Helical CT protocols for the abdomen and pelvis: a survey

Feasibility of a single-phase portal venous CT protocol using bolus tracking technique and lean body weight-based contrast media dose

PURPOSE

To evaluate the impact of the use of lean body weight (LBW)-based contrast material (CM) dose and bolus tracking technique on portal venous phase abdominal CT image quality.

MATERIALS AND METHODS

IRB-approved prospective study; informed consent was acquired. In the period July-November 2023, we randomly selected 105 oncologic patients scheduled for a portal venous phase abdominal CT to undergo our experimental protocol (i.e., 0.7 gI/Kg of LBW CM administration and bolus tracking on the liver). Included patients had performed a "standard" portal venous phase abdominal CT (i.e., 0.6 gI/Kg of total body weight (TBW) contrast material administration and 70 s fixed delay) on the same scanner within the previous 12 months. One reader evaluated CT images measuring liver, portal vein, kidney cortex, and spleen attenuation; values were normalized to paraspinal muscles.

RESULTS

Median administered contrast dose (350 mgI/mL CM) was 99 mL (IQR: 81-115 mL) using the experimental protocol and 110 mL (IQR: 100-120 mL) using the standard one (p < 0.0001). Median acquisition delay using the experimental protocol was 65" (IQR 59-73"). Median normalized hepatic enhancement was significantly higher using the experimental protocol (1.97, IQR: 1.83-2.47 vs. 1.86, IQR: 1.58-2.11; p < 0.0001). Median normalized portal vein enhancement was significantly higher using the experimental protocol (3.43, IQR: 2.73-4.04 vs. 2.91, IQR: 2.58-3.41; p < 0.0001). No statistically significant differences were found in the kidneys' cortex and aorta normalized enhancement (p > 0.05).

CONCLUSION

The combination of LBW-based CM dose administration and bolus tracking allows a significant CM dose reduction and a significant liver and portal vein enhancement increase.

CLINICAL RELEVANCE STATEMENT

Lean body weight-based contrast material (CM) dose administration and bolus tracking technique in portal venous phase CT scans overcome differences in body composition and hemodynamics, improving reproducibility. It allows a significant CM dose reduction with increased liver and portal vein enhancement.

KEY POINTS

Lean body weight (LBW)-based contrast material (CM) dosing could be superior to total body weight dosing. Portal venous phase CT with a liver bolus tracking technique improved liver and spleen enhancement with a reduced contrast dose. The combination of LBW-based CM dosing and liver bolus tracking technique enables more "customized" CT examinations.

Rapid MRI Abdomen for Assessment of Clinically Suspected Acute Appendicitis in the General Adult Population: a Systematic Review

OBJECTIVES

To perform a systematic review on the use of magnetic resonance imaging (MRI) of the abdomen to evaluate clinically suspected appendicitis in the general adult population. We examined the diagnostic accuracy, the reported trends of MRI use, and the factors that affect the utility of MRI abdomen, including study duration and cost-benefits.

METHODS

We conducted a systematic literature search on PubMed, MEDLINE, Embase, Web of Science, and Cochrane Library databases. We enrolled primary studies investigating the use of MRI in diagnosing appendicitis in the general adult population, excluding studies that predominantly reported on populations not representative of typical adult appendicitis presentations, such as those focusing on paediatric or pregnant populations.

RESULTS

Twenty-seven eligible primary studies and 6 secondary studies were included, totaling 2,044 patients from eight countries. The sensitivity and specificity of MRI for diagnosing appendicitis were 96% (95% CI: 93-97%) and 93% (95% CI: 80-98%), respectively. MRI can identify complicated appendicitis and accurately propose alternative diagnoses. The duration of MRI protocols in each primary study ranged between 2.26 and 30 minutes, and only one study used intravenous contrast agents in addition to the non-contrast sequences. Decision analysis suggests significant benefits for replacing computed tomography (CT) with MRI and a potential for cost reduction. Reported trends in MRI usage showed minimal utilisation in diagnostic settings even when MRI was available.

CONCLUSIONS

MRI accurately diagnoses appendicitis in the general adult population and improves the identification of complicated appendicitis or alternative diagnoses compared to other modalities using a single, rapid investigation.

Imaging of Gastrointestinal Tract Ailments

Gastrointestinal (GI) disorders comprise a diverse range of conditions that can significantly reduce the quality of life and can even be life-threatening in serious cases. The development of accurate and rapid detection approaches is of essential importance for early diagnosis and timely management of GI diseases. This review mainly focuses on the imaging of several representative gastrointestinal ailments, such as inflammatory bowel disease, tumors, appendicitis, Meckel's diverticulum, and others. Various imaging modalities commonly used for the gastrointestinal tract, including magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT), and photoacoustic tomography (PAT) and multimodal imaging with mode overlap are summarized. These achievements in single and multimodal imaging provide useful guidance for improved diagnosis, staging, and treatment of the corresponding gastrointestinal diseases. The review evaluates the strengths and weaknesses of different imaging techniques and summarizes the development of imaging techniques used for diagnosing gastrointestinal ailments.

High Pitch Helical CT Reconstruction

To avoid severe limited-view artifacts in reconstructed CT images, current multi-row detector CT (MDCT) scanners with a single x-ray source-detector assembly need to limit table translation speeds such that the pitch p (viz., normalized table translation distance per gantry rotation) is lower than 1.5. When , it remains an open question whether one can reconstruct clinically useful helical CT images without severe artifacts. In this work, we show that a synergistic use of advanced techniques in conventional helical filtered backprojection, compressed sensing, and more recent deep learning methods can be properly integrated to enable accurate reconstruction up to p=4 without significant artifacts for single source MDCT scans.

The role of unenhanced phase of the liver in the scanning protocol of metastatic breast cancer: implications for sensitivity, response evaluation and size measurement

Background

To analyse if performing unenhanced CT of the liver aids in the evaluation of metastatic lesions, response assessment or alter the size of the lesions, compared with portal phase alone, in patients with hepatic metastases from breast carcinoma.

Patients and methods

One-hundred and fifty-three CT scans of 36 women were included. Scans consisted of unenhanced, arterial and portal delayed phases of the liver. Two readers sorted which phase was best for visualization of metastases, evaluated the number of lesions detected in each phase, selected the best phase for assessment of response in two consecutive scans, and measured one target lesion in all the phases. Χ2 was used to compare differences among phases and paired t test for measurement differences.

Results

Unenhanced, arterial and portal phases were considered better phases by readers 1/2 in 68/67%, 27/28% and 69/70%, and some lesions were missed in 2%, 11% and 7%, respectively. Sensitivity was significantly better for unenhanced and portal phases compared to arterial phase. Comparison between consecutive scans was considered better in unenhanced (80/79%), followed by portal (70/69%) and arterial phases (31/31%). Maximum diameter of target lesions was 15% greater in unenhanced phase (p < 0.001).

Conclusions

Portal and unenhanced phases of the liver allow better detection and delineation of metastatic hepatic lesions from breast carcinoma. In most cases, unenhanced CT is the best phase to assess response and provides the largest diameter. Therefore, we recommend the use of unenhanced CT in the evaluation of patients with breast carcinoma and suspected or known hepatic metastatic disease.

Impact of low-energy CT imaging on selection of positive oral contrast media concentration

OBJECTIVES

To determine to what extent low-energy CT imaging affects attenuation of gastrointestinal tract (GIT) opacified with positive oral contrast media (OCM). Second, to establish optimal OCM concentrations for low-energy diagnostic CT exams.

METHODS

One hundred patients (38 men and 62 women; age 62 ± 11 years; BMI 26 ± 5) with positive OCM-enhanced 120-kVp single-energy CT (SECT), and follow-up 100-kVp acquisitions (group A; n = 50), or 40-70-keV reconstructions from rapid kV switching-single-source dual-energy CT (ssDECT) (group B; n = 50) were included. Luminal attenuation from different GIT segments was compared between exams. Standard dose of three OCM and diluted solutions (75%, 50%, and 25% concentrations) were introduced serially in a gastrointestinal phantom and scanned using SECT (120, 100, and 80 kVp) and DECT (80/140 kVp) acquisitions on a ssDECT scanner. Luminal attenuation was obtained on SECT and DECT images (40-70 keV), and compared to 120-kVp scans with standard OCM concentrations.

RESULTS

Luminal attenuation was higher on 100-kVp (328 HU) and on 40-60-keV images (410-924 HU) in comparison to 120-kVp scans (298 HU) in groups A and B (p < 0.05). Phantom: There was an inverse correlation between luminal attenuation and X-ray energy, increasing up to 527 HU on low-kVp and 999 HU on low-keV images (p < 0.05). 25% and 50% diluted OCM solutions provided similar or higher attenuation than 120 kVp, at low kVp and keV, respectively.

CONCLUSIONS

Low-energy CT imaging increases the attenuation of GIT opacified with positive OCM, permitting reduction of 25%-75% OCM concentration.

Evaluating the Patient with Right Lower Quadrant Pain

Right lower quadrant pain is one of the most common indications for imaging evaluation of the abdomen in the emergency department setting. This article reviews important imaging findings associated with acute appendicitis as well as major differential considerations including: mesenteric adenitis, Meckel diverticulum, neutropenic colitis, right-sided diverticulitis, epiploic appendagitis, omental infarction, and inflammatory bowel diseaseRight lower quadrant pain is one of the most common indications for imaging evaluation of the abdomen in the emergency department setting. This article reviews important imaging findings associated with acute appendicitis as well as major differential considerations including: mesenteric adenitis, Meckel diverticulum, neutropenic colitis, right-sided diverticulitis, epiploic appendagitis, omental infarction, and inflammatory bowel disease.

An evaluation of the use of oral contrast media in abdominopelvic CT

OBJECTIVES

To evaluate the diagnostic efficacy of different oral contrast media (OCM) for abdominopelvic CT examinations performed for follow-up general oncological indications. The objectives were to establish anatomical image quality criteria for abdominopelvic CT; use these criteria to evaluate and compare image quality using positive OCM, neutral OCM and no OCM; and evaluate possible benefits for the medical imaging department.

METHODS

Forty-six adult patients attending a follow-up abdominopelvic CT for general oncological indications and who had a previous abdominopelvic CT with positive OCM (n = 46) were recruited and prospectively placed into either the water (n = 25) or no OCM (n = 21) group. Three radiologists performed absolute visual grading analysis (VGA) to assess image quality by grading the fulfilment of 24 anatomical image quality criteria.

RESULTS

Visual grading characteristics (VGC) analysis of the data showed comparable image quality with regards to reproduction of abdominal structures, bowel discrimination, presence of artefacts, and visualization of the amount of intra-abdominal fat for the three OCM protocols.

CONCLUSION

All three OCM protocols provided similar image quality for follow-up abdominopelvic CT for general oncological indications.

KEY POINTS

• Positive oral contrast media are routinely used for abdominopelvic multidetector computed tomography • Experimental study comparing image quality using three different oral contrast materials • Three different oral contrast materials result in comparable CT image quality • Benefits for patients and medical imaging department.

Multidetector computed tomography for the assessment of adnexal mass: is unenhanced CT scan necessary?

OBJECTIVE

To compare the diagnostic performance and radiation dose between contrast-enhanced CT (ECT) alone, and combined unenhanced and contrast-enhanced CT (UE + ECT) for the assessment of adnexal mass.

MATERIALS AND METHODS

This retrospective study was approved by the Institutional Review Board. A total of 146 consecutive patients (mean age, 41.1 years) who underwent preoperative unenhanced and contrast-enhanced multidetector CT of the pelvis and had adnexal masses found at surgery were included. Two readers independently evaluated the likelihood of adnexal malignancy on a 5-point scale on two different imaging datasets (ECT alone and UE + ECT). The area under the receiver operating characteristic curve (AUC) was used to evaluate diagnostic performance. Radiation dose to patients was calculated by the volume CT dose index (CTDIvol) and the dose length products (DLP) on each dataset.

RESULTS

Of the total 178 adnexal masses, 133 masses were benign and 45 masses were malignant. For both readers, there is no significant difference of AUC values between ECT alone and UE + ECT for the detection of adnexal malignancy (reader 1, 0.93 vs. 0.95; reader 2, 0.92 vs. 0.91) (p > 0.05). The mean CTDIvol (12.6 ± 2.2 mGy) and DLP (641.2 ± 137.2 mGy) of ECT alone was significantly lower than the mean CTDIvol (21.5 ± 2.7 mGy) and DLP (923.6 ± 158.8 mGy) of UE + ECT (p < 0.0001).

CONCLUSION

The use of unenhanced CT scan in addition to contrast-enhanced CT scan does not improve the detection of adnexal malignancy, but increases radiation exposure.

Adult small bowel obstruction

BACKGROUND

Small bowel obstruction (SBO) is a clinical condition that is often initially diagnosed and managed in the emergency department (ED). The high rates of potential complications that are associated with an SBO make it essential for the emergency physician (EP) to make a timely and accurate diagnosis.

OBJECTIVES

The primary objective was to perform a systematic review and meta-analysis of the history, physical examination, and imaging modalities associated with the diagnosis of SBO. The secondary objectives were to identify the prevalence of SBO in prospective ED-based studies of adult abdominal pain and to apply Pauker and Kassirer's threshold approach to clinical decision-making to the diagnosis and management of SBO.

METHODS

MEDLINE, EMBASE, major emergency medicine (EM) textbooks, and the bibliographies of selected articles were scanned for studies that assessed one or more components of the history, physical examination, or diagnostic imaging modalities used for the diagnosis of SBO. The selected articles underwent a quality assessment by two of the authors using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Data used to compile sensitivities and specificities were obtained from these studies and a meta-analysis was performed on those that examined the same historical component, physical examination technique, or diagnostic test. Separate information on the prevalence and management of SBO was used in conjunction with the meta-analysis findings of computed tomography (CT) to determine the test and treatment threshold.

RESULTS

The prevalence of SBO in the ED was determined to be approximately 2% of all patients who present with abdominal pain. Having a previous history of abdominal surgery, constipation, abnormal bowel sounds, and/or abdominal distention on examination were the best history and physical examination predictors of SBO. X-ray was determined to be the least useful imaging modality for the diagnosis of SBO, with a pooled positive likelihood ratio (+LR) of 1.64 (95% confidence interval [CI] = 1.07 to 2.52). On the other hand, CT and magnetic resonance imaging (MRI) were both quite accurate in diagnosing SBO with +LRs of 3.6 (5- to 10-mm slices, 95% CI = 2.3 to 5.4) and 6.77 (95% CI = 2.13 to 21.55), respectively. Although limited to only a select number of studies, the use of ultrasound (US) was determined to be superior to all other imaging modalities, with a +LR of 14.1 (95% CI = 3.57 to 55.66) and a negative likelihood ratio (-LR) of 0.13 (95% CI = 0.08 to 0.20) for formal scans and a +LR of 9.55 (95% CI = 2.16 to 42.21) and a -LR of 0.04 (95% CI = 0.01 to 0.13) for beside scans. Using the CT results of the meta-analysis for the 5- to 10-mm slice subgroup as well as information on intravenous (IV) contrast reactions and nasogastric (NG) intubation management, the pretest probability threshold for further testing was determined to be 1.5%, and the pretest probability threshold for beginning treatment was determined to be 20.7%.

CONCLUSIONS

The potentially useful aspects of the history and physical examination were limited to a history of abdominal surgery, constipation, and the clinical examination findings of abnormal bowel sounds and abdominal distention. CT, MRI, and US are all adequate imaging modalities to make the diagnosis of SBO. Bedside US, which can be performed by EPs, had very good diagnostic accuracy and has the potential to play a larger role in the ED diagnosis of SBO. More ED-focused research into this area will be necessary to bring about this change.

Optimised z-axis coverage at multidetector-row CT in adults suspected of acute appendicitis

OBJECTIVE

To compare diagnostic performances of two reduced z-axis coverages to full coverage of the abdomen and pelvis for the diagnosis of acute appendicitis and alternative diseases at unenhanced CT.

METHODS

This study included 152 adults suspected of appendicitis who were enrolled in two ethical committee-approved previous prospective trials. Based on scans covering the entire abdomen and pelvis (set L), two additional sets of images were generated, each with reduced z-axis coverages: (1) from the top of the iliac crests to the pubis (set S) and (2) from the diaphragmatic crus to the pubis (set M). Two readers independently coded the visualisation of the appendix, measured its diameter and proposed a diagnosis (appendicitis or alternative). Final diagnosis was based on surgical findings or clinical follow-up. Fisher exact and McNemar tests and logistic regression were used.

RESULTS

46 patients had a definite diagnosis of appendicitis and 53 of alternative diseases. The frequency of appendix visualisation was lower for set S than set L for both readers (89% and 84% vs 95% and 91% by Readers A and B, respectively; p=0.021 and 0.022). The probability of giving a correct diagnosis was lower for set S (68%) than set L (78%; odds ratio, 0.611; p=0.008) for both readers, without significant difference between sets L and M (77%, p=0.771); z-axis coverage being reduced by 25% for set M.

CONCLUSION

Coverage from diaphragmatic crus to pubis, but not focused on pelvis only, can be recommended in adults suspected of appendicitis.

ADVANCES IN KNOWLEDGE

In suspected appendicitis, CT-coverage can be reduced from diaphragmatic crus to pubis.

Beyond appendicitis: common and uncommon gastrointestinal causes of right lower quadrant abdominal pain at multidetector CT

Right lower quadrant abdominal pain is one of the most common causes of a patient visit to the emergency department. Although appendicitis is the most common condition requiring surgery in patients with abdominal pain, right lower quadrant pain can be indicative of a vast list of differential diagnoses and is thus a challenge for clinicians. Other causes of right lower quadrant pain beyond appendicitis include inflammatory and infectious conditions involving the ileocecal region; diverticulitis; malignancies; conditions affecting the epiploic appendages, omentum, and mesentery; and miscellaneous conditions. Multidetector computed tomography (CT) has emerged as the modality of choice for evaluation of patients with several acute traumatic and nontraumatic conditions causing right lower quadrant pain. Multidetector CT is an extremely useful noninvasive method for diagnosis and management of not only the most common causes such as appendicitis but also less common conditions.

Computed tomography findings in diseases of the adrenal gland

The adrenal gland is a common site of disease, with an abnormality prevalence as high as 9% in autopsy series. With the increasing use of CT, adrenal lesions are frequently found in the daily practice of radiology and are diagnosed in up to 5% of CT examinations performed for varied reasons. Imaging features on CT can establish a specific diagnosis of many of these lesions, including myelolipoma, hematoma and cysts. Once a diagnostic dilemma, now adenomas can be accurately diagnosed using unenhanced CT, chemical shift magnetic resonance imaging and CT contrast washout analysis. Because the adrenal gland is also a frequent site of metastasis, recent literature has focused on imaging characterization of adrenal masses for differentiation of adenomas from metastases. In patients without known malignancy, most adrenal lesions are benign and a specific diagnosis can now be made on the basis of imaging features. It is important to understand the prevalence of adrenal abnormalities because the gland is a common site of disorders, and the increased use of cross-sectional imaging has increased the frequency of detection of adrenal lesions. The prevalence of disease is important in predicting the risk of malignancy when an adrenal mass is discovered in a patient without known cancer. Detection of adrenal gland diseases has increased substantially with the advent and widespread use of imaging techniques. Although several imaging modalities can be used, CT has a central role in both detection and differential diagnosis of an adrenal lesion. The aim of this article is to review the CT findings of adrenal gland diseases.

Comparison of 2 different protocols for ingestion of low-attenuating oral contrast agent for multidetector computed tomography of the abdomen

OBJECTIVE

To evaluate 2 different oral contrast application protocols concerning degree of intestinal contrast filling and distension in multidetector computed tomography.

METHODS

Examinations of 260 patients were retrospectively analyzed. Group 1 (n = 205) was prepared with 1000 mL of water with 28 g of dissolved mannitol which was ingested for 1 hour; group 2 (n = 55) was prepared with 2000 mL of water containing 56 g of mannitol which was ingested for 2 hours. Small intestine was divided into 4 quadrants; colon was divided into 4 segments. Contrast filling and distension of bowel loops were graded with a 3-point scale and compared using chi2 testing.

RESULTS

Besides the right upper quadrant, no significant differences in contrast filling and distention were found for small bowel segments. Colonic segments were significantly better contrast filled and distended in group 2 (0.001 < P < 0.025).

CONCLUSIONS

A higher amount of water with 28 g/L of mannitol and a prolonged ingestion of oral contrast media result in significantly better contrast filling and bowel distension in the ileocecal region, the colon, and the rectum.

Current Concepts in Imaging of Appendicitis

Appendicitis is the most common cause of acute abdominal pain requiring surgery. Early diagnosis is crucial to the success of therapy. CT and ultrasound are widely recognized as very useful in the timely diagnosis of appendicitis. MR imaging is emerging as an alternative to CT in pregnant patients and in patients who have an allergy to iodinated contrast material. This article reviews the current imaging methods and diagnostic features of appendicitis.

MDCT for suspected pulmonary embolism: multi-institutional survey of 16-MDCT data acquisition protocols

The purpose of this study was to determine the extent to which a consensus exists on multidetector row computed tomography (MDCT) protocol parameters for suspected pulmonary embolism (PE). In August of 2004, a questionnaire addressing a number of body MDCT protocols was mailed to 99 fellows of the Society of Computed Body Tomography, representing a total of 46 institutions. In May 2005, this was followed up with a second mailing. The survey requested details pertaining to protocols for the most advanced MDCT scanner in the department. The overall survey response rate of 37% (17/46) yielded 15 protocols for 16-MDCT imaging of suspected PE. This data was tabulated and revealed a consensus for the use of bolus tracking, rapid contrast infusion, caudo-cranial scanning, the narrowest detector row collimation, and thin (<2 mm) reconstruction sections. However, contrast infusion timing, contrast concentration, and implementation of radiation dose modulation were variable. This compilation of protocols reflects recently published studies advocating the use of narrow acquisition collimation and reconstruction sections for MDCT of suspected PE. Future studies are necessary to elucidate the optimal intravenous contrast infusion parameters and further assess the efficacy of reduced radiation dose protocols.

Right Lower Quadrant Pain: Value of the Nonvisualized Appendix in Patients at Multidetector CT

PURPOSE

To retrospectively determine the value of the nonvisualized appendix at multidetector computed tomography (CT) in patients with acute right lower quadrant pain in whom appendicitis was a consideration.

MATERIALS AND METHODS

Institutional review board approval was obtained for this HIPAA-compliant study, with waiver of informed consent. Records were retrospectively reviewed in patients who presented to the emergency department between April 29 and October 31, 2003, with right lower quadrant pain. Scanning was performed with the same eight-detector row CT scanner by using oral and (unless contraindicated) intravenous contrast agents, and transverse and coronal reformations were obtained. Two radiologists prospectively evaluated all scans at the time of the examination and rendered a consensus opinion. Clinical follow-up of at least 3 months' duration was performed retrospectively for patients whose appendix was not visualized to determine whether appendicitis had developed. Statistical analysis and calculation of percentages with confidence intervals (CIs) were performed.

RESULTS

Of the 400 consecutive patients who underwent multidetector CT, 132 (33.0%) were male and 268 (67.0%) were female. Eighty patients (20.0%) had acute appendicitis and 79 (19.8%) had another cause for abdominal pain. A normal appendix with no other cause for pain was seen in 182 patients (45.5%). In 59 patients (14.8%), the appendix was not visualized. Of these 59 patients, 50 had adequate follow-up. Clinical follow-up was uneventful in 49 of these 50 patients. Thus, on otherwise normal multidetector CT scans in patients suspected of having acute appendicitis, nonvisualization of the appendix was negative for appendicitis in 98% (95% CI: 71%, 100%) of cases. Conversely, when the appendix was seen at multidetector CT and was abnormal, appendicitis was present in 95% (95% CI: 72%, 100%) of cases.

CONCLUSION

In patients with right lower quadrant pain, a nonvisualized appendix at multidetector CT reliably excludes acute appendicitis.

Multidetector Computed Tomography for Suspected Appendicitis

PURPOSE

To determine acquisition protocol parameters currently used by different institutions for appendiceal multidetector computed tomography (MDCT).

MATERIALS AND METHODS

A survey inquiring about multiple MDCT protocols was mailed to 99 fellows of the Society of Computed Body Tomography in August of 2004, with a second mailing sent in May 2005. A total of 46 institutions or hospitals are represented by these Society of Computed Body Tomography fellows. Details pertaining to protocols for the most advanced MDCT scanner in the department were requested.

RESULTS

The overall survey response rate was 17 of 46 or 37%. Fifteen protocols using 16-MDCT for suspected appendicitis were collected and tabulated. Parameters that are similar across institutions include a nonfocused acquisition using oral and intravenous contrast. Detector configuration is even divided between submillimeter and greater than 1 mm, and the most common reconstruction section thickness is 5 mm.

CONCLUSIONS

Contrast administration and anatomical coverage are quite consistent across this set of protocols. However, future appendiceal MDCT research will need to address the most efficacious detector row collimation, reconstruction section thickness and interval, and the diagnostic capacity of protocols implementing dose reduction measures.

Computed Tomography Features of Nonalcoholic Steatohepatitis With Histopathologic Correlation

OBJECTIVE

This study was conducted to describe the computed tomography (CT) features of nonalcoholic steatohepatitis (NASH) and to evaluate if the CT features could be used to diagnose and stage NASH.

METHODS

From 1994 until 2004, pathology records revealed 68 patients with NASH. Of these, 12 patients underwent CT scans before (n=6), on the same day as (n=3), or after (n=3) a liver biopsy. Using the same database, 9 patients with steatosis alone evaluated with a CT scan before (n=2), on the same day as (n=3), or after (n=4) the liver biopsy were selected as a control group. Two radiologists measured liver attenuation (compared with spleen) and assessed the pattern of steatosis, craniocaudal liver span, caudate-to-right lobe ratio, preportal space distance, and presence of porta hepatis lymph nodes and ascites. Biopsy specimens were assessed by a pathologist, and the degree of necroinflammatory activity, steatosis, and fibrosis was determined. Histopathologic and CT findings were compared between patients with NASH and patients with steatosis alone using the Mann-Whitney U test and Fisher exact test.

RESULTS

In patients with NASH, the mean liver-to-spleen attenuation ratio was 0.66 (range: 0.1-1.1). Steatosis was diffuse (n=9), geographic or nonlobar (n=2), or diffuse with an area of focal sparing (n=1). The liver craniocaudal span varied from 17.5 to 25.5 cm (mean=21.4 cm), and hepatomegaly was present in 11 (91.7%) patients. The caudate-to-right-lobe ratio (mean=0.43) and preportal space (mean=4.5 mm) were normal in all cases. Porta hepatis lymph nodes were present in 7 (58.3%) patients; their mean dimensions were 16 mmx11 mm. Ascites was absent in all patients. On histopathology, the degree of necroinflammatory activity was mild (n=9), moderate (n=1), or severe (n=2). The degree of steatosis was 33% to 66% (n=5) or >67% (n=7). All but 3 patients had fibrosis; 6 had focal nonbridging fibrosis, 1 had multifocal nonbridging fibrosis, and 2 had bridging fibrosis. There was a significant correlation between the degree of steatosis on pathologic examination and the liver-to-spleen attenuation ratio on CT (P=0.048). The severity of inflammation and stage of fibrosis on pathologic examination did not correlate with the CT features. Among patients with steatosis alone, the mean liver-to-spleen attenuation ratio was 0.80 (range: 0.3-1.2); the craniocaudal liver span varied from 12 to 20 cm (mean=16 cm); hepatomegaly was present in 2 (22.2%) patients; the caudate-to-right lobe ratio was normal in all patients, with a mean of 0.36 (range: 0.22-0.47); the preportal space distance was enlarged in 2 cases (mean=7.5 mm, range: 1-16 mm); porta hepatis lymph nodes were present in 7 (77.8%) patients, and their mean dimensions were 11 mmx8 mm (large axis range: 6-19 mm, short axis range: 4-14 mm); and no patient had ascites. There was a significant difference in the craniocaudal liver span between patients with NASH (mean=21 cm) and patients with steatosis (mean=16 cm) (P<0.05). The caudate-to-right-lobe ratio was also significantly different between patients with NASH (mean=0.43) and patients with steatosis (mean=0.36) (P<0.05). There were no significant differences in liver-to-spleen attenuation ratios, measurements of preportal space, or the presence of porta hepatic lymph nodes.

CONCLUSION

The CT features of NASH include steatosis, hepatomegaly, and porta hepatis lymph nodes, and the liver-to-spleen attenuation ratio correlated with the degree of steatosis on histopathology. Patients with NASH had a greater liver span and increased caudate-to-right-lobe-ratio compared with patients with steatosis alone.

Is direct radiologist supervision of abdominal computed tomography (CT) scans necessary?

AIM

To determine the effect of direct radiological supervision of patients attending for abdominal CT by assessing the frequency of protocol alteration subsequent to radiologist review of the images obtained.

MATERIALS AND METHODS

A prospective questionnaire-based observational study was performed of 187 consecutive patients undergoing abdominal CT. The CT protocol was determined by a radiologist in advance, with reference to the request form. Any subsequent change in the prescribed study that was contingent on radiologist review of the images obtained was documented on the questionnaire. Comparison was made with a second (control) group of 100 patients undergoing cranial CT.

RESULTS

A protocol change was undertaken following radiologist review of the CT images of 17 (9%) of the group undergoing abdominal CT, compared with 14 (14%) of the group undergoing cranial CT. In the abdominal CT group, further scanning was performed for lesion characterization, to guide a subsequent interventional procedure, because of inadequate anatomical coverage or to evaluate an unexpected lung tumour. There was no significant difference in proportions between the two groups (p=0.23).

CONCLUSION

When abdominal and cranial CT studies were compared, there was no significant difference in the proportion of studies requiring a change in the prescribed protocol following radiologist review of the images obtained. There was no evidence to suggest that abdominal CT was any less suited to protocol.

Differentiating a chronic hyperplastic mass from pancreatic cancer: a challenge remaining in multidetector CT of the pancreas

A multitude of clinical symptoms originate from pancreatic inflammatory or neoplastic processes due to their highly complex composition, function, and anatomic relationships to adjacent organs as well as the heterogeneous patterns of vascular perfusion and neural innervation of the pancreatic gland which complicate an early and precise diagnosis. Whereas early assessment of inflammatory or neoplastic pancreatic processes is a prerequisite for a successful curative approach, the classical radiologic signs of chronic pancreatitis and pancreatic carcinoma show significant similarities. This article provides an overview of the pathogenesis and imaging findings in chronic pancreatitis and pancreatic cancer, including some new approaches for visualizing the subtle but distinct differences between these two entities.

The acute right lower quadrant

Acute right lower quadrant pain is a nonspecific but common clinical complaint. Appendicitis is the most common cause of acute right lower quadrant pain and CT has become the most reliable imaging method in the evaluation of these patients. Although there is controversy regarding the best way to perform CT in this setting, oral and i.v. contrast-enhanced CT remains the most commonly used technique. CT with oral and i.v. contrast material facilitates diagnosis of appendicitis and the numerous other entities that may cause right lower quadrant pain.

Multislice helical CT of the pancreas and spleen

Multislice helical CT (MSCT) with its multidetector technology and faster rotation times, has led to new dimensions in spatial and temporal resolution in CT imaging. In contrast to single-slice CT, smaller slice collimations can be applied that lead to almost isotropic voxels and allow high quality multiplanar and 3-D image reconstructions. The high speed of multislice CT can be used to reduce the time needed to cover a given volume, to increase the spatial resolution along the z-axis by applying thinner slice collimations, and to cover longer anatomic volumes. The speed of MSCT allows organ imaging in clearly defined perfusion phases, e.g. the arterial, parenchymal, and portal venous perfusion phases. Contrast agents with higher iodine concentrations (400 mg iodine per ml compared with 300 mg iodine per ml) lead to higher contrast enhancement of the pancreas (arterial+portal venous phases), the kidneys (arterial+portal venous phases), the spleen (arterial phase), the wall of the small intestine (arterial+portal venous phases), the larger and smaller arteries (arterial phase), and the portal vein (portal venous phase). All of these advancements lead to improved visualization of small structures and of various pathologies, such as pancreatic tumors, liver metastases, vessel infiltration, and vascular diseases.

Helical CT of the body: a survey of techniques used for pediatric patients

OBJECTIVE

Our purpose was to assess the current practice of helical CT of the body in pediatric patients through a survey of members of the Society for Pediatric Radiology.

MATERIALS AND METHODS

The survey consisted of 53 questions addressing demographics; oral and IV contrast media administration; and age-based (age groups, 0-4, 5-8, 9-12, and 13-16 years) scanning parameters, including tube current, kilovoltage, slice thickness, and pitch. Respondents accessed the Web-based survey via a uniform resource locator link included in an e-mail to the members of the Society for Pediatric Radiology automatically sent every week for three weeks. Survey results were automatically tabulated.

RESULTS

Most (83%) respondents were based in children's or university hospitals at the time of the survey. Virtually all (99%) used nonionic IV contrast material. For body scanning, 21-32% used less than 2.0 mL/kg of body weight; we found the percentage of respondents who used power injection to be approximately equal to the percentage of those who used manual injection (47%). Age-based adjustments are made; however, 11-26% of CT examinations of children younger than 9 years are performed using more than 150 mA. A notable finding was that 20-25% of respondents did not know specific parameters used for their examinations.

CONCLUSION

Although pediatric radiologists do practice age-adjusted helical CT, variable scanning techniques are used, potentially delivering high doses of radiation. Information on current practices in helical CT of the body in children can serve as a foundation for future recommendations and investigations into helical CT in pediatric patients.

Effect of multislice CT technology on scanner productivity

OBJECTIVE

In this study we analyzed the impact of multislice CT technology on scanner productivity in a tertiary care medical center.

MATERIALS AND METHODS

We compared the productivity of two diagnostic CT scanners during the periods January 1 to August 31, 1999 (when both scanners had single-slice CT capability) and January 1 to August 31, 2000 (when one of these scanners was replaced with a multislice CT scanner). The scanners were used primarily for outpatients during the day shift and for inpatients during the evening shift; the demand for CT services was stable. For this analysis, we queried the hospital's radiology information system and identified the number of CT examinations performed during the two analysis periods. We also determined the examination mix, including proportion of enhanced and unenhanced examinations and the anatomic region examined, to ensure comparable patient populations. Statistical analysis was performed.

RESULTS

The number of CT studies performed on the two scanners increased by 1772 (13.1%) from 13,548 (before multislice CT) to 15,320 (when multislice CT was available). The number of examinations enhanced with contrast media increased from 52% to 65%. Between 9:00 A.M. and 5:00 P.M., the number of CT examinations was similar on the single-slice scanners in the two periods (p > 0.05). However, in the period when multislice CT was available, the number of studies performed on the multislice scanner (5919) was 51.9% higher than those performed using the single-slice scanner (3896) (p < 0.0006).

CONCLUSION

Using a multislice CT scanner leads to an increase in CT productivity, even though multislice studies are performed using more complicated protocols than are used on a single-slice CT scanner.

Helical CT of the body: are settings adjusted for pediatric patients?

OBJECTIVE

Our objective was to determine whether adjustments related to patient age are made in the scanning parameters that are determinants of radiation dose for helical CT of pediatric patients.

SUBJECTS AND METHODS

This prospective investigation included all body (chest and abdomen) helical CT examinations (n = 58) of neonates, infants, and children (n = 32) referred from outside institutions for whom radiologic consultation was requested. Information recorded included tube current, kilovoltage, collimation, and pitch. Examinations were arbitrarily grouped on the basis of the individual's age: group A, 0-4 years; group B, 5-8 years; group C, 9-12 years; and group D, 13-16 years old.

RESULTS

Thirty-one percent (18/58) of the CT examinations were of the chest and 69% (40/58) were of the abdomen. Sixteen percent (9/58) of the CT examinations were combined chest and abdomen. In 22% (2/9) of these combined examinations, tube current was adjusted between the chest and abdomen CT; in one (11%) of these examinations, the tube current was higher for the chest than for the abdomen portion of the CT examination. The mean tube current setting for chest was 213 mA and was 206 mA for the abdomen, with no evident adjustment in tube current based on the age of the patient. Fifty-six percent of the examinations of neonates, infants, or children 8 years old or younger were performed at a collimation of greater than 5 mm and 53% of these examinations were performed using a pitch of 1.0.

CONCLUSION

Pediatric helical CT parameters are not adjusted on the basis of the examination type or the age of the child. In particular, these results suggest that pediatric patients may be exposed to an unnecessarily high radiation dose during body CT.