Independent evaluation of a multi-view multi-task convolutional neural network breast cancer classification model using Finnish mammography screening data.

BACKGROUND: Development of deep convolutional neural networks for breast cancer classification has taken significant steps towards clinical adoption. It is though unclear how the models perform for unseen data, and what is required to adapt them to different demographic populations. In this retrospective study, we adopt an openly available pre-trained mammography breast cancer multi-view classification model and evaluate it by utilizing an independent Finnish dataset. METHODS: Transfer learning was used, and the pre-trained model was finetuned with 8,829 examinations from the Finnish dataset (4,321 normal, 362 malignant and 4,146 benign examinations). Holdout dataset with 2,208 examinations from the Finnish dataset (1,082 normal, 70 malignant and 1,056 benign examinations) was used in the evaluation. The performance was also evaluated on a manually annotated malignant suspect subset. Receiver Operating Characteristic (ROC) and Precision-Recall curves were used to performance measures. RESULTS: The Area Under ROC [95%CI] values for malignancy classification obtained with the finetuned model for the entire holdout set were 0.82 [0.76, 0.87], 0.84 [0.77, 0.89], 0.85 [0.79, 0.90], and 0.83 [0.76, 0.89] for R-MLO, L-MLO, R-CC and L-CC views respectively. Performance on the malignant suspect subset was slightly better. On the auxiliary benign classification task performance remained low. CONCLUSIONS: The results indicate that the model performs well also in an out-of-distribution setting. Finetuning allowed the model to adapt to some of the underlying local demographics. Future research should concentrate to identify breast cancer subgroups adversely affecting performance, as it is a requirement for increasing the model's readiness level for a clinical setting.

Defective WNT signaling may protect from articular cartilage deterioration - a quantitative MRI study on subjects with a heterozygous WNT1 mutation.

OBJECTIVE: WNT signaling is of key importance in chondrogenesis and defective WNT signaling may contribute to the pathogenesis of osteoarthritis and other cartilage diseases. Biochemical composition of articular cartilage in patients with aberrant WNT signaling has not been studied. Our objective was to assess the knee articular cartilage in WNT1 mutation-positive individuals using a 3.0T MRI unit to measure cartilage thickness, relaxation times, and texture features. DESIGN: Cohort comprised mutation-positive (N = 13; age 17-76 years) and mutation-negative (N = 13; 16-77 years) subjects from two Finnish families with autosomal dominant WNT1 osteoporosis due to a heterozygous missense mutation c.652T>G (p.C218G) in WNT1. All subjects were imaged with a 3.0T MRI unit and assessed for cartilage thickness, T2 and T1ρ relaxation times, and T2 texture features contrast, dissimilarity and homogeneity of T2 relaxation time maps in six regions of interest (ROIs) in the tibiofemoral cartilage. RESULTS: All three texture features showed opposing trends with age between the groups in the medial tibiofemoral cartilage (P = 0.020-0.085 for the difference of the regression coefficients), the mutation-positive individuals showing signs of cartilage preservation. No significant differences were observed in the lateral tibiofemoral cartilage. Cartilage thickness and means of T2 relaxation time did not differ between groups. Means of T1ρ relaxation time were significantly different in one ROI but the regression analysis displayed no differences. CONCLUSIONS: Our results show less age-related cartilage deterioration in the WNT1 mutation-positive than the mutation-negative subjects. This suggests, that the WNT1 mutation may alter cartilage turnover and even have a potential cartilage-preserving effect.

Validation of a MOSFET dosemeter system for determining the absorbed and effective radiation doses in diagnostic radiology.

This study aimed to validate a MOSFET dosemeter system for determining absorbed and effective doses (EDs) in the dose and energy range used in diagnostic radiology. Energy dependence, dose linearity and repeatability of the dosemeter were examined. The absorbed doses (ADs) were compared at anterior-posterior projection and the EDs were determined at posterior-anterior, anterior-posterior and lateral projections of thoracic imaging using an anthropomorphic phantom. The radiation exposures were made using digital radiography systems. This study revealed that the MOSFET system with high sensitivity bias supply set-up is sufficiently accurate for AD and ED determination. The dosemeter is recommended to be calibrated for energies <60 and >80 kVp. The entrance skin dose level should be at least 5 mGy to minimise the deviation of the individual dosemeter dose. For ED determination, dosemeters should be implanted perpendicular to the surface of the phantom to prevent the angular dependence error.

Alterations in subchondral bone plate, trabecular bone and articular cartilage properties of rabbit femoral condyles at 4 weeks after anterior cruciate ligament transection.

OBJECTIVE: To quantify early osteoarthritic-like changes in the structure and volume of subchondral bone plate and trabecular bone and properties of articular cartilage in a rabbit model of osteoarthritis (OA) induced by anterior cruciate ligament transection (ACLT). METHODS: Left knee joints from eight skeletally mature New Zealand white rabbits underwent ACLT surgery, while the contralateral (CTRL) right knee joints were left unoperated. Femoral condyles were harvested 4 weeks after ACLT. Micro-computed tomography imaging was applied to evaluate the structural properties of subchondral bone plate and trabecular bone. Additionally, biomechanical properties, structure and composition of articular cartilage were assessed. RESULTS: As a result of ACLT, significant thinning of the subchondral bone plate (P < 0.05) was accompanied by significantly reduced trabecular bone volume fraction and trabecular thickness in the medial femoral condyle compartment (P < 0.05), while no changes were observed in the lateral compartment. In both lateral and medial femoral condyles, the equilibrium modulus and superficial zone proteoglycan (PG) content were significantly lower in ACLT than CTRL joint cartilage (P < 0.05). Significant alterations in the collagen orientation angle extended substantially deeper into cartilage from the ACLT joints in the lateral femoral condyle relative to the medial condyle compartment (P < 0.05). CONCLUSIONS: In this model of early OA, significant changes in volume and microstructure of subchondral bone plate and trabecular bone were detected only in the femoral medial condyle, while alterations in articular cartilage properties were more severe in the lateral compartment. The former finding may be associated with reduced joint loading in the medial compartment due to ACLT, while the latter finding reflects early osteoarthritic changes in the lateral compartment.

Adiabatic rotating frame relaxation of MRI reveals early cartilage degeneration in a rabbit model of anterior cruciate ligament transection.

OBJECTIVE: To investigate the sensitivity of seven quantitative magnetic resonance imaging (MRI) parameters (adiabatic T1ρ, adiabatic T2ρ, continuous wave (CW) T1ρ, relaxation along a fictitious field (RAFF), T2 measured with adiabatic double echo (DE) and Carr-Purcell-Meiboom-Gill (CPMG) sequence, and T1 during off-resonance saturation [magnetization transfer (MT)]) to detect early osteoarthritic changes in a rabbit model of anterior cruciate ligament transection (ACLT). METHODS: ACLT was unilaterally induced in the knees of New Zealand White rabbits (n = 8) while contralateral joints served as controls. Femoral condyles of the joints were harvested 4 weeks post-ACLT. MRI was performed at 9.4 T. For reference, quantitative histology, Mankin grading and biomechanical measurements were conducted. RESULTS: Reference methods demonstrated early, superficial cartilage degeneration in the ACLT group, including significant loss of proteoglycans in both medial and lateral compartments, increased collagen fibril anisotropy in the lateral condyle and decreased biomechanical properties at both medial and lateral compartments. CW-T1ρ was prolonged in the lateral compartment of ACLT joints while adiabatic T1ρ and T2ρ detected degenerative changes in tissue in both lateral and medial condyles (P < 0.05). DE-T2 was significantly (P < 0.05) elevated only in the lateral compartment while CPMG-T2, MT or RAFF did not show a statistically significant difference between the groups. CONCLUSIONS: Adiabatic T1ρ and T2ρ relaxation times detected most sensitively early degenerative changes in cartilage 4 weeks post-ACLT in a rabbit model.

In vivo comparison of delayed gadolinium-enhanced MRI of cartilage and delayed quantitative CT arthrography in imaging of articular cartilage.

OBJECTIVE: To compare delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) and delayed quantitative computed tomography (CT) arthrography (dQCTA) to each other, and their association to arthroscopy. Additionally, the relationship between dGEMRIC with intravenous (dGEMRIC(IV)) and intra-articular contrast agent administration (dGEMRIC(IA)) was determined. DESIGN: Eleven patients with knee pain were scanned at 3 T MRI and 64-slice CT before arthroscopy. dQCTA was performed at 5 and 45 min after intra-articular injection of ioxaglate. Both dGEMRIC(IV) and dGEMRIC(IA) were performed at 90 min after gadopentetate injection. dGEMRIC indices and change in relaxation rates (ΔR(1)) were separately calculated for dGEMRIC(IV) and dGEMRIC(IA). dGEMRIC and dQCTA parameters were calculated for predetermined sites at the knee joint that were International Cartilage Repair Society (ICRS) graded in arthroscopy. RESULTS: dQCTA normalized with the contrast agent concentration in synovial fluid (SF) and dGEMRIC(IV) correlated significantly, whereas dGEMRIC(IA) correlated with the normalized dQCTA only when dGEMRIC(IA) was also normalized with the contrast agent concentration in SF. Correlation was strongest between normalized dQCTA at 45 min and ΔR(1,IV) (r(s) = 0.72 [95% CI 0.56-0.83], n = 49, P < 0.01) and ΔR(1,IA) normalized with ΔR(1) in SF (r(s) = 0.70 [0.53-0.82], n = 52, P < 0.01). Neither dGEMRIC nor dQCTA correlated with arthroscopic grading. dGEMRIC(IV) and non-normalized dGEMRIC(IA) were not related while ΔR(1,IV) correlated with normalized ΔR(1,IA) (r(s) = 0.52 [0.28-0.70], n = 50, P < 0.01). CONCLUSIONS: This study suggests that dQCTA is in best agreement with dGEMRIC(IV) at 45 min after CT contrast agent injection. dQCTA and dGEMRIC were not related to arthroscopy, probably because the remaining cartilage is analysed in dGEMRIC and dQCTA, whereas in arthroscopy the absence of cartilage defines the grading. The findings indicate the importance to take into account the contrast agent concentration in SF in dQCTA and dGEMRIC(IA).

Production of carcinogenic acetaldehyde by Candida albicans from patients with potentially malignant oral mucosal disorders.

OBJECTIVES: Production of carcinogenic acetaldehyde by Candida has been suggested to contribute to epithelial dysplasia and oral carcinogenesis. Oral lichen planus (OLP), oral lichenoid lesion (OLL) and oral leukoplakia (OL) are potentially carcinogenic oral diseases where colonisation by Candida is common, but acetaldehyde production by Candida has not been studied. STUDY DESIGN: Acetaldehyde production in ethanol (11 mM), glucose (100 mM), ethanol-glucose (11 mM and 100 mM) or red wine (1200 mM ethanol) incubation by Candida albicans from patients with OLL (n = 6), OLP (n = 16), OL (n = 6) and controls (n = 6) was measured by gas chromatography. Participants completed a questionnaire regarding their smoking habits and alcohol consumption. RESULTS: All Candida albicans isolates produced potentially carcinogenic levels of acetaldehyde (>100 µM) in all incubations containing ethanol. The control group isolates produced the highest acetaldehyde levels. Isolates from smokers produced more acetaldehyde in all incubations than those from non-smokers. The difference was significant in ethanol-glucose incubation. Isolates from patients who were both smokers and drinkers produced the highest amounts when incubated in ethanol, ethanol-glucose and wine. CONCLUSIONS: Candida albicans isolated from potentially carcinogenic oral diseases can produce mutagenic amounts of acetaldehyde. Cigarette smoking and alcohol consumption may favour adaptational changes resulting in the upregulation of candidal acetaldehyde metabolism.

A comparison of radiation exposure between diagnostic CTA and DSA examinations of cerebral and cervicocerebral vessels.

BACKGROUND AND PURPOSE: While the number of CTA examinations is continually increasing compared with DSA examinations, there is little comparative dose information about the different imaging techniques. We compared patient radiation exposure resulting from diagnostic CTA and DSA examinations for both cerebral and cervicocerebral vessels. MATERIALS AND METHODS: An anthropomorphic phantom was irradiated by using typical diagnostic CTA and DSA setups and imaging parameters. For both imaging techniques, the imaging area of cerebral vessels included intracranial vessels only, while the imaging area of cervicocerebral vessels included both cervical and intracranial vessels from the aortic arch to the vertex. The effective dose was determined by using RPLDs. The DSA examination was simulated by using a biplane angiography system, and the CTA examination, by using a 64-row multidetector CT scanner. RESULTS: For the imaging of cerebral vessels, the effective dose according to ICRP 103 was 0.67 mSv for CTA and 2.71 mSv for DSA. For the imaging of cervicocerebral vessels, the effective dose was 4.85 mSv for CTA and 3.60 mSv for DSA. The maximum absorbed dose (milligray) for skin, brain, salivary glands, and eyes was 166.2, 73.5, 35.6, and 21.8 mGy for DSA and 19.0, 16.9, 20.4, and 14.8 mGy for CTA, respectively. The conversion factors from DAP and DLP to effective dose were calculated. CONCLUSIONS: The effective dose for CTA assessment of cerebral vessels was approximately one-fifth the dose compared with DSA. In the imaging of cervicocerebral vessels, the effective dose for CTA was approximately one-third higher compared with DSA.

The applicability of radiophotoluminescence dosemeter (RPLD) for measuring medical radiation (MR) doses.

The applicability of radiophotoluminescence dosimetry was determined by assessing various radiophotoluminescence dosemeter (RPLD) properties for measuring medical radiation doses from radiation sources of a continuous spectrum. The RPLD was found to be accurate for measuring doses in diagnostics (50-125 keV) and radiation therapy (6, 10 and 18 MV photons, 6 and 15 MeV electrons). The RPLD shows excellent dose linearity (R(2) > 0.99), reproducibility and batch uniformity, and minimal fading and accurate accumulated dose measurement. The dosemeter material is independent of photon energy in the diagnostic range; however, the dosemeter requires additional calibration in the mammography energy range and also for accurate dose measurement with photon or electron energies in radiation therapy. RPLD measurements with a tin filter show considerable angular dependence at angles exceeding 50° between the photon beam and the normal to the long axis of the dosemeter. The RPLD measurement accuracy at high doses can be improved with optimised pre-heating schemes.

Determining air kerma from pixel values in digital mammography.

The pixels in digital detectors used in x-ray imaging can be considered as small dose meters. In mammography, the image detector area is commonly only partly covered by tissue and the incident air kerma could be monitored by using pixel values from the detector elements in the unattenuated primary beam area. The measured air kerma could be used for patient dose estimation. The air kerma and radiation quality dependence of the response of pixel values within a large exposure range for two direct digital detector types was experimentally investigated for this purpose. Using these calibration results, air kerma was measured from clinical images and compared with tube output calculation. The differences between the two methods were typically below 2% and measurements based on pixel values can therefore be recommended.

Comparison of novel clinically applicable methodology for sensitive diagnostics of cartilage degeneration.

In order efficiently to target therapies intending to stop or reverse degenerative processes of articular cartilage, it would be crucial to diagnose osteoarthritis (OA) earlier and more sensitively than is possible with the existing clinical methods. Unfortunately, current clinical methods for OA diagnostics are insensitive for detecting the early degenerative changes, e.g., arising from collagen network damage or proteoglycan depletion. We have recently investigated several novel quantitative biophysical methods, including ultrasound indentation, quantitative ultrasound techniques and magnetic resonance imaging, for diagnosing the degenerative changes of articular cartilage, typical for OA. In this study, the combined results of these novel diagnostic methods were compared with histological (Mankin score, MS), compositional (proteoglycan, collagen and water content) and mechanical (dynamic and equilibrium moduli) reference measurements of the same bovine cartilage samples. Receiver operating characteristics (ROC) analysis was conducted to judge the diagnostic performance of each technique. Indentation and ultrasound techniques provided the most sensitive measures to differentiate samples of intact appearance (MS=0) from early (13) degeneration. Furthermore, these techniques were good predictors of tissue composition and mechanical properties. The specificity and sensitivity analyses revealed that the mechano-acoustic methods, when further developed for in vivo use, may provide more sensitive probes for OA diagnostics than the prevailing qualitative X-ray and arthroscopic techniques. Noninvasive quantitative MRI measurements showed slightly lower diagnostic performance than mechano-acoustic techniques. The compared methods could possibly also be used for the quantitative monitoring of success of cartilage repair.

Patellar cartilage lesions: comparison of magnetic resonance imaging and T2 relaxation-time mapping.

PURPOSE: To evaluate the detection and the size of focal patellar cartilage lesions in T2 mapping as compared to standard clinical magnetic resonance imaging (MRI) at 1.5T. MATERIAL AND METHODS: Fifty-five consecutive clinical patients referred to knee MRI were imaged both with a standard knee MRI protocol (proton-density-weighted sagittal and axial series, T2-weighted sagittal and coronal series, and T1-weighted coronal series) and with an axial multislice multi-echo spin-echo measurement to determine the T2 relaxation time of the patellar cartilage. MR images and T2 maps of patellar cartilage were evaluated for focal lesions. The lesions were evaluated for lesion width (mm), lesion depth (1/3, 2/3, or 3/3 of cartilage thickness), and T2 value (20-40 ms, 40-60 ms, or 60-80 ms) based on visual evaluation. RESULTS: Altogether, 36 focal patellar cartilage lesions were detected from 20 human subjects (11 male, nine female, mean age 40+/-15 years). Twenty-eight lesions were detected both on MRI and T2 maps, while eight lesions were only visible on T2 maps. Cartilage lesions were significantly wider (P = 0.001) and thicker (P<0.001) on T2 maps as compared to standard knee MRI. Most lesions 27 had moderately (T2 40-60 ms) increased T2 values, while two lesions had slightly (T2 20-40 ms) and seven lesions remarkably (T2 60-80 ms) increased T2 relaxation times. CONCLUSION: T2 mapping of articular cartilage is feasible in the clinical setting and may reveal early cartilage lesions not visible with standard clinical MRI.

Evaluation of cartilage repair in the distal femur after autologous chondrocyte transplantation using T2 relaxation time and dGEMRIC.

OBJECTIVES: To investigate the potential of combining T2 relaxation time and delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) measurements after autologous chondrocyte transplantation (ACT). MATERIALS AND METHODS: T2 and dGEMRIC maps were measured in the sagittal and coronal directions in 12 patients 10-15 months after ACT surgery. Grafts were assessed for bulk full thickness, superficial and deep tissue T2 and dGEMRIC values, and were compared to control cartilage. RESULTS: All ACT grafts showed filling of the repair area to the level of or above the articular surface. Matrix of the grafts lacked the classical laminar structure and appeared more heterogenous on T2 maps than control cartilage. As compared to control cartilage, ACT grafts showed significantly longer T2 values for bulk tissue as well as for the superficial 50% and deep 50% of tissue except for superficial cartilage in the coronal direction. dGEMRIC assessment in the sagittal and coronal directions did not show a significant difference between bulk, superficial or deep tissue as compared to the control cartilage. Superficial and deep ACT tissue did not differ statistically in terms of their T2 or dGEMRIC values. CONCLUSIONS: These preliminary results suggest that, according to T2 measurements, ACT repair tissue at 10-15 months differs from normal cartilage and probably lacks the preferential collagen arrangement of normal cartilage, while according to dGEMRIC a varying degree of proteoglycan replenishment takes place. Combining these two quantitative magnetic resonance imaging techniques enables a more comprehensive characterization of cartilage repair than before.

Potential of diffusion imaging in brain tumors: a review.

Diffusion magnetic resonance imaging (MRI) is a method for quantifying the microscopic random motion of water molecules in tissues. Diffusion imaging provides indirect structural information of a kind not available on basic MRI sequences of many pathological conditions. Lately, especially brain tumors have been under active investigation, with numerous papers already published, and their number continues to increase. This review summarizes the heterogeneous and complex research data on diffusion imaging of brain tumors.

Novel mechano-acoustic technique and instrument for diagnosis of cartilage degeneration.

Fibrillation of articular surface and depletion of proteoglycans are the structural changes related to early osteoarthrosis. These changes make cartilage softer and prone to further degeneration. The aim of the present study was to combine mechanical and acoustic measurements towards quantitative arthroscopic evaluation of cartilage quality. The performance of the novel ultrasound indentation instrument was tested with elastomers and bovine articular cartilage in vitro. The instrument was capable of measuring elastomer thickness (r = 1.000, p < 0.01, n = 8) and dynamic modulus (r = 0.994, p < 0.01, n = 13) reliably. Osteochondral plugs were tested before and after enzymatic degradation of cartilage proteoglycans by trypsin or chondroitinase ABC, and of cartilage collagens by collagenase. Trypsin and collagenase induced a mean decrease of -31.2 +/- 12.3% (+/- SD, p < 0.05) and -22.9 +/- 20.8% (p = 0.08) in dynamic modulus, respectively. Rate of cartilage deformation, i.e. creep rate, increased by +117.8 +/- 71.4% (p < 0.05) and +24.7 +/- 35.1% (p = 0.17) in trypsin and chondroitinase ABC treatments, respectively. Collagenase induced a greater decrease in the ultrasound reflection from the cartilage surface (-54.2 +/- 29.6%, p < 0.05) than trypsin (-17.1 +/- 13.5%, p = 0.08). In conclusion, combined quantitation of tissue modulus, viscoelasticity and ultrasound reflection from the cartilage surface provides a sensitive method to distinguish between normal and degenerated cartilage, and even to discern proteoglycan loss and collagen degradation from each other.

Estimation of the Young's modulus of articular cartilage using an arthroscopic indentation instrument and ultrasonic measurement of tissue thickness.

We evaluated whether the use of cartilage thickness measurement would improve the ability of the arthroscopic indentation technique to estimate the intrinsic stiffness of articular cartilage. First, cartilage thickness and ultrasound reflection from the surface of bovine humeral head were registered in situ using a high-frequency ultrasound probe. Subsequently, cartilage was indented in situ at the sites of the ultrasound measurements using arthroscopic instruments with plane-ended and spherical-ended indenters. Finally, full-thickness cartilage disks (n=30) were extracted from the indented sites (thickness=799-1654microm) and the equilibrium Young's modulus was determined with a material testing device in unconfined compression geometry. We applied analytical and numerical indentation models for the theoretical correction of experimental indentation measurements. An aspect-ratio (the ratio of indenter radius to cartilage thickness) correction improved the correlation of the indenter force with the equilibrium Young's modulus from r(2)=0.488 to r(2)=0.642-0.648 (n=30) for the plane-ended indenter (diameter=1.000mm, height=0.300mm) and from r(2)=0.654 to r(2)=0.684-0.692 (n=30) for the spherical-ended indenter (diameter=0.500mm, height=0.100mm), depending on the indentation model used for the correction. The linear correlation between the ultrasound reflection and the Young's modulus was r(2)=0.400 (n=30). These results suggest that with large indenters, knowledge of the cartilage thickness improves the reliability of the indentation measurements, especially in pathological situations where cartilage thickness may be significantly lower than normal. Ultrasound measurements also provide diagnostically important information about cartilage thickness as well as knowledge of the integrity of the superficial zone of cartilage.

Comparison of epidural and spinal blockade with 0.5% bupivacaine for transurethral surgery.

The suitability of spinal versus epidural blockade for transurethral resection of the prostate was studied in 60 patients randomly allocated to spinal and epidural anaesthesia groups. 0.5% bupivacaine (Marcain, Astra, Sweden) was injected at the L3-L4 interspace, the dose being 3 ml in the spinal group and 19 (16-25) ml in the epidural group. The blood pressure decreased similarly after both epidural and spinal injections, but the heart rate was not significantly altered. No statistically significant differences were found between the groups in any of the variables measured, including blood pressure, heart rate, intraoperative blood loss and per- and post-operative complications. However, altogether eight patients in the epidural group, but none in the spinal group, had to be treated because of hypotension (P less than 0.001). The main advantage of the spinal blockade was a faster and more reliable blockade of the lowest sacral segments, and the main advantage of the epidural blockade was a less pronounced and shorter duration of motor blockade.

Heated humidification in major abdominal surgery.

The influence of heated humidification on body temperature and postoperative shivering was studied in 30 patients undergoing major intra-abdominal surgery. In the control group (I) the anaesthetic gases, administered in a non-rebreathing system, were humidified by a sponge heat and moisture exchanger. In group II the gases were humidified and heated to 37 degrees C and in group III up to 40 degrees C. Anaesthesia, surface insulation and warming of the infusions were standardized. The temperature was registered at the lower oesophagus and the big toe. Shivering and the feeling of cold were estimated at 15 min intervals postoperatively. A good correlation was found between heat gain during the first hour of recovery, the feeling of cold and intensity of shivering. Intraoperative heat loss was minimal in all groups. Heated humidification had no statistically significant effect on the body temperatures or postoperative shivering and thus provided no additional advantage compared to the control group.

Temperature gradients in cardiac surgical patients--a comparison of halothane and fentanyl.

Narcotics and potent inhalation anesthetics have different effects on thermoregulation and the distribution of body heat. This study was designed to compare the effect of halothane vs fentanyl anesthesia on temperature gradients developed during and after hypothermic cardiopulmonary bypass. Twenty-two adult patients undergoing coronary artery surgery were given either fentanyl (100 micrograms/kg) or halothane (0.5-1.5%) and oxygen. Thermistor probes were inserted in rectum, esophagus, and deltoid muscle. Surface temperatures were measured on the ring finger and upper arm. All patients were cooled during cardiopulmonary bypass to 28 degrees C, and ambient temperature was maintained at 22-23 degrees C. The times to cool and rewarm were comparable in both groups. Rectal, esophageal, and skin temperatures had not reached equilibrium by 60 min after bypass, but changes in temperature were virtually identical at all sites in both groups. Regardless of differences in the effects of halothane and fentanyl on hormonal responses, blood flow, or central thermoregulation, their net effects on body temperature were the same.