Taking conflicts over new solar energy projects on the agricultural landscape in the global North as its backdrop, the chapter demonstrates how work and labour (including that performed in the North by workers from the global South) are erased both by the opponents and the proponents of such projects. The erasure is consistent with prevailing ways of knowing the human-environment nexus, shaped by an underlying political economy derivative of how international law has constructed and maintained the foundational liberal mythology that separates labour from land. Grounded in our commitment to pursuing a ‘just transition’ to decarbonisation – that is to say, a transition that attends to the distributional effects and disproportionate impacts of decarbonisation on workers and communities – we strive to reconceptualise work and labour as embodied practices of working and living on the land. Everyday socio-spatial practices structured by law implicate ordinary people in the making of landscapes and continuing relations of settler capitalism, shaping how ‘we’ live together on the land, including who belongs and who gets to decide.

There is growing involvement of Indigenous communities in renewable energy development across their traditional territories in what is now called Canada.1 Here, we explore Indigenous participation in large-scale “green” energy generation as a response to encroachment, displacement, and dispossession wrought by the extractivist orientation of contemporary settler capitalism.

Introduction

Of all the standard clinical imaging techniques ultrasound is by far the least expensive and most portable (including handheld units smaller than a laptop computer), and can acquire continuous images at a real-time frame rate with few or no safety concerns. In addition to morphological and structural information, ultrasound can also measure blood flow in real-time, and produce detailed maps of blood velocity within a given vessel. Ultrasound finds very wide use in obstetrics and gynaecology, due to the lack of ionizing radiation or strong magnetic fields. The real-time nature of the imaging is also important in measuring parameters such as foetal heart function. Ultrasound is used in many cardiovascular applications, being able to detect mitral valve and septal insufficiencies. General imaging applications include liver cysts, aortic aneurysms, and obstructive atherosclerosis in the carotids. Ultrasound imaging is also used very often to guide the path and positioning of a needle in tissue biopsies.

Ultrasound is a mechanical wave, with a frequency for clinical use between 1 and 15 MHz. The speed of sound in tissue is ∼1540 m/s, and so the range of wavelengths of ultrasound in tissue is between ∼0.1 and 1.5 mm. The ultrasound waves are produced by a transducer, as shown in Figure 4.1, which typically has an array of up to 512 individual active sources. In the simplest image acquisition scheme, small subgroups of these elements are fired sequentially to produce parallel ultrasound beams.

Introduction

Of the four major clinical imaging modalities, magnetic resonance imaging (MRI) is the one developed most recently. The first images were acquired in 1973 by Paul Lauterbur, who shared the Nobel Prize for Medicine in 2003 with Peter Mansfield for their shared contribution to the invention and development of MRI. Over 10 million MRI scans are prescribed ever year, and there are more than 4000 scanners currently operational in 2010.

MRI provides a spatial map of the hydrogen nuclei (water and lipid) in different tissues. The image intensity depends upon the number of protons in any spatial location, as well as physical properties of the tissue such as viscosity, stiffness and protein content. In comparison to other imaging modalities, the main advantages of MRI are: (i) no ionizing radiation is required, (ii) the images can be acquired in any two- or three-dimensional plane, (iii) there is excellent soft-tissue contrast, (iv) a spatial resolution of the order of 1 mm or less can be readily achieved, and (v) images are produced with negligible penetration effects. Pathologies in all parts of the body can be diagnosed, with neurological, cardiological, hepatic, nephrological and musculoskeletal applications all being widely used in the clinic. In addition to anatomical information, MR images can be made sensitive to blood flow (angiography) and blood perfusion, water diffusion, and localized functional brain activation.

Introduction

In nuclear medicine scans a very small amount, typically nanogrammes, of radioactive material called a radiotracer is injected intravenously into the patient. The agent then accumulates in specific organs in the body. How much, how rapidly and where this uptake occurs are factors which can determine whether tissue is healthy or diseased and the presence of, for example, tumours. There are three different modalities under the general umbrella of nuclear medicine. The most basic, planar scintigraphy, images the distribution of radioactive material in a single two- dimensional image, analogous to a planar X-ray scan. These types of scan are mostly used for whole-body screening for tumours, particularly bone and metastatic tumours. The most common radiotracers are chemical complexes of technetium (99mTc), an element which emits mono-energetic γ-rays at 140 keV. Various chemical complexes of 99mTc have been designed in order to target different organs in the body. The second type of scan, single photon emission computed tomography (SPECT), produces a series of contiguous two-dimensional images of the distribution of the radiotracer using the same agents as planar scintigraphy. There is, therefore, a direct analogy between planar X-ray/CT and planar scintigraphy/SPECT. A SPECT scan is most commonly used for myocardial perfusion, the so-called ‘nuclear cardiac stress test’. The final method is positron emission tomography (PET). This involves injection of a different type of radiotracer, one which emits positrons (positively charged electrons).

Introduction

X-ray planar radiography is one of the mainstays of a radiology department, providing a first ‘screening’ for both acute injuries and suspected chronic diseases. Planar radiography is widely used to assess the degree of bone fracture in an acute injury, the presence of masses in lung cancer/emphysema and other airway pathologies, the presence of kidney stones, and diseases of the gastrointestinal (GI) tract. Depending upon the results of an X-ray scan, the patient may be referred for a full three-dimensional X-ray computed tomography (CT) scan for more detailed diagnosis.

The basis of both planar radiography and CT is the differential absorption of X-rays by various tissues. For example, bone and small calcifications absorb X-rays much more effectively than soft tissue. X-rays generated from a source are directed towards the patient, as shown in Figure 2.1(a). X-rays which pass through the patient are detected using a solid-state flat panel detector which is placed just below the patient. The detected X-ray energy is first converted into light, then into a voltage and finally is digitized. The digital image represents a two-dimensional projection of the tissues lying between the X-ray source and the detector. In addition to being absorbed, X-rays can also be scattered as they pass through the body, and this gives rise to a background signal which reduces the image contrast. Therefore, an ‘anti-scatter grid’, shown in Figure 2.1(b), is used to ensure that only X-rays that pass directly through the body from source-to-detector are recorded.

Introduction

A clinician making a diagnosis based on medical images looks for a number of different types of indication. These could be changes in shape, for example enlargement or shrinkage of a particular structure, changes in image intensity within that structure compared to normal tissue and/or the appearance of features such as lesions which are normally not seen. A full diagnosis may be based upon information from several different imaging modalities, which can be correlative or additive in terms of their information content.

Every year there are significant engineering advances which lead to improvements in the instrumentation in each of the medical imaging modalities covered in this book. One must be able to assess in a quantitative manner the improvements that are made by such designs. These quantitative measures should also be directly related to the parameters which are important to a clinician for diagnosis. The three most important of these criteria are the spatial resolution, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). For example, Figure 1.1(a) shows a magnetic resonance image with two very small white-matter lesions indicated by the arrows. The spatial resolution in this image is high enough to be able to detect and resolve the two lesions. If the spatial resolution were to have been four times worse, as shown in Figure 1.1(b), then only the larger of the two lesions is now visible. If the image SNR were four times lower, illustrated in Figure 1.1(c), then only the brighter of the two lesions is, barely, visible.