bone marrow imaging of bone marrow transplanted multiple myeloma patients.

Eighteen bone marrow transplanted multiple myeloma patients had imaging studies on 24 occasions with radiography as well as bone and bone marrow scintigraphy within 2 months. Twelve of the radionuclide bone marrow studies were performed with Tc-99m human serum albumin colloid and 12 were performed with a Tc-99m tagged monoclonal antigranulocyte antibody. The total detection rate of bone marrow lesions increased by 5% when the findings on bone marrow scintigraphy were combined with the findings and at radiography bone scintigraphy. For lesions in the spine and sacrum, the increase was 25% and 33% respectively, including patients with focal radiotherapy. Peripheral red bone marrow expansion was noted in 17 patients. In a comparison of Mab and Tc-99m HSA colloid imaging, Mab resulted in a higher bone marrow to soft tissue uptake and to a much smaller part of the skeleton being obscured by liver and spleen uptake. It is concluded that bone marrow imaging is valuable for showing red bone marrow distribution. It thereby shows possible sites for malignant lesions; it also shows that Mab imaging is superior to Tc-99m HSA colloid imaging in bone marrow transplanted multiple myeloma patients.

Rater agreement at lung scintigraphy after consensus training.

PURPOSE: Using the PIOPED criteria in the interpretation of lung scintigraphy, perfect agreement between experienced raters with training in consensus interpretation has been demonstrated. In a previous paper we found a kappa value of 0.54 (0.45-0.63) between experienced raters with no experience of interpretation in consensus; this is significantly lower than the perfect agreement described between consensus-trained raters. The purpose of this study was to reinvestigate the same study population with the same raters, but this time after they had undergone consensus training. MATERIAL AND METHODS: Lung scintigrams of 192 patients were reviewed and categorized according to the PIOPED criteria by 2 raters after consensus training. The 2 raters reviewed a training material of 59 cases, which was not part of the study population, in order to reach a full consensus interpretation. RESULTS: After consensus training the kappa value was 0.57 (0.48-0.66). Three cases had a discrepancy of 2 categories (1.6%), and the remaining discrepancies were of one category. CONCLUSION: Consensus training did not significantly improve the agreement rate between experienced raters from different hospitals. A substantial improvement in agreement rates between hospitals may make heavy demands on resources.

Instant technetium 99m hexamethyl propylenamine oxime-labeled leukocyte scan compared with colonoscopy in early assessment of disease extent and activity in acute colitis.

AIM: This study was undertaken to evaluate technetium 99m (Tc 99m) hexamethyl propylenamine oxime (HMPAO)-labeled leukocyte scintigraphy for assessment of disease extent and activity in acute colitis. PATIENTS AND METHODS: Twenty-seven patients, hospitalized because of acute watery and/or bloody diarrhea, were investigated using both total colonoscopy and Tc 99m HMPAO-labeled leukocyte scintigraphy within 48 hours after admittance. RESULTS: Final diagnoses were ulcerative colitis in 14 patients, Crohn's disease in 7 patients, and infectious colitis in 6 patients. Using colonoscopy as the reference method, the maximum extent of colitis was correctly assessed by the leukocyte scan in 18 patients (67 percent), although rectal engagement was not visualized in 5 (19 percent). In six additional patients, there was almost complete agreement between the two methods. One other patient, with leftsided ulcerative colitis, was erroneously assessed as having total extent. Two other patients (one with Crohn's colitis and one with infectious colitis) had different segments incorrectly assessed. Sensitivity, specificity, and diagnostic accuracy of scintigraphy in detecting active inflammatory segments were 0.85, 0.83, and 0.85, respectively. Intensity of inflammatory activity assessed by the leukocyte scan correlated significantly with colonoscopic assessment (r = 0.719; P < 0.0001). CONCLUSION: Information regarding extent, localization, and disease activity in patients with acute colitis of inflammatory or infectious origin may be satisfactorily obtained using Tc 99m HMPAO-labeled leukocyte scanning. The noninvasive nature of the method makes it an attractive early alternative to other investigational procedures such as total colonoscopy or barium examination, particularly in cases with an established diagnosis of inflammatory bowel disease.

Rater agreement in lung scintigraphy.

PURPOSE: The PIOPED criteria in their original and revised forms are today's standards in the interpretation of ventilation-perfusion scintigraphy. When the PIOPED criteria are used by experienced raters with training in consensus interpretation, the agreement rates have been demonstrated to be excellent. Our purpose was to investigate the rates of agreement between 2 experienced raters from different hospital who had no training in consensus interpretation. MATERIAL AND METHODS: The 2 raters investigated a population of 195 patients. This group included 72 patients from a previous study who had an intermediate probability of pulmonary embolism and who had also been examined by pulmonary angiography. RESULTS: The results demonstrated moderate agreement rates with a kappa value of 0.54 (0.45-0.63 in a 95% confidence interval), which is similar to the kappa value of the PIOPED study but significantly lower than the kappa values of agreement rates among consensus-trained raters. There was a low consistency in the intermediate probability category, with a proportional agreement rate of 0.39 between the experienced raters. CONCLUSION: The moderate agreement rates between raters from different hospitals make it difficult to compare study populations of a certain scintigraphic category in different hospitals. Further investigations are mandatory for accurate diagnosis when the scintigrams are in the category of intermediate probability of pulmonary embolism.

Gastrointestinal activity following bone marrow scintigraphy with technetium-99m nanocolloid in patients with multiple myeloma.

Unexpected abdominal activity was registered later than 1 h post injection in technetium-99m bone marrow scintigrams of 13 multiple myeloma patients and of five controls. The activity was considered to be localised in the gastro-intestinal tract. It is attributed to accumulation of degradation products of the used nanocolloid tracer. Corresponding results are known in patients with inflammatory bowel disease when scintigraphy is performed with other radiopharmaceuticals.