A review of screening mammography participation and utilization in Canada.

INTRODUCTION: Participation rate is an important indicator for a screening program's effectiveness; however, the current approach to measuring participation rate in Canada is not comparable with other countries. The objective of this study is to review the measurement of screening mammography participation in Canada, make international comparisons, and propose alternative methods. METHODS: Canadian breast cancer screening program data for women aged 50 to 69 years screened between 2004 and 2006 were extracted from the Canadian Breast Cancer Screening Database (CBCSD). The fee-for-services (FSS) mammography data (opportunistic screening mammography) were obtained from the provincial ministries of health. Both screening mammography program participation and utilization were examined over 24 and 30 months. RESULTS: Canada's screening participation rate increases from 39.4% for a 24-month cut-off to 43.6% for a 30-month cut-off. The 24-month mammography utilization rate is 63.1% in Canada, and the 30-month utilization rate is 70.4%. CONCLUSION: Due to the differences in health service delivery among Canadian provinces, both programmatic participation and overall utilization of mammography at 24 months and 30 months should be monitored.

MR ventilation-perfusion imaging of human lung using oxygen-enhanced and arterial spin labeling techniques.

Magnetic resonance ventilation-perfusion (V/Q) imaging has been demonstrated using oxygen and arterial spin labeling techniques. Inhaled oxygen is used as a paramagnetic contrast agent in ventilation imaging using a multiple inversion recovery (MIR) approach. Pulmonary perfusion imaging is conducted using a flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER) technique. A half Fourier single-short turbo spin echo (HASTE) sequence is used for data acquisition in both techniques. V/Q imaging was performed in ten of the twenty volunteers, while either ventilation or perfusion was imaged in the other ten. This V/Q imaging scheme is completely noninvasive, does not involve ionized radiation, and shows promising potential for clinical use in the diagnosis of lung diseases such as pulmonary embolism.

Temporal dynamics of blood flow effects in half-Fourier fast spin echo (1)H magnetic resonance imaging of the human lungs.

A cardiac-triggered half-Fourier single-shot turbo spin echo (HASTE) technique is currently the method of choice for MR imaging of the lung parenchyma without the use of exogenous contrast agents. In this study, we specifically examined the effects of the cardiac cycle on the HASTE signal intensity of the lungs. Images were obtained from six healthy human volunteers at an end expiration breath-hold using a HASTE sequence and a variable cardiac-triggered delay time. Analysis of the data sets showed a 30% decrease in the lung signal intensity during systole, and a 15% decrease during mid-diastole. These decreases correlate with phases of the cardiac cycle when the blood flow in the lungs is expected to be greatest. Misregistration artifacts, particularly from the pulmonary arteries and aorta, are worse during these periods of signal decrease. To minimize cardiac dependent signal losses, HASTE lung imaging should be performed after systole but before rapid filling of the ventricles.

Gravity-dependent perfusion of the lung demonstrated with the FAIRER arterial spin tagging method.

Magnetic resonance imaging of lung perfusion using an arterial spin tagging (AST) sequence called flow sensitive alternating inversion recovery with an extra RF pulse (FAIRER) was performed in the left and right lateral positions in five volunteers. Coronal slices were obtained and the average intensity of each lung was measured. In both positions, an increase in the intensity of the dependent lung was found (229% for left lateral, 40% for right lateral). No change was seen along an isogravitational plane. Lung volumes were measured in each position to account for the compression of the lungs by the heart. This effect was found to be symmetric and did not contribute to the perfusion gradient. This demonstrates that AST is sensitive to gravity-dependent perfusion gradients in the lung.

Effect of lung inflation on arterial spin labeling signal in MR perfusion imaging of human lung.

The effect of lung inflation on arterial spin-labeling signal in lung perfusion is investigated. Arterial spin-labeling schemes, called alternation of selective inversion pulse (ASI) and its hybrid (HASI), which uses blood water as an endogenous, freely diffusible tracer, were applied to magnetic resonance (MR) perfusion imaging of the lung. Perfusion-weighted images of the lung from nine healthy volunteers were obtained at different time delays. There was a significant signal difference in ASI images acquired at different respiratory phases. Greater signal enhancement has been observed when the volunteers performed breath holding on end expiration than on end inspiration. This is in agreement with the normal physiologic effect of lung inflation on the pressure-flow relationship of pulmonary vasculature. ASI and HASI perfusion-weighted images show similar lung features and image quality. Preliminary results from pulmonary embolism patients indicate that arterial spin labeling is sensitive for the detection of areas of perfusion deficit. J. Magn. Reson. Imaging 2001;13:954-959.

Ultrafast MR grid-tagging sequence for assessment of local mechanical properties of the lungs.

While MR imaging with tagged magnetization has shown great utility in the study of muscle mechanics, the evaluation of pulmonary mechanics has long been hindered by the technical difficulties in MR imaging of lung parenchyma. In this study, a fast MR grid-tagging technique is described for dynamic assessment of regional pulmonary deformation. The method is based on a fast FLASH sequence with short TR and short TE. Tagging was achieved by using double DANTE pulse train or inversion pulses. Our results show that this technique is able to detect changes of the tagging grid caused by physiological deformation of the lung. Quantitative analysis of the data shows that this method is capable of assessing local pulmonary mechanics. The application of this technique could improve our understanding of ventilatory control, and thus provide a unique metric for assessing pulmonary disorders. Magn Reson Med 45:24-28, 2001.

Imaging pulmonary blood flow and perfusion using phase-sensitive selective inversion recovery.

A technique is described for imaging pulmonary blood flow using a phase-sensitive selective inversion recovery (PS-SIR) sequence. PS-SIR image reconstruction provides excellent contrast, differentiating fully relaxed inflowing blood from inverted blood and lung tissue. The magnetization of the inverted tissues remains negative at any inversion delay less than that at which the magnetization of the lung tissue is nulled, whereas that of the fully relaxed inflowing blood is always positive. Pulmonary blood flow can be observed by tracking the propagation of the pixels with positive values. Five healthy volunteers were imaged. The normal pattern of blood flow advancing from the central arteries toward the peripheries and into the lung parenchyma with return toward the center via draining veins was depicted. The method offers promise for evaluating pulmonary blood flow without the need for image subtraction or contrast administration. Magn Reson Med 43:793-795, 2000.

Multiple inversion recovery MR subtraction imaging of human ventilation from inhalation of room air and pure oxygen.

The feasibility of MR subtraction imaging of lung ventilation using air against oxygen using a multiple inversion recovery half-Fourier single-shot turbo spin echo (MIR-HASTE) sequence was investigated. Eight healthy, nonsmoking volunteers (3 males, 5 females; from 27 to 48 years of age) were studied on a 1.5 T MR unit. The ventilation image was obtained from the subtraction of the images acquired with the subject inhaling room air and 100% oxygen. By suppressing the signal from subcutaneous fat and thoracic muscle, MIR-HASTE improved the subtraction of signal arising from background tissues. Lung parenchyma, pulmonary veins, descending aorta, spleen, and kidney showed high signal difference, but pulmonary arteries exhibited minimal signal difference. Because of minimal signal change in the pulmonary arteries after inhalation of 100% oxygen, the average signal decreases in the left and right lungs including hilus and periphery amounted to only 19.4+/-4.5 and 20.2+/-3.4%, respectively, compared with regional averages of 23.6+/-5.4 and 24.1+/-3.1% for both lung peripheries alone. Magn Reson Med 43:913-916, 2000.

Magnetic resonance imaging of the thorax. Past, present, and future.

Magnetic resonance imaging is a valuable modality of extreme flexibility for specific problem-solving capability in the thorax. This article reviews MR applications in the imaging of great vessels, which are currently the most important applications in the thorax; other established applications in the thorax; and pulmonary functional MR imaging.

1H magnetic resonance imaging of human lung using inversion recovery turbo spin echo.

Evaluation of lung pathologies using magnetic resonance imaging remains limited, primarily due to the lung's low proton density and high density of magnetic field susceptibility gradients. It is hypothesized that visualization of the lung is possible if signal intensity from muscle and/or fat is suppressed or reduced. Using the inversion recovery and frequency selective saturation pulse with a half-Fourier single-shot turbo spin-echo (HASTE) or a segmented, centric reordered turbo spin-echo (TSE) readout, signal intensity and contrast of tissues can be manipulated to enhance the visibility of the lung. Multislice images of the lung from 10 healthy volunteers were acquired with negligible motion artifacts. Peripheral pulmonary vessels appear well delineated. T(1) maps of the lung are also presented; the overall average was 1335 +/- 85 msec and 1245 +/- 93 msec with the volunteers performing breath-holding on end-expiration and end-inspiration, respectively. This difference is statistically significant, at P < 0.01.

Effect of respiratory phases on MR lung signal intensity and lung conspicuity using segmented multiple inversion recovery turbo spin echo (MIR-TSE).

The purpose of this study was to determine the effect of respiratory phase on signal intensity of the lung. Lung images were obtained from eleven healthy human volunteers using a multiple inversion recovery segmented turbo spin echo sequence (MIR-TSE). MIR exploits the difference in T(1) between different tissues to effectively null signal contributions from fat and muscle for improved visualization of the lung. The volunteers were asked to perform breath-holding on end inspiration or end expiration. There was a significant decrease in signal intensity of the lung with average SNR of 7.3 +/- 0.9 vs. 14.4 +/- 0.8 for coronal slices, and 9.5 +/-1.5 vs. 16.0 +/-2.4 for sagittal breath-hold images acquired during end inspiration compared with end expiration. It is concluded that MRI of the lungs should be performed during end expiration in order to optimize image quality.

Detection of regional pulmonary perfusion deficit of the occluded lung using arterial spin labeling in magnetic resonance imaging.

Detection of regional perfusion deficit in the lung has been demonstrated using an arterial spin labeling technique called flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER). A pulmonary artery was occluded using a nondetachable balloon catheter to simulate an acute pulmonary embolism in 3 of 10 rabbits. Inflating the balloon occludes the artery, and deflating the balloon allows for reperfusion. Perfusion imaging was performed pre-occlusion, during occlusion, and after reperfusion. Signal enhancement due to perfusion of the pulmonary parenchyma was observed in the perfusion images with negligible artifacts. The perfusion deficit of the pulmonary parenchyma was detected distal to the site of occlusion in all three rabbits. Return of the pulmonary parenchymal perfusion was observed after reperfusion. Magnetic resonance imaging using FAIRER can detect signal loss due to absence of perfusion caused by pulmonary embolism.

Magnetic resonance imaging of the thorax. Past, present, and future.

Magnetic resonance is a valuable modality of extreme flexibility for specific problem-solving capability in the thorax. This article reviews MR applications in the imaging of great vessels, which are currently the most important applications in the thorax; other established applications in the thorax; and pulmonary functional MR imaging.

Perfusion of the kidney using extraslice spin tagging (EST) magnetic resonance imaging.

This study was undertaken to determine whether extraslice spin tagging (EST) perfusion-weighted magnetic resonance imaging is suitable for screening persons for renal perfusion deficits. Six normal and seven patient volunteers with suspected decreased renal perfusion due to renal vascular disease were imaged. X-ray angiograms were also obtained on all patients. The normalized EST signal intensity showed a linear correlation with respect to the percent stenosis measured from the X-ray angiograms. This demonstrates the potential utility of using EST for the evaluation of kidney perfusion, which was done without the need for exogenous MR contrast agents. EST is fast and less expensive than contrast-based methods. These features make EST a candidate for routine screening of patients for renal vascular disease and for the assessment of angiographically equivocal renal artery stenoses. J. Magn. Reson. Imaging 1999;10:886-891.

Improved visualization of the human lung in 1H MRI using multiple inversion recovery for simultaneous suppression of signal contributions from fat and muscle.

1H magnetic resonance imaging of the lung is hampered by the low contrast between lung parenchyma, and muscle and fat in the thorax. We show that it is possible to improve contrast greatly and thereby enhance the visibility of the lung, by suppression of signal of surrounding muscle and fat based on differences in T1 relaxation times using a double inversion recovery preparation pulses (TI1 800 msec, and TI2 150 msec) and a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence. The measured T1 values for the right and left lungs at 1.5 T were 1.37 +/- 0.18 and 1.41 +/- 0.21 sec, respectively.

Perfusion imaging of the human lung using flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER).

Pulmonary perfusion is an important parameter in the evaluation of lung diseases such as pulmonary embolism. A noninvasive MR perfusion imaging technique of the lung is presented in which magnetically labeled blood water is used as an endogenous, freely diffusible tracer. The perfusion imaging technique is an arterial spin tagging method called Flow sensitive Alternating Inversion Recovery with an Extra Radiofrequency pulse (FAIRER). Seven healthy human volunteers were studied. High-resolution perfusion-weighted images with negligible artifacts were acquired within a single breathhold. Different patterns of signal enhancement were observed between the pulmonary vessels and parenchyma, which persists up to TI = 1400 ms. The T1s of blood and lung parenchyma were determined to be 1.46s and 1.35 s, respectively.

MR perfusion imaging of pulmonary parenchyma using pulsed arterial spin labeling techniques: FAIRER and FAIR.

Magnetic resonance imaging of pulmonary parenchyma perfusion using pulsed arterial spin labeling (ASL) techniques is presented. ASL uses magnetically labeled water as an endogenous, freely diffusible tracer. Presented are comparative results of ASL methods called Flow sensitive Alternating Inversion Recovery (FAIR), and FAIR with an Extra Radiofrequency pulse (FAIRER). Six healthy human volunteers were imaged. Perfusion-weighted images at different time delays, TI, were calculated from the subtraction of the control and tag images, which were acquired within a single breathhold. Detailed pulmonary structures can be visualized with negligible cardiac or respiratory motion artifacts. Different patterns of signal enhancement between the pulmonary vessels and parenchyma are shown in the perfusion images acquired at different TIs.

Extraslice spin tagging (EST) magnetic resonance imaging for the determination of perfusion.

A new magnetic resonance technique to measure perfusion is described in detail. The means by which this is done is to invert all the spins in the radiofrequency RF coil with a non-spatially selective pulse and immediately re-invert the spins in the imaging plane. The net effect is that the spins in the imaging plane experience minimal perturbation of their magnetization while the spins outside the plane (extraslice) are inverted, or tagged. Tagged spins that flow into the imaging plane before image data are acquired decrease the signal intensity in the imaging plane when compared with an image in which the inflowing spins are not tagged. This decrease in signal can be used to calculate the number of spins that have flowed into the imaging plane, i.e., can be used to calculate the perfusion in mL x 100 g(tissue)(- 1)x min(-1). The extraslice spin tagging (EST) magnetization preparation period was coupled with a fast imaging sequence to obtain perfusion maps for normal volunteers.