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The order of a Fresnel lighthouse lens reflects its size. First order lenses are the largest. Our lens is a third order lens.

Research tells us that our lens is one of only three lenses in the United States made by the English firm of Chance Brothers. It is in very good condition and needs little mechanical work. Restoring the Fresnel lens and putting it back into operation preserves a significant piece of our maritime heritage for future generations. It is the heart of the Point Cabrillo Light Station.

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At the Point Cabrillo Light Station State Historic Park, lightkeeping has made a comeback. Since the return of the Fresnel lens to service in 1999, the volunteer lightkeepers from Coast Guard Auxiliary Flotilla 87 have been trained to perform maintenance on both the lens and lantern room.

This evaluates the noise within the image and the uniformity of the CT number. The presence of noise in an image limits the low contrast resolution and can make differentiation between structures of similar values difficult. ROI are placed in the centre of the image at 12 o’clock and 3 o’clock positions, as shown in Fig. 1.29c and the CT number and standard deviation recorded. The noise and uniformity should be equal throughout the image.

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Reviving the Fresnel as a modern, automated light was no easy matter. It had to be made as reliable as the DCB (Directional Code Beacon, commonly in airports), which had replaced the Fresnel in 1972. Advanced technical support is provided as needed by the US Coast Guard Aids to Navigation Team. The Point Cabrillo Light House combines 19th century technology with the sophisticated electronics of today, and was nurtured to fruition by the lightkeepers’ finest attributes: a passion for detail, creative problem solving, and copious elbow grease.

Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020

Filippo Cademartiri, Giancarlo Casolo, Alberto Clemente, Sara Seitun, Cesare Mantini, Eduardo Bossone, Luca Saba, Nicola Sverzellati, Stefano Nistri, Bruna Punzo, Carlo Cavaliere, Ludovico La Grutta, Giovanni Gentile, Erica Maffei

In cellular imaging, US is limited due to its inherent low contrast resolution. To address this issue, many types of contrast agents have been developed [98]. Clinically, the only class of US contrast agents consists of gas-filled microbubbles [97]. Contrast-enhanced US (CEUS) imaging relies on the ultrasonic detection of microbubble contrast agents during their microvascular transit. Molecular imaging using CEUS has recently become possible with the development of novel ‘site-targeted’ microbubbles [99]. Unlike CEUS methods to assess tissue perfusion which use free-flowing non-targeted microbubbles, this method uses custom-designed microbubble contrast agents that are retained in regions of disease under their shell composition or by the conjugation of specific targeting ligands to their outer surface [99,100]. The development and use of these contrast agents allow now the site-targeted imaging of specific disease-related molecular events that occur at a cellular level [101]. Microbubbles can be controlled to deliver and image the cells in the targeted area, but due to their large size they are limited to the cell surface, preventing intracellular labeling; thus, they can quickly become dissociated from the cells and result in aberrant signaling [98]. Microbubbles are also unstable and fail to generate contrast beyond 30 min, which is not sufficient for a typical cell-tracking study [96]. To overcome these issues, contrast agent nanoparticles have been developed made of phosphate-based glass [102], silica [96], mesoporous silica [103] and gold [104] with encouraging results for future clinical US cell tracking.

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Changjie Shao, Juntao Zhang, Jing Guo, Liang Zhang, Yuhan Zhang, Leiyuan Ma, Chuanxin Gong, Yaqi Tian, Jingjing Chen, Ning Yu

The invention of the Fresnel lens was an enormous technological breakthrough in 1820 that affects us today – for example, in theater lights and car head lamps. These lenses revolutionized lighthouses and saved countless lives. The lighthouse lenses are not in widespread use now and are rapidly disappearing through vandalism and neglect. Not much is known about working on them, which makes the educational aspect of the lens restoration very valuable. We want to record and disseminate this information as thoroughly as possible, to make it possible for others to care for and, hopefully, restore other lenses.

Since there is such variability in patient body habitus, 2D settings will require adjustments throughout the duration of the scan as it pertains to the gain, TGC, depth, and focal zone. Proper utilization of the gain and TGC provide increased image quality so that disease is not overlooked. Increasing the 2D gain enhances the brightness of the entire field of view without amplifying the transmitted sound energy. Contrast resolution may also improve by either increasing or decreasing the gain, providing adequate visualization. It is important to recognize that if the gain is set too high, the signals become obliterated and lose image detail. The optimal gain setting must employ a mixed range of signals that are low to high in their echo amplitude. When the gain is set too low and the image is consistently dark, disease can very easily be completely missed (Figure 4.18).

The phrase lighthouse keeper conjures a romantic image of stalwart men and women braving storms and a solitary life in remote outposts. There are still many lighthouses in operation today, but the transistorized NAVAID panel, automated lamp changers, and other electronic innovations, have made the profession of lightkeeper virtually obsolete. In 1972, our own Fresnel lens was disengaged, and an aero-marine type rotating beacon was mounted on the roof.

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To understand the added value of MRI to clinical sciences, it is useful to compare it with CT. CT can produce images of high spatial resolution, which are interpreted on the basis of anatomy. A distinct feature of MRI is that anatomically correct images are produced, but these images are based on molecular events that produce much higher soft tissue contrast between tissues and between abnormal and normal tissues. It has been shown for most clinically important applications, including the brain and the solid organs of the body, that soft tissue contrast resolution is more important than spatial resolution. Even on contrast-enhanced CT, the ability to generate soft tissue contrast resolution is less than that of MRI, and this difference may contribute to the relative advantage that MRI provides for lesion detection (Fig. 3).

A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha

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Radiomics extracts a large number of quantitative features from medical images in a high-throughput way, which makes it possible to analyze the heterogeneity in tumors non-invasively. Many studies have shown that radiomics features have potential applicable values in the differential diagnosis of pancreatic cancer [10,11], pathological grade [12], and prognosis prediction [13,14]. Guo et al. [11] mentioned that CT imaging features and texture parameters help distinguish pancreatic neuroendocrine carcinoma from pancreatic ductal adenocarcinoma. Attiyeh et al. [15] illustrated that CT texture feature quantitative analysis shows that heterogeneous low density tumor is a prognostic factor for low survival rate of patients with pancreatic ductal adenocarcinoma. CT images have been used in texture analysis by many researchers, it is found that it can be used as a biomarker of pathology and prognosis of patients with invasive tumor. MRI has the advantages of multi-directional imaging, multi-parameter imaging, and excellent contrast resolution. Furthermore, more valuable radiomics features may be found. According to related reports [13,16], radiomics features based on MRI images can predict the survival and prognosis of patients with pancreatic cancer. These results are encouraging. However, currently, the radiomics studies related to the prognosis of PDAC are limited.

The generic definition of contrast resolution can be simplified as the capability of distinguishing two neighboring structures with (slightly) different atomic characteristics. When the native contrast between two different structures is high, this is less important but when the native contrast is low, it can become a significant limitation [4]. In CCT this is a little bit less relevant when we perform coronary lumen assessment, but it becomes extremely relevant for the assessment of coronary artery wall atherosclerosis. For instance, you could have a very high spatial resolution which is significantly impaired by a low contrast resolution; in this scenario you would have the capability to distinguish well the edge between structures with significantly different density, but you would miss the capability to have a proper texture analysis within the same tissue with homogeneous characteristics. As a comparison, Magnetic Resonance has much higher native (i.e. prior to the administration of intravenous contrast material) contrast resolution capabilities (vs. CCT) but with significantly lower spatial resolution, hence it is very good for the assessment of myocardium and not as much for the assessment coronary arteries, and even less for the assessment of coronary artery walls.

The restored Fresnel has operated reliably since 1999. It’s only a little finicky, requiring, as it did in the past, some human care and attention to keep it happy. Every week, the protective storm window panes of the lantern room are checked and cleaned, surfaces dusted, and brass polished. Quarterly, the lens is shut down for a complete mechanical check and a thorough cleaning.