Patrick D. McLaughlin

Diagnostic Accuracy of Computed Tomography Using Lower Doses of Radiation for Patients With Crohn's Disease

BACKGROUND & AIMS Magnetic resonance and ultrasonography have increasing roles in the initial diagnosis of Crohns disease, but computed tomography (CT) with positive oral contrast agents is most frequently used to identify those with acute extramural complications. However, CT involves exposure of patients to radiation. We prospectively compared the diagnostic accuracy of low-dose CT (at a dose comparable to that used to obtain an abdominal radiograph) with conventional-dose CT in patients with active Crohns disease. METHODS Low and conventional dose CT of the abdomen and pelvis were acquired from 50 patients with Crohns disease, referred from an inflammatory bowel disease service (20 male; median age, 34 years). Acute complications of Crohns disease were suspected. Iterative reconstruction was performed on all CT datasets to facilitate dose reduction. Three radiologists reviewed the low-dose CT images before the conventional-dose CT images. RESULTS The median effective dose (interquartile range) of radiation for the low-dose CT was reduced by 72% from that of conventional CT: from 3.5 mSv (3-5.08 mSv) to 0.98 mSv (0.77-1.42 mSv) (P < .001). As expected, the quality indexes of the low-dose images were inferior to those of the conventional-dose images, but no clinically significant diagnostic findings were missed with low-dose imaging. Follow-up CT examinations were recommended for 5 patients; 1 had a cervical tumor, 1 had a pancreatic lesion, and 3 had intra-abdominal abscess. In each case, the image obtained by low-dose CT was considered sufficient for diagnosis. CONCLUSIONS Although low-dose CT images are of lower quality than images obtained with conventional doses of radiation, no clinically significant diagnostic findings were missed from low-dose CT images of patients with Crohns disease. The low-dose CT was obtained at a median effective dose equivalent to 1.4 abdominal radiographs.

Cardiac CT angiography for device surveillance after endovascular left atrial appendage closure

AIMS Left atrial appendage (LAA) device imaging after endovascular closure is important to assess for device thrombus, residual leak, positioning, surrounding structures, and pericardial effusion. Cardiac CT angiography (CCTA) is well suited to assess these non-invasively. METHODS AND RESULTS We report our consecutive series of non-valvular atrial fibrillation patients who underwent CCTA post-LAA closure with Amplatzer Cardiac Plug (ACP), Amulet (second generation ACP), or WATCHMAN devices. Patients underwent CCTA typically 1-6 months post-implantation. Prospective cardiac-gated CCTA was performed with Toshiba 320-detector or Siemens 2nd generation 128-slice dual-source scanners, and images interpreted with VitreaWorkstation™. GFR <30 mL/min/1.73 m(2) was an exclusion. We assessed for device thrombus, residual LAA leak, device embolization, position, pericardial effusion, optimal implantation, and device lobe dimensions. Forty-five patients underwent CCTA at median 97 days post-LAA closure (18 ACP, 9 Amulet, 18 WATCHMAN). Average age was 75.5 ± 8.9 years, mean CHADS2 score 3.1 ± 1.3, and CHADS-VASc score 4.9 ± 1.6. All had contraindications to oral anticoagulation. Post-procedure, 41 (91.1%) were discharged on DAPT. There was one device embolization (ACP, successfully retrieved percutaneously) and one thrombus (WATCHMAN, resolved with 3 months of warfarin). There were two pericardial effusions, both pre-existing and not requiring intervention. Residual leak (patency) was seen in 28/44 (63.6%), and the mechanisms of leak were readily identified by CCTA (off-axis device, gaps at orifice, or fabric leak). Mean follow-up was 1.2 ± 1.1year, with no death, stroke, or systemic embolism. CONCLUSION CCTA appears to be a feasible alternative to transoesophageal echocardiography for post-LAA device surveillance to evaluate for device thrombus, residual leak, embolization, position, and pericardial effusion.

Comparing Measurements of CT Angiography, TEE, and Fluoroscopy of the Left Atrial Appendage for Percutaneous Closure

Left atrial appendage (LAA) closure requires accurate preprocedural measurements, and trans‐esophageal echocardiography (TEE), cardiac computed tomography angiography (CCTA) and fluoroscopy can be utilized. However, correlations between these measurements remain inadequately assessed.

Peering through the glare: using dual-energy CT to overcome the problem of metal artefacts in bone radiology.

ObjectiveImaging of patients with large metal implants remains one of the most difficult endeavours for radiologists. This article reviews the theory of dual-energy CT (DECT) and its ability to reduce metal artefact, thus enhancing the diagnostic value of musculoskeletal imaging. The strengths, weaknesses, and alternative applications of DECT, as well as areas requiring further research, will also be reviewed.ConclusionCurrently, DECT stands as the frontier for metal artefact reduction in musculoskeletal imaging. DECT requires no additional radiation and provides significantly enhanced image acquisition. When considered along with its other capabilities, DECT is a promising new tool for musculoskeletal and trauma radiologists.

Cyclophosphamide-refractory scleroderma-associated interstitial lung disease: remarkable clinical and radiological response to a single course of rituximab combined with high-dose corticosteroids.

We would like to report our experience of using rituximab in cyclophosphamide refractory, rapidly progressive interstitial lung disease (ILD) in a patient with limited scleroderma. A 40-year-old man presented with 10-week history of inflammatory polyarthritis, which responded to a short course of oral corticosteroids. However, 3 weeks later, he developed new onset of exertional dyspnoea. High-resolution CT of the thorax was suggestive of early ILD. Surgical lung biopsy showed features of fibrotic non-specific interstitial pneumonia. He was diagnosed with scleroderma on the basis of: presence of anticentromere antibodies, Raynaud’s phenomenon, pulmonary fibrosis, digital oedema and hypomotility along with a dilated oesophagus. He was treated aggressively with pulse doses of corticosteroids and cyclophosphamide; however, his ILD continued to deteriorate. At this stage, he received rituximab (two pulses of 1 g each), which led to a gradual clinical improvement. Now, 12 months since his rituximab infusion, he walks 2 miles daily without any exertional dyspnoea.

Dual-energy computed tomographic virtual noncalcium algorithm for detection of bone marrow edema in acute fractures: early experiences.

Abstract Computed tomography (CT) is often used to assess the presence of occult fractures when plain radiographs are equivocal in the acute traumatic setting. While providing increased spatial resolution, conventional computed tomography is limited in the assessment of bone marrow edema, a finding that is readily detectable on magnetic resonance imaging (MRI). Dual-energy CT has recently been shown to demonstrate patterns of bone marrow edema similar to corresponding MRI studies. Dual-energy CT may therefore provide a convenient modality for further characterizing acute bony injury when MRI is not readily available. We report our initial experiences of 4 cases with imaging and clinical correlation.

The emergence of ultra-low--dose computed tomography and the impending obsolescence of the plain radiograph?

Until recently, computed tomographic (CT) examinationsacquired at a radiation exposure equivalent to correspondingplain radiographs would be of grossly substandard imagequality, almost certainly resulting in a failure to adequatelyvisualize many anatomic structures. Over the past decade,successive technical breakthroughs have facilitateddiagnostic-quality CTs to be acquired at rapidly decliningionizing radiation exposures. Today, the mean effectivedose of a radiographic series of the abdomen at 0.7 mSv,pelvis at 0.6 mSv, thoracic and lumbar spine at 1.0 and1.5 mSv, respectively [1] appear licentious when comparedwith exposures achieved in recent low-dose CT trials(Table 1). In an era in which low-dose CT has facilitateda 20% reduction in mortality among smokers [7]. and inwhich doses continue to substantially fall, we propose thatradiologists and clinicians should critically reevaluate therisks and benefits of performing many plain radiographicexaminations.Technical BackgroundIn brief summary, there have been 3 key developments inCT dose reduction technology that have facilitated theaforementioned trend. Automated exposure control ensuresefficient dose delivery by modulating tube current accordingto patient width and attenuation profile [8e10]. Fixed tubecurrent settings were commonplace in older-generation CTsystems and resulted in wider, more attenuating areas, suchas the shoulders receiving the same exposure as narrower lessattenuating regions such as the upper lungs. More recently,algorithms that modulate CT voltage according to patientsize and CT application have also been implemented withgood success [11].After ensuring efficient dose delivery, the largest chal-lenge to obtaining diagnostically acceptable CT images atexposure levels similar to plain radiographs is the severity ofrandom variation in attenuation values that occur within thenormal anatomic structures in these images otherwiseknown as noise. The magnitude of image noise at low CTexposure is fundamentally related to the image reconstruc-tion process [12]. Iterative reconstruction algorithms usea varyingly complex model of the physical characteristics ofthe x-ray tube, beam, and the 3-dimensional interaction ofthe x-ray beam within the patient to reduce noise and areclearly better than more traditional methods of reconstruc-

The “Misty Mesentery”: Mesenteric Panniculitis and Its Mimics

KEY POINTS 1. The term “misty mesentery” was coined by Mindelzun et al. in 1996 to describe a regional increase in mesenteric fat density that is seen frequently at abdominopelvic CT. 2. Mesenteric panniculitis (MP) is one of the broad range of disorders that may result in the imaging finding of a misty mesentery on CT. 3. MP cannot be diagnosed on CT without the exclusion of many other possible causes of a misty mesentery including disorders that result in mesenteric edema, lymphedema, hemorrhage, and infiltration with inflammatory or neoplastic cells. 4. Retractile mesenteritis results in irregular fibrotic mesenteric masses that simulate a number of neoplastic conditions of the mesentery and peritoneum such as carcinoid tumors, desmoid tumors, and perito-neal carcinomatosis.

Virtual monoenergetic reconstruction of contrast-enhanced dual energy CT at 70 keV maximizes mural enhancement in acute small bowel obstruction

PURPOSE In patients with small bowel obstruction (SBO), it is challenging to detect early ischemia. The purpose of this study is to evaluate the quantitative and qualitative benefits of virtual monoenergetic image (VMI) reconstruction in the assessment of small bowel mural enhancement on dual source dual energy computed tomography (CT) scans of the abdomen. MATERIALS AND METHODS Institutional review board approval was obtained, for this retrospective analysis. 72 consecutive patients with acute SBO were scanned using a second generation 128-slice dual source, CT system. Images were reconstructed at VMI energy levels from 40 to 110keV in 10keV increments and were analysed quantitatively and qualitatively. Contrast to noise ratios (CNR) and signal to noise ratios (SNR) for mural enhancement were recorded for all VMI datasets and compared to conventional polychromatic images (PCI) at 120kVp. Subjective analysis of mural enhancement on VMI and PCI was performed by 3 blinded readers. RESULTS Optimal CNR values for small intestinal mural enhancement were observed at 70keV. Qualitative assessment revealed that there was no statistical difference in diagnostic accuracy between VMI and PCI. All readers reported improved confidence when assessing the contrast enhancement on the 70keV VMI dataset and in our series, 2 additional cases of ischemia were identified on this reconstruction. CONCLUSION Contrast-enhanced dual source dual energy CT with VMI reconstruction at 70keV maximizes the CNR of small bowel mural enhancement and increases the overall diagnostic confidence in assessing mural enhancement in patients with SBO.

Getting the Most From Your Dual-Energy Scanner: Recognizing, Reducing, and Eliminating Artifacts

OBJECTIVE Dual-energy CT (DECT) is an innovative imaging modality that allows superior detection of pulmonary embolism, enhanced detection of urate in gout, and improved assessment of metal prostheses when compared with conventional CT. CONCLUSION The primary aim of this review is to describe these DECT protocols and compare each to its respective diagnostic reference standards. Moreover, this review will describe how to recognize, reduce, and eliminate DECT artifacts, thereby maximizing its diagnostic capabilities.