Thickened submucosal layer: a sonographic sign of acute gastrointestinal abnormality representing submucosal edema or hemorrhage. 2000 ARRS Executive Council Award II. American Roentgen Ray Society.

OBJECTIVE: We correlated the sonographic appearance of bowel wall thickening with the acuity of the underlying disease process. SUBJECTS AND METHODS: Sonograms of thickened bowel walls were reviewed in 37 patients with proven gastrointestinal abnormalities. Sonographic findings were correlated with clinical presentation, endoscopy, histology, laboratory data, barium studies, and CT. RESULTS: Twenty-eight patients presented acutely, and nine patients had chronic or subacute disease processes. Two of the 28 patients had concurrent acute and chronic processes. In 27 of 28 patients with acute processes, the abnormal bowel segments were characterized by an echogenic submucosal layer thicker than 2.5 mm. In contrast, nine patients with chronic or subacute processes had relatively uniform hypoechoic thickening of the bowel wall with loss of visualization of a discrete echogenic submucosal layer. CT was available for comparison in 30 of 37 patients. Of the 28 patients with acute abnormalities, the thickened echogenic submucosal layer on sonography corresponded to either low-attenuation submucosal edema (n = 25) or acute submucosal hemorrhage (n = 3). CONCLUSION: The finding of a thickened submucosal layer suggests an acute disease process of the bowel and corresponds to either submucosal edema or hemorrhage.

Nephrotoxicity of high-dose gadolinium compared with iodinated contrast.

To determine if high-dose gadolinium chelates are less nephrotoxic than iodinated contrast. Records of 342 patients who had received high-dose gadolinium (.2 to .4 mmol/kg) for magnetic resonance imaging were reviewed to identify patients who had also received iodinated contrast for radiographic examinations. Their clinical course and laboratory data were reviewed to identify changes in serum creatinine attributable to the contrast agents. In 64 patients, serum creatinine data were available pre and post both gadolinium and iodinated contrast. The mean change in serum creatinine after gadolinium in these 64 patients was -.07 mg/dL (-6 mumol/L). By comparison, the mean change in serum creatinine in the same patients after iodinated contrast was .35 mg/dL (+31 mumol/L) from 2.0 +/- 1.4 to 2.3 +/- 1.8 (P = .002). Eleven of the 64 patients had iodinated contrast-induced renal failure (.5 mg/dL or greater rise in serum creatinine); none had gadolinium contrast-induced renal failure despite the high gadolinium dose and high prevalence of underlying renal insufficiency. High-dose gadolinium chelates are significantly less nephrotoxic than iodinated contrast.

Anatomy of the jaw, dentition, and related regions.

The jaw has traditionally been evaluated by dentists and oral surgeons using conventional panoramic and intraoral films. Recently, CT software programs specifically developed to evaluate dental implant patients have provided radiologists with a new window through which to assess anatomy and pathology of the jaw. The anatomy of this region, including the dentitian, and related structures are discussed in this section.

Localization of absorbers in scattering media by use of frequency-domain measurements of time-dependent photon migration.

Frequency-domain studies of time-dependent light propagation in tissuelike phantoms that contain optical heterogeneities are described. Specifically the phase shift and amplitude modulation of reemergent light were measured when illuminated by an amplitude-modulated light source. Changes in the phase angle and the extent of modulation revealed the presence of a light-absorbing object. Furthermore the magnitude and direction of these changes were sensitive to the absorber depth and the light modulation frequency in a manner that could be used to infer the location of the heterogeneity. These data suggest the feasibility of optical imaging by frequency-domain methods.

Pharmacokinetics of a fluorescent drug using laser-induced fluorescence.

Laser-induced fluorescence has been used to measure tissue levels of chloroaluminum sulfonated phthalocyanine in vivo in an implanted hamster cheek pouch carcinoma tumor model. The drug was excited at 610 nm via a pulsed nitrogen laser-pumped dye laser, and fluorescence intensity was monitored at 684 nm for up to 30 days after drug administration. Data were acquired noninvasively with high temporal and spatial resolution using the laser-induced fluorescence apparatus and were analyzed with a multicompartment pharmacokinetic model. In addition, our published data on a C6-BAG glioma rat brain tumor model were analyzed to illustrate the effect of different tumor models on the rates. The rates extracted from the pharmacokinetic model elucidate the mechanisms of drug uptake and retention in the cheek pouch and brain tumor models. The laser-induced fluorescence approach should lead to better drug dosimetry for photochemotherapy and allow quick characterization of the pharmacokinetics of new photosensitizers in tissue.

Beta-carotene accumulation in serum and skin.

The accumulation of beta-carotene in serum and skin was evaluated in human volunteers. A single 51-mg dose of beta-carotene given in the absence of dietary fat resulted in no detectable change in serum beta-carotene. The same dose administered with 200 g fat increased serum beta-carotene 2.5-fold at 40 h. Similarly, administering beta-carotene daily in three divided doses with meals raised the serum beta-carotene concentration three times as high compared with the same total dose administered once a day; both regimens had the same time constant for serum accumulation; 9-10 d. Remittance measurements of skin color demonstrated that the accumulation of beta-carotene in skin was delayed by up to 2 wk compared with serum accumulation. These data indicate that beta-carotene absorption requires dietary fat and is enhanced by administering with meals but there is a long time constant for serum (10 d) and tissue (several weeks) accumulation.

Beta carotene uptake into atherosclerotic plaque: enhanced staining and preferential ablation with the pulsed dye laser.

The yellow color of atherosclerotic plaque is due to the presence of carotenoids, which absorb light between 430-530 nm and account for the preferential ablation of plaque by the pulsed dye laser operating at 480 nm. This study was designed to examine tissue uptake of beta-carotene and the effect of uptake on arterial plaque ablation. Forty-two atherosclerotic NZW rabbits were given intravenous beta-carotene at a dose of 40 mg/kg, twice weekly and killed between 1 hour and 28 days after the initial injection. beta-carotene was not detected in control specimens but was significantly greater in plaque than in normal wall at all time points following beta-carotene injection (P < 0.04 Mann Whitney U test). The ablation threshold was significantly lower in beta-carotene treated plaque than in untreated plaque or normal arterial wall (P < 0.01, Fisher's exact test). In this model beta-carotene is preferentially taken up into arterial plaque, resulting in increased absorption of laser radiation at 480 nm and enhanced tissue ablation.

Ultraviolet laser-induced fluorescence of colonic polyps.

Ultraviolet laser-induced fluorescence was examined in vivo to determine whether the technique can reliably distinguish between hyperplastic and adenomatous polyps of the colon. Spectra from 86 normal colonic sites, 35 hyperplastic polyps, and 49 adenomatous polyps were recorded in vivo. Polyp type was independently determined by two senior pathologists who were unaware of the fluorescence measurement. A multivariate linear regression analysis was used to differentiate spectra from hyperplastic and adenomatous polyps and resulted in a sensitivity, specificity, predictive value positive, and predictive value negative for identifying adenomatous polyps of 86%, 80%, 86%, and 80%, respectively. These values were not significantly different from the accuracy of routine clinical pathology. Thus, ultraviolet laser-induced fluorescence appears to show promise as a means for distinguishing tissue types. However, further experience is needed before its routine clinical use can be recommended. Significant changes in the fluorescence spectra occurred postmortem, suggesting that future studies of laser-induced fluorescence of colonic tissue must use data acquired in vivo.

Ultraviolet laser-induced fluorescence of colonic tissue: basic biology and diagnostic potential.

Laser-induced fluorescence (LIF) of colonic tissue was examined both in vitro and in vivo to assess the ability of the technique to distinguish neoplastic from hyperplastic and normal tissue and to relate the LIF spectra to specific constituents of the colon. Spectra from 86 normal colonic sites, 35 hyperplastic polyps, 49 adenomatous polyps, and 7 adenocarcinomas were recorded both in vivo and in vitro. With 337-nm excitation, the fluorescence spectra all had peaks at 390 and 460 nm, believed to arise from collagen and NADH, and a minimum at 425 nm, consistent with absorption attributable to hemoglobin. The spectra of colonic tissue recorded both in vivo and in vitro are different, primarily in the NADH fluorescence component, which decays exponentially with time after resection. When normal colonic tissue is compared to hyperplastic or adenomatous polyps, the predominant changes in the fluorescence spectra are a decrease in collagen fluorescence and a slight increase in hemoglobin reabsorption. A multivariate linear regression (MVLR) analysis was used to distinguish neoplastic tissue from non-neoplastic tissue with a sensitivity, specificity, predictive value positive, and predictive value negative toward neoplastic tissue of 80%, 92%, 82%, and 91%, respectively. When the MVLR technique was used to distinguish neoplastic polyps from non-neoplastic polyps, values of 86%, 77%, 86%, and 77% respectively, were obtained. The data suggest that the LIF measurements sense changes in polyp morphology, rather than changes in fluorophores specific to polyps, and it is this change in morphology that leads indirectly to discrimination of polyps.

Rapid serum carotene loading with high-dose beta-carotene: clinical implications.

The kinetics of serum beta-carotene loading were evaluated to help determine the minimum time required to load fatty tissues, including atherosclerotic plaque and skin, with beta-carotene. Loading atherosclerotic plaque with yellow beta-carotene pigment increases absorption of blue laser radiation, potentially enhancing the selectivity and quality of laser angioplasty. Five healthy volunteers received 300 mg beta-carotene daily (the maximum FDA recommended dose) for 21 days in three divided doses with meals. Serum total carotenoid levels increased exponentially with a 10-day time constant from an average of 1.7-6.5 micrograms/ml (p less than 10(-4]. The skin began to yellow visibly at 10 days and became increasingly yellow for several weeks thereafter, suggesting that augmenting the yellow color of fatty tissues and atherosclerotic plaque with oral beta-carotene may require a minimum of several weeks to attain the maximum effect.