How Can New Imaging Modalities Help in the Practice of Radiology ?

©Copyright 2016 by the Atatürk University School of Medicine Available online at www.eurasianjmed.com ABSTRACT The purpose of this article was to provide an up-to-date review on the spectrum of new imaging applications in the practice of radiology. New imaging techniques have been developed with the objective of obtaining structural and functional analyses of different body systems. Recently, new imaging modalities have aroused the interest of many researchers who are studying the applicability of these modalities in the evaluation of different organs and diseases. In this review article, we present the efficiency and utilization of current imaging modalities in daily radiological practice.


Introduction
Radiological imaging techniques encompass techniques that could be performed to evaluate a patient.Physicians and radiologists should be familiar with the advantages of new imaging modalities [1].Advanced imaging techniques have permitted the meaningful acquiring of images with higher accuracy [2].The ensuing review article presents the use of these new imaging modalities in neuroradiology, abdomen imaging, musculoskeletal imaging, interventional radiology breast imaging, pediatric radiology, and other radiological procedures.

Brain Perfusion Imaging
Perfusion MRI techniques are advanced methods that reveal information unavailable in conventional MRI.In particular, these techniques have numerous applications with regard to the characterization of tumors (Figure 1) [3].Perfusion imaging techniques also reveal information on the hemodynamic state of the brain tissue.Concordantly, they reveal details about hypoperfused areas [4,5].
Arterial spin labeling (ASL) was developed in the 2000s [6].It does not involve any contrast agent.Because of nephrogenic systemic fibrosis, perfusion imaging in patients with renal deficiency has induced massive alarm in radiologists.If a contrast agent is not required, ASL escapes a potential needle rod in the pediatric population [7][8][9].
Perfusion imaging accessible is quantitative presenting changes in cerebral blood volume, cerebral blood flow, and mean transit time.Dynamic contrast-enhanced perfusion applications are first-pass methods that are T2-or T2*-weighted sequences.The regional evaluations of a cerebral perfusion reveal, for simple assessment, the therapy, ischemic stroke evaluation, and brain tumors [10][11][12].CT perfusion imaging was first performed in 1980.As CT involves ion-izing radiation, MRI may be preferred in daily practice [13,14].

Diffusion-weighted Imaging
Diffusion-weighted imaging (DWI) is based on the principle of mobile molecules.Mobile molecules undergo a substantial loss of signals that are related to the diffusion coefficient, as well as sequence parameters chosen by different b-values [15].The apparent diffusion coefficient (ADC) corresponds to microscopic water diffusion characteristics.DWI can reveal the cellularity of tumors because cells represent a barrier to water diffusion [3,4].Diffusion kurtosis imaging is an attempt to account for this variation, to reveal a more accurate model of diffusion, and to capture non-Gaussian diffusion.It can evaluate whether the variant distribution pattern can reveal important microstructural information about the brain and improve white matter characterization.Important imaging features for assessing disease progression and treatment responses can be determined via diffusion kurtosis imaging [16].

Diffusion Tensor Imaging (DTI) and Functional Brain Imaging
Diffusion tensor MRI is a method that has been advanced more recently than the isotropic diffusion technique.It can be utilized in some disorders because normal brain white matter is extremely integrated [15].Diffusion tensor MRI reveals a good design for determining changes in the integrity of white matter structures.White matter disorders can be detected by DTI studies that are not evident on conventional MRI examinations.It is a good application for evaluating guidance in preoperatively detecting white matter tracts (Figure 2) [17].Functional magnetic resonance (MR) imaging has been used in many studies to better understand how a healthy brain works [18,19].

Proton MR Spectroscopy
There are some important diagnostic challenges in the differentiation of benign neoplasms from malignant neoplasms, cystic neoplasms from brain abscess, and tumor recurrence from radiation-induced necrosis.Proton MR spectroscopy (MRS) can reveal knowledge methods or stimulated-echo acquisition mode or point-resolved excitation spin-echo.Important metabolites detected by MRS involve N-acetyl aspartate (NAA), creatine, choline, lactate, myoinositol, and lipids.As soon as the delivery of oxygen and nutrients ceases, anaerobic glycolysis takes over.Lactate is easily determined by its characteristic doublet appearance at 1.3 ppm.A high peak of choline is seen in both intra-axial and extra-axial tumors (Figure 3).A high choline peak, however, is not confined to neoplastic conditions and can be seen in other diseases, for example, in tumefactive multiple sclerosis.The lactate peak and mobile lipid peaks are seen in more malignant tumors and in tumors with necrosis.Radiation necrosis produces a rather flat spectrum because of a reduction in the amount of NAA and choline.Lactate may be seen [20][21][22][23].

Susceptibility-weighted Imaging
Susceptibility-weighted imaging (SWI) is sensitive to compositions that distort the local magnetic competition and make it available in determining hemorrhages and calcium deposits.The most common use of SWI is in the detection of small amounts of hemorrhage or calcium deposits that may be absent on MRI examinations.Phase images could be available in measuring iron content and other substances that change the local field.The development of SWI has opened the door to upgraded contrast and upgraded the determination of hemorrhage in tumors [24,25].phase-contrast MRI (Figure 4).A typical CSF flow value is 5-8 cm/s.In patients with hyperdynamic circulation, much higher CSF flow values of up to 25 cm/s can be seen [26].

Ultrasound Elastography
Ultrasound (US) elastography is performed with the transmission of a pulse to the surface of the area of interest.A newer US elastography technique called acoustic radiation force impulse has recently been developed within a regular ultrasonography device (Figure 5).It differs from past elastography systems, which perform a pressure manually to the surface of the organ or a mechanical vibration to induce an elastic shear wave with only M-mode US imaging.It is the simple relationship between palpation and elastography that calls for many applications of this palpation imaging such as breast tumor characterization and hepatic fibrosis staging [27][28][29].

Contrast-enhanced Ultrasonography
US contrast agents are often gas-filled microbubbles.These contrast materials have been developed for enhancing B-mode and Doppler US examinations.The effect of US contrast agents is principally due to increased backscattering compared with that from blood and former structures.Using the color Doppler technique, US contrast agents enhance the frequency or power intensity, giving rise to stronger color encodings.During the vascular phase, in patients with hemangiomas, hepatocellular carcinoma and metastasis have revealed that the use of the harmonic mode with US contrast agents can renovate the characterization of these lesions [30][31][32].

Dual Energy CT Imaging
Dual energy CT imaging is a recent method that differentiates tissues and relies on CT density treasures obtained from two simultaneous CT acquisitions at different tube potentials.Tube currents that are 80 and 140 kVp are commonly used as these lead to maximum density differences between different organs.Potential clinical applications include the evaluation of liver masses, gout, and pancreatic and bowel diseases (Figure 6) [2, [33][34][35].

CT Perfusion Imaging
CT perfusion imaging is a recently developed method for quantitatively assessing tissue blood   features.Hepatic CT perfusion imaging enables the analysis of liver function and the measurement of the following: tissue blood flow (BF, mL/ min/100 g) and tissue blood volume (BV; mL/100 g).CT perfusion imaging is becoming a preferred functional tool in the field of oncology, and it has the potential to play a crucial role in the management of oncological procedures.The perfusion parameters of hepatocellular carcinoma can be separated from background liver parenchyma.Hepatocellular carcinoma has higher BF and BV than the background liver levels.CT perfusion is a recently reveals for quantitative evaluation of hemodynamic changes in tissue (Figure 7) [36][37][38][39].

Advanced Diffusion-Weighted and MR Perfusion Imaging in the Abdomen
Diffusion-weighted imaging is increasingly performed in the abdomen for obtaining results, particularly in the assessment of diffuse and focal liver disorders.Restricted diffusion in a mass determines the higher signal intensity on diffusion images and corresponding lower ADC values.The echo-planar method is most frequently used in combination with fat suppression in the abdomen.Neoplasms show restricted diffusion on higher b-value (≥400-500 s/mm 2 ) images and correspondingly lower ADC values.
Intravoxel incoherent motion created with the use of different b-values is a promising technique for the differentiation between benign and malignant liver masses (Figure 8) [40][41][42][43].
Perfusion-weighted MRI is a technique for evaluating perfusion characteristics in liver masses.It yields a consider between spatial resolution and temporal resolution.We offer the utilization of 10 mL of intravenous contrast agent followed by 20 mL saline, with injection order of 3-5 ml/s.Perfusion-weighted MRI is a good technique for detecting the fibrosis, cirrhosis, and angiogenesis features of hepatocellular carcinoma.K-trans is a measure of capillary permeability obtained using dynamic contrastenhanced perfusion MRI.It is calculated by measuring the accumulation of contrast material in the extravascular space [44,45].

Hepatocyte-specific Contrast Agents
Contrast-enhanced MR cholangiography using hepatobiliary contrast agents, such as gadobenate dimeglumin (Gd-BOPTA) and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA), has emerged in the last decade as a technique to image the biliary tree due to its capability of visualizing biliary complications.Approximately 3e5% of the injected dose of Gd-BOPTA and 50% of Gd-EOB-DTPA are excreted in the human biliary system.Therefore, Gd-EOB-DTPA may provide adequate biliary

MR elastography
Recently, 3D MR elastography has been developed as a technique for assessing the viscoelastic properties of the liver.MR elastography is usually performed with a spin-echo sequence with a time of approximately 20 min.The replacement of the spin-echo sequence by echo-planar sequences has the potential to decrease the acquisition time, which is significant in the radiological applications of MR elastography [48,49].

Dixon Sequences and 1H MRS in the Abdomen
Several imaging techniques have been assessed for the evaluation of hepatosteatosis, includ-ing US, CT, Dixon-weighted sequences, and proton MRS.Although proton MRS and MRI rely on the signal phase, for example, Dixon techniques have appeared as safe and available tools for evaluating hepatosteatosis, their widespread application is prevented by the time-consuming acquisition process (Figure 9) [50].

Contrast-enhanced Mammography and Tomosynthesis
Contrast-enhanced mammography is suitable for the temporal subtraction of images obtained before and after contrast application and the dual energy technique.Skarpathiotakis et al. [51] previously used computer modeling and the processing of contrast-enhanced digital mammography images and found the attainable concentration of a contrast medium detectable with this technique [52].
Tomosynthesis is generally performed by a stationary detector while only the X-ray source moves.As tomosynthesis is performed from different angles, images are acquired without using a grid [53,54].

Dual Energy Cardiac Imaging
Iodine, as a contrast agent, has unique absorption characteristics when penetrated with X-rays of different energy levels.Therefore, iodine mapping shows the myocardial iodine distribution.Dark areas in the iodine map mean that iodine is absent.Dual energy CT is a very fast method, shows cardiac and extra-cardiac pathologies in trauma, has a user-independent modality, and is available in many centers.It has all the benefits of MDCT and many advantages for emergency medical applications (Figure 11) [58].

3D volume rendering angiography imaging
Despite recent technical innovations, including contrast-enhanced CT, high-resolution CT Biplane DSA with multiple projections is an efficient technique.3D DSA images provide valuable information on aneurysmal anatomy, including the relationship with the parent and adjacent vessels (Figure 12).This technique allows fast and safe decision-making regarding the feasibility of endovascular or surgical treatment and provides useful information for performing the chosen treatment.Images are acquired in the 3D rotational DSA mode over an angle of 180°.The run may be performed in one of three different angulations of the C-arm (−30° cranial, 0° axial, or +30° caudal) depending on the orientation of the object of interest [59][60][61].

Biopsy-guiding imaging
In recent radiology practice, biopsy-guiding imaging can be performed via US, CT, MRI, PET-CT, and mammography.The preprocedural assessment of biopsy should include consideration of the indication for the procedure and the preprocedural evaluation should include a review of the patient' s medical history.Warfarin should be stopped 5-7 days prior to the procedure and may be resumed the day following biopsy.Heparin should be withheld 6-12 h prior to biopsy [62][63][64][65][66][67].

Ultra-low-dose Imaging in the Pediatric Population
The largest increase in the use of CT imaging has been in the diagnosis of pediatric disorders.Thorax spiral CT is an imaging method with definitive indications and has a confirmed higher sensitivity and specificity than usual chest radiographies [68].Evans et al. [69] reported a 40% dose reduction by narrowing the beam collimation from 10 mm to 3 mm with the scan interval kept constant at 10 mm.By reducing the radiation dose of a head CT scan, one can obtain critical diagnostic information, such as trauma and hydrocephalus, needed in a preselected group of pediatric patients.In our radiology department, we use ultra-low-dose CT imaging for evaluating a head CT scan in pediatric trauma patients and detecting a foreign body in the trachea and bronchial tree (Figure 13).

Arthrography Imaging
MR arthrography of the ankle joint is the preferred imaging technique for evaluating ligamentous damage, osteochondral lesions of the talus, adhesive capsulitis, impingement syndrome, tarsal sinus structures, and loose bodies.At our institution, we prefer direct MR arthrography for identifying the labroligamentous complex and rotator cuff tendons in the shoulder (Figure 14).In our department, we prepare the diluted contrast medium (0.5 mmol/L gadoterate meglumine, Dotarem, Guerbet, USA) at a concentration of 1:200 (0.1 mL contrast medium diluted in 20 mL normal saline) for the injection procedure.A hemorrhagic effusion is usually an expected complication after dislocation of the glenohumeral joint.The hemorrhage resolves over time, but hemosiderin particles may accumulate in the synovium.These particles are usually not visualized by routine sequences.Concordantly, the VIBE sequence is sensitive and will reveal hemosiderin particles in the synovium and joint space as well as intra-articular air bubbles [70-72].

Computer-aided Detection
Computer-aided detection (CAD) uses pattern recognition software that identifies suspicious findings on the image and brings it to the attention of the radiologist.CAD algorithms search for micro-calcifications and masses on breast mammograms.Current CAD applications include its evaluation of pulmonary densities [82,83].

Conclusion
New imaging modalities are useful and valuable imaging methods in radiology practice.We recommend that radiologists should be aware of and perform these new imaging modalities.

Figure 1 .Figure 2 .
Figure 1.a-d.A meningioma is located at the right cerebral hemisphere: (a) moderately high TTP, (b) significantly high CBF, (c) high MTT, and (d) significantly high CBV TTP: time to peak; CBF: cerebral blood flow; MTT: cerebral blood volume

Figure 5 .
Figure 5.An elastography image shows a lymphoma located at the upper lobe of the right kidney.The lesion strain value is 0.113%.

Figure 6 .
Figure 6.3D dual energy BT shows a monosodium urate monohydrate crystal (red circle).

Figure 7 .
Figure 7. a-e.There is an HCC lesion located at segment V in the liver.(a-d) CT perfusion characteristics.(e) the perfusion graphics of these lesions.CT: computed tomography; HCC: Hepatocellular carcinoma

4. 1 .
Cardiac MRI with T1 and T2 Mapping Cardiac MRI has grown over the past several decades into a noninvasive diagnostic imaging tool with a pivotal role in cardiac morphological and functional assessment and tissue characterization.With traditional cardiac MRI examinations, the assessment of various pathologic conditions ranging from ischemic to non-ischemic cardiomyopathy.New T1 and T2 myocardial mapping techniques offer a quantitative assessment of the myocardium using T1 and T2 relaxation times, which may be helpful in focal disease, and demonstrate a special utility in evaluating diffuse myocardial diseases such as edema and fibrosis.By providing a reproducible standard of T1 and T2 values, myocardial mapping may reduce the interpretation variability and error related to subjective analysis and image artifact.T1 and T2 myocardial mapping are quantitative techniques for detecting changes in the myocardial composition.The T2 relaxation time is altered by the water content in the tissue.Myocardial edema has been described in patients with acute myocardial infarction, myocarditis, etc… As with traditional T1 mapping, qualitative T2-weighted imaging is performed with dark-blood turbo spin-echo sequences.The T1 map is a single image that represents a pixel map of the T1 values generated by curve fitting all images in a sequence such as LL, MOLLI, or ShMOLLI.T1 and T2 mapping can have applications in myocardial infarction, cardiomyopathy, myocarditis, thalassemia, amyloidosis, and sarcoidosis (Figure10)[55][56][57].

Figure 13 .Figure 14 .
Figure 13.a, b.(a) A foreign body located at the left main bronchus in the ultra-low-dose coronal CT image.(b) Low-dose parameters.
[75,76]n emission tomography (PET) and MRI might have a high enough diagnostic efficiency to PET-CT for application.Multimodality image fusion has a key role in staging and the evaluation of responses to treatment and surgery.Image registration techniques develop a single fused image in which the functional SPECT or PET image is displayed in color over a grayscale CT or MR image of the same anatomic region.It can reveal a combined functional and molecular imaging evaluation of an extensive diversity of oncological, neurological, and musculoskeletal disorders[75,76].Frontier helps entrepreneurs develop their solutions and get them to the market faster, making our industrial customers more competitive.3Dprintingis sufficiently simple, reliable, and secure for widespread industrial use.It could accelerate the development of these ideas and get them to market so that our customers can benefit [80].9.4.Volume Measurement ProgramsVolume measurement programs are used to process patient examinations from all modalities in a unified and ergonomic work environment.It is a new-generation workstation for interpreting results and the advanced 3D/4D post processing.It can be adapted to every modality and every organ.It is multipurpose and can be used on a workstation or an application server.It is Eurasian J Med 2016; 48: 213-21 Pirimoglu et al.New Imaging Modalities in Radiology Practice • 219 [79]74] metabolites of interest in muscle physiology and diseases.More recently, improved spectral acquisition and analysis techniques, including both single-voxel and MR spectroscopic imaging, along with enhanced gradient performance, have led to the application of proton MRS for the evaluation of musculoskeletal pathology[73,74].8.Positron emission tomography-MR Imaging9.Further Radiological Imaging Applications9.1.Silent Scan MRISilent scan is a radical neuro-application method that performs the sound of an MRI as silent as a breath.To further the Humanizing MRI commitment, GE Healthcare has introduced many new technologies including the wide bore w Series.The new Silent Scan MRI sequences reveal image quality that is as good as the traditional techniques, but in a way that is much more comfortable for patients.We could perform MRI examinations in many elderly and pediatric patients[77, 78]9.2.Magnetic Resonance Image CompilationMagnetic Resonance Image Compilation is a series of standard magnetic resonance weighted images by processing raw data into parametric T1, T2, and PD maps.An operator can change the image contrast by manipulating the time to repetition (TR), time to echo (TE), and inversion time (TI) even after the scan is completed and the patient has exited the MR room[79].9.3.Frontier Program and 3D PrintingThe Frontier Partner Program is looking for startup partners to help us transform manufacturing.