Quantitative renal cortical perfusion in human subjects with magnetic resonance imaging using iron-oxide nanoparticles: influence of T1 shortening.

BACKGROUND: Using conventional contrast agents, the technique of quantitative perfusion by observing the transport of a bolus with magnetic resonance imaging (MRI) is limited to the brain due to extravascular leakage. PURPOSE: To perform quantitative perfusion measurements in humans with an intravascular contrast agent, and to estimate the influence of the T1 relaxivity of the contrast agent on the first-pass response. MATERIAL AND METHODS: Renal cortical perfusion was measured quantitatively in six patients with unilateral renal artery stenosis using a rapid gradient double-echo sequence in combination with an intravenous bolus injection of NC100150 Injection, an intravascular contrast agent based on iron-oxide nanoparticles. The influence of T1 relaxivity was measured by comparing perfusion results based on single- and double-echo data. RESULTS: The mean values of cortical blood flow, cortical blood volume, and mean transit time in the normal kidneys were measured to 339+/-60 ml/min/100 g, 41+/-8 ml/100 g, and 7.3+/-1.0 s, respectively, based on double-echo data. The corresponding results based on single-echo data, which are not compensated for the T1 relaxivity, were 254+/-47 ml/min/100 g, 27+/-3 ml/100 g, and 6+/-1.2 s, respectively. CONCLUSION: The use of a double-echo sequence enabled elimination of confounding T1 effects and consequent systematic underestimation of the perfusion.

Improved visualization of artificial pulmonary nodules with a new subvolume rendering technique.

BACKGROUND: The detection of small nodules in pulmonary multidetector computed tomography (MDCT) data sets is challenging, and there is a need for visualization techniques that can improve reader sensitivity and efficiency. We have developed a subvolume rendering technique ("Softslice") with nonlinear, symmetrical modulation of the relative signal intensity along the viewing direction. Our hypothesis was that this technique might provide an advantageous visual differentiation between nodules and overlapping vessels in pulmonary MDCT subvolumes. PURPOSE: To compare the Softslice subvolume rendering technique and maximum intensity projection (MIP) rendering for visualization of artificial pulmonary nodules in MDCT data sets. MATERIAL AND METHODS: Virtual, artificial pulmonary nodules were created with custom-made software. The nodules had the same signal intensity as pulmonary vessels. Approximately 50 nodules with diameter 2-7 mm were inserted in the Digital Imaging and Communications in Medicine (DICOM) image files of pulmonary MDCT data sets obtained without intravenous contrast. Each data set contained approximately 300 slices with 1-mm slice spacing. Four types of subvolumes were rendered: MIP with 10- and 20-mm subvolume thickness, and Softslice with 20- and 30-mm subvolume thickness. Three radiologists performed readings with free scrolling using 1-, 4- or 8-mm increments between subvolume positions. RESULTS: No significant differences in the number of detected nodules were found between the different renderings with free scrolling using 1- and 4-mm increments. When 8-mm increment was used, nodule detection with the 30-mm Softslice rendering was significantly superior to the other renderings (P = 0.012 vs. MIP 10 mm, P = 0.018 vs. MIP 20 mm, P = 0.021 vs. Softslice 20 mm). When the subvolume increments were changed from 4 mm to 8 mm, the most marked reduction in the number of detected nodules was seen for MIP subvolumes with 10-mm thickness (P = 0.018). CONCLUSION: The Softslice rendering technique is promising for the detection of pulmonary nodules in MDCT data sets, and may allow more efficient reading than the standard MIP subvolume technique. With 10-mm MIP rendering, the detection rate for small pulmonary nodules substantially influenced by the incremental distance between subvolumes positions.

Computed tomography/magnetic resonance based volume changes of the primary tumour in patients with prostate cancer with or without androgen deprivation.

BACKGROUND AND PURPOSE: To evaluate changes of the volume of the cancerous prostatic gland during androgen deprivation (AD) started immediately after diagnosis (IAD). Hypothetically, these data would assist the radiotherapist to determine the appropriate duration of pre-radiotherapy downsizing neoadjuvant luteinizing hormone releasing hormone (LHRH) treatment. A second aim was to assess any increase of the prostatic volume during the 1st year of diagnosis in patients who were allocated to a deferred treatment policy (DAD). METHODS AND MATERIALS Thirteen patients in the IAD cohort and 13 patients in the DAD group, all with T1-3pN1-2M0 prostate cancer, had regular computed tomography/magnetic resonance (CT/MR) examinations during the 1st year after randomization within the EORTC-GU trial 30846. Pre-treatment prostate specific antigen (PSA) values were available in only 12 patients. RESULTS: In the IAD group the prostate gland decreased with significant difference as compared with the DAD patients (P=0.033). As compared with the pre-treatment situation the prostate gland in the IAD group was reduced in size by 18, 35, and 46% at 1, 6, and 12 months, respectively. In four of six evaluable IAD patients the prostatic volume continued to shrink after achievement of the nadir PSA level (at 3 months). In three of the 13 DAD patients the prostate volume increased by >25% during the 1st 3 months after randomization. CONCLUSION: If neoadjuvant androgen deprivation is applied before local treatment to downsize the volume of the cancerous prostate gland, our limited data suggest that such treatment should last at least 6 months in order to achieve a maximal effect in the majority of patients. In about 1/4 of untreated patients an increase in the prostate volume by >25% may occur within 3 months of diagnosis. If no AD is given, radiotherapy should start within this period.

Evaluation of a pressure-recording guidewire in patients with coronary arterial disease.

The accuracy and feasibility of coronary arterial pressure measurements with a 0.018-in. pressure-recording guidewire (PRGW) was evaluated in patients. Transstenotic pressure gradients were measured with the PRGW and a guiding catheter, at baseline and during coronary vasodilatation. Proximal intracoronary pressure was measured with both systems before and after gradient measurements. Zero pressure was measured with the PRGW before and after intracoronary use. The average of all proximal intracoronary PRGW readings were close to guiding catheter values, but there were substantial individual deviations. Average change in proximal deviation before and after gradient measurements was -1 mm Hg, standard deviation (S.D.) 7.6, range -16 to 15. Errors in zero pressure measurements after intracoronary use (average 2.8 mm Hg, S.D. 8.8, range -9 to 35) were much greater than before use (average 0.1 mm Hg, S.D. 1.4, range -4 to 3, P < 0.001). The PRGW was successfully introduced through an 8F guiding catheter and positioned across the stenosis in 21 of 26 attempts (81%). Intracoronary advancement of the PRGW through a double-lumen multifunctional probing catheter was successful in all nine attempts. In conclusion, errors in PRGW-measurements caused uncertainty in gradient interpretation. However, we found the wire useful in several cases, particularly for exclusion of hemodynamically significant lesions. The steerability of the wire is inferior to ordinary guidewires, but it can be advanced to a distal intracoronary position through an over-the-wire catheter.

Effect of ultrasound contrast medium in color Doppler and power Doppler visualization of blood flow in canine kidneys.

PURPOSE: To examine the effect of an ultrasound contrast medium (UCM) in the visualization of parenchymal blood flow by means of color Doppler and power Doppler sonography. MATERIAL AND METHODS: Nonenhanced and UCM-enhanced Doppler images of canine kidneys were obtained in a transversal plane during various states of flow reduction in the anterior branch of the renal artery. The UCM consisted of air-filled shell-stabilized microballoons (half-life approximately 2 min). The images were evaluated blindly by 4 observers who rated the amount of flow signal in the cortex and medulla, and categorized the flow state (normal, reduced or no flow) in the anterior part of the kidney. RESULTS: The UCM increased the area of Doppler signals in the cortex and outer medulla during normal or reduced blood flow. The border between nonperfused and normally perfused parenchyma was more distinct with the UCM. The categorization of the regional flow state was more correct with the UCM. Improvement with the UCM was greatest when the nonenhanced Doppler images had suboptimal intensity, but positive effects with the UCM were also seen in recordings with adequate precontrast intensity. Color blooming artifacts sometimes occurred on the side of the kidney facing away from the transducer. CONCLUSION: The UCM improved the color Doppler and power Doppler visualization of the parenchymal blood flow in the canine kidney, and allowed a more correct categorization to be made of the regional blood flow state.

Effects of maximal effort strength training with different loads on dynamic strength, cross-sectional area, load-power and load-velocity relationships.

The effects of maximal effort strength training with different loads on maximal strength, muscle cross-sectional area, the load-power and load-velocity relationship were investigated in the elbow flexors. Physical education students were matched into three groups; G90 (n = 9) trained with a load of 90%. G35 (n = 11) with 35%, and G15 (n = 10) with 15% of IRM (1 repetition maximum). Training consisted of three to five sets, performed three times a week for 9 weeks. Each set consisted of two, seven and ten repetitions in G90. G35 and G15, respectively. Training was performed with the nondominant arm, and the dominant arm served as control. The IRM increased 15.2 (SD 4.5)% (P < 0.001) in G90, 10.1 (SD 5.9)% (P < 0.001) in G35 and 6.6 (SD 7.9)% (P < 0.05) in G15. The increase in G90 was significantly larger than for G15 (P < 0.05). In the untrained arm, IRM also increased for G90 and G15. In contrast to G90. G15 showed a similar increase in IRM in both arms. Cross-sectional area of the elbow, flexors did not change for G90 and G15. while G35 increased 2.8% (P < 0.05). Maximal power and velocity were tested at 2.5 kg and at 15%, 25%, 35%, 50%, 70% and 90% of pretraining IRM. Power increased for all tested loads in G90 and G35, and G15 showed an increase in power at 15%, 25% and 50% of IRM. No significant differences in increase in power could be found among the three groups at loads equal to or less than 50%, but at 70% and 90% of IRM the increase was larger for G90 and G35 than for G15 (P < 0.05). The G35 showed a similar increase in power at all loads tested whereas G90 showed load specificity in the effect of the training. There was a correlation between IRM and maximal power (r = 0.93, P < 0.0001), and between IRM and power at load 2.5 kg (r = 0.73, P < 0.0001). In conclusion, training with loads of 15% and 35% of IRM resulted in an increase in IRM. Although the increase in maximal power after training at 90% of IRM showed some load specificity. It also increased maximal power at 15% of IRM. Training at loads near maximal power output would seem to increase power efficiently over a wide load range. The high correlation between IRM and maximal power at load 2.5 kg also would indicate that maximal strength is important for performance at light loads.

Use of sonicated albumin (Infoson) to enhance arterial spectral and color Doppler imaging.

PURPOSE: To examine the effect of an ultrasound contrast medium (UCM), Infoson, on Doppler examination of stenotic arteries. METHODS: Stenoses were created in the common carotid artery of six piglets, and examined with spectral Doppler and color Doppler imaging during UCM infusion in the left ventricle. RESULTS: UCM caused a mean increase in recorded maximal systolic and end-diastolic velocities of 5% and 6%, respectively, while blood flow remained constant. Increased spectral intensity with UCM was accompanied by spectral broadening. Reduction of spectral intensity by adjustment of Doppler gain counteracted the velocity effects and the spectral broadening. With color Doppler, UCM caused dose-dependent color artifacts outside the artery. Flow in narrow stenoses could be visualized with UCM. CONCLUSION: The effects of UCM on velocity measurements were slight, and were related to changes in spectral intensity. With color Doppler, UCM may facilitate flow detection, but color artifacts may interfere.

A pressure-recording guidewire for measuring arterial transstenotic gradients: in vivo validation.

RATIONALE AND OBJECTIVES: We used an 0.018-inch guidewire with a pressure sensor to measure arterial transstenotic pressure gradients. Our aim was to evaluate the pressure-recording properties of this device in vivo. METHODS: Stenoses in the common carotid artery of piglets were created with external cylindrical constrictors. Pressures and pressure gradients were measured with the pressure wire and compared with reference measurements and with a 3.1-French fluid-filled catheter. RESULTS: The averages of several pressure measurements were close to the reference, but there were individual deviations. Twenty-nine percent of zero-corrected systolic measurements deviated more than 5 mm Hg from the reference, and 10% deviated more than 10 mm Hg. Errors canceled out somewhat in gradient measurements. CONCLUSION: Although some measurement errors were found, the guidewire represents an important new concept for gradient measurements. The small diameter minimizes gradient augmentation caused by the measuring device lying across the stenosis. Further refinement would increase its usefulness.

A pressure-recording guide wire for measurements of trans-stenotic gradients in arteries. In vitro validation.

RATIONALE AND OBJECTIVES: A 0.018'' guide wire with a pressure sensor near the tip has been developed for measuring arterial trans-stenotic pressure gradients. The pressure-recording properties of this system in vitro are evaluated. METHODS: Static and dynamic tests were performed with five guide wires. Dynamic tests (step response and recordings of phase and frequency response) were performed with a pressure generator connected to a recording system and a spectrum analyzer. RESULTS: Zero drift at 3 hours ranged from -1.9 to 2.2 mmHg/hour. Sensitivity drift ranged from 0.3% to 2.1%/hour. Hysteresis ranged from 0.2% to 4.3% (mean 2.4%). Bending in arcs of 180 degrees with diameters < 4 cm changed sensitivity and zero pressure recordings in all guide wires. Dynamic recordings showed a slight undershoot and no oscillation. CONCLUSION: Static errors exceeded those of external pressure transducers for fluid-filled catheters, indicating suboptimal recordings of absolute pressures. However, the small size, and the good dynamic properties, make this pressure wire a promising device for recording trans-stenotic pressure gradients in arteries.

Increasing contrast when viewing radiographic images.

Illuminating a developed photographic film with parallel or nearly parallel light provides increased contrast compared with the contrast obtained with diffuse incident light. The viewer of radiographic images can obtain increased contrast simply by increasing the distance between the view box and the radiograph, since this results in more parallel incident light. The authors found a contrast increase of more than 40% when x-ray film was positioned 4 m from a view box. Tilting the film relative to the surface plane of the view box gave additional contrast increase at the cost of somewhat distorted geometry. The photographic effects involved deserve a more thorough discussion in textbooks of radiologic and radiographic physics.

Comparison of 12-bit and 8-bit gray scale resolution in MR imaging of the CNS. An ROC analysis.

A reduction in gray scale resolution of digital images from 12 to 8 bits per pixel usually means halving the storage space needed for the images. Theoretically, important diagnostic information may be lost in the process. We compared the sensitivity and specificity achieved by 4 radiologists in reading laser-printed films of original 12-bit MR images and cathode ray tube displays of the same images which had been compressed to 8 bits per pixel using a specially developed computer program. Receiver operating characteristic (ROC) curves showed no significant differences between film reading and screen reading. A paired 2-tailed t-test, applied on the data for actually positive cases, showed that the combined, average performance of the reviewers was significantly better at screen reading than at film reading. No such differences were found for actually negative cases. Some individual differences were found, but it is concluded that gray scale resolution of MR images may be reduced from 12 to 8 bits per pixel without any significant reduction in diagnostic information.

Computed tomography after modified Whipple procedure with pancreatic duct occlusion.

Eighty-two CT examinations performed on 28 patients who had undergone a modified Whipple procedure including pancreatic duct occlusion were reviewed. Reduction of the antero-posterior diameter of the body and tail of the pancreatic remnant was observed on consecutive scans in 8 patients (29%). Decreasing liver attenuation was seen in 4 patients (14%) postoperatively, and pseudocysts in the pancreatic remnant in 6 (21%). In 10 examinations performed because of suspected intraabdominal abscess postoperatively, abscess was diagnosed in 2 patients. In 62 routine follow-up CT examinations, significant positive findings were diagnosed in 5 patients: tumor recurrence or metastases in 4, and a large pseudocyst in one. CT is of value in the early postoperative phase to reveal postoperative complications and in the follow-up of patients with specific symptoms indicating tumor recurrence or metastases.

[Should doctors contribute more to the development of computer-based information systems at hospitals?]. / Bør leger delta mer aktivt i utvikling av EDB-løsninger ved sykehus?

In our X-ray department we have used a commercially available database computer program to design a system for storing information about the X-ray examinations performed. The system runs on a local area network. We have been able to quickly modify the system in the light of feedback from the users. Using modern database programs for personal computers has made it quite easy for doctors to participate directly in the design of information systems for use in hospitals.

Enlargement of the thymus following chemotherapy for non-seminomatous testicular cancer.

The thickness of the largest thymic lobe at computed tomography (CT) was measured retrospectively in 21 relapse free patients who had undergone chemotherapy for non-seminomatous testicular cancer. CT was performed at initial staging, at completion of chemotherapy and 3 to 12 months later. Enlargement of the thymus occurred in 7 patients, one of whom had a reduced thymic size at the first two examinations after chemotherapy. A temporary reduction was detected in another patient in whom the original thymic size was regained 19 months after start of chemotherapy. The mean age of the group with thymic enlargement was 21 years compared with a mean age of 28 years in the group with no increased size. The age difference between the two groups was significant (p less than 0.05, Mann-Whitney U test). To reduce the number of explorative thoracotomies the frequent occurrence of thymic enlargement after chemotherapy for non-seminomatous testicular cancer should be kept in mind.