1 MRI: Fruit Quality Measurements
Michael J. McCarthy, Young Jin Choi and Siwalak Pathaveerat
Department of Food Science and Technology
University of California, Davis, California USA

INTRODUCTION
The quality of fruit depends upon both the external and internal fruit properties. The properties of fruit may vary as a function of weather, harvest conditions, natural biological diversity and handling conditions. Fruit purchasers such as retailers and consumers desire a uniform known external and internal quality for each fruit. Current state-of-the-art sorting and sensing technology is primarily focused on external surface quality features like color. External quality features are assessed for each and every fruit using automated color sorting equipment. In contrast, internal quality features are generally assessed off-line by taking a sampling of fruit for destructive testing. As the fruit market becomes more competitive and international there is a greater need to determine internal quality of fruit to successfully meet market demands and limit losses. A shipment of citrus fruit that contains a single fruit infected with a green mold can result in damage to the entire shipment. This type of damage results in rejection of the lot and a significant economic loss on the shipment. Additionally, the fruit producer who sent the mold contaminated shipment potentially looses the customer to a competing fruit producer. This type of scenario has increased the interest in new internal quality sensors that are nondestructive and can operate at fruit sorting line speeds of 8-12 fruit per second. Nuclear magnetic resonance imaging (MRI) has been shown to be an effective method to measure internal fruit quality (1, 2) and can theoretically operate at the required speed.
MRI has been demonstrated to be sensitive to a large number of internal defects and quality factors in fruit including insect damage, bruising, dry regions, browning and maturity (1, 3). These quality features and defects are quantified in MRI using differences in spin-spin relaxation time, diamagnetic susceptibility, diffusion coefficient, and signal intensity (4-9). A recent review by Hills and Clark summarizes defects and quality parameters that have been measured using nuclear magnetic resonance spectroscopy (1). While MRI has proven successful at detecting quality attributes and defects additional knowledge is needed to actually implement an in-line MRI based sensor. These steps include the design of suitable hardware, development of sensitivity scales between MRI parameters and fruit quality attributes, and testing season-to-season as well as growing location impact on the developed sensitivity scales. The development of data on seasonal and growing location impact on MRI parameters, the automated detection of a defect and the internal spatial variation of fruit properties will be presented as examples of the next stage in development of MRI for sorting fruit. These examples will be demonstrated through detection of freeze damage in Navel oranges, detection of mold damage in citrus peel and the variation of composition within an avocado fruit, respectively.

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Last paragraph of conclusion of this chapter………..

The distribution of oil and water and hence the spatially localized maturity of an avocado varies significantly. Achieving an accurate determination of the average maturity in the fruit by any measurement technique depends upon the volume of the sampled flesh. Ideally the entire flesh would be measured. However for on-line sensors and off-line tests the actual volume sampled is usually much smaller than the entire fruit. Consider the case of measuring percent dry matter of an avocado using the standard microwave drying technique, where only a small section of the fruit is used for determination of the percent dry weight. This method uses a thin longitudinal slice a few mm thick. The result of this procedure could easily be influenced if the thickness of the slice were not uniform (e.g. calyx end thicker than stem end). Likewise the NMR technique determined value can be influenced by what volume is sampled. Table 8 shows the variation in measured maturity level as a function of sampled volume size in the chemical shift image. Each pixel in the image represents volume of [(7.0/32) (7.0/32) 0.2] cm3. As the volume of the measurement is increased the value of the measured maturity increases towards the average value for maturity of the avocado. The table demonstrates that a volume with ~ 2 cm diameter is insufficient to accurately predict the intensity of the entire slice. The data in Table 8 also explains the results obtained by varying the diameter of surface coil (results not shown).

References:

1. Hills BP, Clark CK. Quality assessment of horticultural products by NMR. Annual Reports on NMR Spectroscopy 2003:50:76-120.

2. McCarthy MJ. 1994. Magnetic Resonance Imaging in Foods. Chapman &Hall. New York, NY.

3. Chen P, McCarthy MJ, Kauten R. NMR for internal quality evaluation of fruits and vegetables. Trans. ASAE 1989:32:1747-1753.

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(IMAGES: Out of 9 figures - figure 5 is given below)

Figure 5. MRI orange images: (a) and (c) for good quality fruit, and (b) and (d) for mold damaged fruit.

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4 Functional NMR : PLANTS
Markus Rokitta
School of Integrative Biology, The University of Queensland,
St. Lucia, QLD 4072, Australia
and
Universität Würzburg, Experimentelle Physik V
Am Hubland, 97074 Würzburg, Germany

INTRODUCTION
Of all resources a plant needs, water is the most abundant and at the same time the most limiting one for agricultural productivity [1]. Therefore, an understanding of the mechanisms of water uptake and water loss are of particular interest.
First theories about long distance water transport mechanisms in plants arose with the cohesion theory more than a century ago [2]. One might expect that all aspects of this problem have been understood since. However, there is still a very controversial discussion going on in the very latest literature: see [3] and reply in the same issue as well as [4,[5,[6].
NMR imaging is particularly suitable for measurement of functional parameters such as flow due to its non-invasive nature although the obtainable resolution does not reach the resolution of optical microscopy. In this context functional means that physiological parameters can be investigated dynamically over time. During an experiment one can alter certain conditions and observe the plant's response to these changes.

ADVANTAGES OF MRI FOR PLANT EXPERIMENTS

The advantages of NMR as compared to other imaging methods include non-invasive monitoring of anatomy, solute distribution and time dependent changes of active and passive transport of substances (water, ions, primary and secondary metabolites) in plants. No special preparation of the sample is necessary so that plants can be examined under controlled external conditions like humidity, temperature, illumination, nutrition and so on without perturbance by the measurement itself. All parts of the plant are accessible at any stage of their development.
Advantages of NMR should be obvious when applied to transgenic plants. The effects of a genetic modification on plant anatomy, solute transport, metabolism and ways to compensate for genetic defects can be studied at the quite different level, inaccessible for other techniques. However, while the spatial resolution of NMR at the current state of the art is approximately ten times less compared to optical microscopy, NMR should be seen as complimentary to other techniques. Meaningful applications of plant NMR must therefore take advantage of the integrated observation of intact plants. There are a number of fundamental questions in plant biology that need to be addressed with the non-destructive, in vivo, contact-less NMR technique:
How are solutes (water, sugar, lipids, amino acids, ions) distributed in plants and how is solute distribution related to structural and functional characteristics of tissues during development and under stress conditions at the whole plant or whole organ level?
How does structural and metabolic crosstalk of different organs/tissues occur within an interactive system, for example within the seed (seed coat - endosperm - embryo)?
What forces and mechanisms play a role in water and solute transport in plants?
What effects have genetic modifications on the intact plant? What compensation mechanisms exist for genetically modified plants?

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(IMAGES: Out of 7 figures - figure 5 is given below)

Figure5
Figure 5: Cross-sections of the shoot of a 35 days old intact and transpiring castor bean plant made by NMR micro-imaging (a, b, d) and light microscopy (c). (a) FLASH image with a spatial resolution of 47 m; (b) flow velocity map superimposed on the previous image; (c) light microscopy; the size of one pixel in NMR flow imaging (b) is indicated in the upper right corner of the picture. (d) spin echo image with a spatial resolution of 12 m. Reproduced from Rokitta et al., Protoplasma, 209:126-131, 1999 [33]

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19. MR of Lung
David C. Ailion and Gernot Laicher
Department of Physics, University of Utah, 115 South 1400 East, Salt Lake City, Utah 84112

Even though lung is one of the most important organs in the human body, in the past it has received relatively little magnetic resonance study. However, with the advent of hyperpolarized gas NMR imaging, this situation is changing. Proton imaging has been particularly difficult, primarily for two reasons: (1) the presence of air-tissue interfaces in the outer (alveolar) portion of the lung results in severe internal inhomogeneous broadening of the NMR line which can cause blurring of the image and (2) the lung is a relatively low density object which is near much higher density objects (the beating heart and chest wall) that are moving asynchronously, thereby causing severe motional artifacts. In this Chapter, techniques are presented for overcoming both these difficulties in proton imaging. In particular, asymmetric imaging (as a way to utilize the inhomogeneous broadening to gain information about lung microgeometry) and techniques like the rapid line scan and radial and spiral k-space acquisitions (for reducing or eliminating motion artifacts) are described. In addition, MRI of hyperpolarized (hp) gases (3He and 129Xe), which provides an alternate approach that is much less sensitive to inhomogeneous broadening, is explained. Applications of NMR to the study of restricted diffusion of water molecules are presented in which the diffusion of water within different microscopic compartments can be distinguished. Finally, applications of these magnetic resonance techniques to the study of lung diseases like pulmonary edema and emphysema are discussed.

I. INTRODUCTION

Magnetic resonance imaging (MRI) has made enormous contributions to medical diagnostics in recent years and has become one of the major weapons in the physician's arsenal for detecting and diagnosing diseased regions of the human body. Even though lung is one of the most essential organs in most animals, with lung disease being responsible for hundreds of thousands of human deaths each year, there have been relatively few applications of MRI to lung, primarily because of technical difficulties that are peculiar to the lung. These difficulties arise primarily from three sources: (1) inflated lung has a much lower water density (approximately 20% that of free water) than do other biological tissues and will thus be characterized by a correspondingly smaller proton NMR signal; (2) the NMR line shape in the outer, mainly parenchymal region (i.e., containing the alveoli) is inhomogeneously broadened; and (3) the NMR image of the lung (a relatively low-density object) may be affected by the asynchronous motions of nearby high-density objects (the heart and the chest walls). The inhomogeneous internal line broadening can cause a blurring of the NMR image unless special imaging techniques are employed. In Section II, we discuss the physical origins of this phenomenon and also describe techniques that will utilize this feature to allow the imaging of the inflated regions of the lung. The asynchronous motions of the heart (due to beating) and the chest wall and lung (due to breathing) give rise to severe non-local motional artifacts (ghosts) in many MRI applications (typically those employing the 2D imaging or spin-warp technique). Several techniques for minimizing these errors will be discussed in Section III. Section IV describes relaxation time (T1, T2, and T1?) measurements and techniques as well as possible mechanisms responsible for these relaxation times. Section V describes pulse gradient techniques for studying diffusion with NMR and summarizes the results of measurements of diffusion of water molecules in lung. These include data acquired using pulsed magnetic field gradients of moderate strength (~20 gauss/cm) as well as data obtained using ultrahigh static field gradients (~ 1 Tesla/cm); the results reflect the motion of water molecules within compartments of different dimensions.

NMR measurements in lung have usually involved proton resonance and have been limited primarily to NMR in the lung tissue. Conventional NMR of the airways and gas-exchanging regions (bronchi, alveoli, ducts) has been very difficult because of the very low molecular density in the vapor phase. However, in the last 5-10 years a very promising approach has been developed for enhancing the NMR signal for certain nuclei (3He and 129Xe) and has resulted in improvements in the NMR sensitivity of 4-5 orders of magnitude for these nuclei. The hyperpolarization (hp) technique, which is described in more detail in Section VI, involves the transfer of polarization from laser-polarized electrons of an alkali metal (Rb) to a noble gas nucleus (3He and 129Xe).

Section VII is a brief summary of some of the medical applications of the NMR techniques described earlier in this Chapter.

A comprehensive presentation of conventional (i.e., not using hyperpolarized nuclei) NMR and MRI studies of lung, including medical applications with emphasis on pulmonary edema, is given in the book, Application of Magnetic Resonance to the Study of Lung, edited by A.G. Cutillo [ ]. A brief summary of lung NMR can be found in an article, "Lung & Mediastinum: A Discussion of the Relevant NMR Physics", in the Encyclopedia of Nuclear Magnetic Resonance [ ].

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There are 100 references.

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Some images from the book

Figure 7 from Ch.2 Wine Grapes - Sugar content is shown as different intensities of shading.

Figure 3 from Chp 6 - Evolution of MRI : Flora To Fauna
Surface rendered images of strawberry fruit infected by Botrytis cinerea. Image (a) after one day; Image (b) after 2 days.

Fig. 2 from Chp-16MR Spectroscopy in oncology
(A) T1-weighted sagittal contrast enhanced MR image of a patient suffering from brain stem glioma showing the voxel location from which the proton MR spectrum is obtained.
(B) Water suppressed proton MR spectrum from an 20 x 20 x 20 mm3 voxel recorded using PRESS sequence that an echo time of 270 ms with a repetition time of 2 s.