Nanosecond pulses in a THz gyrotron oscillator operating in a mode-locked self-consistent Q-switch regime.

An experimental study of a nanosecond pulsed regime in a THz gyrotron oscillator operating in a self-consistent Q-switch regime has been carried out. The gyrotron is operated in the TE(7,2) transverse mode radiating at a frequency of 260.5 GHz. The 5 W nanosecond pulses are obtained in a self-consistent Q-switch regime in which the cavity diffraction quality factor dynamically varies by nearly 2 orders of magnitude on a subnanosecond time scale via the nonlinear interaction of different mode-locked frequency-equidistant sidebands. The experimental results are in good agreement with numerical simulations performed with the TWANG code based on a slow time scale formulation of the self-consistent time-dependent nonlinear wave particle interaction equations.

Steady-state fully noninductive current driven by electron cyclotron waves in a magnetically confined plasma

A steady-state, fully noninductive plasma current has been sustained for the first time in a tokamak using electron cyclotron current drive only. In this discharge, 123 kA of current have been sustained for the entire gyrotron pulse duration of 2 s. Careful distribution across the plasma minor radius of the power deposited from three 0. 5-MW gyrotrons was essential for reaching steady-state conditions. With central current drive, up to 153 kA of current have been fully replaced transiently for 100 ms. The noninductive scenario is confirmed by the ability to recharge the Ohmic transformer. The dependence of the current drive efficiency on the minor radius is also demonstrated.

Storage phosphor digital mammography.

Digital mammography using storage phosphor CR is still in the investigational stage. It is the only digital mammography system that has been tested in preliminary clinical trials with promising early results. Further clinical studies are needed to assess the impact of the limited spatial resolution of storage phosphor technology on its application as a digital screening mammography system. Further studies also are needed to determine the optimum image processing parameters needed in digital mammography.

Chorionic villus sampling.

Chorionic villus sampling in the first trimester of pregnancy has the potential to become a major tool in the prenatal diagnosis and therapy of genetic disorders. Villus samples can be used for cytogenetic and biochemical studies as well as DNA analysis. However, little is known about the effects of chorionic villus sampling on a continuing pregnancy, or the long-term effects on the subsequently delivered infants. Despite these limitations, chorionic villus sampling appears to be a major breakthrough in prenatal diagnosis.

Positive identification by post-surgical defects from unilateral lambdoid synostectomy: a case report.

The comparison of pre- and postmortem radiographs as a method of identification of unknown human remains is well established in the forensic and radiologic literature. Identification can be based on a single bony feature when there is evidence of prior surgery, trauma or unusual anatomic variation. We present a case in which a positive identification was made using bony changes in the skull secondary to prior surgery for correction of unilateral lambdoid craniosynostosis. The unusual radiographic appearance of the bony defect initially raised the question of trauma and foul play.

Radiographic identification of unknown human remains and interpreter experience level.

The use of radiographs as a means of identification of unknown remains is a well-established method as performed by radiologists, forensic anthropologists, or pathologists. We devised a test to determine whether the degree of radiographic and medical knowledge of a film interpreter correlates with the degree of accuracy in making comparisons of radiographic unknowns. Three groups considered to be distinctly different in their level of medical knowledge and radiographic interpretive skills were chosen to evaluate forensic identification cases. Although all three groups identified a majority of cases correctly, none were completely accurate. The group with training in radiographic interpretation performed significantly better. Our study supports the need for trained interpreters in cases of forensic identification.

Measurement of the expansion of the calcaneal fat pad upon weightbearing.

The width of the calcaneal fat pad during weightbearing differs from its width during nonweightbearing. In this study, the medial-to-lateral width of the calcaneal fat pad was measured during weightbearing as well as nonweightbearing, and the two measurements were compared. The difference between weightbearing width and nonweightbearing width was found to vary widely across individuals. This measurement has implications for the manufacture of functional foot orthoses, which are made from nonweightbearing impressions of the foot. The significance of the authors' findings with regard to patient comfort is discussed.

The potential benefits of advanced therapeutic modalities in the treatment of diabetic foot wounds.

This article discusses the advantages and disadvantages of primary wound healing as compared with primary amputation in individuals with chronic diabetic foot wounds. The authors review the potential benefits of vascular surgical procedures and advanced dressings, including two of the most promising modalities in modern wound care: growth factors and bioengineered skin. In this era of cost-conscious health-care administration, it is incumbent on the practitioner to consider not only the basic science of wound care, but also the economic aspect of treatment rendered. These various interventions, dressings, growth factor delivery systems, and new modalities could significantly reduce healing time, thereby reducing the risk of infection, hospitalization, and amputation while improving quality of life. If so, they may be truly cost-effective.

Note: stacked rings for terahertz wave-guiding.

We demonstrate the construction of corrugated waveguides using stacked rings to propagate terahertz frequencies. The waveguide allows propagation of the same fundamental mode as an optical-fiber, namely, the HE(11) mode. This simple concept opens the way for corrugated wave-guides up to several terahertz, maintaining beam characteristics as for terahertz applications.

Preconception genetic counseling.

The purpose of this chapter has not been to be all-inclusive, but to raise awareness of the benefits of preconception consultation in the prevention of birth defects. If there is to be a significant decrease in the incidence of congenital malformations, it will come only by intervention that occurs prior to organogenesis, and that opportunity is lost by the first prenatal visit. For the practitioner interested in a more in-depth analysis of the subject of preconception counseling, the two books listed as supplementary reading provide a wealth of information essential to the care of the patient planning a pregnancy.

Prenatal diagnosis of cytomegalovirus (CMV) infection: a preliminary report.

Eight patients were referred for prenatal diagnosis for suspected fetal cytomegalovirus infection (CMV): six for documented first-trimester infection and two for abnormal ultrasound evaluation suggestive of fetal infection. Three methods of diagnosis were employed: (1) amniotic fluid viral cultures and CMV-specific IgM in fetal serum; (2) amniotic fluid cultures and detection by polymerase chain reaction amplification of CMV-specific DNA in chorionic villi; and (3) detection of CMV-specific DNA in villus samples only. Amniotic fluid cultures detected all cases of infection, but CMV-specific IgM was not a reliable indicator of infection in any case. DNA analysis correlated well with both culture results and clinical outcome.

Update in digital mammography.

Digital mammography is a rapidly developing technology that has great potential to improve upon and ultimately replace conventional film-screen mammography for the early detection of breast cancer. This article reviews current progress in digital mammographic systems, computer-aided diagnostic programs, and artificial neural networks. Digital mammographic systems are currently in an investigational phase only. Large-scale clinical trials are needed in all areas of digital mammography before this exciting new technology can be implemented outside of research centers.

Does exhaustive search for microcalcifications improve diagnostic yield in stereotactic core needle breast biopsies?

Stereotactic core needle biopsy (SCNB) of the breast is a cost-effective alternative to needle localization biopsy for the diagnosis of mammographic calcifications. We questioned whether an exhaustive search for calcium in the small samples obtained in SCNB yields more diagnostic information than that obtained with examination of a standard number of sections. We retrospectively reviewed 168 specimens from 123 patients with mammographic calcifications, including cases in which radiographic suspicion ranged from low to high. Microcalcifications were identified on three initial levels in 112 specimens. Additional sections were examined in 50 specimens. The final diagnosis differed from the diagnosis based on three levels in 11/50 cases (22%). In 6/50 (12%), complete sectioning yielded a specific diagnosis. The increase in technical cost associated with the additional levels was 414% per case. We conclude that exhaustive searching for microcalcifications in SCNB yields a small increase in specific diagnostic information and a high technical cost. In individual cases, the additional information may be critical for appropriate patient management.

Increased echogenicity in the fetal abdomen: use of DNA analysis to establish a diagnosis of cystic fibrosis.

The sonographic finding of increased echogenicity within the fetal abdomen presents a diagnostic dilemma, with a differential diagnosis ranging from normal variation to CF. We report the diagnostic evaluation of four cases, two of which were found to be the result of CF. On the basis of this experience, we believe that persistence of an echogenic bowel pattern, especially with bowel dilation, after 20 weeks' gestation should prompt an evaluation for CF. Using DNA analysis, approximately 75% of the cases involving CF can be detected with noninvasive studies of the parents, and confirmation by amniocentesis is performed only in those cases in which both parents are carriers of known mutations.

The mammographic spectrum of fat necrosis of the breast.

Fat necrosis of the breast is a benign condition that most commonly occurs as the result of minor breast trauma. The radiographic and clinical significance of fat necrosis of the breast is that it may mimic a breast malignancy, requiring biopsy for diagnosis. The mammographic appearance of fat necrosis ranges from a lipid cyst to findings suspicious for malignancy, including clustered microcalcifications, a spiculated area of increased opacity, or a focal mass. The changes of fat necrosis may be seen following blunt trauma, cyst aspiration, biopsy, lumpectomy, radiation therapy, reduction mammoplasty, breast reconstruction with a transverse rectus abdominis myocutaneous (TRAM) flap, implant removal, and anticoagulant therapy, as well as in patients without a relevant history. Fat necrosis may also be detected mammographically as an incidental finding in benign lipomas. It is important to recognize the mammographic spectrum of appearances of fat necrosis to avoid unnecessary biopsy and to avoid overlooking breast cancer.

Unusual breast lesions: radiologic-pathologic correlation.

Unusual lesions of the breast can present a diagnostic challenge. These lesions include systemic diseases, benign tumors, and primary and metastatic malignancies. Lymphadenopathy is the most common mammographic finding associated with collagen vascular disease. Wegener granulomatosis may manifest as an irregular, high-density mass simulating breast cancer. Diabetic fibrous mastopathy manifests at mammography as very dense breast tissue and at ultrasonography (US) as an irregular, hypoechoic mass with striking posterior acoustic shadowing simulating malignancy. Fibromatosis simulates malignancy at mammography as an irregularly shaped, uncalcified, high-density mass and at US as an irregular, hypoechoic mass with posterior acoustic shadowing. At US, granular cell tumor may manifest as a solid, poorly marginated mass with marked posterior acoustic shadowing or may appear more benign. At mammography, hamartomas are typically well-circumscribed, round to oval masses with a thin, radiopaque pseudocapsule; at US, they manifest as a sharply defined, heterogeneous oval mass or as normal glandular tissue. Phyllodes tumor manifests at mammography as a large, well-circumscribed oval or lobulated mass; at US, it usually manifests as an inhomogeneous, solid-appearing mass. At mammography, primary breast lymphoma manifests as a relatively circumscribed mass or a solitary, indistinctly marginated, uncalcified mass. Metastatic lesions may manifest mammographically as single or multiple masses or as diffuse skin thickening; at US, they tend to have circumscribed margins with low-level internal echoes. Radiologists should be familiar with the characteristic mammographic appearances of these lesions and should consider benign and systemic causes in the differential diagnosis when malignant-appearing findings are encountered.

Mammography of autologous myocutaneous flaps.

Autologous myocutaneous flaps (AMFs) are used increasingly as a method of breast reconstruction after mastectomy for breast cancer. Autogenous breast reconstruction may be performed with a rectus abdominis, latissimus dorsi, or gluteus maximus myocutaneous flap. Mammographic imaging of AMFs is controversial but has been recommended by some authors because mammographic detection of nonpalpable local recurrences in AMFs continues to be reported. At mammography, AMFs have a predominantly fatty appearance with variable density due to the muscle component and postoperative scarring. Normal mammographic findings include the vascular pedicle, surgical clips, and surgical scars, which produce radiopaque lines in predictable locations. Abnormal mammographic findings include fat necrosis appearing as a spiculated mass, noncalcified or calcified lipid cysts, calcifications, lymph nodes, epidermal inclusion cysts, and locally recurrent carcinoma.

Insights into the pathogenesis and natural history of fetuses with multicystic dysplastic kidney disease.

To better delineate the natural history of multicystic displastic kidney disease (MCDKD) and provide insights into the pathogenesis of this condition, we report our experience in 102 prenatally detected cases. MCDKD is most commonly an incidental finding on prenatal ultrasound examination. The abnormality may be unilateral (76 per cent) or bilateral (24 per cent). In unilateral cases, abnormality of the contralateral kidney is common (33 per cent). Associated non-renal abnormalities occur frequently with both unilateral (26 per cent) and bilateral (67 per cent) MCDKD, and increase the risk for an abnormal chromosome study. Males are more likely to be affected than females with a ratio of 2.4:1, but females are twice as likely to have bilateral MCDKD and associated non-renal abnormalities, and four times more likely to have an abnormal chromosome study. We suggest that the option of chromosomal analysis should be discussed with all patients diagnosed with MCDKD in their fetus, if there is bilateral renal involvement or if an associated non-renal abnormality is present. Unilateral MCDKD without associated renal or non-renal abnormalities was not associated with an abnormal chromosome study, and resulted in favourable outcomes. While unilateral MCDKD, lack of associated anomalies, normal chromosome study and adequate amniotic fluid are all reassuring findings, a complete neonatal urologic work-up should be performed in all newborns. We believe the evaluation should include voiding cystourethrography to rule out vesicoureteral reflux. Our findings allow more precise counselling of patients regarding prognosis, and subsequent management of the fetus found to have MCDKD.