Use of iodine mapping with hepatocellular carcinoma (HCC) recurrence

Kurume University Hospital
Dr. Akiko Sumi, Dept. of Radiology, Kurume University School of Medicine

DATE : 2021

Introduction
Case explanation
Imaging findings
Photography protocol
Roles of contrast computed tomography (CT) in diagnosis of the disease
CT techniques and imaging protocol settings

Introduction

Patient’s background

Female; 70s; body weight: 65 kg; HCC

Assessment objectives

Monitoring of progression after treatment of HCC

Contrast agent used

Iopromide 300 injection syringe, 100 mL

Case explanation

The patient was a woman in her 70s. An interferon preparation had been administered for chronic hepatitis C 17 years previously. However, HCC had developed 12 years previously, and then recurred repeatedly. It had been treated with percutaneous radiofrequency ablation (RFA) and transcatheter arterial chemoembolization (TACE). With dynamic contrast CT during monitoring of progression, early dark staining in the arterial phase was found in a part of S7 of the liver where there was no accumulation of injected iodized poppy-oil fatty-acid ethyl ester, and in the equilibrium phase a low-absorption region was found there, so recurrence was considered to be probable.

Imaging findings

A nodule associated with accumulation of injected iodized poppy-oil fatty-acid ethyl ester can be seen, and in part of the nodule interior such accumulation is absent (arrowhead).

Fig. 1. Simple CT

Faint, early dark staining can be seen in the area where accumulation of injected iodized poppy-oil fatty-acid ethyl ester is absent (arrowhead).

Fig. 2. Late arterial phase

Although mild wash-out can be seen, changes have occurred since treatment, and the status is difficult to understand (arrowhead).

Fig. 3. Equilibrium phase

Early dark staining can be clearly seen in the area where accumulation of injected iodized poppy-oil fatty-acid ethyl ester is absent (arrowhead).

Fig. 4. Late arterial phase iodine mapping image

In comparison with usual images, wash-out can be clearly seen (arrowhead).

Fig. 5. Equilibrium phase iodine mapping image

Photography protocol

Equipment used	CT device model	Revolution Apex / GE Healthcare
	Number of CT detector rows / number of slices	256
	Workstation	AW server / GE Healthcare

Imaging conditions	Imaging phase	Simple	Late arterial phase	Portal phase	Equilibrium phase
	Tube voltage (kV)	GSI/80kV-140kV	GSI/80kV-140kV	GSI/80kV-140kV	GSI/80kV-140kV
	AEC	NI : 10.0	NI : 9.0	NI : 9.0	NI : 9.0
	(AEC settings)	ー	ー	ー	ー
	Beamwidth	80mm	80mm	80mm	80mm
	Slice thickness (mm)	0.625	0.625	0.625	0.625
	Focal-spot size	Large	Large	Large	Large
	Scan mode	Helical	Helical	Helical	Helical
	Scan speed (s/rotation)	0.5	0.5	0.5	0.5
	Pitch	0.992:1	0.992:1	0.992:1	0.992:1
	Scan range	Upper abdomen	Upper abdomen	Upper abdomen	Chest to pelvis
	Imaging duration (s)	2.6	2.6	2.6	5.4
	Imaging direction	Head to foot	Head to foot	Head to foot	Head to foot

Reconstruction conditions		Simple	Late arterial phase	Portal phase	Equilibrium phase
	Routine: Reconstructed slice thickness / interval (mm/mm)	5 / 5	5 / 5	5 / 5	5 / 5
	Routine: Reconstruction function / iterative approximation method	Stnd / ASiR-V 0%	Stnd / ASiR-V 0%	Stnd / ASiR-V 0%	Stnd / ASiR-V 0%
	3D / multiplanar reformation: Reconstructed slice thickness / interval (mm/mm)	1.25 / 1.25	1.25 / 1.25	1.25 / 1.25	1.25 / 1.25
	3D / multiplanar reformation: Reconstruction function / iterative approximation method	Stnd / TFI H	Stnd / TFI H	Stnd / TFI H	Stnd / TFI H
	Material density: Reconstructed slice thickness / interval (mm/mm)	ー	1.25 / 1.25	1.25 / 1.25	1.25 / 1.25
	Material density: Reconstruction function / iterative approximation method	ー	iodine(water)st-d/ASiR-V 50%	iodine(water)st-d/ASiR-V 50%	iodine(water)st-d/ASiR-V 50%

Contrast conditions		Simple	Late arterial phase	Portal phase	Equilibrium phase
	Automatic injector model and manufacturer	Dual Shot GX7 (Nemoto Kyorindo)
	Contrast agent used	Iopromide 300 injection syringe
	Contrast agent: Dose	ー	600mgI/kg	ー	ー
	Contrast agent: Injection speed, injection duration	ー	Injection duration: 30 s	ー	ー
	Physiological saline solution: Dose	ー	ー	ー	ー
	Physiological saline solution: Injection speed, injection duration	ー	ー	ー	ー
	Scan timing	ー	Fixation method	ー	ー
	Delay time	ー	45 s	22 s	108 s
	Indwelling needle size (G)	22G
	Injection pressure limit (kg/cm²)	13kg/cm²

In order to establish a consistent iodine dose, a test was performed consistently with the previous injection speed and duration.

Roles of contrast computed tomography (CT) in diagnosis of the disease

Even among cases of HCC that develop when chronic hepatitis and hepatic cirrhosis are background conditions, classical HCC is characterized by early dark staining in the arterial phase of dynamic contrast CT, and wash-out in the equilibrium phase. However, if HCC recurs frequently and is unresectable, treatments such as RFA, TACE and radiotherapy are performed repeatedly. Sometimes, modification due to repeated treatment, and the effects of chronic hepatitis and hepatic cirrhosis, result in crude CT values for the background liver, making it difficult to evaluate recurrent HCC lesions by means of dynamic contrast CT. In that situation, use of iodine mapping facilitates judgment even with very little contrast enhancement. Although accumulation of injected iodized poppy-oil fatty-acid ethyl ester and post-RFA changes were found in this patient’s lesions, early dark staining in the arterial phase and wash-out in the equilibrium phase were evaluated more readily with iodine mapping than with the usual CT. However, injected iodized poppy-oil fatty acid ethyl ester is also delineated as high absorption, so care must be taken.

CT techniques and imaging protocol settings

Revolution Apex (GE Healthcare) was used with the present patient. As a technique for reducing radiation exposure, the number of CT devices capable of the iterative approximation reconstruction method and filtered back-projection (FBP) method has been increased. In addition, with CT devices capable of dual-energy CT, it has become possible to obtain images that enable diagnosis while reducing radiation exposure. However, noise and artifacts present problems with low-dose images. Image reconstruction software (True Fidelity Image) using deep-learning algorithms, a type of artificial intelligence, is installed in Revolution Apex, making it possible to obtain images of a quality that could only be obtained at high radiation doses with image reconstruction using the conventional FBP method, and also to reduce the imaging noise at lower doses. In addition, imaging with Gemstone Spectral Imaging, which uses the ultra-high-speed Fast kV Switching system (80 and 140 kVp), can be used to obtain material-density images, such as water-equivalent and iodine-equivalent density images, and also monochromatic images for different energy levels. Reconstruction of iodine mapping images using this technique will be useful for determining very low contrast enhancement. The iodine level can be measured by positioning the region of interest on the iodine mapping image, enabling quantification of the iodine level, and this technique is expected to be useful as a new parameter in hepatic blood-flow imaging.

- Precautions for use [excerpt from Package Insert]

1. Careful administration (particular care should be taken with administration to the following patients)
(11) Elderly patients (see “Administration to elderly people” section)
5. Administration to elderly people
This drug is excreted primarily by the kidneys, but in elderly patients renal function is often depressed, so high blood concentrations may persist. Therefore, it should be administered carefully, at the minimum essential dose, while monitoring the patient's condition.

*The case introduced is just one clinical case, so the results are not the same as for all cases.
*Please refer to the Package Insert for the effects and indications, dosage and administration method, and warnings, contraindications, and other precautions with use.