Pre-FESS Imaging of Paranasal Sinuses and Nasal Cavity: Using Multi-detector Computed Tomography (MDCT) in Understanding Normal Anatomy and Anatomical Variations: Tips and Tricks

With the advent of Multi-detector Computed Tomography (MDCT), imaging evaluation of paranasal sinuses (PNS) and nasal cavity has witnessed a paradigm shift. Submillimetric slice thickness with superior quality multiplanar reconstructions in orthogonal as well as non-orthogonal planes have resulted in better understanding of the intricate details of complex sino-nasal anatomy and their normal variations. Sagittal plane images have gained increasing acceptance among the sinus surgeons for understanding frontal sinus drainage pathway as well as lateral nasal wall. Analyzing the axial volume dataset in three dimensions has become a routine both for the radiologists as well as sinus surgeon. Besides default window settings, customized window settings enable better appreciation of air containing structures and their boundaries. Mandatory scan check list and template based structured reporting helps the sinus surgeon in better pre-operative planning. Regular mutual interaction between radiologists and sinus surgeon helps better understanding of the surgically relevant anatomy and anatomical variations.

Computed tomographic angiography (CTA) diagnosis of a rare meandering right pulmonary vein (MRPV)

Meandering right pulmonary vein (MRPV) is an exceedingly rare congenital pulmonary vascular variant with less than 20 reported cases. MPVR is a tortuous aberrant venous drainage of the right pulmonary upper lobe anastomosing with the right lower pulmonary vein instead of directly joining the left atrium. The variant is benign with an orthotopic venous drainage without any kind of shunting. The differential diagnosis mostly comprises the scimitar syndrome but also primary varix, arteriovenous malformations, and pulmonary sequestration. We report a case of MRPV fortuitously diagnosed in a 70-year-old patient. Multi-detector computed tomographic angiography (CTA) with MPR, MIP, and 3D reconstructions allowed the diagnosis obviating the need for invasive procedures.

In vivo measurement of esophageal hiatus surface area using MDCT: description of the methodology and clinical validation

PURPOSE

Accurate estimation of esophageal hiatus surface area (HSA) prior to surgical repair of hiatal hernia is difficult. The ability to do so may assist with following progression of hiatal hernias, choosing the optimal surgical approach and post-surgical evaluation. We developed a method for measurement of HSA using multi-planar reconstruction (MPR) of multi-detector computed tomography (MDCT) scans and sought to validate our method using intra-operative HSA measurements.

METHODS

Patients with thoracic or abdominal CT scans who were scheduled to undergo hiatal hernia repair were identified. A radiologist performed MPR of each MDCT scan to obtain the measured HSA (mHSA). Estimated HSA (eHSA) was obtained using intra-operative measurements of crura length and distance between crural edges. The association between eHSA and the corresponding mHSA was assessed using Pearson correlation. The intra-class correlation coefficient was calculated to assess both intra-observer and inter-observer agreement for the MDCT-MPR technique.

RESULTS

Of 30 subjects included, 16 (53.3%) were female and the median age was 68.5 years. All patients underwent robotic-assisted laparoscopic hiatal hernia repair. The median HSA was 8.1 cm² based on intra-operative measurements and 9.9 cm² based on CT measurements. The correlation coefficient for eHSA and corresponding mHSA was 0.83 (p < 0.001). The intra-class correlation coefficient was 0.97 (p < 0.001) for intra-observer agreement and 0.97 (p < 0.001) for inter-observer agreement.

CONCLUSION

We developed a MDCT-MPR technique that measures HSA in vivo. This technique is reproducible and can be used for pre-operative planning and post-operative follow-up of patients with symptomatic hiatal hernia.

Retropharyngeal internal carotid artery: a review of three cases

INTRODUCTION

The internal carotid artery (ICA) can take multiple pathways as it extends from the carotid bifurcation to the skull base. An aberration of its normal pathway may place the ICA in a retropharyngeal position in close proximity to the posterior pharyngeal wall. Radiographic classification is based on its proximity to the pharynx and/or pathway. We present a series of three cases of retropharyngeal ICAs, our goal is to report and classify these variations.

CASE PRESENTATION

CASE 1: Retropharyngeal right ICA. Minimum distance to the pharyngeal wall was ~ 4.9 mm (high risk of vascular injury) with a tortuous pathway. CASE 2: Bilateral retropharyngeal ICA. ICAs were in contact with the posterior pharyngeal wall (very high risk of vascular injury). The left has a kinking pathway, the right tortuous. CASE 3: Bilateral retropharyngeal ICA. Minimum distances of the right and left ICAs to the posterior pharyngeal wall were ~ 3.5 mm and ~ 3.3 mm, respectively (high risk of vascular injury). The right has a kinking pathway, the left tortuous.

DISCUSSION

Closeness of the vessel to the retropharyngeal wall increases the risk of surgical and non-surgical complications. Noteworthy is that the position of the artery is not constant and can change in position over periods of time.

CONCLUSION

Knowledge of the anatomy and variations of the ICA is important for oral and maxillofacial radiologists and surgeons to enable clinicians to take necessary precautions to decrease complications if performing any procedure in the region.

Tumour volume comparison between 16-row multi-detector computed tomography and 320-row area-detector computed tomography in patients with small lung tumours treated with stereotactic body radiotherapy: Effect of respiratory motion

PURPOSE

We compared image quality and volume of a moving simulated tumour and of lung tumours in patients who were treated with stereotactic body radiotherapy (SBRT) in a 16-row multi-detector CT (MDCT) versus a 320-row area-detector CT (ADCT). Tumour volumes in each respiratory phase were also evaluated.

MATERIALS AND METHODS

We acquired static and four-dimensional CT (4DCT) images of a moving phantom with 10- and 30-mm amplitudes with three periods of patterns (2, 4, and 6 s). Breath-hold and 4DCT images were acquired for 12 lung tumour patients who underwent SBRT. Image data were acquired via MDCT and ADCT. The tumours were delineated in each respiratory phase and their volumes in end-expiratory/end-inspiratory phase and mid-respiratory phase were compared.

RESULTS

In the phantom study, tumour volumes were smaller and closer to the static image when evaluated by ADCT than by MDCT. In the clinical study, average tumour volumes ± standard deviations were 9.58 ± 1.07 cm³ with MDCT (2.5-mm slice), and 7.12 ± 0.23 cm³ with ADCT (p < 0.01). Tumour volumes were closer to that of the breath hold CT in all patients evaluated by ADCT than by MDCT. Unlike MDCT, tumour volumes acquired by ADCT were smaller in end-expiratory or end-inspiratory phase than in the mid-respiratory phase.

CONCLUSIONS

Tumour volumes in each of the respiratory phases in ADCT were significantly smaller and closer to the static image than the corresponding volumes in MDCT. This suggests that treated volume can be reduced if ADCT is used in treatment planning.

Clinical and CT findings of small bowel obstruction caused by rice cakes in comparison with bezoars

PURPOSE

Rice cakes have not been recognized as a cause of small bowel obstruction (SBO) worldwide. We compared clinical and CT findings of rice cake SBO versus SBO due to bezoars, the most common cause of food-induced SBO.

METHODS

Twenty-four patients with rice cake SBO (n = 17) or bezoar SBO (n = 7) were retrospectively evaluated for clinical findings and the following multi-detector CT (MDCT) features: identification of the transition zone, presence of intraluminal lesions, degree of obstruction, and length and attenuation of obstructing materials. Categorical variables were compared by Fisher's exact test, and continuous variables by independent t test.

RESULTS

None of the rice cake SBO patients required surgery, whereas 4/7 (57%) bezoar SBO patients underwent surgery. On MDCT, rice cake residues were recognized as well-defined intraluminal lesions of shorter length (29.8 ± 4.6 mm vs. 47.7 ± 10.8 mm for bezoars; p < 0.0001) and higher attenuation (106 ± 27.8 HU vs. - 62.8 ± 14.7 HU for bezoars; p < 0.0001).

CONCLUSIONS

Rice cake SBO patients did not require surgery. On MDCT, rice cake residues were significantly shorter and higher in attenuation than bezoars. These findings facilitate diagnosis and support the conservative management of rice cake SBO.

Imaging findings of recurrent pancreatic cancer following resection

Pancreatic cancer is a challenging malignancy to treat, largely due to aggressive regional involvement, early systemic dissemination, high recurrence rate, and subsequent low patient survival. Generally, 15-20% of newly diagnosed pancreatic cancers are candidates for possible curative resection. Eighty percent of these patients, however, will experience locoregional or distant recurrence in first 2 years. Although there is no strong evidence-based guideline for optimal surveillance after pancreatic cancer resection, careful comparison of surveillance follow-up multi-detector CT (MDCT) studies with a postoperative baseline MDCT examination aids detection of early recurrent pancreatic cancer. In this review article, we describe imaging findings suggestive of recurrent pancreatic cancer and review routine and alternative imaging options.

MDCT of the liver in obese patients: evaluation of a different method to optimize iodine dose

PURPOSE

To prospectively compare two different approaches for estimating the amount of intravenous contrast media (CM) needed for multiphasic MDCT of the liver in obese patients.

MATERIALS AND METHODS

This single-center, HIPAA-compliant prospective study was approved by our Institutional Review Board. Ninety-six patients (55 men, 41 women), with a total of 42 hypovascular liver lesions, underwent MDCT of the liver. The amount of contrast medium injected was computed according to the patient's lean body weight which was estimated using either a bioimpedance device (Group A) or the James formula (Group B). The following variables were compared between the two groups: the amount of contrast medium injected (in grams of Iodine, gI), the contrast enhancement index (CEI) and the lesion-to-liver contrast-to-noise ratio.

RESULTS

Protocols A and B yielded significant differences in the amount of CM injected (mean values 41.9 ± 4.41 gI in Group A vs. 35.9 ± 5.75 gI in Group B; P = 0.021). The mean CEI value and lesion-to-liver contrast-to-noise ratio measured on the portal phase were significantly higher with protocol A than with protocol B (P < 0.05).

CONCLUSIONS

Our study shows that the adoption of a bioimpedance device in obese patients improves liver parenchymal enhancement and lesion conspicuity.

Impact of heart rate on diagnostic accuracy of second generation 320-detector computed tomography coronary angiography

OBJECTIVE

To assess the impact of elevated heart rate (HR) on the diagnostic accuracy and image quality of second-generation 320-detector computed tomography coronary angiography (320-CTCA).

METHODS

Consecutive patients with suspected coronary disease referred for invasive coronary angiography (ICA) were prospectively recruited and underwent 320-CTCA. Pre-scan beta-blockers were administered if native HR>80 bpm and post-scan cohorts stratified by traditional (HR ≤60 bpm) and elevated HR (61-80 bpm). A wider phase window was used for the elevated HR group (30-80%). 320-CTCA and ICA were analyzed by independent readers blinded to other data. Significant disease was defined as ≥50% visual stenosis on ICA. Uninterpretable segments by 320-CTCA were considered to be significant on an intention-to-diagnose principle. Image quality was assessed by 5-point Likert score.

RESULTS

Of 107 patients studied (1,662 segments), there was no significant difference in sensitivity, specificity, positive and negative predictive value between patients with HR ≤60 bpm (n=55) vs. HR 61-80 bpm (n=52): 97%, 88%, 95%, 94% vs. 100%, 88%, 95%, 100%; Receiver operator characteristic-area under the curve 0.93 vs. 0.94, P=0.82). Overall per-patient diagnostic accuracy was 96% in both groups with no significant difference in interpretable segments (Likert ≥2) or median radiation dose (2.4 mSv vs. 2.7 mSv, P=0.35). Only 4/1,662 (0.2%) segments were uninterpretable by motion artefact in the whole cohort.

CONCLUSIONS

In patients with HR >60 and up to 80bpm, second generation 320-CTCA provides comparably adequate diagnostic accuracy to HR ≤60 without significantly impacting upon overall segmental evaluability.

Pulsatile Tinnitus: Differential Diagnosis and Radiological Work-Up

PURPOSE OF REVIEW

Identification of the underlying cause of pulsatile tinnitus is important for treatment decision making and for prognosis estimation. For this, an adequate diagnostic imaging strategy is crucial.

RECENT FINDINGS

Both CT and MRI can be useful, and in general, these modalities provide complementary diagnostic information. The scanning protocol can be optimized based on the estimated a priori chance for finding specific pathology, or the need to rule out more rare but clinical significant disease. In recent years, dynamic CTA, also referred to as 4D-CTA, has become available as a new technique that enables non-invasive evaluation of hemodynamics for the detection, classification, and follow-up of vascular malformations.

SUMMARY

The value of different diagnostic imaging modalities in the work-up of pulsatile tinnitus is discussed in relation to the differential diagnosis. Furthermore, imaging findings of different diseases are presented, both for CT and MRI.

Three-dimensional quantification of myocardial perfusion during regadenoson stress computed tomography

BACKGROUND

There is no accepted methodology for CT-based vasodilator stress myocardial perfusion imaging and analysis. We developed a technique for quantitative 3D analysis of CT images, which provides several indices of myocardial perfusion. We sought to determine the ability of these indices during vasodilator stress to identify segments supplied by coronary arteries with obstructive disease and to test the accuracy of the detection of perfusion abnormalities against SPECT.

METHODS

We studied 93 patients referred for CT coronary angiography (CTCA) who underwent regadenoson stress. 3D analysis of stress CT images yielded segmental perfusion indices: mean X-ray attenuation, severity of defect and relative defect volume. Each index was averaged for myocardial segments, grouped by severity of stenosis: 0%, <50%, 50-70%, and >70%. Objective detection of perfusion abnormalities was optimized in 47 patients and then independently tested in the remaining 46 patients.

RESULTS

CTCA depicted normal coronary arteries or non-obstructive disease in 62 patients and stenosis of >50% in 31. With increasing stenosis, segmental attenuation showed a 7% decrease, defect severity increased 11%, but relative defect volume was 7-fold higher in segments with obstructive disease (p<0.001). In the test group, detection of perfusion abnormalities associated with stenosis >50% showed sensitivity 0.78, specificity 0.54, accuracy 0.59. When compared to SPECT in a subset of 21 patients (14 with abnormal SPECT), stress CT perfusion analysis showed sensitivity 0.79, specificity 0.71, accuracy 0.76.

CONCLUSIONS

3D analysis of vasodilator stress CT images provides quantitative indices of myocardial perfusion, of which relative defect volume was most robust in identifying segments supplied by arteries with obstructive disease. This study may have implications on how CT stress perfusion imaging is performed and analyzed.

Comprehensive Evaluation of Cardiac Hydatid Using 256 Slice Dual Source CT: One Stop Shop

Hydatid disease results from infection with larval stage of Echinococcus granulosus tapeworm. Dogs and other canines are the definitive hosts; Human beings are common accidental intermediate hosts. Liver is the most common organ to be involved in this condition. Cardiac hydatid, seen in only 0.5 to 2% cases, is a rare entity because of myocardial contractility. Larvae reach the myocardium through coronary circulation. Among various locations of cardiac hydatid, due to its rich coronary arterial supply Left ventricle (LV) myocardium is the most common site of involvement followed by interventricular septum and right ventricle. Rare locations include pericardium, right atrium and left atrium. A 50-year-old woman presented with dyspnoea for 11 months, chest X-ray showed a well defined, homogenous left paracardiac mass, which is not separable from left heart border. Transthoracic echocardiography revealed a complex multicystic mass lesion abutting antero-lateral wall of left ventricle. Contrast enhanced computed tomography showed a well-circumscribed multicystic mass lesion with honeycomb appearance arising from myocardium of anterolateral wall of left ventricle. Indirect haemagglutination test for hydatid disease was positive. At surgery the cyst was seen to arise from LV myocardium. It was incised and grape like contents were evacuated. The cavity was irrigated with scolicidal solution. Thereafter, the cyst was marsupialised. Histopathological examination revealed grape like cyst contents consistent with the diagnosis of hydatid cyst.

Coronary CT angiography findings based on smoking status: Do ex-smokers and never-smokers share a low probability of developing coronary atherosclerosis?

The relationship of coronary artery disease (CAD) in ex-smokers has not been elucidated, although smoking is considered to be one of the major risk factors of CAD. We investigate subclinical coronary atherosclerosis (SCA) in asymptomatic subjects with coronary computed tomography angiography (CCTA), according to smoking status, and determine whether ex-smokers share a low probability of developing CAD with never-smokers. We retrospectively enrolled 6930 self-referred asymptomatic adults who underwent both coronary artery calcium score (CACS) and CCTA. The prevalence and characteristics of SCA were assessed according to smoking status (never-, ex- and current smokers). After adjusting for variable risk factors, we used multivariate logistic regression for adjusted odds ratios (AOR) of high CACS (>100), SCA (any plaque), significant stenosis (>50 % in luminal stenosis) and each plaque type (non-calcified, mixed and calcified plaque) among the three groups. The prevalence of SCA was highest in the ex-smokers (35.4 %) and the prevalence of significant stenosis in ex-smokers (6.9 %) was as high as in current smokers (6.4 %). However, after adjusting for variable risk factors, SCA was significantly correlated with both ex-smokers (AOR; 1.21) and current smokers (AOR; 1.25), whereas significant stenosis was correlated only with current smokers (AOR; 1.91). The association between SCA and ex-smokers is as strong as with current smokers, although significant stenosis is only correlated with current smokers; thus, not only quitting smoking but also never initiating smoking would be helpful to reduce the progression of the SCA.

MDCT findings of right circumaortic renal vein with ectopic kidney

Anomalies of renal vasculature combined with ectopic kidneys were found on a multi-detector CT scan. Knowledge of renal vascular variation is very important for surgical exploration, radiologic intervention and staging for urologic cancer. We present an extremely rare case of a right circumaortic renal vein combined with a right ectopic kidney. The right kidney was located at the level between the third and fifth lumbar vertebra. The right circumaortic renal vein crossed the aorta and returned to the inferior vena cava behind the aorta.

Virtual bronchoscopy in the era of multi-detector computed tomography: Is there any reality?

Virtual bronchoscopy, in conjunction with axial and MPR MDCT images, can enhance diagnostic accuracy of tracheo-bronchial endoluminal pathologies. We describe a few cases highlighting the utility of virtual bronchoscopy in the diagnosis of varied tracheo-bronchial pathologies encountered in the setting of a tertiary care Armed Forces Hospital of India.

Low-dose unenhanced computed tomography for diagnosing stone disease in obese patients

Objective

To evaluate the detectability, size, location and density of urinary stones with unenhanced computed tomography (CT), using the half-radiation (low) dose (LDCT) technique, compared with the standard-dose CT (SDCT), in obese patients.

Patients and methods

The study included 50 patients with a body mass index of >30 kg/m² and bilateral renal stones diagnosed with SDCT, and managed on one side. All the patients had LDCT during the follow-up and SDCT was used as a reference for comparison.

Results

Of the 50 patients, the right side was affected in 27 and the left side in 23. In all, 35 patients had a single stone while the remaining 15 had multiple stones. With SDCT, 95 stones were detected; there were 45 of ⩽5 mm, 46 of 6–15 mm and only four of >15 mm. LDCT barely detected three stones of <3 mm, compared with SDCT, while larger stones had the same appearance at both scans. The site of stone in the kidney or the ureter did not affect its detection on LDCT vs. SDCT. The mean stone diameter was identical in both techniques. At LDCT, all stones were detected with no difference in their number, location or density vs. SDCT. However, the tube current and radiation dose were significantly lower with LDCT.

Conclusions

In obese patients with stone disease, LDCT is as accurate as SDCT, while avoiding exposure of the patient to high-dose radiation.

Small bowel volvulus induced by mesenteric lymphangioma in an adult: a case report

Mesenteric lymphangiomas are rare abdominal masses that are seldom associated with small bowel volvulus, and especially in adult patients. We report here on an unusual case of small bowel volvulus that was induced by a mesenteric lymphangioma in a 43-year-old man who suffered from repeated bouts of abdominal pain. At multidetector CT, we noticed whirling of the cystic mesenteric mass and the adjacent small bowel around the superior mesenteric artery. Small bowel volvulus induced by the rotation of the mesenteric lymphangioma was found on exploratory laparotomy. Lymphangioma should be considered as a rare cause of small bowel volvulus in adult patients.

Multiplanar reformations and minimum intensity projections using multi-detector row CT for assessing anomalies and disorders of the pancreaticobiliary tree

CT scan is regarded as the imaging modality of choice in patients with pancreaticobiliary ductal abnormalities. However, the axial orientation of the CT images provides only limited anatomical view of pancreaticobiliary ductal abnormalities. The technological advances of multi-detector row CT and three-dimensional image processing in workstations allows rapid image acquisition and a short postprocessing time. In particular, multiplanar reformations (MPR) and minimum intensity projections (MinIP) offer rapid and accurate images of the anatomy and abnormalities of the pancreaticobiliary tree. Moreover, MPR and MinIP help determine the relationship between the pancreaticobiliary ductal anatomy and the surrounding structures. This pictorial review illustrates the wide spectrum of images obtained by the MPR and MinIP of the anomalies and disorders of the pancreaticobiliary tree.

Detection of hypervascular hepatocellular carcinoma: Comparison of multi-detector CT with digital subtraction angiography and Lipiodol CT

AIM: The purpose of this study was to compare the diagnostic accuracy of biphasic multi-detector row helical computed tomography (MDCT), digital subtraction angiography (DSA) and Lipiodol computed tomography (CT) in detection of hypervascular hepatocellular carcinoma (HCC).

METHODS: Twenty-eight patients with nodular HCC underwent biphasic MDCT examination: hepatic arterial phase (HAP) 25 s and portal venous phase (PVP) 70 s after injection of the contrast medium (1.5 mL/kg). They also underwent hepatic angiography and intra-arterial infusion of iodized oil. Lipiodol CT was performed 3-4 wk after infusion. MDCT images were compared with DSA and Lipiodol CT images for detection of hepatic nodules.

RESULTS: The three imaging techniques had the same sensitivity in detecting nodules >20 mm in diameter. There was no significant difference in the sensitivity among HAP-MDCT, Lipiodol CT and DSA for nodules of 10-20 mm in diameter. For the nodules <10 mm in diameter, HAP-MDCT identified 47, Lipiodol CT detected 27 (χ² = 11.3, P = 0.005<0.01, HAP-MDCT vs Lipiodol CT) and DSA detected 16 (χ² = 9.09, P = 0.005<0.01 vs Lipiodol CT and χ² = 29.03, P = 0.005<0.01vs HAP-MDCT). However, six nodules <10 mm in diameter were detected only by Lipiodol CT.

CONCLUSION: MDCT and Lipiodol CT are two complementary modalities. At present, MDCT does not obviate the need for DSA and subsequent Lipiodol CT as a preoperative examination for HCC.