Bettina Siewert

The ischemic penumbra Operationally defined by diffusion and perfusion MRI

BACKGROUND Identifying tissue at risk for infarction is important in deciding which patients would benefit most from potentially harmful therapies and provides a way to evaluate newer therapies with regard to the amount of ischemic tissue salvaged. OBJECTIVE To operationally define and characterize cerebral tissue at risk for stroke progression. METHODS We retrospectively selected 25 patients with an acute onset of a hemispheric stroke from our database who had undergone a combination of two diffusion-weighted MRI studies and a perfusion-weighted MRI study. We applied a logistic regression model using maps of the relative mean transit time and relative cerebral blood flow (rCBF) as well as three different maps of the relative cerebral blood volume (rCBV) to predict an operationally defined penumbra (region of mismatch between the diffusion lesion on day 1 and its extension 24 to 72 hours later). RESULTS Maps of the rCBF and initial rCBV were significant predictors for identifying penumbral tissue. Our operationally defined penumbral region was characterized by a reduction in the initial rCBV (47% of contralateral control region [CCR]), an increase (163% of CCR) in the total rCBV, and a reduction (37% of CCR) in the rCBF, whereas the operationally defined ischemic core showed a more severe reduction in the rCBF (12% of CCR) and in the initial rCBV (19% of CCR). CONCLUSION These MR indexes may allow the identification and quantification of viable but ischemically threatened cerebral tissue amenable to therapeutic interventions in the hyperacute care of stroke patients.

Time course of the apparent diffusion coefficient (ADC) abnormality in human stroke

Diffusion-weighted MRI can rapidly detect acute cerebral ischemic injury as hyperintense signal changes, reflecting a decline in the apparent diffusion coefficient (ADC) of water through brain parenchyma, whereas ADC is elevated in the chronic stage because of increased extracellular water content. To determine the time course of these ADC changes, we analyzed 157 diffusion-weighted MRI studies performed at varying time points from the initial ischemic event from 101 patients. Data were expressed as the relative ADC (rADC), the ratio of lesion to control regions of interest. We observed two phases in the time course of rADC changes in acute human stroke: a significant (p < 0.005) reduction in rADC lasting for at least 96 hours from stroke onset (mean, 58.3% of control; SEM, 1.47) and an increasing trend from reduction to pseudonormalization to elevation of rADC values at later subacute to chronic time points (≥7 days). We suggest that the persistent reduction of rADC within the first four days may reflect ongoing or progressive cytotoxic edema to a greater degree than extracellular edema and cell lysis.

Prefrontal cortex fMRI signal changes are correlated with working memory load

WE investigated whether a nonspatial working memory (WM) task would activate dorsolateral prefrontal cortex (DLPFC) and whether activation would be correlated with WM load. Using functional magnetic resonance imaging we measured regional brain signal changes in 12 normal subjects performing a continuous performance, choice reaction time task that requires WM. A high WM load condition was compared with a non-WM choice reaction time control condition (WM effect) and a low WM load condition (load effect). Significant changes in signal intensity occurred in the DLPFC, frontal motor regions and the intraparietal sulcus (IPS) in both comparisons. These findings support the role of DLPFC and IPS in WM and suggest that signal changes in DLPFC correlate with WM load.

Impact of CT-guided drainage in the treatment of diverticular abscesses : Size matters

OBJECTIVE Our objective was to determine whether abscess size can be used as a discriminating factor to guide management of patients with diverticular abscesses. MATERIALS AND METHODS We performed a word search of our CT database between July 2001 and July 2002 for the CT diagnosis of diverticulitis. CTs were retrospectively reviewed as consensus opinion of two reviewers. CTs were evaluated for presence of an abscess, its location, maximum diameter, and feasibility of percutaneous abscess drainage. Abscesses were categorized into smaller than 3 cm and larger than or equal to 3 cm, and the management of these groups was compared. RESULTS Thirty-one abscesses were noted in 30 (17%) of 181 patients with a CT diagnosis of diverticulitis. Twenty-two (73%) of 30 patients had 23 abscesses, all of which were smaller than 3 cm and were treated and resolved with antibiotics alone (p < 0.001). Eight (36%) of 22 required surgical treatment. Eight (26%) of 31 abscesses had a maximum diameter larger than or equal to 3 cm. Four (50%) of eight patients with abscesses 3.4-4.1 cm were treated with antibiotics alone. Four (50%) of eight abscesses, all larger than 4.1 cm, were treated with CT-guided drainage and one abscess required repeat drainage. After resolution of symptoms, surgery was performed in five (62.5%) of eight of the larger abscesses. CONCLUSION Patients with abscesses smaller than 3 cm in size can be treated with antibiotics alone and, in some cases, as outpatients, and may not uniformly require surgery. This is also likely true for patients with abscesses 3-4 cm in size, although our results in this group were limited by a small sample size. Patients with abscesses larger than or equal to 4 cm can be managed with CT-guided abscess drainage followed by referral for surgical treatment.

Factors associated with conversion to laparotomy in patients undergoing laparoscopic appendectomy.

BACKGROUND Laparoscopic appendectomy (LA) has been increasingly adopted for its advantages over the open technique, but there is a possibility of conversion to open appendectomy (OA) if complications occur or the extent of inflammation prohibits successful dissection. This study aimed to identify the preoperative predictors for conversion from laparoscopic to open appendectomy. STUDY DESIGN Medical records of 705 consecutive patients who underwent surgery for suspected appendicitis were reviewed retrospectively. LA was attempted in 595 patients by 25 different surgeons. Factors evaluated were age, gender, body mass index, previous abdominal surgery, previous appendicitis attack, pain, nausea, vomiting, fever, duration of symptoms, local or diffuse tenderness, leukocyte count and surgeons experience in LA. RESULTS Conversion to OA occurred in 58 patients (9.7%). The most common reason for conversion was dense adhesions due to inflammation, followed by localized perforation and diffuse peritonitis. Based on 261 patients evaluated by CT scan preoperatively, significant factors in the final multivariate analysis associated with conversion to OA were age > or = 65 [Odds ratio (OR) = 3.78, 95% CI:1.11-12.84], diffuse tenderness on physical examination (OR = 11.32, 95% CI: 1.32-96.62), and a surgeon with less experience in LA (< or = 10 operations, OR = 3.38, 95% CI:1.02-11.17). The presence of significant fat stranding associated with fluid accumulation, inflammatory mass or localized abscess in CT scan also significantly increased the possibility of conversion (OR = 5.60, 95% CI:2.48-12.65). CONCLUSIONS Identifying the potential factors for conversion preoperatively may assist the surgeons in making decisions concerning the management of patients with appendicitis and in the judicious use of LA.

Comparison of EPISTAR and T2*-weighted gadolinium-enhanced perfusion imaging in patients with acute cerebral ischemia

Article abstract-Purpose: To compare echo-planar imaging with signal targeting and alternating radiofrequency (EPISTAR), an arterial spin-labeling technique, to a T2 *-weighted gadolinium-enhanced (T2 *-WGE) MR perfusion technique for the evaluation of acute cerebrovascular disease. Method: Twenty-one EPISTAR and T sub 2 *-WGE perfusion studies were performed on 18 patients with the clinical diagnosis of acute stroke (12 men, 6 women, age range 34 to 89 years, mean age 68 years). For qualitative analysis, perfusion studies of both techniques were grouped into categories (hyperperfusion, normal perfusion, delayed perfusion, or absent perfusion) and compared with a Wilcoxon signed rank test. Quantitative analysis was performed using signal intensity measurements in a region of interest that was defined by diffusion-weighted imaging abnormalities. These signal intensity measurements were compared with a mirror region in the contralateral unaffected hemisphere. Signal intensity ratios (infarcted region versus the unaffected contralateral region) were calculated and compared using a paired t test. Results: Qualitative analysis demonstrated agreement between the two techniques in 17 of 21 studies (hyperfusion, n = 3 patients; normal perfusion, n = 3; delayed perfusion, n = 4; and absent perfusion, n = 7). In four studies, the two techniques disagreed when EPISTAR demonstrated absent and T2 *-WGE perfusion demonstrated delayed perfusion (p > 0.05). Quantitative analysis revealed a mean signal intensity ratio of 0.73 +/- 0.79 for the T2 *-WGE perfusion technique and 0.69 +/- 0.68 for the EPISTAR technique (p > 0.05). Conclusion: The noninvasive EPISTAR technique can assess perfusion abnormalities similarly to the T2 *-WGE perfusion technique and may provide a valuable alternative in the diagnosis of acute stroke patients. Differences between the two techniques can be explained by the applied inflow times in the EPISTAR technique. NEUROLOGY 1997;48: 673-679

Cystic Lesions of the Liver

Simple cyst Benign developmental hepatic cyst von Meyenburg complex Caroli disease Adult polycystic liver disease Complex cyst Neoplasm Biliary cystadenoma or cystadenocarcinoma Cystic metastases Hepatocellular carcinoma Cavernous hemangioma Embryonal sarcoma Inflammatory or infectious Abscess Pyogenic Amebic Echinococcal cyst Postraumatic and miscellaneous Pseudocyst Hematoma Biloma Infected or hemorrhagic cysts Cystic liver lesions, or fluid-containing lesions of the liver, are commonly encountered findings on radiologic examinations that may represent a broad spectrum of entities ranging from benign developmental cysts to malignant neoplasms (Table 1). The wide range of pathologic processes that may result in cystic liver lesions can present a difficult diagnostic conundrum. The radiologist must carefully assess such imaging features as location, size, and unifocal or multifocal nature of the cyst or cysts as well as evaluate cyst complexity and associated findings. In addition, because radiologic features of various cystic liver lesions overlap, it is necessary to integrate imaging with clinical and laboratory findings to allow more definitive diagnosis. An important first step in narrowing the differential diagnosis is to determine the presence or absence of complex features in cystic liver lesions. To this end, fluid-containing liver lesions can be grouped broadly into simple or complex cysts. Vachha et al. Cystic Lesions of the Liver

Split-bolus spectral multidetector CT of the pancreas: assessment of radiation dose and tumor conspicuity.

PURPOSE To assess tumor conspicuity and radiation dose with a new multidetector computed tomography (CT) protocol for pancreatic imaging that combines spectral CT and split-bolus injection. MATERIALS AND METHODS This study was approved by the institutional review board and compliant with HIPAA. The requirement for informed consent was waived. One hundred sixty-three consecutive patients referred for possible pancreatic mass underwent CT with either a standard or split-bolus spectral CT protocol depending on scanner availability. Split-bolus spectral CT (CT unit with spectral imaging) combines pancreatic and portal venous phases in a single scan: 70 seconds before CT, 100 mL of contrast material is injected for the portal venous phase followed approximately 35 seconds later by injection of 40 mL of contrast material to boost the pancreatic phase. Bolus tracking after the second bolus initiates scanning 15 seconds after aorta enhancement reaches 280 HU. Images were reconstructed at 60 and 77 keV. The standard protocol (64-detector row unit) included unenhanced and pancreatic and portal venous phase imaging, with a single contrast material injection timed with bolus tracking 15 seconds after aortic enhancement of 300 HU for the pancreatic phase and 32 seconds later for the portal venous phase. Tumor conspicuity (difference in attenuation between tumor and pancreatic parenchyma) and contrast-to-noise ratio (CNR) were determined. Attenuation of aorta, main portal vein, and liver were measured. Patient size and per-examination radiation dose were recorded. The heteroscedastic t test, Fisher exact test, and Mann-Whitney test were used for statistical analysis. RESULTS There were no significant differences in age, weight, and body mass index between patients in the standard CT (46 of 80 patients had lesions) and split-bolus spectral CT (39 of 83 patients had lesions) groups; however, there were significantly more women in the split-bolus group (P = .02). Tumor conspicuity and CNR were higher with the 60-keV split-bolus protocol (89.1 HU ± 56.6 and 8.8 ± 6.2, respectively) than with the pancreatic or portal venous phase of the standard protocol (43.5 HU ± 28.4 and 4.5 ± 3.0, and 51.5 HU ± 30.3 and 5.6 ± 4.0, respectively; P < .01 for all comparisons). Dose-length product was 1112 mGy · cm ± 437 with the standard protocol and 633 mGy · cm ± 105 with the split-bolus protocol (P < .001). CONCLUSION Split-bolus spectral multidetector CT resulted in vascular, liver, and pancreatic attenuation and tumor conspicuity equal to or greater than that with multiphase CT, with a 43% reduction in radiation dose.

Reviewing Imaging Examination Results With a Radiologist Immediately After Study Completion: Patient Preferences and Assessment of Feasibility in an Academic Department

OBJECTIVE The purpose of this study was to assess patient preferences about receiving radiology results and reviewing the images and findings directly with a radiologist after completion of an examination. SUBJECTS AND METHODS A prospective survey of English-speaking outpatients undergoing either nononcologic CT of the chest, abdomen, and pelvis or nonobstetric ultrasound examinations was completed between December 2010 and June 2011. Responses to survey items such as preferences regarding communication of results, knowledge of a radiologist, and anxiety level before and after radiologist-patient consultation were recorded. The average wait time between the end of the imaging examination and the consultation and the duration of consultation were documented. RESULTS Eighty-six patients (43 men, 43 women; mean age, 52 years) underwent 37 CT and 49 ultrasound examinations). Forty-eight patients (56%) identified a radiologist as a physician who interprets images. Before imaging, 70 patients (81%) preferred hearing results from both the ordering provider and the radiologist. This percentage increased to 78 (91%) after consultation (p=0.03). Before consultation, 84 of the 86 patients (98%) indicated they would be comfortable hearing normal results or abnormal results from the person interpreting the examination; the number increased to 85 (99%) after consultation. Eighty-five patients (99%) agreed or strongly agreed that reviewing their examination findings with a radiologist was helpful. Eighty-four patients (98%) indicated they wanted the option of reviewing or always wanted to review future examination findings with a radiologist. After consultation, anxiety decreased in 41 patients (48%), increased in 13 (15%), and was unchanged in 32 (37%) (p=0.0001). The average wait for consultation and the duration of consultation were 9.9 and 10.4 minutes for CT and 1.2 and 7.1 minutes for ultrasound. CONCLUSION Patients prefer hearing examination results from both their ordering provider and the interpreting radiologist. Most patients find radiologist consultation beneficial. Patients are comfortable hearing results from the radiologist, with most displaying decreased anxiety after consultation.

Can radiologist training and testing ensure high performance in CT colonography? Lessons from the national CT colonography trial

OBJECTIVE The objective of this article is to describe the experience of the National CT Colonography Trial with radiologist training and qualification testing at CT colonography (CTC) and to correlate this experience with subsequent performance in a prospective screening study. SUBJECTS AND METHODS Ten inexperienced radiologists participated in a 1-day educational course, during which partial CTC examinations of 27 cases with neoplasia and full CTC examinations of 15 cases were reviewed using primary 2D and 3D search. Subsequently 15 radiologists took a qualification examination composed of 20 CTC cases. Radiologists who did not pass the first qualification examination attended a second day of focused retraining of 30 cases, which was followed by a second qualification examination. The results of the initial and subsequent qualification tests were compared with reader performance in a large prospective screening trial. RESULTS All radiologists took and passed the qualification examinations. Seven radiologists passed the qualification examination the first time it was offered, and eight radiologists passed after focused retraining. Significantly better sensitivities were obtained on the second versus the first examination for the retrained radiologists (difference = 16%, p < 0.001). There was no significant difference in sensitivities between the groups who passed the qualification examination the first time versus those who passed the second time in the prospective study (88% vs 92%, respectively; p = 0.612). In the prospective study, the odds of correctly identifying diseased cases increased by 1.5 fold for every 50-case increase in reader experience or formal training (p < 0.025). CONCLUSION A significant difference in performance was observed among radiologists before formalized training, but testing and focused retraining improved radiologist performance, resulting in an overall high sensitivity across radiologists in a subsequent, prospective screening study.