Clinical issues and challenges in imaging of gastrointestinal diseases: A minireview and our experience

Table 1 Main limitations/difficulties, approaches to improve them, and benefits/advantages of gastrointestinal imaging techniques available currently

	Limitations and difficulties	Approaches to improve the limitations	Benefits and advantages	Ref.
Fluoroscopy of the GIT with contrast media	Direct visualization of the lumen and mucosa only	Digital fluoroscopy has been introduced to reduce the dosage and better the image quality	High temporal and spatial resolution	[24,25]
	High radiation exposure		Fast image acquisition
	No postprocessing possible		Using intraluminal contrast, the function can be assessed – i.e., motility
	Patient cooperation is needed		The only method that can show swallow reflex
	Contraindicated in case of acute bleeding and perforation
Ultrasound	High doctor expertise is needed	The technique of strain rate imaging by Doppler allows for obtaining a detailed description of the walls	Ideal for image-guided interventions	[26-30]
	Patient preparation is needed	Contrast-enhanced ultrasound has a role in identifying hypervascular tumors and wall hyperemia and edema in case of inflammation	High resolution for soft tissues
	Difficult for interpretation artifacts	The bowel walls are assessed with high-frequency endosonography	Suitable for repeated examination and research due to no radiation exposure
	Total visualization of the entire intestines is impossible	During contractions of the GIT musculature, the cross-sectional area of the outer longitudinal muscle increases – this was shown in endosonography	Intestinal wall and intraluminal evaluation
			Information of function – i.e., motility and flow
Endoscopy	Invasive procedure that requires preparation	Chromoendoscopy – betters the image quality by adding colors	Direct visualization of the mucosal surfaces	[31-33]
	Risk of perforation, bleeding, and other procedure-related complications	Virtual chromoendoscopy – addition of "missing colors"	Intervention – i.e., biopsies, polypectomy, endoscopic surgery
	No visualization of deeper layers and surroundings	Filters (i-scan, SPIES, FICE) - alter the wavelength ranges of reflected light
		Capsule endoscopy – better patient tolerance
Multidetector computed tomography	High radiation exposure	New software reconstruction options – virtual colonography, unfolding and dissection of the intestinal wall, and computer-aided detection improve the diagnosis	Fast image acquisition, fewer motion artifacts	[34,35]
	No direct information on the function		Evaluation of total intestines and surroundings
	Less suitable for healthy subjects' examination		3D reconstructions and virtual endoscopy
	Risk of contrast-induced nephropathy in patients with kidney function impairment		High temporal and spatial resolution
Magnetic resonance imaging	3D reconstructions and virtual endoscopy (lower image resolution than CR)	Motion artifacts can be overcome by applying spasmolytics	Suitable for soft tissues	[36-40]
	Long image acquisition	Optimal distention of the bowel walls can be reached by applying water-soluble contrast materials with hyperosmotic agents, such as polyethylene glycol, methylcellulose, and mannitol	Ideal for repeated examination and research due to no radiation exposure
	Motion artifacts due to intestinal motility	Inflammatory changes in the bowel walls are better shown in contrast-enhanced studies	Evaluation of total intestines and surroundings
	Potentially long-term adverse effects of gadolinium-based contrast media (risk of nephrogenic systemic fibrosis development)	GIT function is shown by functional cine-magnetic resonance imaging	Information of function – i.e., motility and flow
		Development of resonance imaging colonography is in the process
		Patient preparation is needed to avoid false positive results because of intestinal residual stools. Bowels need to be filled with water.
		New postprocessing techniques have been introduced, such as 3D models of the properties of the intestinal walls
PET	High radiation doses	PET in combination with CT – PET/CT allows the use of both methods, thus usage of their benefits	PET enables visualization of metabolic changes, which can precede structural transformation	[18, 41-44]
	Only useful in case of tumors
	Lower spatial and temporal resolution compared to CT
Impedance planimetry known as Functional Lumen Imaging Probe	Not directly applicable to GI distension studies	Modifications in terms of dimensions, electronics, signal processing, and distension protocols are needed to improve the image	Allows direct online imaging of the luminal geometry of the GIT	[45-49]
			Suitable for visualization of the complex physiology of the GI sphincters
Oesophageal high-resolution manometry	Provides insufficient explanation of non-obstructive dysphagia	Probably, the esophageal stress tests add value	Allows online visualization of oesophageal peristalsis	[50-55]
	No sufficient data on specific factors (i.e., technique and patients) impact the measurements	Panesophageal pressurization during multiple rapid swallows is a sign of true stasis, justifying a diagnosis of achalasia	High accuracy in oesophageal motor dysfunction visualization
	More expensive than conventional manometry (i.e., equipment and maintenance costs)
Scintigraphy and single photon emission computed tomography	Low radiation burden	N/A	For emptying and motility studies of the GI conditions	[56-60]
	Long scan times and low-resolution images prone to artifacts and attenuation		Can localize bleeding, especially in patients with a history of previous operations or cancer
	Some artifacts can mimic perfusion defects		Can quickly detect altered anatomy and bleeding from the tumor or operation site
	Does not provide a quantifiable estimate of the blood flow, unlike PET		Useful for guiding surgeons for more accurate localization
			Provides information on the oesophagus
			Scintigraphy with a radiolabeled somatostatin analogue (the gold standard for evaluating gastric emptying in patients with dyspepsia)

Technological advancements in endoscopy have greatly improved the diagnosis of digestive disorders. GI: Gastrointestinal; GIT: GI tract; SPIES: Storz professional image enhancement system; FICE: Fujinon intelligent chromoendoscopy; CR: Computed Radiography; PET: Positron emission tomography; CT: Computed tomography.