Adjunctive Use of C-Arm CT May Eliminate Technical Failure in Adrenal Vein Sampling

Utilizing the renal and vertebral contours as landmarks for right adrenal vein localization in primary aldosteronism: a retrospective analysis of 310 cases

Background

Adrenal Vein Sampling (AVS) is the gold standard for categorizing primary aldosteronism (PA). However, catheterization of the right adrenal vein (RAV) can be technically challenging. This study aimed to investigate the validity of the right renal vertebral contour as fluoroscopic landmarks to help RAV orifice localization during AVS.

Methods

Imaging data of 310 PA patients were retrospectively analyzed. Patients were divided into Normal, Overweight, and Obese group based on their body mass index (BMI). A novel Renal-Vertebral-Angle (R-V-A) model was employed to delineate the distribution of the RAV orifice. This model concerned a cruciate cross formed by the upper edge of the right renal and the right edge of vertebral contour under fluoroscopy. The area within a 2 cm×2 cm square in the left upper quadrant of this cross was defined as the R-V-A. The success rate of AVS was compared across different BMI groups, as well as the differences in the distribution of the RAV orifice within the R-V-A.

Results

Successful RAV sampling was achieved in 270 cases, while the success rate of RAV sampling was found to be lower in the Obese group. The majority of the RAV orifices were located within the R-V-A region (249/270, 92.2%). There was no significant difference in the distribution of RAV orifices across the BMI groups (Normal vs. Overweight vs. Obese: 92.2% vs. 91.9% vs. 93.3%, p=0.968). In contrast to patients with successful RAV sampling, a significantly lower proportion of sampling site were found within the R-V-A in cases with mis-catheterized cases (92.2% vs. 55.6%, p<0.001).

Conclusion

The R-V-A model could be utilized as an anatomical landmark for the RAV orifice localization on fluoroscopy, that might help to narrow down the exploration range for RAV catheterization, and might offer beneficial assistance in enhancing the success rate for AVS.

Pre-procedural and intra-procedural computerized tomography: providing a roadmap for successful adrenal venous sampling procedures

BACKGROUND AND PURPOSE

Adrenal venous sampling (AVS) is used for the diagnosis of primary hyperaldosteronism. Technical difficulties with right adrenal vein (RAV) catheterization can lead to erroneous results. Our purpose was to delineate the location of the RAV on pre-procedural CT imaging in relation to the location identified during AVS and to report on the impact of successful RAV cannulation with and without the use of intra-procedural CT scanning.

METHODS

Retrospective case series including patients who underwent AVS from October 2000 to September 2022. Clinical and laboratory values were abstracted from the electronic medical record. Successful cannulation of the RAV was defined as a selectivity index > 3.

RESULTS

110 patients underwent 124 AVS procedures. Pre-AVS CT imaging was available for 118 AVS procedures. The RAV was identified in 61 (51.7%) CT datasets. Biochemical confirmation of successful RAV cannulation occurred in 98 (79.0%) of 124 AVS procedures. There were 52 (85.2%) procedures in which the RAV was identified on pre-AVS CT and there was biochemical confirmation of successful RAV sampling. Among these 52 procedures, the RAV was localized during AVS at the same anatomic level or within 1 vertebral body level cranial to the level identified on pre-AVS CT in 98.1% of cases. The rate of successful RAV cannulation was higher in patients who underwent intra-procedural CT (93.8% versus 63.9%), P < 0.01.

CONCLUSIONS

Pre-AVS and intra-procedural CT images provide an invaluable roadmap that resulted in a higher rate of accurate identification of the RAV and successful AVS procedures; in particular, search for the RAV orifice during AVS can be limited to 1 vertebral body cranial to the level identified on pre-AVS CT imaging and successful cannulation can be confidently verified with intra-procedural CT.

Adrenal Vein Sampling: Tips and Tricks

Adrenal vein sampling (AVS) is the standard method for distinguishing unilateral from bilateral sources of autonomous aldosterone production in patients with primary aldosteronism. This procedure has been performed at limited specialized centers due to its technical complexity. With recent advances in imaging technology and knowledge of adrenal vein anatomy in parallel with the development of adjunctive techniques, AVS has become easier to perform, even at nonspecialized centers. Although rare, anatomic variants of the adrenal veins can cause sampling failure or misinterpretation of the sampling results. The inferior accessory hepatic vein and the inferior emissary vein are useful anatomic landmarks for right adrenal vein cannulation, which is the most difficult and crucial step in AVS. Meticulous assessment of adrenal vein anatomy on multidetector CT images and the use of a catheter suitable for the anatomy are crucial for adrenal vein cannulation. Adjunctive techniques such as intraprocedural cortisol assay, cone-beam CT, and coaxial guidewire-catheter techniques are useful tools to confirm right adrenal vein cannulation or to troubleshoot difficult blood sampling. Interventional radiologists should be involved in interpreting the sampling results because technical factors may affect the results. In rare instances, bilateral adrenal suppression, in which aldosterone-to-cortisol ratios of both adrenal glands are lower than that of the inferior vena cava, can be encountered. Repeat sampling may be necessary in this situation. Collaboration with endocrinology and laboratory medicine services is of great importance to optimize the quality of the samples and for smooth and successful operation. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Utility of right adrenal signature veins in venous sampling for primary aldosteronism

BACKGROUND

This study aimed to identify the appropriate signature veins for the right adrenal gland using a 3D model fused with adrenal venography images and to verify their accuracy through the selectivity index (SI) >2.

METHODS

We analyzed the right adrenal venography images of 41 patients who underwent adrenal venous sampling (AVS). These images were merged with a 3D structure of the adrenal gland to identify the signature veins of the right adrenal gland. We then used the signature veins observed during adrenal venography to determine the optimal position of the catheter tip during AVS for 53 other patients. Finally, we verified the accuracy of this method according to the SI.

RESULTS

We successfully fused the 3D models of 41 cases with adrenal venography images. We identified the trunk branch type as the major venous morphology in the right anterior oblique at degrees of 30 (38 cases, 92.7%). In addition, the central vein, brush vein, uvula vein, and capsular vein were identified as signature veins for the right AVS. The accuracy of AVS was 100% in the other 53 patients, as verified by an SI >2.

CONCLUSIONS

Our study identified the right adrenal signature veins, including the previously overlooked uvula vein, which can be used to determine the position of the catheter tip and improve the success rate of AVS.

Utility of Carbon Dioxide Venography and Intraprocedural CT for Adrenal Venous Sampling in Patients with an Allergy to Iodinated Contrast Media

PURPOSE

To assess the diagnostic performance of carbon dioxide (CO2) and intraprocedural unenhanced computed tomography (CT) for adrenal venous sampling (AVS) (CO2-intraprocedural unenhanced CT-AVS) in patients with primary aldosteronism (PA) and a history of iodine contrast medium allergy.

MATERIALS AND METHODS

CO2-intraprocedural unenhanced CT-AVS was performed in 18 patients with iodine contrast media allergies at the authors' hospital between December 2015 and January 2021. CT and noncontrast magnetic resonance angiography were used to evaluate the preoperative adrenal vein anatomy. CO2 venography was performed to confirm adrenal vein catheterization. Additionally, intraprocedural unenhanced CT was also performed to confirm catheter position in the right adrenal gland.

RESULTS

In all cases in which CO2-intraprocedural unenhanced CT-AVS was performed, the right and left adrenal veins were catheterized appropriately, leading to a localized diagnosis. Catheterization of the left adrenal vein was confirmed using CO2 venography in all cases. In 7 of the 18 cases, CO2 venography demonstrated selection of the right adrenal vein. In 15 of 18 cases, intraprocedural unenhanced CT demonstrated selection of the right adrenal vein.

CONCLUSIONS

CO2-intraprocedural unenhanced CT-AVS demonstrated the same diagnostic ability for PA localization as conventional AVS with iodine contrast media. The proposed method is clinically feasible for AVS, in which iodine contrast media use is restricted.

Pre-interventional assessment of right renal to right adrenal vein distance: Impact on procedure time and radiation dose in adrenal vein sampling

PURPOSE

Adrenal vein sampling (AVS) is the reference standard for evaluation of lateralized hormone production in primary aldosteronism. We aimed to investigate the impact of pre-interventional right renal vein (RRV) to right adrenal vein (RAV) distance measurement on fluoroscopy time, contrast agent exposure and radiation dose during AVS.

MATERIALS AND METHODS

Forty-five patients with primary aldosteronism undergoing AVS were enrolled in our retrospective study and divided into three groups. In the group "ruler" (n = 14), RRV-RAV-distances were determined pre-interventionally by cross-sectional imaging (CT/MRI) and AVS was performed by one interventional radiologist with limited experience in AVS. CT/MRI-derived and fluoroscopy-derived RRV-RAV-distances were correlated for aimed cannulation of the RAV. Patients in group "no ruler" (n = 24, three interventional radiologists with limited experience in AVS) and in group "expert", (n = 7, one expert interventional radiologist) underwent AVS without pre-interventional estimation of RRV-RAV-distances. Procedure parameters (fluoroscopy time, contrast agent volume, radiation dose) of group "ruler" were compared to both other groups by Kruskal-Wallis rank-sum test.

RESULTS

Correlation of CT/MRI-derived and fluoroscopy-derived RRV-RAV-distances was good (r = 0.74;p = 0.003). The median RRV-RAV-distance was 4.5cm at CT/MRI (95%-CI:4.2-5.0cm) and 4.0cm at fluoroscopy (95%-CI:3.8-4.5cm). Fluoroscopy time (p<0.0001), contrast agent exposure (p = 0.0003) and radiation dose (air kerma and dose area product both p = 0.038) were significantly lower in group "ruler" compared to group "no ruler" (all p<0.05), and similar to group "expert" (all p>0.05).

CONCLUSIONS

CT/MRI-derived pre-interventional renal-adrenal vein distance measurements correlate well with angiographic distance measurements. Pre-interventional estimation of the RRV-RAV-distance allows for aimed cannulation of the RAV with potential reduction of fluoroscopy time, contrast agent exposure and radiation-dose during AVS.

Use the right kidney contour as a landmark in adrenal vein sampling

Adrenal Vein Sampling (AVS) is the gold standard for categorizing primary aldosteronism (PA). However, catheterization of the right adrenal vein (RAV) is challenging due the small size and variable location. This study aims to explore the relationship between the RAV orifice and the right kidney contour (RKC) on fluoroscopy, thus evaluating the potential of use the RKC as an anatomic marker for localizing RAV. Imaging data of 107 PA patients with successful bilateral AVS were retrospectively analyzed. Based on the body mass index (BMI), all patients were divided into the Normal Group (BMI < 24 kg/m²), Overweight Group (24 kg/m² ≤ BMI < 28 kg/m²) and Obese Group (BMI ≥ 28 kg/m²). At the anterior view, the height level of RAV orifice was determined relative to vertebral bodies and disks. The distance from the RAV orifice to the upper edge of RKC was measured manually. The RAV orifice height level was mainly distributed from vertebral T11 to T12 (90.6%), and tended to be higher in patients with a larger BMI. The mean distance from the RAV orifice to the upper edge of RKC was 13.9±7.8mm, and had no difference among Normal group (n = 53, 14.1±8.2mm), Overweight group (n = 39, 13.7±8.0mm), and Obese group (n = 15, 13.9±5.5mm) (p = 0.981). Based on these findings, the RKC might be used as a landmark for localizing RAV on fluoroscopy, which is conductive to narrow down the exploration range and increase the success rate of RAV catheterization.

Adrenal venous sampling in primary hyperaldosteronism: correlation of hormone indices and collimated C-arm CT findings

PURPOSE

To evaluate the feasibility and effect of an approach to adrenal venous sampling (AVS) analysis by combining established selective cortisol and aldosterone indices with the acquisition of a collimated C-arm CT(CACT_Coll).

METHODS

Overall, 107 consecutive patients (45f,62 m; 54 ± 10 years) undergoing 111 AVS procedures without hormonal stimulation from 7/13 to 2/20 in a single institution were retrospectively analysed. Hormone levels were measured in sequential samples of the suspected adrenal veins and right iliac vein, and selectivity indices (SI) computed. Stand-alone SI_Cortisol and/or SI_Aldosterone ≥ 2.0 as well as SI_Cortisol and/or SI_Aldosterone ≥ 1.1 combined with positive right-sided CACT_Coll of the adrenals (n = 80; opacified right adrenal vein) were defined as a successful AVS procedure. Radiation exposure of CACT was measured via dose area product (DAP) and weighed against an age-/weight-matched cohort (n = 66).

RESULTS

Preliminary success rates (SI_Cortisol and/or SI_Aldosterone ≥ 2.0) were 99.1% (left) and 72.1% (right). These could be significantly increased to a 90.1% success rate on the right, by combining an adjusted SI of 1.1 with a positive CACT_Coll proving the correct sampling position. Sensitivity for stand-alone collimated CACT (CACT_Coll) was 0.93, with 74/80 acquired CACT_Coll confirming selective cannulation by adrenal vein enhancement. Mean DAP_{Coll_CACT} measured 2414 ± 958 μGyxm², while mean DAP_{Full-FOV_CACT} in the matched cohort measured 8766 ± 1956 μGyxm² (p < 0.001).

CONCLUSION

Collimated CACT in AVS procedures is feasible and leads to a significant increase in success rates of (right-sided) selective cannulation and may in combination with adapted hormone indices, offer a successful alternative to previously published AVS analysis algorithms with lower radiation exposure compared to a full-FOV CACT.

Use of Bony Landmarks during Adrenal Venous Sampling to Guide Catheterization of the Left Adrenal Vein

Purpose The aim of this study was to examine the utility of fluoroscopic bony landmarks in predicting the location of the left adrenal vein during adrenal vein sampling (AVS).

Methods Eighty-six AVS procedures were performed in 81 patients between August 2013 and March 2020. A selectivity index was calculated for each case by dividing the measured left adrenal vein cortisol level by the peripheral vein cortisol level. Successful “target” left adrenal vein catheterization was confirmed in cases with a selectivity index of three or greater. Intraprocedural AVS fluoroscopic images were selected that demonstrated catheter position in the left adrenal vein. Lateral distance from the catheter tip in the left adrenal vein to the lateral margin of the left pedicle at the associated vertebral body level was measured.

Results Mean patient age was 56.4 years (range: 19–80 years) and 48 (59.3%) patients were male. Target sampling in the left adrenal vein was confirmed in 82 (95.3%) cases. In 78 (95.1%) targeted cases, the catheter terminated less than 25 mm from the left lateral pedicle at a mean distance of 11.2 mm. The catheter was most frequently placed at the T12 and L1 vertebral body levels. Four (4.7%) cases demonstrated nontarget catheter positioning, two (50.0%) of these cases were within 25 mm.

Conclusion The position of the left adrenal vein is generally located in a predictable position relative to bony landmarks. By utilizing these landmarks, positioning of the sampling catheter during AVS can be more reliable with the potential to avoid repeat procedures and delays in patient care.

Success rate of adrenal venous sampling and predictors for success: a retrospective study

Purpose

To report the success rate of adrenal venous sampling (AVS) and identify the predictors for procedural success.

Material and methods

Sixty-four patients (18 men and 46 women) with a mean ± SD age of 50 ± 11.8 years (range 28-69 years) diagnosed as primary hyperaldosteronism, and who underwent AVS from January 2009 to December 2016, were retrospectively reviewed. In our institution, the initial period to perform the AVS was set from 2009 to 2013, and the post-initial period was defined as procedures performed after 2013. Successful sampling was determined when the ratio of cortisol from the adrenal vein to the level of cortisol in the inferior vena cava ≥ 5. The procedural success and subject factors between success and failure were analysed. A p value < 0.05 was considered statistically significant.

Results

The success rate of bilateral AVS was 71.9%. The success rates of right and left AVS were 76.6% and 90.6%, respectively. Male patients were more likely to succeed than female patients (adjusted odds ratio [aOR], 9.83; 95% confidence interval [CI], 1.14-85.14; p = 0.009). In our institution, the procedure performed in the post-initial period also succeeded more often compared to the initial period (aOR, 5.05; 95% CI, 1.2-21.16; p = 0.017). No other factors were associated with the success rate in this study.

Conclusions

The success rate of bilateral AVS in our institution was rather high. Male gender and procedure performed in the post-initial period were significant predictive factors for a successful procedure.

C-Arm Computed Tomography-Assisted Adrenal Venous Sampling Improved Right Adrenal Vein Cannulation and Sampling Quality in Primary Aldosteronism

BACKGROUND

Adrenal venous sampling (AVS) is a gold standard for subtype classification of primary aldosteronism (PA). However, this procedure has a high failure rate because of the anatomical difficulties in accessing the right adrenal vein. We investigated whether C-arm computed tomography-assisted AVS (C-AVS) could improve the success rate of adrenal sampling.

METHODS

A total of 156 patients, diagnosed with PA who underwent AVS from May 2004 through April 2017, were included. Based on the medical records, we retrospectively compared the overall, left, and right catheterization success rates of adrenal veins during the periods without C-AVS (2004 to 2010, n=32) and with C-AVS (2011 to 2016, n=124). The primary outcome was adequate bilateral sampling defined as a selectivity index (SI) >5.

RESULTS

With C-AVS, the rates of adequate bilateral AVS increased from 40.6% to 88.7% (P<0.001), with substantial decreases in failure rates (43.7% to 0.8%, P<0.001). There were significant increases in adequate sampling rates from right (43.7% to 91.9%, P<0.001) and left adrenal veins (53.1% to 95.9%, P<0.001) as well as decreases in catheterization failure from right adrenal vein (9.3% to 0.0%, P<0.001). Net improvement of SI on right side remained significant after adjustment for left side (adjusted SI, 1.1 to 9.0; P=0.038). C-AVS was an independent predictor of adequate bilateral sampling in the multivariate model (odds ratio, 9.01; P<0.001).

CONCLUSION

C-AVS improved the overall success rate of AVS, possibly as a result of better catheterization of right adrenal vein.

Adrenal hormones before and after venography during adrenal venous sampling: a self-controlled study

OBJECTIVE

A stress reaction involving increased adrenal hormone release occurs when starting adrenal venous sampling (AVS). The purpose of the present study was to investigate the effect of single shot venography on adrenal hormone production during AVS.

SUBJECTS AND METHODS

This was a prospective self-controlled study. We enrolled 54 consecutive patients (21 men, 33 women; mean age 52 ± 11 years) with primary aldosteronism who underwent AVS from May 2014 to February 2015. Under non-stimulated conditions, blood samples were obtained from a common trunk of the left adrenal vein before and after single shot venography. The initial plasma aldosterone and cortisol concentration (PAC and PCC) were compared with those measured after venography for each patient.

RESULTS

PAC and PCC were slightly but significantly decreased between before and after venography (after log transformation 2.12 ± 0.73 vs 2.07 ± 0.72, P = 0.00066, 1.89 ± 0.52 vs 1.83 ± 0.53, P = 0.00031, respectively).

CONCLUSIONS

During non-stimulated left AVS, adrenal hormone secretion was slightly but significantly decreased after venography, similar to the normal time-related stress reaction. Venography did not increase the adrenal hormone secretion.

Non-stimulated adrenal venous sampling using Dyna computed tomography in patients with primary aldosteronism

In this retrospective study, we aimed to examine the effect of applying Dyna computed tomography (CT) on the success rate of adrenal venous sampling (AVS) without adrenocorticotropic hormone stimulation. A total of 100 consecutive patients with primary aldosteronism who underwent AVS between May 2012 and July 2015 were enrolled. In all the cases, Dyna CT was used in AVS to validate catheter position in the right adrenal vein. A selectivity index (cortisol_{adrenal vein} /cortisol_{inferior vena cava}) of ≥2.0 of both adrenal veins were required for successful AVS. Dyna CT indicated misplaced catheters in 16 patients; of these patients, 75% (12/16) eventually had successful right AVS after catheter repositioning. The success rate of initial sampling at the right adrenal vein was 76% (76/100), which increased to 88% (88/100) after Dyna CT was applied (p < 0.001). The most common inadvertently catheterised vessels detected using Dyna CT were the accessory hepatic veins (56.3%, 9/16), followed by the renal capsular veins (37.5%, 6/16). The overall success rate of non-stimulated AVS using Dyna CT was 87% (87/100). Thus, the application of Dyna CT further increased the success rate of non-stimulated AVS.

Can an enhanced thin-slice computed tomography delineate the right adrenal vein and improve the success rate?

PURPOSE

To evaluate the usefulness of enhanced thin-slice computed tomography (TSCT) for delineating the right adrenal vein (RAV) anatomy before adrenal vein sampling (AVS).

MATERIALS AND METHODS

A total of 151 consecutive AVSs with CT during angiography (interventional CT) were included. Of them, TSCT was performed before AVS for 72 patients. Successful RAV cannulation was confirmed using cortisol measurement. The RAV on TSCT was classified as certain, probable, or unidentified, and cases with certain or probable RAV identification were classified as useful. In the cases where AVS was successful, the anatomical features of the presumed RAV from the useful TSCT, including the position along the inferior vena cava, vertebral level, and distance from the upper pole of the right kidney, were compared with the RAV features identified on interventional CT. Estimated successful cannulation rates before interventional CT were compared between patients with and without useful TSCT.

RESULTS

In total, 66 TSCTs were classified as useful. The anatomical features identified on TSCT were significantly correlated with those on interventional CT. The estimated successful cannulation rates for cases with and without useful TSCT were 92.4 and 82.4 %, respectively.

CONCLUSIONS

TSCT clearly shows the anatomical features of the RAV, facilitating accurate sampling and increasing the success rate.

Diagnostic criteria for adrenal venous sampling

PURPOSE OF REVIEW

Primary aldosteronism accounts for 3 to 5% of all hypertension cases. Unilateral aldosterone hypersecretion can be treated with adrenalectomy. Guidelines for primary aldosteronism management recommend adrenal vein sampling (AVS) to ascertain unilateral primary aldosteronism before surgery. Many different protocols are used to perform AVS and for the interpretation of its results, but without hard evidence of why one should be given preference. Experts have proposed recommendations to guide clinical practice and the grounds for future research to address this situation.

RECENT FINDINGS

Proper patient preparation is a prerequisite for interpretable results. New trends are emerging to improve adequate cannulation of adrenal veins including: training of a limited number of dedicated radiologists, contrast computed tomography of adrenal veins before or during AVS, and rapid assays to measure cortisol concentrations during AVS. Cosyntropin stimulation is performed in several centers to avoid the variability of cortisol secretion during AVS, but whether this improves diagnostic performance is unknown.

SUMMARY

Better markers of adequate catheter placement are currently under investigation, including other adrenal steroids and metanephrines. Innovative strategies for interpreting partially failed AVS are also being developed. Other approaches to ascertain primary aldosteronism subtype will be necessary because of limited patient access to AVS.

Collimation and Image Quality of C-Arm Computed Tomography: Potential of Radiation Dose Reduction While Maintaining Equal Image Quality

OBJECTIVES

The aim of this study was to assess the potential for radiation dose reduction in collimated C-arm computed tomography (CACT) while maintaining the image quality of the full field of view (FFOV) acquisition.

MATERIAL AND METHODS

A whole-body anthropomorphic phantom representing a 70-kg male was used in this study. The upper abdomen of the phantom was imaged using an angiographic system (Artis Zeego Q; Siemens Healthcare, Germany) with either the standard detector radiation dose level (RDL; D100, 360 nGy) or 14 experimental reduced RDLs ranging from 95% (D95, 342 nGy) to 30% D100 (D30, 108 nGy). Either the FFOV (craniocaudal coverage, 18 cm) or a collimated field of view (CFOV; craniocaudal coverage, 6 cm) was applied. The organ dose was measured using thermoluminescence detector dosimetry, and the mean effective dose was computed according to the recommendations by the International Commission on Radiological Protection Publication 103. To compare the CFOV and the FFOV data sets, image quality was assessed in terms of high- and low-contrast resolution by calculating the modulation transfer function using the wire method as well as the image noise, signal-to-noise ratio, and contrast-to-noise ratio using a low-contrast insert placed in the upper abdomen (Δ50 HU).

RESULTS

Collimated imaging (CFOV) covering 33% of the FFOV led to an increase in the x-ray tube output of 152% for CFOV (D100; FFOV, 95.5 mGy; CFOV, 147.7 mGy) to maintain the detector dose. The mean effective dose of D100 was 6.0 mSv (male) and 6.2 mSv (female) for the FFOV and 3.7 mSv (male) and 4.1 mSv (female) for the CFOV. High-contrast resolution was comparable for all acquisition protocols (mean 10% modulation transfer function ± 95% confidence interval; FFOV, 8.8 ± 0.1 line pairs/cm; CFOV, 8.8 ± 0.1 line pairs/cm). Low-contrast resolution was superior for the CFOV compared with that for the FFOV for each RDL (D100; image noise: FFOV, 34 ± 2 HU; CFOV, 22 ± 1 HU; contrast-to-noise ratio: FFOV, 1.3 ± 0.2; CFOV, 1.8 ± 0.3). Low-contrast resolution of the standard (D100) FFOV acquisition was achieved for the CFOV at 84% D100 of the FFOV and 54% D100 of the CFOV. Therefore, collimation up to 33% of the FFOV combined with the lower detector dose allows overall reduction of a patient's radiation exposure to 33% × 84% = 28% compared with FFOV acquisition. In the upper abdomen, this results in a nearly 50% reduction of the mean effective radiation dose (male, 2.0 mSv; female, 2.2 mSv) without loss of image quality compared with the standard FFOV acquisition.

CONCLUSIONS

Craniocaudal collimation in CACT should be used whenever possible to increase the image quality and reduce the patient's overall radiation exposure. Therefore, new smart acquisition protocols are required for collimated CACT to improve the trade-off between radiation exposure and image quality requirements considering the collimation used.

Retrospective Study in 40 Patients of Utility of C-arm FDCT as an Adjunctive Modality in Technically Challenging Image-Guided Percutaneous Drainage Procedures

PURPOSE

To explore the utility of C-arm flat detector computed tomography (FDCT) as an adjunctive modality in technically challenging image-guided percutaneous drainage procedures.

METHODS

Clinical and image data were reviewed on 40 consecutive patients who underwent percutaneous drainage of fluid collections in technically challenging anatomic locations that required the use of C-arm FDCT between 2009 and 2013. Percutaneous drainage was performed under ultrasound and fluoroscopic guidance with the use of C-arm FDCT as a problem-solving tool to identify appropriate needle/wire placement prior to drainage catheter placement (n = 33) or to confirm catheter positioning within the fluid collection (n = 8). Technical success and procedural complications were recorded and retrospectively analyzed.

RESULTS

Forty one fluid collections were identified in 40 patients. Mean number of C-arm FDCT rotational acquisitions per patient was 1.25. Mean procedure time per patient was 59.3 min. Mean fluoroscopy time was 5.5 min, and mean air kerma was 394.3 mGy. Percutaneous drainage with the use of C-arm FDCT was successful in 35 of 40 patients (87.5%). Technical failure was encountered in 5 of 40 patients due to too narrow window (n = 1), too small or no fluid collection noted on C-arm FDCT images (n = 2), and poor image quality requiring the use of a conventional CT scan (n = 2). Three procedure-related complications occurred (7.5%), which included traversed rectum, traversed spleen, and sepsis.

CONCLUSION

C-arm FDCT is useful as an adjunctive modality in the interventional suite for technically challenging percutaneous drainage procedures by providing sufficient anatomic detail. Complications of catheter misplacement can be avoided if C-arm FDCT is used prior to tract dilatation. If C-arm FDCT image quality of needle and/or wire placement is poor, conventional CT guidance is recommended.

The inferior emissary vein: a reliable landmark for right adrenal vein sampling

BACKGROUND

Right adrenal vein (RAV) catheterization can be a very challenging step in adrenal venous sampling (AVS). Visualization of the inferior emissary vein (IEV) may be an indication of successful RAV catheterization.

PURPOSE

To compare the rate of successful RAV sampling in the presence of the IEV.

MATERIAL AND METHODS

Retrospective review of all consecutive patients with PA who underwent AVS between April 2009 and April 2012 was performed. A total of 30 patients were identified. Procedural images, cortisol, and aldosterone values obtained from sampling of the RAV and inferior vena cava (IVC) were reviewed. Cortisol measurements obtained from RAV samples were divided by measurements from the infra-renal IVC blood samples in order to calculate the selectivity index (SI). An SI >3 was considered indicative of technically successful RAV sampling.

RESULTS

RAV sampling was considered technically successful in 29 out of 30 cases (97%). In cases of successful RAV sampling (29 patients), the IEV was identified in 25 patients (86%). The IEV was visualized in isolation in 16 patients (64%), and in conjunction with visualization of the RAV or right adrenal gland stain in nine patients (36%). The IEV was not visualized in the one case of unsuccessful RAV sampling. Visualizing the IEV had a sensitivity of 86.2% for successful RAV sampling.

CONCLUSION

The IEV may serve as a reliable landmark for the RAV during RAV sampling.

Pathophysiology, diagnosis, and treatment of mineralocorticoid disorders

The renin-angiotensin-aldosterone system (RAAS) is a major regulator of blood pressure control, fluid, and electrolyte balance in humans. Chronic activation of mineralocorticoid production leads to dysregulation of the cardiovascular system and to hypertension. The key mineralocorticoid is aldosterone. Hyperaldosteronism causes sodium and fluid retention in the kidney. Combined with the actions of angiotensin II, chronic elevation in aldosterone leads to detrimental effects in the vasculature, heart, and brain. The adverse effects of excess aldosterone are heavily dependent on increased dietary salt intake as has been demonstrated in animal models and in humans. Hypertension develops due to complex genetic influences combined with environmental factors. In the last two decades, primary aldosteronism has been found to occur in 5% to 13% of subjects with hypertension. In addition, patients with hyperaldosteronism have more end organ manifestations such as left ventricular hypertrophy and have significant cardiovascular complications including higher rates of heart failure and atrial fibrillation compared to similarly matched patients with essential hypertension. The pathophysiology, diagnosis, and treatment of primary aldosteronism will be extensively reviewed. There are many pitfalls in the diagnosis and confirmation of the disorder that will be discussed. Other rare forms of hyper- and hypo-aldosteronism and unusual disorders of hypertension will also be reviewed in this article.

Role of C-arm cone-beam CT in chemoembolization for hepatocellular carcinoma

With the advent of C-arm cone-beam computed tomography (CBCT), minimally-invasive procedures in the angiography suite made a new leap beyond the limitations of 2-dimensional (D) angiography alone. C-arm CBCT can help interventional radiologists in several ways with the treatment of hepatocellular carcinoma (HCC); visualization of small tumors and tumor-feeding arteries, identification of occult lesion and 3D configuration of tortuous hepatic arteries, assurance of completeness of chemoembolization, suggestion of presence of extrahepatic collateral arteries supplying HCCs, and prevention of nontarget embolization. With more improvements in the technology, C-arm CBCT may be essential in all kinds of interventional procedures in the near future.

Evaluation of right adrenal vein cannulation by computed tomography angiography in 140 consecutive patients undergoing adrenal venous sampling

OBJECTIVE

As it is now known that primary aldosteronism (PA) is more prevalent than was previously recognized, and is a potentially curable cause of hypertension and related cardiovascular diseases, the search for a safe and effective means of its diagnosis has reemerged as a topic of interest. Adrenal venous sampling is the gold standard for diagnosis of PA, but the technique is challenging and the small right adrenal vein can be particularly difficult to cannulate. Our objective was to evaluate the usefulness of computed tomography during angiography (angio-CT) in increasing the success of adrenal venous sampling and to identify factors associated with cannulation failure.

DESIGN

Retrospective review.

METHODS

A total of 140 consecutive patients with suspected PA except Cushing's syndrome treated at a single hospital from June 2008 to May 2013 were included. Catheter misplacement and correct cannulation rates before angio-CT and success rate of sampling after angio-CT were calculated. Univariate analysis for factors related to incorrect cannulation included gender, age, height, weight, BMI, and adrenal nodules. Successful sampling was biochemically defined according to cortisol concentrations in the venous blood samples.

RESULTS

Angio-CT detected misplaced catheters in 13 patients (9.3%). The calculated correct cannulation rate of adrenal vein sampling increased from 86.4% before angio-CT to 95.7% after CT (P<0.001, McNemar's test). Univariate analysis showed a tendency for a higher rate of failure of right adrenal venous sampling in taller patients (P=0.052, Mann-Whitney's U test).

CONCLUSION

Angio-CT improved success of adrenal venous sampling.

Right adrenal venography findings correlated with C-arm CT for selection during C-arm CT-assisted adrenal vein sampling in primary aldosteronism

PURPOSE

This study was designed to evaluate retrospectively the efficacy of C-arm CT to confirm right adrenal vein catheterization during adrenal vein sampling (AVS) and to correlate adrenal venography findings with C-arm CT and/or biochemical results for right adrenal vein selection.

METHODS

Forty-two consecutive primary aldosteronism patients (M:F = 21:21; age: 29-70 years) underwent C-arm CT assisted sequential AVS. After catheterization of right adrenal vein, C-arm CT was performed to confirm catheter position. Catheter was repositioned when right adrenal gland was not opacified. Radiological images, medical records, and biochemical results were reviewed for technical/biochemical success rates and complications. Right adrenal venography findings of pinnate pattern, visualization of renal capsular vein, and retroperitoneal vein other than renal capsular vein were correlated with C-arm CT and/or biochemical results for right adrenal vein selection.

RESULTS

Both the technical and biochemical success of AVS was achieved in 40 patients (95.2%). C-arm CT failed due to catheter instability in one, and adrenal/vena cava cortisol gradient was <3 in one patient. Catheter was repositioned in four patients (9.5%) according to C-arm CT findings. Right adrenal venography finding of renal capsular vein significantly correlated with C-arm CT and/or biochemical results (100%) for right adrenal vein selection (p = 0.011, χ(2) test), whereas pinnate pattern (p = 0.099) and other retroperitoneal veins (p = 0.347) did not. There was no procedure-related complication.

CONCLUSIONS

C-arm CT increases confidence of right adrenal vein catheterization during AVS. Visualization of renal capsular vein on adrenal venography suggests right adrenal vein catheterization and C-arm CT may not be required.

Adrenal venous sampling: promises and pitfalls

PURPOSE OF REVIEW

To describe the current indications for adrenal vein sampling (AVS), variability in institutional protocols for performing the procedure, shortage of expert interventional radiologists trained in this procedure, pitfalls in technique and strategies to improve success. A major emphasis of the review will focus on the interpretation of the AVS results.

RECENT FINDINGS

Published protocols for performance of the AVS procedure and variability in the diagnostic criteria differentiating aldosterone-producing adenoma from bilateral adrenal hyperplasia vary significantly. Inability to catheterize the right adrenal vein is the major reason for technical failure of AVS. Preplanning computed tomography, stat intraprocedural cortisol levels and cone-beam computed tomography are helpful in identifying the right adrenal vein. The administration of adrenocorticotropic hormone stimulation during AVS varies significantly between different studies.

SUMMARY

More interested interventional radiologists need to acquire the necessary technical expertise for AVS due to increased demand for the procedure, which is the diagnostic reference standard for primary aldosteronism. Unresolved issues include variability in the AVS procedure protocol, use of adrenocorticotropic hormone stimulation and standardization of the interpretation of the results. Despite all these variables, many different approaches still appear to be clinically successful, as indicated by the extensive published reports.

Detection of adrenal veins on selective retrograde CT adrenal venography in comparison with digital subtraction angiography in subjects with established diagnosis of one-sided adrenal aldosterone-producing tumor confirmed by adrenal vein sampling, histopathology and clinical course

PURPOSE

Adrenal vein (AV) sampling (AVS) is the diagnostic gold standard for primary aldosteronism (PA), but right-sided AVS is difficult. We compared detection of AVs by selective retrograde CT adrenal venography (SRCTAV) with digital subtraction angiography (DSA).

MATERIALS AND METHODS

Data on 29 subjects (11 males, mean age 55 y) with increased serum aldosterone concentrations (SAC) and a diagnosed right or left aldosterone-producing tumor (APT) by AVS who underwent laparoscopic adrenalectomy were retrospectively analyzed. Before AVS, visualizing AVs was attempted by DSA and SRCTAV (Aquilion). If after the adrenocorticotropic hormone loading test serum cortisol concentration (SCC) from either AV was >200 μg/dl, AVS was considered successful. If the SAC/SCC ratio for one side was ≥4 times higher than the other side, we diagnosed a one-sided APT.

RESULTS

Left and right AV, respectively, were visualized in 29 (100%) and 22 subjects (76%) by DSA and 29 (100%) and 28 subjects (97%) by SRCTAV, with right-AV detection significantly higher by SRCTAV (p<0.05). Cannulations were regarded successful in 28 subjects having both AVs observed on SRCTAV but not in the remaining subject whose adrenocortical scintigram was positive, however. Adrenalectomy was performed with a diagnosis of adenoma. Among 28 subjects with successful AVS, histopathological diagnoses included adenoma (25), nodular hyperplasia (2) and normal (1). After adrenalectomy, antihypertensive drug usage in 28 patients was reduced or stopped with decreases in SAC (97%).

CONCLUSIONS

Detection of AV was significantly higher by SRCTAV than DSA, especially on the right side, in 29 subjects diagnosed with one-sided APT.

Use of angiographic CT imaging in the cardiac catheterization laboratory for congenital heart disease

OBJECTIVES

This study sought to retrospectively evaluate our initial experience using angiographic computed tomography (ACT) in a pediatric cardiac catheterization laboratory.

BACKGROUND

ACT provides cross-sectional CT images from a rotational angiography run using a C-arm mounted flat-panel detector in the interventional suite. A 3-dimensional (3D) angiographic image can be created from the CT volume set and used in real time during the procedure. To our knowledge, its use has never previously been described for congenital heart disease.

METHODS

3D reconstructions were created and we retrospectively reviewed cases during our first year of ACT use. Images obtained were independently evaluated to determine their diagnostic utility. Radiation dose reduction protocols were defined using phantom testing and radiation dose calculation.

RESULTS

ACT was used during 41 cardiac catheterizations in patients at a median age of 5.1 years (range: 0.4 to 58.8 years) for evaluation of: right ventricular outflow tract (RVOT)/central pulmonary arteries (PAs) in 20; cavopulmonary connection (CPC) in 11; pulmonary veins in 5; distal PAs in 4; and other locations in 5. Four subjects had 2 anatomic areas studied by ACT. The mean contrast volume for ACT was 1.2 ± 0.4 ml/kg. Diagnostic-quality imaging was obtained in 71% of cases: 13/20 RVOT/central PAs; 9/11 CPC; 4/5 pulmonary veins; 2/4 distal PAs; and 4/5 others. In 12 cases, ACT contributed to clinical outcomes beyond standard angiography. Radiation dose reduction protocols allowed ACT to be comparable in exposure to a standard biplane cineangiogram.

CONCLUSIONS

Diagnostic-quality imaging can be obtained using ACT in 71% of cases without a significant increase in contrast or radiation exposure. In certain cases, ACT provides additional anatomic detail and may aid complex catheter manipulations. Future work is needed to continue to define applications of this new technology.

Patient radiation management and preprocedure planning and consent

Protection of patients from excessive medical radiation has become a high priority in health care. As clinical physicians, interventional radiologists must remain cognizant of the radiation we use in daily practice. Radiation reduction begins before the procedure itself, as with appropriate preprocedural planning the amount of fluoroscopy and angiography used can then be reduced. Patients should be counseled regarding the potential for use of significant amounts of radiation when procedures associated with such doses are planned, as part of the process of obtaining informed consent. If significant radiation is used, patients should be alerted to have appropriate follow-up. The amount of radiation used can be reduced by careful attention to imaging technique.

C-arm cone beam computed tomography needle path overlay for fluoroscopic guided vertebroplasty

STUDY DESIGN

Retrospective review.

OBJECTIVE

To report our early clinical experience using C-arm cone beam computed tomography (C-arm CBCT) with fluoroscopic overlay for needle guidance during vertebroplasty.

SUMMARY OF BACKGROUND DATA

C-arm CBCT is advanced three-dimensional (3-D) imaging technology that is currently available on state-of-the-art flat panel based angiography systems. The imaging information provided by C-arm CBCT allows for the acquisition and reconstruction of "CT-like" images in flat panel based angiography/interventional suites. As part of the evolution of this technology, enhancements allowing the overlay of cross-sectional imaging information can now be integrated with real time fluoroscopy. We report our early clinical experience with C-arm CBCT with fluoroscopic overlay for needle guidance during vertebroplasty.

METHODS

This is a retrospective review of 10 consecutive oncology patients who underwent vertebroplasty of 13 vertebral levels using C-arm CBCT with fluoroscopic overlay for needle guidance from November 2007 to December 2008. Procedural data including vertebral level, approach (transpedicular vs. extrapedicular), access (bilateral vs. unilateral) and complications were recorded. Technical success with the overlay technology was assessed based on accuracy which consisted of 4 measured parameters: distance from target to needle tip, distance from planned path to needle tip, distance from midline to needle tip, and distance from the anterior 1/3 of the vertebral body to needle tip. Success within each parameter required that the distance between the needle tip and parameter being evaluated be no more than 5 mm on multiplanar CBCT or fluoroscopy.

RESULTS

Imaging data for 12 vertebral levels was available for review. All vertebral levels were treated using unilateral access and 9 levels were treated with an extrapedicular approach. Technical success rates were 92% for both distance from planned path and distance from midline to final needle tip, 100% when distance from needle tip to the anterior 1/3 border of the vertebral body was measured, and 75% when distance from target to needle tip was measured. There were no major complications. Minor complications consisted of 3 cases (25%) of cement extravasation.

CONCLUSION

C-arm CBCT with needle path overlay for fluoroscopic guided vertebroplasty is feasible and allows for reliable unilateral therapy of both lumbar and thoracic vertebral bodies. Extrapedicular approaches were performed safely and with good accuracy of reaching the targets.

[Use of C-arm CT for improving the hit rate for selective blood sampling from adrenal veins]

Primary hyperaldosteronism is the most common curable cause of hypertension with a prevalence of up to 12% among patients with hypertension. Selective blood sampling from adrenal veins is considered the diagnostic gold standard. However, it is underutilized due to the high technical failure rate. The use of C-arm CT during the sampling procedure can reduce or even eliminate this failure rate. If adrenal vein sampling is augmented by native C-arm CT to check for the correct catheter position, the technical success rate increases substantially. General use of this technique will result in correct diagnosis and treatment for patients with primary hyperaldosteronism.

Three-dimensional C-arm cone-beam CT: applications in the interventional suite

C-arm cone-beam computed tomography (CT) with a flat-panel detector represents the next generation of imaging technology available in the interventional radiology suite and is predicted to be the platform for many of the three-dimensional (3D) roadmapping and navigational tools that will emerge in parallel with its integration. The combination of current and unappreciated capabilities may be the foundation on which improvements in both safety and effectiveness of complex vascular and nonvascular interventional procedures become possible. These improvements include multiplanar soft tissue imaging, enhanced pretreatment target lesion roadmapping and guidance, and the ability for immediate multiplanar posttreatment assessment. These key features alone may translate to a reduction in the use of iodinated contrast media, a decrease in the radiation dose to the patient and operator, and an increase in the therapeutic index (increase in safety-vs-benefit ratio). In routine practice, imaging information obtained with C-arm cone-beam CT provides a subjective level of confidence factor to the operator that has not yet been thoroughly quantified.

C-arm cone beam computed tomographic needle path overlay for fluoroscopic-guided placement of translumbar central venous catheters

C-arm cone beam computed tomography is an advanced 3D imaging technology that is currently available on state-of-the-art flat-panel-based angiography systems. The overlay of cross-sectional imaging information can now be integrated with real-time fluoroscopy. This overlay technology was used to guide the placement of three percutaneous translumbar inferior vena cava catheters.

Usefulness of cone-beam computed tomography during ultraselective transcatheter arterial chemoembolization for small hepatocellular carcinomas that cannot be demonstrated on angiography

This study evaluated the usefulness of cone-beam computed tomography (CBCT) during ultraselective transcatheter arterial chemoembolization (TACE) for hepatocellular carcinomas (HCC) that could not be demonstrated on angiography. Twenty-eight patients with 33 angiographically occult tumors (mean diameter 1.3 +/- 0.3 cm) were enrolled in the study. The ability of CBCT during arterial portography (CBCTAP), during hepatic arteriography (CBCTHA), and after iodized oil injection (LipCBCT) to detect HCC lesions was retrospectively analyzed. The technical success of TACE was divided into three grades: complete (the embolized area included the entire tumor with at least a 5-mm wide margin), adequate (the embolized area included the entire tumor but without a 5-mm wide margin in parts), and incomplete (the embolized area did not include the entire tumor) according to computed axial tomographic (CAT) images obtained 1 week after TACE. Local tumor progression was also evaluated. CBCTAP, CBCTHA, and LipCBCT detected HCC lesions in 93.9% (31 of 33), 96.7% (29 of 30), and 100% (29 of 29) of patients, respectively. A single branch was embolized in 28 tumors, and 2 branches were embolized in five tumors. Twenty-seven tumors (81.8%) were classed as complete, and 6 (18.2%) were classed as adequate. None of the tumors were classed as incomplete. Twenty-five tumors (75.8%) had not recurred during 12.0 +/- 6.2 months. Eight tumors (24.2%), 5 (18.5%) of 27 complete success and 3 (50%) of 6 adequate success, recurred during 10.1 +/- 6.2 months. CBCT during TACE is useful in detecting and treating small HCC lesions that cannot not be demonstrated on angiography.

Three-dimensional C-arm cone-beam CT: applications in the interventional suite

C-arm cone-beam computed tomography (CT) with a flat-panel detector represents the next generation of imaging technology available in the interventional radiology suite and is predicted to be the platform for many of the three-dimensional (3D) roadmapping and navigational tools that will emerge in parallel with its integration. The combination of current and unappreciated capabilities may be the foundation on which improvements in both safety and effectiveness of complex vascular and nonvascular interventional procedures become possible. These improvements include multiplanar soft tissue imaging, enhanced pretreatment target lesion roadmapping and guidance, and the ability for immediate multiplanar posttreatment assessment. These key features alone may translate to a reduction in the use of iodinated contrast media, a decrease in the radiation dose to the patient and operator, and an increase in the therapeutic index (increase in the safety-vs-benefit ratio). In routine practice, imaging information obtained with C-arm cone-beam CT provides a subjective level of confidence factor to the operator that has not yet been thoroughly quantified.