Patients
Ethical approval for this retrospective study was obtained from the institutional ethics and medical research committee. Informed consent was obtained in all cases. A total of 43 TACE procedures utilizing C-arm CBCT PBVI were performed on 25 patients between June 17, 2014 and August 7, 2015. Of these, 18 TACEs on 13 patients were evaluated with both immediate post-TACE PBVI and a subsequent multi-phase MDCT or MRI for assessment of treatment response, without intervening TACE. All 18 TACE procedures were included. Of the 13 patients, 12 were male and one was female. Patient age ranged from 31 to 73 years (median 62). All patients were BCLC stage A or B at the time of treatment. The underlying diagnoses were alcohol-related liver disease (5 patients), hepatitis B infection (3 patients), hepatitis C infection (3 patients), hemochromatosis (1 patient) and alpha 1-antitrypsin deficiency (1 patient).
TACE protocol
In all cases, prior MDCT angiography or MRI angiography was evaluated to identify variant hepatic arterial anatomy and assess for possible extra-hepatic arterial tumor supply. All procedures were performed by one of two operators (J.McC. or E.R.R.), with procedural details depending on operator preference. A 5-Fr or 6-Fr right common femoral artery sheath was placed with ultrasound guidance. A 5-Fr hydrophilic C2 catheter (Terumo, Leuven, Belgium) or Sim1 catheter (Boston Scientific, Marlborough MA, USA) was used to cannulate the superior mesenteric artery; DSA was performed with delayed images to confirm portal vein patency. The coeliac artery was then cannulated and the hydrophilic C2 catheter was advanced into the proper hepatic artery or, in cases using a Sim1, a microcatheter (Renegade, Boston Scientific, Marlborough MA, USA) was advanced into the proper hepatic artery. C-arm CBCT PBVI was then performed through the C2 catheter or microcatheter as outlined later. Super-selective drug-eluting bead TACE (DEB-TACE) was performed in each case by using the microcatheter system to access the hepatic arterial branch supplying the targeted lesion or lesions. Fourteen TACEs were performed using doxorubicin loaded on 100–300-μm DC-Beads (BTG, Farnham, United Kingdom); in one of these 14 cases, the treatment was supplemented with bland embolization using 500–700-μm Embosphere particles (Merit Medical, Paris, France). The supplementation with bland embolic was in a case where residual tumor enhancement was visible on DSA despite the entirety of the available chemo-embolic having been administered. Three treatments were performed using doxorubicin loaded onto 50–100-μm Hepasphere beads (Merit Medical, Paris, France). One treatment used doxorubicin loaded on 30–60-μm Hepasphere beads (Merit Medical, Paris France). Chemoembolization was performed until slow forward flow in all cases.
C-arm CBCT and PBVI protocol
The same angiography system was used in all procedures for C-arm CBCT acquisition (Artis Q, Siemens Healthcare AG, Forchheim, Germany); PBVI was performed before and after TACE. Post-processing was performed using Siemens Syngo DynaPBV Body (Siemens Healthcare AG, Forchheim, Germany). Each PBVI study involved two C-arm rotations. A catheter or microcatheter was positioned in the proper hepatic artery beyond the gastroduodenal artery origin. The first 5-s C-arm rotation was performed prior to contrast injection (mask run). Contrast injection was initiated immediately following this first rotation. After a 7-s delay as the C-arm returned to its starting position, a second 5-s CBCT was performed (fill run). Twelve milliliters of contrast agent (Omnipaque 350 mg I/mL, General Electric Healthcare, Oslo, Norway) was added to 24 mL of 0.9% saline solution, for a total volume of 36 mL. The contrast injection rate was 3 mL/s. The injection lasted 12 s. A total 17-s breath-hold was required. A non-rigid registration algorithm was used to correct for motion between the two CBCTs. Following segmentation of bone and air, the mask run was subtracted from the fill run allowing the calculation and color map depiction of blood volume values. Examples of the resulting images are shown in Figs. 1, 2 and 3. Conventional C-arm CBCT images were also reconstructed from the pre-TACE fill run to allow standard vessel mapping and procedure planning.
MDCT/MRI protocol
Follow-up imaging was performed with multiphase MDCT or MRI. MDCT was performed using a 64-slice CT scanner (Siemens Somatom Sensation 64, Forchheim, Germany), with non-contrast, arterial, portal venous and 5-min delayed phase images. The contrast used was Omnipaque 350 mg I/mL (General Electric Healthcare, Oslo, Norway) at a dose of 150 mL MRI was performed on a 1.5-T scanner (Siemens Magnetom Avanto, Forchheim, Germany) and sequences including at least T1-weighted fat-suppressed non-contrast, arterial, portal venous and 5-min delayed phases. The gadolinium-based contrast agent used was gadoterate meglumine (Dotarem, Guerbet, Roissy, France) at a dose of 20 mL. In 17 cases, follow-up was performed with MDCT and in one case follow-up with MRI. The choice of follow-up imaging modality was dictated by the pre-procedure imaging modality in order to facilitate accurate comparison. Follow-up imaging was performed between 9 and 104 days (mean 60 days).
Image analysis
All images were reviewed retrospectively by two interventional radiologists with 14-year (J.McC.) and 10-year (E.R.R.) experience in DEB-TACE by consensus. Analysis was lesion-based. Only lesions within the treated segment or segments were evaluated. In each case, a visual qualitative inspection was made of the post-TACE PBVI and an assessment was made for the presence or absence of residual tumor perfusion that would necessitate repeat TACE. Residual tumor perfusion requiring repeat TACE was recorded as either present or absent. The follow-up MDCT or MRI was analyzed in an identical manner, again for the presence or absence of residual enhancing tumor necessitating repeat TACE. As in the case of PBVI, residual lesion enhancement was recorded as present or absent.
Statistical analysis
Sensitivity and specificity of post-TACE CBCT PBVI were calculated using follow-up MDCT/MRI as a reference standard. Point estimates were obtained along with their 95% confidence intervals.