MRI protocol of the Dynamic Contrast-Enhanced MRI in Prostate

In all patients, the DCE-MRI examination was performed 1 or 2 days before the systematic octant biopsy. All images were obtained using a 1.5 T superconducting MR system (Gyroscan Intera, Philips Medical Systems, Best, The Netherlands) with a 5-channel phased array coil. After obtaining three plain localizer images, T2 weighted turbo spin-echo images were acquired in the axial plains using the following parameters: (4700/120/17 [repetition time (TR), ms/echo time (TE), ms/echo train length]) four signal excitations; axiaalT1 weighted images (500/9/5), two signal excitations; and sagittal T2weighted images (4700/120/17). All examinations were performed using a 4 mm section thickness, a 0.4 mm intersection gap, a 200 mm field of view and a 256 × 256 matrix. A right-to-left phase-encoding direction was used to decrease motion artefacts from the abdominal wall. The DCE-MRI was obtained using a 3D-fast field echo sequence in the axial plain (4.5/1.5/30 [TR/TE/flip angle]) with a 50 mm slab thickness and 10 partitions, a 200 mm field of view and a 64 × 128 matrix. In most patients, the scan slab allowed a full coverage from the apex to the base of the prostate gland. After a bolus injection (3 ml s−1) of 0.1 mmol of gadopentetate dimeglumine (Magnevist, Nihon Schering, Osaka, Japan) per kilogram body weight using an auto injector (SPECTRIS, Nihon Medrad, Osaka, Japan) with a 15 ml saline flush, dynamic MRIs were obtained every 3 s for 3 min. In total 600 DCE-MRI images were obtained. Finally, post-contrast fat suppressed T1 weighted turbo spin-echo images (500/9/5) were obtained using two signal excitations.

Dynamic MRIs were transferred to a diagnostic workstation (EasyVision, Philips Medical Systems, Best, The Netherlands) and dynamic MR analysis software was used for the evaluation. First, multislice dynamic MRIs were displayed in cine mode with subtraction from the first scan image for every slice position. For both the right and left peripheral zones, one slice was selected if a strongly enhanced lesion, as compared with the surrounding tissue, was observed. A region of interest (ROI) was placed and traced on the enhanced lesion on a consensus basis by two radiologists who were aware only of the PSA and DRE findings and were not involved in obtaining the TRUS or PDUS findings. Despite knowledge of PSA and DRE findings, we selected ROIs with only subtracted images. If a strongly enhanced lesion was not visible, a slice through the middle of the gland was selected and a ROI was placed over the area encompassing both peripheral zones. For the right and left inner glands, a slice through the middle of the gland was selected and ROIs were placed over the area encompassing both sides of the inner gland because there was inhomogeneous enhancement from coexisting benign prostatic hyperplasia (BPH) in many cases.

A time–intensity curve (TIC) for each site was obtained from the dynamic images. TICs were classified into three types, based on their shapes (Figure 1⇓). The time-to-peak was defined as the delay time between the point on the curve of enhancement at which the signal was above the noise level and signal peak of TIC. The Type A TIC was characterized by an early peak enhancement and a time-to-peak value of no more than 60 s. The Type B TIC was characterized by an intermediate early enhancement and a time-to-peak value of no less than 60 s, and not greater than 100 s. The Type C TIC was characterized by delayed enhancement and no signal peak after a continuous increase in signal intensity for 3 min.

For the peripheral zone sites, we defined Type A and B TICs as positive and Type C TIC as negative on DCE-MRI. Most normal peripheral zones did not show hypervascularity. As to the inner gland sites, normal inner glands and coexisting BPH often showed moderate vascularity. Thus, we defined only Type A TIC as positive and Type B and C TICs as negative on DCE-MRI.

Diffusion-weighted MRI imaging of the Prostrate Cancer

Diffusion-weighted imaging assesses the diffusion of water molecules within different tissues. Normal prostate glandular tissue has a higher water diffusion rate than cancer tissue owing to restricted diffusion in tightly packed cancer cells. DWI is an inherently T2-weighted sequence but, unlike conventional T2-weighted imaging, prostate cancer frequently demonstrates increased signal intensity on standard DWI scans, making the tumor difficult to visualize within the normal high-signal peripheral zone. To reduce the effect of this T2 'shine through' effect, the apparent diffusion coefficient (ADC) is calculated, which corresponds to the difference of diffusion. Prostate cancer appears as an area of high signal on DWI images, but as a low-signal region on ADC mapping, owing to restricted diffusion .

The advantages of DWI are high-contrast resolution between normal prostate and cancerous tissue, and its short acquisition time. The disadvantages of DWI are its low spatial resolution (due to low signal:noise ratio), increased susceptibility to artifacts and overlap of diffusion values between benign and malignant lesions.There is no ADC threshold value that will reliably differentiate between benign and malignant lesions. In addition, there are age-related changes in diffusion within the prostate and intersubject variability.


Recent studies have demonstrated that DWI, when used as an adjunct to T2-weighted MRI, improved sensitivity and specificity for prostate cancer detection to 84 and 85%, respectively.[68,69] The sensitivity of DWI is better in the peripheral zone than the central gland.[70] DWI has also been shown to be helpful in the identification of prostate cancer in patients with previous negative biopsies and persistently elevated PSA.

Diffusion-weighted imaging is also helpful in differentiating between low-, intermediate- and high-risk patients as there is a significant correlation between the Gleason score of the tumor and the ADC value. There is also an inverse relationship between the ADC value and the percentage of tumor involvement in core biopsies. Pre- and post-radiotherapy ADC values can also be used to assess response to treatment. In patients managed by active surveillance, the reduction of the ADC value by 10% or more indicates disease progression.

A recent study has demonstrated that DWI can be used to accurately differentiate between benign and malignant pelvic nodes in patients with prostate cancer and the ADC value is significantly superior to size criteria

BASIC PHYSICAL PRINCIPLES OF MR SPECTROSCOPY

The resonant frequencies of nuclei are at the lower end of the electromagnetic spectrum between FM radio and radar. The resonant frequencies of protons range between about 10 MHz at 0.3 T to about 300 MHz on a 7 T magnet. The advantages of higher field strength are higher signal-to-noise and better separation of the metabolite peaks. In a proton spectrum at 1.5 T, the metabolites are spread out between 63,000,000 and 64,000,000 Hertz. Rather than use these large numbers, some very smart person decided to express the resonant frequencies in parts per million (ppm), and he/she positioned NAA at 2.0 ppm and let the other metabolites fall into their proper positions on the spectral line. Then, for unknown reasons, he/she reversed the ppm scale so that it reads from right to left. 
For MR imaging, the total signal from all the protons in each voxel is used to make the image. If all the signal were used for MRS, the fat and water peaks would be huge and scaling would make the other metabolite peaks invisible. Since we aren't interested in fat and water anyway, the fat and water are eliminated. Fat is avoided by placing the voxel for MRS within the brain, away from the fat in bone marrow and scalp. Water suppression is accomplished with either a CHESS (CHEmical-Shift Selective ) or IR (Inversion Recovery) technique. These suppression techniques are used with a STEAM or PRESS pulse sequence acquisition. A Fourier transform is then applied to the data to separate the signal into individual frequencies. Protons in different molecules resonate at slightly different frequencies because the local electron cloud affects the magnetic field experienced by the proton.
The STEAM (STimulated Echo Acquisition Mode) pulse sequence uses a 90o refocusing pulse to collect the signal like a gradient echo. STEAM can achieve shorter echo times but at the expense of less signal-to-noise. The PRESS (Point REsolved SpectroScopy) sequence refocuses the spins with a 180o rf pulse like a spin echo. Two other acronyms require definition. CSI (Chemical Shift Imaging) refers to multi-voxel MRS. SI (Spectroscopic Imaging) displays the data as an image with the signal intensity representing the concentration of a particular metabolite.
As in MR imaging, the echo time affects the information obtained with MRS. With a short TE of 30 msec, metabolites with both short and long T2 relaxation times are observed. With a long TE of 270 msec, only metabolites with a long T2 are seen, producing a spectrum with primarily NAA, creatine, and choline. One other helpful TE is 144 msec because it inverts lactate at 1.3 ppm.
As a general rule, the single voxel, short TE technique is used to make the initial diagnosis, because the signal-to-noise is high and all metabolites are represented.Multi-voxel, long TE techniques are used to further characterize different regions of a mass and to assess brain parenchyma around or adjacent to the mass. Multi-voxel, long TE techniques are also used to assess response to therapy and to search for tumor recurrence.
The brain metabolites that are commonly seen on the MR spectrum are listed on the right. Each metabolite appears at a specific ppm, and each one reflects specific cellular and biochemical processes. NAA is a neuronal marker and decreases with any disease that adversely affects neuronal integ-rity. Creatine provides a measure of energy stores. Choline is a measure of increased cellular turnover and is elevated in tumors and inflammatory processes. The observable MR metabolites provide powerful information, but unfortunately, many notable metabolites are not represented in brain MR spectra. DNA, RNA, most proteins, enzymes, and phospholipids are missing. Some key neurotransmitters, such as acetylcholine, dopamine, and serotonin, are absent. Either their concentrations are too low, or the molecules are invisible to MRS.
Normal MR spectra obtained from gray matter and white matter are shown on the right. The predominant metabolites, displayed from right to left, are NAA, creatine, choline, and myo-inositol. The primary difference between the two spectra is that gray matter has more creatine.Hunter's angle is the line formed by the metabolites on the white matter spectrum. The common way to analyze clinical spectra is to look at metabolite ratios, namely NAA/Cr, NAA/Cho, and Cho/Cr. Normal and abnormal values are shown in the chart to the right. By including a known reference solution when acquiring the MR spectral data, absolute concentrations of metabolites can be calculated.

Cartilage Imaging Sequences in Knee Joint MRI imaging

The most common sequences used in clinical practice to evaluate the articular cartilage of the knee joint are 2D fast spin-echo (FSE) sequences with T2-weighted and intermediate-weighted contrast . The advantages of FSE sequences include their high in-plane spatial resolution and their ability to evaluate the menisci, ligaments, and osseous structures in addition to the articular cartilage . Because of their multiple off-resonance pulses, FSE sequences also produce a magnetization transfer effect that can help distinguish between normal articular cartilage and areas of early cartilage degeneration . However, FSE sequences have relatively thick slices and gaps between slices that can obscure small cartilage lesions secondary to partial volume averaging. In addition, T2-weighted FSE sequences have poor contrast between articular cartilage and subchondral bone, which can make it difficult to detect diffuse cartilage thinning and estimate the exact depth of cartilage lesions. Intermediate-weighted FSE sequences are also limited by image blurring secondary to acquisition of high spatial frequencies late in the echo-train and by poor contrast between articular cartilage and synovial fluid . However, image blurring can be reduced by minimizing echo-train length and using short interecho spacing, whereas contrast between articular cartilage and synovial fluid on intermediate-weighted FSE sequences can be improved with the use of fat suppression.

In clinical practice, 3D sequences also have been used to evaluate the articular cartilage of the knee joint. Fat suppression is typically added to these sequences to reduce chemical-shift artifact and to optimize the overall dynamic contrast range of the image. Frequency-selective fat-saturation is the most commonly used method to suppress fat signal . However, 3D sequences with higher cartilage signal-to-noise ratio (SNR) and greater contrast between cartilage and adjacent joint structures can be obtained using recently developed fat-suppression techniques, such as water excitation , linear combination , and iterative decomposition of water and fat with echo asymmetry and least-squares estimates (IDEAL) . By acquiring thin, continuous slices through the knee joint, 3D cartilage imaging sequences can reduce partial volume averaging. The 3D sequences also can be used to create multiplanar reformat images that allow articular cartilage to be evaluated in any orientation after a single acquisition. The disadvantages of 3D cartilage imaging sequences include their long acquisition times; increased susceptibility to artifacts; and limited ability to evaluate the menisci, ligaments, and osseous structures of the knee joint when compared with 2D FSE sequences.

The 3D cartilage imaging sequences can be broadly divided into dark-fluid sequences and bright-fluid sequences on the basis of the signal intensity of synovial fluid. Dark-fluid sequences consist of T1-weighted gradient-recalled echo (GRE) sequences such as spoiled gradient recalled-echo (SPGR) and fast low-angle shot (FLASH). These sequences have been successfully used to evaluate articular cartilage in clinical practice  and to perform cartilage volume measurements in osteoarthritis research studies . However, the main disadvantage of using SPGR and FLASH sequences for clinical cartilage imaging is the low signal intensity of synovial fluid, which may decrease the conspicuity of superficial cartilage lesions . Dark-fluid sequences have lower contrast between articular cartilage and synovial fluid than bright-fluid sequences (Kijowski R, et al., presented at the 2008 annual meeting of the International Society of Magnetic Resonance in Medicine). In addition, the surface properties of degenerative cartilage may influence the ability of 3D sequences to detect superficial cartilage lesions. Superficial degeneration shortens the T2 relaxation time of cartilage. For dark-fluid sequences, the T2 shortening of degenerative cartilage has no effect on its signal intensity and contrast relative to synovial fluid. However, for bright-fluid sequences, the effect of T2 shortening is to decrease the signal intensity of degenerative cartilage and thus increase its contrast relative to synovial fluid, which may result in greater conspicuity of superficial cartilage lesions .

Various 3D cartilage imaging sequences with bright synovial fluid have been used to evaluate the articular cartilage of the knee joint. These bright-fluid sequences include dual-echo in the steady-state (DESS); driven equilibrium Fourier transform (DEFT); and T2*-weighted gradient-echo sequences, such as gradient-recalled echo acquired in the steady-state (GRASS) and gradient-recalled echo (GRE). The DESS sequence combines two gradient echoes separated by a refocusing pulse into a single image that increases the signal intensity of both articular cartilage and synovial fluid . The DEFT sequence uses a –90° pulse to return transverse magnetization to the z-axis, which increases the signal intensity of synovial fluid and other tissues with long T1 relaxation times . GRASS and GRE sequences produce images with high-signal-intensity synovial fluid because of coherence of transverse magnetization with secondary T2* weighting . The bright synovial fluid on DESS, DEFT, and T2*-weighted gradient-echo sequences creates an arthrogram-like effect within the knee joint that may increase the conspicuity of superficial cartilage lesions.

Sagittal fat-saturated FSE-Cube image of knee joint performed 4 months after A shows progression of cartilage degeneration and formation of superficial partial-thickness cartilage defect (arrow) with obtuse margins on medial femoral condyle.

Balanced steady-state free precession (SSFP) sequences are additional 3D sequences that have been used to evaluate the articular cartilage of the knee joint. Balanced SSFP sequences include commercially available sequences such as fast imaging employing steady-state acquisition (FIESTA) and true fast imaging with steady-state precession (true FISP) and variants such as fluctuating equilibrium MR (FEMR) [58] and vastly undersampled isotropic-projection steady-state free precession (VIPR-SSFP) [46]. These sequences have high SNR efficiency and produce images of the knee joint with T2-/T1-weighted contrast and bright synovial fluid. Balanced SSFP sequences and their variants have higher cartilage SNR and greater contrast between cartilage and adjacent joint structures than 2D FSE and fat-saturated SPGR sequences [39, 49, 59]. When combined with VIPR radial k-space trajectory and alternating TR fat–water separation, balanced SSFP images of the knee joint with 0.3-mm isotropic resolution can be obtained in as little as 8 minutes (Klaers JK, et al., presented at the 2010 annual meeting of the Society of Magnetic Resonance in Medicine) .

Recently, 3D FSE sequences, such as FSE-Cube (GE Healthcare)  and sampling perfection with application oriented contrast using different flip angle evolutions (SPACE, Siemens Healthcare) , have been used to evaluate the articular cartilage of the knee joint. These sequences use variable flip angle modulation to constrain T2 decay over an extended echo-train, which allows intermediate-weighted images of the knee joint with bright synovial fluid to be acquired with minimal blurring. FSE-Cube and SPACE sequences have higher cartilage SNR but lower contrast between cartilage and synovial fluid when compared with 2D FSE sequences . The 3D FSE sequences acquire volumetric data sets with isotropic resolution that allow high-quality multiplanar reformat images to be obtained in any orientation after a single acquisition. However, these sequences have lower in-plane spatial resolution when compared with other 3D cartilage imaging sequences with similar acquisition times, which may reduce the conspicuity of superficial cartilage lesions.

Magnetic Resonance Imaging (MRI) of Knee Joint

MRI is an imaging technique used to get cross-sectional images using strong magnetic field and radio waves (radio frequency pulses) instead of X-rays. In MRI scanning, patients are placed inside a very large and strong magnet, so that all the protons in the atoms of the patient's body can be aligned to a magnetic field. Then, radio waves (called radio frequency pulses) are directed at the protons (the nuclei of hydrogen atoms) to excite the protons.
  Knee MRI
  MR image of the knee - articular cartilage is shown particularly well.
Once the radio waves are stopped, excited atoms emit radio signals received by an antenna (a surface coil in the MRI machine), which are then measured and processed to form an image using a computer. In the human body, protons are most abundant in the hydrogen atoms of water. Thus, MRI images represent the water content in the area of the exam. The more water present, the more radio signals emitted, and the whiter the image. All intra-articular structures, including menisci, ligaments and articulating surfaces, can be visualised in great detail. The indications for MRI of the knee are difficult to define and depend on the specific clinical situation and the particular information needed. Routine MR knee imaging is usually very accurate and helpful diagnostically. MRI is also safe. There are no known side effects to having an MRI scan performed but you should be aware of the following:
The strong magnetic field can cause metal implants to dislodge, burn,and causeadditional injuries. When you have any metal implant in your body, such as a pacemaker, prosthetic valves, or clips, you should let your radiologist or MR technician know. If it is not confirmed to be compatible with the magnet, you should not take the MRI. If you have had bullet injuries or possible metal fragments in your body, X-rays can be taken instead for detection of metal objects. 
Metallic implants or fragments that might be affected by magnet: Cardiac pacemakers, Artificial cardiac valves, Cerebral aneurysm clips, vascular clips, Epidural electrodes, Prosthetic (implanted) hip, knee or ankle joint, Chemotherapy or insulin pumps, Intrauterine device (IUD), Metallic bone plates, pins, screws, surgical staples, especially within 4-6 weeks after surgery, Bullets, shrapnel, metal fragments, especially in and around eyes, Metallic ear implants, etc. 
Women in the first 12 weeks of pregnancy should avoid MRI and the contrast medium. There are no known harmful effects to pregnant women and unborn babies. However, because it is a recently-developed technology, the long term effects of MRI are not known. 
Allergic reactions to the contrast medium are possible, but very rare. 
Claustrophobia: lying alone inside the tunnel of huge magnet may provoke intense fear of confinement. If you hav any history of claustrophobia, you should inform your radiologist or technologist. Sedatives can be given before scanning.

Physiology and Pathophysiology of Cerebral Perfusion

Autoregulation is the process by which the brain maintains almost constant cerebral blood flow (CBF, ml/100 gm/min) in the presence of fluctuations in cerebral perfusion pressure (CPP, mm Hg).[28] Little change in CBF is observed over a broad range of CPP (50 to 130 mm Hg) because of the ability of precapillary resistance to adjust in response.[11,20] When CPP increases above 140 mm Hg, vasoconstriction becomes maximal and CBF increases dramatically.[14]  When CPP decreases below 40 mm Hg, vasodilation becomes maximal and CBF diminishes linearly.  This autoregulatory vasodilation is known as Stage 1 hemodynamic compromise.[27] As CPP decreases further, the ability to vasodilate is lost and CBF decreases.  The brain compensates by increasing the extraction of oxygen from the blood to maintain the cerebral metabolism of oxygen.[11,22]  Stage 2 hemodynamic failure or misery perfusion is characterized by decreased CBF and increased oxygen extraction.[20,36]  As CPP diminishes further, oxygen metabolism is disrupted causing cellular dysfunction and eventually cell death.

The normal range of CBF has been established by PET and varies widely (45 to 110 ml/100 g/min).[31]  The range of CBF in the setting of acute stroke has been stratified in an attempt to identify potentially recoverable tissue.  Typically, CBF values below 10 ml/100 g/min indicate infarction whereas values between 10 and 22 ml/100 g/min identify tissue that is ischemic but not yet infarcted.  The latter range is referred to as the ischemic penumbra.[7,15]  CBF values between 23 and 44 ml/100 g/min represent oligemic tissue.  Autoregulatory control can result in normal CBF in the setting of decreased CPP.  Moreover, when the metabolic demands of the brain are low, CBF values can decrease even though CPP is normal.

As a single hemodynamic parameter, CBF is insufficient to assess perfusion status.  Other hemodynamic parameters such as cerebral blood volume (CBV, ml/100 g) and mean transit time (MTT, secs) have been investigated in an attempt to elucidate microcirculatory perfusion.  The relationship of these three parameters is reflected by the central volume principle, which states that MTT=CBV/CBF.

Gastrointestinal MRI Contrast Agents

      The  gastrointestinal tract cannot be reliably studied by  MRI  without the use of contrast agents.  Oral  contrast agents  may dramatically improve utility of MRI for  gastro- diagnostics.  The only clinically approved agents  for  that purpose  are  soluble  iron compounds.  (ferrous  gluconate, ferric  ammonium citrate) and Gd-DTPA. There  is  a  problem with  dosage of iron salts, which may not exceed the  levels above those when iron supplementation is used. There are  no particulate  agents approved for oral use yet.              

Medicines given during an MRI scan for Kids

We may give your child some medicine during the MRI scan to make the image clearer. The radiographer will tell you which medicines your child has had in case of later side effects. The medicines we use most often at Great Ormond Street Hospital (GOSH) include:

Secretin – This is a naturally occurring hormone that increases the volume of juice within the duct of the pancreas. It is given as an injection. Possible side effects include: loose or runny poo, cramplike stomach ache, headache, skin itching and a rash.

Hyoscine butylbromide (Buscopan®) – This medicine relaxes the smooth muscle of the intestine. Possible side effects immediately after the injection include: dilated pupils, dry mouth, flushing of the skin, dislike of bright light and palpitations. In the hours following the injection, other side effects may occur: constipation, urinary retention and urinary urgency.

Furosemide – This medicine increases the production of urine immediately after injection. Possible side effects include: low blood pressure and dehydration. You can reduce these side effects by encouraging your child to drink plenty of fluids in the hours after the scan.

Mannitol – This medicine is drunk and allows clear imaging of the wall of the bowel. A common side effect is loose or runny poo, so in the first few hours after the scan, your child should have access to a toilet. Dehydration may also occur, so ensure plenty of fluids in the hours following the scan.

Gadoteric acid (Dotarem®) – This is a dye that makes blood vessels and any inflammation show up more clearly on the pictures. It is given as an injection. A possible side effect is hypersensitivity, but this will normally be an immediate effect. There are no reported long term side effects of gadoteric acid.

Differences between the 3T vs 1.5T?

Consider if imaging the abdomen, pelvis and spinal cord is important when booking your whole body scan.

A casual study of MRI literature shows that 3T imaging does not increase image quality in the body [1]. In fact 3T imaging of the abdomen and pelvis is “inferior owing to problems with dielectric effects” [1]. These effects lead to information loss rendering the scan undiagnostic.  At 3T anatomy is misrepresented at “air, bone or soft-tissue interfaces” far more than at 1.5T [2]. Image quality of the spinal cord is reduced with 3T and “raises important safety concerns” [2]. One of these concerns is “significant cardiovascular stress” [3].

3T imaging presents health risks which are not a concern at 1.5T.

Using a 3T scanner requires heating the body tissue 4 times more than a clinically accepted 1.5T scanner. This presents an increased risk particularly for children, elderly, and anyone who has an impaired ability to dissipate heat. This is particularly concerning when imaging the abdominal and pelvic organs [1], a major component of whole body imaging.

As stated by [1] “some major problems at higher field strength (3T) have to be solved before high field magnetic resonance systems can really replace the well established and technically developed magnetic resonance systems operating at 1.5T.”

Problems with MRI

It may not be possible, or safe, to have a MRI scan if you have any of these items:

• Cardiac pacemaker
• Surgical clips in your head (particularly aneurysm clips)
• some artificial heart valves
• Electronic inner ear implants (bionic ears)
• Metal fragments in your eyes
• Electronic stimulators
• Implanted pumps

Let the MRI Unit know well before your appointment if you have any of these. Experienced MRI staff will have to discuss the exact implant or metal with you to decide if it is safe to perform the scan. Deciding which implants cannot be scanned takes special knowledge and experience. Before the scan you will be asked a series of questions to check that it is safe for you to enter the scan room.

People with dental fillings and bridges, hip and knee replacements, and tubal ligation clips can all be scanned safely. The Radiographers will want to know about these things to minimize the effect they have on your images.

Claustrophobia

If you have experienced claustrophobia, or have trouble in enclosed spaces talk about it with the MRI staff before your appointment date. For mild claustrophobia, the staff can help you to relax enough to get rid of the anxiety in a few minutes. If your claustrophobia is severe you may need an anti-anxiety prescribed by your referring doctor or G.P. Staff at the MRI unit can be contacted about this and can offer your doctors some advice. You shouldn't drive after taking such drugs, so arrange a safe way to get home. Because there are no side effects of MRI you can bring a friend into the scan room for support if that will help your anxiety. Children in particular should feel free to bring an adult in with them. Everyone coming into the scan room will be asked the questions about metal and implants.

Contrast Injections (Dye)

Most MRI tests do not need you to have an injection, but in some situations a contrast agent can greatly improve the accuracy of the scan. The contrast is injected into a vein, and the dose is quite small. MRI contrast is not the same as X-ray contrast. Very few people notice when it is injected. Make sure to tell the technologist if you have any allergies to contrast dye.

Pregnancy

If you are pregnant or could be pregnant at the time of your scan appointment, please call us early so we can discuss the situation with you and consult your doctor. MRI causes a slight heating of your body, so most MRI sites avoid scanning during the first 3 months of pregnancy unless the diagnosis cannot wait and the only alternative test uses X-rays. Beyond that period, MRI is still avoided if the diagnosis can wait till your child is born as a matter of extreme caution. In many sites around the world MRI is used to examine pregnant women and their babies to avoid the need for X-ray tests. MRI contrast is not used during pregnancy.