Hypersensitivity to intravenous contrast material causing CT appearance of bowel wall thickening.
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Abdominal Pain↗
Biomedical subjects
M M McNicholas
Publications and source records attributed to M M McNicholas.
Abdominal helical CT: milk as a low-attenuation oral contrast agent.
One hundred ten consecutive patients were given either whole (4%) milk, 2% milk, water, barium suspension, or no oral contrast agent before abdominal computed tomography (CT). Results with whole milk were superior to those with all other agents for gastrointestinal distention, mural visualization, and pancreas-duodenum discrimination. In bowel loop discrimination, results with 4% milk were equal to those with barium but superior to those with all other agents. Whole (4%) milk is an effective low-attenuation oral contrast agent.
Administration, Oral↗
Multiplanar CT pancreatography and distal cholangiography with minimum intensity projections.
PURPOSE: To develop a technique of projectional computed tomographic (CT) cholangiopancreatography (CTCP). MATERIALS AND METHODS: Sixty-one patients underwent CT for suspected biliary or pancreatic abnormalities. The axial CT and CTCP techniques included spiral scanning during the portal venous phase and thick-slab minimum intensity projections. Visualization of pancreatic and extrahepatic bile ducts (divided in five duct segments per patient) was graded blindly on a scale of 1-5 by a consensus of two radiologists. Two hundred seventy-seven duct segments were used to compare axial CT and CTCP in the depiction of duct segments and dilatation; 109 segments were used to compare CTCP with ERCP. RESULTS: Fifty-six of 277 duct segments were not visualized on axial CT images; 15 segments were not visualized on CTCP images (P < .001). There was no statistically significant difference between the number of segments missed with ERCP and the number missed with CTCP: nine and three of 109 segments, respectively. Duct visualization was equal on axial CT and CTCP images in 35 of 109 duct segments and was superior on CTCP images in all but one of the remaining segments (P < .001). Duct visualization on CTCP images was equal to that on ERCP images in 35 segments, superior in nine, and significantly inferior in 66 (P < .001). CONCLUSION: CTCP improves CT depiction of pancreatic and bile ducts with a quality that approaches that of ERCP.
Aged↗
Development of virtual CT cholangiopancreatoscopy.
Endoluminal virtual computed tomographic (CT) cholangiopancreatoscopic views of the pancreatic and common bile ducts were generated in 16 patients by using helical CT data sets and endoscopic three-dimensional reconstruction images. In all patients with ductal dilatation, virtual images were obtained and findings correlated with those at helical CT and endoscopic retrograde cholangiopancreatography. Virtual CT cholangiopancreatoscopy is a feasible technique, and initial experience shows promising results.
Cholangiopancreatography, Endoscopic Retrograde↗
Excretory phase CT urography for opacification of the urinary collecting system.
OBJECTIVE: The purpose of our study was threefold: to evaluate the ability of excretory phase CT urography to opacify the urinary collecting system by comparing opacification seen on CT with the opacification seen on a series of unmatched IV urography examinations; to determine the optimal CT urography technique for ureteral filling by comparing studies of patients who were imaged supine, prone, and with abdominal compression; and to assess the possible value that reformatted planar images might add to axial excretory phase images. SUBJECTS AND METHODS: Seventy patients with hematuria were imaged in one of four ways. Twenty-five patients underwent contrast-enhanced excretory phase helical CT of the kidneys, ureters, and bladder. All patients were imaged in a supine position. Ten other patients underwent a similar CT protocol in which we used abdominal compression. Ten further patients underwent excretory phase CT while in a prone position. A final 25 patients underwent IV urography. Each patient's collecting system was arbitrarily divided into 10 parts (both right and left sides of calices; pelvis; upper, mid, and lower ureters) for scoring of images on a five-point scale for opacification by contrast material. Opacification scores for the four groups of patients were then compared. For patients who underwent CT, reformatted images of the collecting systems were generated and evaluated for their potential to add value to the conventional axial images. RESULTS: We found no significant difference in the ability of CT urography and IV urography to yield opacification of the calices, pelvis, and upper or mid ureters. Opacification of the distal ureter was less well seen on supine CT urography than on IV urography. Prone and compression CT urography resulted in better opacification of the collecting system than the supine noncompression technique. Opacification of the distal ureter was best seen with compression CT and was as good as that seen with IV urography. Reformatted CT urography was judged to be of probable or definite additional value to the axial images in 44% of cases. In each case, we saw a pathologic finding whose relationship to the kidney and collecting system was not as easy to appreciate on the axial CT scans. CONCLUSION: CT urography with abdominal compression results in reliable opacification of the collecting system that is comparable with opacification seen on IV urography. In patients with abnormalities, reformatted images were a useful adjunct to axial images. CT urography has potential as an imaging tool for the urothelium.
Abdomen↗
Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature.
OBJECTIVE: Unenhanced CT scanning can reliably characterize incidentally detected adrenal masses when observers use density measurements of the adrenal gland. However, controversy exists as to the optimal density threshold required to differentiate benign from malignant lesions. This study attempts to establish a consensus by performing a pooled analysis of data found in the CT literature. MATERIALS AND METHODS: Ten CT reports were analyzed, from which individual adrenal lesion density measurements were obtained for 495 adrenal lesions (272 benign lesions and 223 malignant lesions). Threshold analysis generated a range of sensitivities and specificities for lesion characterization at different density thresholds. RESULTS: Sensitivity for characterizing a lesion as benign ranged from 47% at a threshold of 2 H to 88% at a threshold of 20 H. Similarly, specificity varied from 100% at a threshold of 2 H to 84% at a threshold of 20 H. CONCLUSION: The attempt to be absolutely certain that an adrenal lesion is benign may lead to an unacceptably low sensitivity for lesion characterization. The threshold chosen will depend on the patient population and the cost-benefit approach to patient care.
Adrenal Gland Diseases↗
Nonopaque crystal deposition causing ureteric obstruction in patients with HIV undergoing indinavir therapy.
OBJECTIVE: We describe the unique CT features of ureteric calculi in six HIV-infected patients receiving indinavir, the most commonly used HIV protease inhibitor, which is associated with an increased incidence of urolithiasis. CONCLUSION: Ureteric obstruction caused by precipitated indinavir crystals may be difficult to diagnose with unenhanced CT. The calculi are not opaque, and secondary signs of obstruction may be absent or minimal and should be sought carefully. Images may need to be obtained using i.v. contrast material to enable diagnosis of ureteric stones or obstruction in patients with HIV infection who receive indinavir therapy.
Adult↗
Imaging of pelvic postpartum complications.
Differentiation between endometritis and RPOC in febrile postpartum patients is commonly requested by clinicians. Sonography is the screening technique of choice to assess the endometrial contents. For cases in which the retained placenta is calcified or still has demonstrable blood flow, a specific diagnosis of RPOC can be made. In more complicated cases, a CT scan or an MR image may be requested. In addition to evaluating the uterus and any intra- or extrauterine fluid collections, attention must be paid to the ovarian veins to exclude the diagnosis of ovarian vein thrombosis.
Adult↗
Multiplanar helical CT enterography in patients with Crohn's disease.
OBJECTIVE: The purpose of this study was to assess the feasibility and usefulness of helical CT with multiplanar reformations in revealing complications in patients with Crohn's disease. SUBJECTS AND METHODS: Twenty-two patients with Crohn's disease and clinically suspected complications underwent helical CT enterography. The imaging protocol began with the administration of a large volume (1600 ml) of oral contrast material followed by helical scanning with axial and multiplanar two-dimensional coronal projections. Three independent observers assessed the adequacy of bowel opacification and the contribution of two-dimensional coronal projections to the interpretation of axial images. CT enterography was compared with conventional barium studies in 14 patients. Statistical analysis included repeated measures analysis of variance, the Wilcoxon signed-rank test, and the McNemar test. RESULTS: The large oral contrast medium dose was well tolerated and provided optimal bowel opacification in 21 of 22 patients. The addition of multiplanar to conventional axial images did not reveal additional abnormalities; however, multiplanar imaging significantly improved observers' confidence in their interpretation of imaging and in their assessment of the extent of bowel wall thickening (p < .01). Interobserver agreement was 78%. Findings on helical CT were comparable with those on barium studies in nine of 14 patients, superior to those on barium studies in four patients, and inferior in one patient. CONCLUSION: CT enterography is a useful technique for bowel imaging. In patients with complicated Crohn's disease, multiplanar imaging improves confidence in assessing the presence and extent of disease. CT enterography is complementary and often superior to conventional barium studies.
Adult↗
T2 relaxation times of hypervascular and non-hypervascular liver lesions: do hypervascular lesions mimic haemangiomas on heavily T2-weighted MR images?
AIM: To correlate the T2 relaxation times of liver lesions with their vascularity at angiography and to determine whether hypervascular lesions have similar signal intensity to haemangiomas on heavily T2-weighted MR images. PATIENTS AND METHODS: Thirty-four patients with histologically proven malignant liver lesions had both angiography and T2W (SE 3000/80,160) MR imaging (1.5 T) of the liver. Angiographically, the lesions were hypervascular in 15 and non-hypervascular in 19 patients. Fifteen additional patients with proven haemangioma also had MR imaging during the same time period. The T2 relaxation time of a representative lesion was calculated for each patient and the results compared. RESULTS: The mean T2 time for hypervascular lesions was 76 +/- 21 ms compared with 79 +/- 18 ms for non-hypervascular lesions (P = 0.61). The mean T2 relaxation time for haemangiomas was significantly longer than either group: 147 +/- 46 ms (P = 0.0001). CONCLUSION: The T2 relaxation times of hypervascular and non-hypervascular liver lesions are similar and are significantly shorter than those of haemangiomas. Therefore, hypervascular lesions should not mimic haemangiomas on heavily T2-weighted images.
Carcinoma, Hepatocellular↗
Prostatic biopsy after proctocolectomy: a transgluteal, CT-guided approach.
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Aged↗
Indeterminate adrenal mass in patients with cancer: evaluation at PET with 2-[F-18]-fluoro-2-deoxy-D-glucose.
PURPOSE: To evaluate the ability of positron emission tomography (PET) to characterize adrenal masses in patients with cancer. MATERIALS AND METHODS: Twenty-four adrenal masses (size range, 1.5-10.0 cm [mean, 2.8 cm]) in 20 patients (13 men and seven women) with cancer (lung [n = 10], colon [n = 3], lymphoma [n = 3], miscellaneous [n = 4]) were evaluated. PET was performed in fasting patients 45 minutes after infusion of 5-10 mCi (185-370 MBq) of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG). PET images were correlated with findings at computed tomography (CT), surgery, and/or percutaneous biopsy. RESULTS: Fourteen adrenal masses were proved malignant at surgery (n = 4), biopsy (n = 7), or follow-up (n = 3). Ten lesions were proved benign at biopsy (n = 4) or follow-up CT (n = 6). PET helped correct differentiation of benign from malignant adrenal lesions in all patients. A statistically significant difference (P < .001) was seen between mean tumor-to-background ratios for malignant (mean, 7.4; range, 2.9-16.6; median, 6.9) versus benign (mean, 0.8; range, 0.2-1.2; median, 0.6) adrenal lesions. CONCLUSION: PET helped correct differentiation of benign from malignant adrenal lesions.
Adrenal Gland Diseases↗
Ocular trauma: evaluation with US.
PURPOSE: To examine the value of real-time ultrasonography (US) in the assessment of traumatized eyes with opaque ocular media. MATERIALS AND METHODS: Sixty-one eyes in 60 patients were prospectively examined with US; findings were correlated with findings of clinical and surgical follow-up. Patients with an intraocular foreign body (IOFB) also underwent computed tomography (CT). RESULTS: US demonstrated 56 vitreous hemorrhages, 21 retinal detachments, 12 vitreous detachments, five choroidal detachments, seven IOFBs, three dislocated lenses, and two retrohyaloid hemorrhages. Findings of US and surgery or clinical follow-up were in complete concurrence in 55 cases (90%) and partial concurrence in two cases (3%). US findings were incorrect in four cases (7%). In four cases, US allowed diagnoses that were unsuspected clinically. CONCLUSION: US accurately demonstrates ocular damage and may reveal unsuspected problems. US was superior to CT in demonstration of intraocular damage associated with IOFBs, although CT was superior in determination of the size and site of the IOFB. The presence of dense vitreous traction bands may indicate impending retinal detachment.
Adult↗
Characterization of adrenal masses (< 5 cm) by use of chemical shift MR imaging: observer performance versus quantitative measures.
OBJECTIVE: The purposes of this study were to evaluate the ability of chemical shift MR imaging to differentiate 1- to 5-cm adrenal adenomas from metastases and to compare subjective interpretation with several different quantitative measures. SUBJECTS AND METHODS: Forty-three patients with 46 proved adrenal lesions (28 adenomas and 18 metastases) had MR imaging with a gradient-echo breath-hold technique and echo time varied to obtain in-phase and out-of-phase images. Qualitative analysis of the MR images was done by three experienced observers, who reported their confidence in diagnosing the benignity versus the malignancy of the adrenal masses on the basis of signal loss on out-of-phase images. Quantitative analysis was performed by calculating the difference in signal intensity between in-phase and out-of-phase images by use of regions of interest (signal intensity index) and by use of adrenal-liver, adrenal-spleen, and adrenal-muscle signal intensity ratios. Results between quantitative and qualitative measures were compared by use of receiver operating characteristic (ROC) analysis. RESULTS: The mean signal intensity was significantly different between adenomas and metastases on out-of-phase images (64 versus 98) (p < .0005) but not in-phase images (130 versus 122) (p = .47). The adrenal-spleen ratio discriminated between adenomas and metastases better than did the adrenal-liver ratio, the adrenal-muscle ratio, or the signal intensity index. No significant difference in interpretation among the three observers was evident (areas under the ROC curves, 0.93, 0.95, and 0.96). The performance of the observers was comparable to the results obtained with the adrenal-spleen ratio measurement (area under the ROC curve, 0.97). CONCLUSION: Experienced observers were able to differentiate adrenal adenomas from metastases just as well as quantitative measures. The adrenal-spleen ratio is the best quantitative means of distinguishing benign from malignant adrenal masses. Chemical shift MR imaging is a good but imperfect discriminator of adrenal adenomas.
Adenoma↗
Percutaneous drainage of subphrenic fluid collections that occur after splenectomy: efficacy and safety of transpleural versus extrapleural approach.
OBJECTIVE: The purpose of this study was to compare the safety and efficacy of transpleural and extrapleural approaches for draining left subphrenic abscesses in patients who have had splenectomy. MATERIALS AND METHODS: Twenty-five patients who had percutaneous catheter drainage (28 drainages) of postsplenectomy fluid collections were studied. Twenty drainages were transpleural and eight were extrapleural. In eight of the 20 transpleural drainages, it was elected to place the catheter transpleurally. In the remaining 12 patients, catheter drainage was judged to be transpleural on review, despite efforts to use an extrapleural approach. RESULTS: Sixteen of 18 patients who had transpleural percutaneous drainage and six of seven patients who had true extrapleural (subcostal) percutaneous drainage were cured by catheter drainage requiring no further intervention. The mean number of days of drainage was not significantly different (p > .05) for the group drained transpleurally (mean, 18 days; range, 1-90 days) versus the group drained extrapleurally (mean, 20 days; range, 6-43 days). Complications (pneumothorax) requiring treatment were seen in two patients in whom a transpleural approach was used and in none of the patients in whom an extrapleural approach was used. Complications that did not require treatment were seen in four further patients drained transpleurally. These were inadvertent placement of catheter into pleural space (two patients) and pneumothorax not requiring treatment (two patients). No patient had an empyema. CONCLUSION: Transpleural drainage of left subphrenic collections occurring after splenectomy is associated with a slightly increased complication rate but has a success rate similar to that of extrapleural drainage.
Adult↗
An imaging algorithm for the differential diagnosis of adrenal adenomas and metastases.
OBJECTIVE: The purpose of this study was to develop an algorithm using CT and chemical-shift MR imaging for the characterization of adrenal masses in patients with a primary cancer and no other evidence of metastatic disease. SUBJECTS AND METHODS: Thirty-three patients with 37 adrenal masses (19 metastases, 18 adenomas), all of whom had a known primary cancer, were studied with noncontrast CT and chemical-shift MR imaging (1.5 T). Lesion size and density in Hounsfield units (H) were determined by CT. Adrenal signal intensity normalized to that of spleen was used to calculate adrenal-spleen ratio (ASR), defined as the percentage of signal remaining in the opposed-phase image relative to the in-phase image. Lesions less than or equal to 0 H were classified as benign, lesions greater than 20 H were regarded as malignant, and lesions between 0 and 20 H were regarded as indeterminate. Diagnoses were confirmed by biopsy (for 19 lesions) or by follow-up imaging (for 18 lesions). An imaging algorithm was derived by determining the relative value of CT and MR imaging for diagnosing the lesions. The reimbursement rates for CT-guided biopsy and MR imaging of the abdomen were obtained from Medicare. RESULTS: All 13 lesions of 0 or less H were correctly classified as benign by CT. ASR was less than 70 in 10 of these 13. In another 13 lesions, H was greater than 20; all were malignant and all had an ASR greater than 80. Of 11 CT-indeterminate lesions, four of five adenomas had an ASR less than 70, and four of six metastases had an ASR greater than 80. Two malignant lesions had ASRs between 70 and 80 and were diagnosed by biopsy findings. One CT-indeterminate adenoma had an ASR of 84 and was diagnosed by biopsy findings. The reimbursement rate by Medicare is similar for CT-guided biopsy with pathologic interpretation and for MR imaging of the abdomen. CONCLUSION: An algorithm was developed for diagnosis of adrenal lesions that uses the density reading on noncontrast CT as the first step, with chemical-shift MR imaging for CT-indeterminate lesions. In this algorithm, lesions of 0 H or less may be regarded as benign and further work-up is not required. Lesions with a density greater than 20 H are likely malignant and should be biopsied when the result will influence management. For CT-indeterminate lesions, we recommend chemical-shift MR imaging. An ASR threshold of 70 indicates a benign lesion, and no further workup is required in these patients. Lesions with an ASR greater than 70 should have a biopsy performed, depending on the clinical situation. The above algorithm is cost-effective and reduces the number of biopsies required without reducing the sensitivity of detecting malignant lesions.
Adrenal Cortex↗
Magnetic resonance imaging of rectal carcinoma: a prospective study.
Accurate preoperative staging of rectal cancer is necessary to identify patients who might benefit from adjuvant therapy. Magnetic resonance imaging (MRI) was evaluated in 20 consecutive patients with rectal cancer undergoing 'curative' surgery. Detailed histopathological examination of the resected lesion was correlated with findings of MRI. MRI staging concurred with histological staging in 18 of 20 patients using the Dukes or tumour node metastasis classification but in only 14 using the modified Astler-Coller system. MRI diagnosed transmural invasion in all but one patient with microscopic mural invasion (positive predictive value, 100 per cent; negative predictive value, 80 per cent; overall accuracy, 95 per cent). MRI correctly diagnosed tumour deposits or involved lymph nodes in 12 patients. MRI overstaged one patient, in whom nodes that were enlarged on imaging studies were negative at histological examination (positive predictive value, 92 per cent; negative predictive value, 100 per cent; overall accuracy, 95 per cent). MRI has a role in selected cases for the preoperative assessment of rectal carcinoma.
Aged↗
Imaging of primary vaginal lymphoma.
Two cases of primary vaginal lymphoma are reviewed and their imaging features presented. On sonography, both lesions appeared as well defined, slightly lobulated masses of medium to low echogenicity. On computed tomography (CT) the lesions were well circumscribed and of homogeneous density similar to that of muscle. Magnetic resonance (MR) imaging in one case after treatment showed a non-enhancing lesion of intermediate signal intensity on T1- and T2-weighted images. Ultrasound was particularly useful in one case where the lesion was shown to be separate to the uterus--a fact which was not easily appreciated on CT. The differential diagnosis is discussed.
Adult↗