Biexponential T2 relaxation time analysis of the brain: correlation with magnetization transfer ratio.

RATIONALE AND OBJECTIVES: To measure T2 relaxation times of normal white and gray matter using a novel CPMG sequence and investigate if any correlation exists between magnetization transfer ratio (MTR) and T2 relaxation-related parameters. MATERIALS AND METHODS: Seventeen normal volunteers participated on this study. A single-slice 32-echo sequence was used to calculate the T2 relaxation time of frontal and occipital white matter and cortical gray matter. T2 relaxation analysis included monoexponential and biexponential fitting whereas an F test was used to determine if biexponential fitting was statistically more accurate than monoexponential fitting. Short and long T2 constants were calculated as well as the signal fractions of each pool. MTR calculations were based on a three-dimensional gradient echo (3D FFE) proton density weighted sequence with and without an on-resonance composite prepulse. MTR and T2 relaxation times were calculated and linear regression analysis was applied. RESULTS: Biexponential fitting was more accurate comparing with monoexponential fitting in all WM and GM regions (F > 2.47, P < 0.01). Mean values of short T2 constant for frontal white matter (fWM), occipital white matter (oWM) and gray matter (GM) were 8.10, 9.36, and 22.23 milliseconds, respectively, whereas the mean values of long T2 constant were 85.1, 93.02, and 118.72 milliseconds, respectively. Mean restricted water percentages (RWP)-corresponding to the signal fraction of the protons with short T2-for the fWM, oWM, and GM were 22.01%, 23.36%, and 18.7%. Mean free water percentages (FWP)-corresponding to the signal fraction of the protons with long T2-for the fWM, oWM and GM were 77.99%, 76.64%, and 81.3%. Mean MTR values for fWM, oWM and GM were 68.4%, 68.2%, and 61.3%, respectively. No significant correlation was found in fWM and oWM between MTR and RWP, short and long T2 components while a moderate correlation existed in GM between MTR and RWP (r = 0.57; P = 0.02), MTR and short T2 component (r = -0.69; P = 0.004) and MTR and long T2 component (r = -0.62; P = 0.012). CONCLUSIONS: Two proton pools with different T2 decay characteristics can be separated in normal gray and white matter when using a multiecho sequence with short echo spacing. MTR and T2 relaxation times were significantly correlated in gray matter and the combination of both types of measurements may be helpful in studying myelin related disorders.

Thyroglossal duct cyst carcinoma: case report and review of the literature, with emphasis on CT findings.

Carcinoma arising in a thyroglossal duct cyst (TDC) is rare. To the best of our knowledge, 155 cases have been reported, 12 of which were studied with CT. The diagnosis is established after surgical excision of the lesion but CT findings may raise the suspicion of malignancy. We present a case of TDC carcinoma and a review of the literature, with emphasis on CT findings.

Assessment of intraocular foreign bodies by helical-CT multiplanar imaging.

The aim of this study was to examine the effectiveness of helical CT in the assessment of intraocular foreign bodies, evaluating two protocols with different collimation. We performed helical-CT studies in 30 patients. Fifteen patients were examined with 1.5-mm collimation and the other 15 patients with 3.0-mm collimation. All other imaging parameters were identical in both protocols. Multiplanar images were reconstructed. The examinations were reviewed for presence, localization and size of intraocular foreign bodies. We compare our results with the surgical data. We estimate the required examination time. In the first group (collimation 1.5 mm) an intraorbital foreign body was detected in 8 of 15 patients. In 3 of 8 patients an intraocular foreign body (all were metallic) was detected. In the second group (collimation 3.0 mm) an intraorbital foreign body was detected in 9 of 15 patients. In 8 of 9 patients an intraocular foreign body (all were metallic) was detected. Our results were confirmed by surgery in all cases. Examination time was 36 s in the first group and 18 s in the second group. Computed tomography should be considered the imaging modality of choice in the assessment of metallic intraocular foreign bodies and 3.0-mm collimation is optional, because of reduced examination time and radiation exposure.

Perforation of the alimentary tract: evaluation with computed tomography.

BACKGROUND: To assess the value of computed tomography (CT) in the diagnosis of perforation of the alimentary tract (AT). METHODS: During a 4-year period 76 patients with proven AT perforation underwent CT within 1 week before surgery or endoscopy. We retrospectively reviewed these CT scans to determine the signs of AT perforation. There were 41 men and 35 women (28-90 years old). Our goal was to establish the diagnosis of AT perforation and, if this was possible, to identify the site and cause of the AT wall rupture. The CT diagnosis of perforation was based on (a) direct findings of extraluminar air or gastrografin and (b) indirect findings of an abscess or an inflammatory mass surrounding an enterolith in the region of appendix or a bowel wall-related phlegmon or abscess with fluid in the mesentery or surrounding radiopaque foreign body. RESULTS: There were 65 true-positive and 11 false-negative cases. Levels of perforation were the esophagus (two), stomach (five), duodenum (12), small bowel (15), appendix (six), and colon (36). Causes were peptic ulcer (11), foreign body (five), trauma (seven), iatrogenic (nine), appendicitis (six), diverticulitis (21), Crohn disease (five), AT carcinoma (eight), and ischemia (four). Level and cause were correctly predicted in 55 and 51 instances, respectively. The sensitivity was estimated to 85.5%. CONCLUSION: CT is a valuable method in the diagnosis of AT perforation. The diagnosis can be established rapidly, without patient preparation and with a high sensitivity.

High-resolution physical map and transcript identification of a prostate cancer deletion interval on 8p22.

A genomic interval of approximately 1-1.5 Mb centered at the MSR marker on 8p22 has emerged as a possible site for a tumor suppressor gene, based on high rates of allele loss and the presence of a homozygous deletion found in metastatic prostate cancer. The objective of this study was to prepare a bacterial contig of this interval, integrate the contig with radiation hybrid (RH) databases, and use these resources to identify transcription units that might represent the candidate tumor suppressor genes. Here we present a complete bacterial contig across the interval, which was assembled using 22 published and 17 newly originated STSs. The physical map provides twofold or greater coverage over much of the interval, including 17 BACs, 15 P1s, 2 cosmids, and 1 PAC clone. The position of the selected markers across the interval in relation to the other markers on the larger chromosomal scale was confirmed by RH mapping using the Stanford G3 RH panel. Transcribed units within the deletion region were identified by exon amplification, searching of the Human Transcript Map, placement of unmapped expressed sequence tags (ESTs) from the Radiation Hybrid Database (RHdb), and from other published sources, resulting in the isolation of six unique expressed sequences. The transcript map of the deletion interval now includes two known genes (MSR and N33) and six novel ESTs.

Peritoneal metastases from transitional cell carcinoma of the urinary tract: CT and MR imaging.

We present three patients with peritoneal metastases from transitional cell carcinoma of the urinary tract. CT scan in one patient showed massive ascites with subtle peritoneal thickening and infiltration of omental fat. We had the opportunity to study the other patients with both CT and MR. Both examinations showed numerous large and small peritoneal implants in the abdomen and pelvis, mostly in the greater omentum.