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Technology 1 Contrast Media and Contrast studies

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1 Technology 1 Contrast Media and Contrast studies
Jeremy Oates Michal Smolski Thiru Gunendran

2 References Campbell Walsh FRCS Lectures Scientific basis of Urology
Standards for intravascular contrast agent administration to adult patients. RCR 2010 Manual on Contrast Media. ACR 2012 Literature

3 Technology 1 Types media and basic structures
Toxicity of media, Contrast mediated nephrotoxicity Principles of contrast studies (KUB, IVU, retrograde, angiography) How do X-Rays work?

4 Types media and basic structures
Radiological (Iodine based, Barium sulfate, Thorium dioxide – past) MR ( Gadolinium ) Ultrasound (CEUS – Contrast –enhanced ultrasound – microbubbles )

5 Why use contrast media Where considerable difference between the densities of two organs exists then the outlines of the structures can be visualised on a radiograph due to natural contrast. Similarly, if there is a difference between the average atomic numbers of two tissues, then the outlines of the different structures can be seen by natural contrast. However, if the two organs have similar densities and similar average atomic numbers, then it is not possible to distinguish them on a radiograph, because no natural contrast exists. This situation commonly occurs - it is not possible to identify blood vessels within an organ, or to demonstrate the internal structure of the kidney, without artificially altering one of the factors mentioned earlier.

6 Radiological Contrast media
CBD 55 years of age male presented to a Urologist with recurrent UTI’s CT shows 22 mm mid polar L kidney stone Treatment: PCNL What type of contrast will you use for CTU What contrast will you use for retrograde pyelogram? Explain the choice of CM

7 Radiological Contrast media
Iodine - provides radio-opacity (discovered treating syphilis in the 1920’s with sodium iodide) Other elements of RCM molecule = carrier  toxicity,  solubility of iodine, non-radioopaque All IV RCM Benzene ring 3 atoms of iodine at C 2,4,6 positions Classification Ionic or non-ionic High or Low osmolar Monomeric or Dimeric

8 Osmolality Dependent solely on number of dissociated particles (not number of molecules). The closer the osmolality of RCM to that of plasma the better the tolerance. Osmolality is directly responsible for a number of clinically important effects. The sensations of heat and discomfort or even pain from contrast media are directly related to the osmolality.

9 Viscosity Resistance of a liquid to various forces (and hence to flow)
Related to concentration of the Iodine in a contrast medium Inversely related to temperature Not related to pressure

10 Radiological Contrast Media
4 types RCM Ionic monomer = high osmolar Ionic dimer = low osmolar Non-ionic monomer = low osmolar Non-ionic dimer = iso-osmolar Distribution Hydrophilic Capillary permeability throughout extracellular compartment. Filtered unchanged in glomerulus. Excreted - 90% by glomerular filtration in 12 hrs

11 Ionic Monomer RCM Iodine atoms = 3 Osmotic particles = 2 Ratio 3:2
High osmolar 1550 mOsm /kg water e.g. Diatrizoate = Hypaque 50 ( 300 mg Iodine/ mL ) Urografin, Gastrografin Metrizoate = Isopaque 370 ( 370 mg Iodine/ mL ) Ionic high osmolar RCMs not used IV Retrogrades Cheap Side effects 10x non-ionic Also used to treat tape worms

12 Ionic Dimer Iodine atoms per molecule = 6
Osmotic particles per molecule = 2 Ratio = 6:2 Low osmolar = ~600 mOsm/kg water e.g. Ioxaglate = Hexabrix ( 320 mg Iodine/ mL) Toxicity - High protein binding Electrical charge

13 Non-Ionic RCM Cation replaced by non-dissociating organic chain
Tri-iodinated non-ionising compounds Fewer particles per iodine atom Lower osmolality Fewer side effects More expensive

14 Non-Ionic Monomer RCM Iodine atoms = 3 Osmotic particles = 1 Ratio 3:1
Low osmolar e.g. Iohexol = Omnipaque

15 Non-Ionic Dimer RCM Iodine atoms = 6 Osmotic particles = 1 Ratio 6:1
Iso-osmolar ~ 300 mOsm eg Iodixanol = Visipaque


17 Points to Remember for RCM
Radio-opacity Iodine conc. of solution No. of iodine atoms per molecule Conc. of molecules in solution Osmolality No. of particles Ionic vs. Non-ionic Low osmolality Fewer side effects / reactions  pain of injection High osmolality Greater risk reactions Causes osmotic diuresis The osmalility of blood, and of the cerebrospinal fluid, which surrounds the brain and spinal cord, is about 290mOsm/kg. Almost all of the currently available ionic, non-ionic monomeric and ionic dimeric contrast media have osmolalities in excess of this figure, though some are very much higher than others (see Fig. 2). Osmolality is directly responsible for a number of clinically important effects. The sensations of heat and discomfort or even pain that many patients experience when undergoing arteriography with some contrast media are directly related to the osmolality. Other clinically significant effects that can be attributed to the osmolality problem include damage to the blood-brain barrier, renal damage and disturbance or electrolyte balance in small children. Both the viscosity of a contrast medium and its osmolality are related to the concentration of the contrast medium, usually referred to as its strength. The strength of a contrast medium is usually given as its concentration in iodine, a figure after the brand name, indicating the concentration in milligrams of iodine per millilitre. With increasing strength of contrast medium, the opacifying power of the solution increases, but so, of course, do the osmolality and viscosity, while tolerance tends to decline. These considerations

18 Points to Remember for RCM
Dimers Large size  higher viscosity Less lipophilic  more inert Strength = conc. of iodine mg/mL Viscosity & osmolality related to conc. of media Omnipaque Type Strength mg/mL Osmolality mOsm/kg H2O Viscosity Use 140 290 1.5 Video UDS , Retrograde 240 510 3.3 Retrograde 300 640 6.1 IVU, CTU

19 MCQ Types media and basic structures

20 MCQ Types media and basic structures

21 MCQ Types media and basic structures

22 Toxicity of media, Contrast mediated nephrotoxicity
CBD 55 years of age male presented to a Urologist with recurrent UTI’s, CT shows 22 mm mid polar L kidney stone Treatment: PCNL What do you need to ask/ check with a patient before performing CTU What are the contraindications for contrast use? What is an alternative test which can be used and why?

23 Toxicity of media Osmolality Electrical charge Lipophilicity
Ionic vs. Non-ionic Dimer vs. Monomer Electrical charge Lipophilicity Correlates with the toxicity of ionic contrast media. Non-ionic contrast media very hydrophilic, properties other than lipophilicity (e.g. hydrogen bonding) are responsible for interactions with biological molecules and membranes. Protein binding Protein receptors Membranes Mediator release Chemotoxicity The term 'chemotoxicity' refers to the mechanism responsible for causing the toxic effects of contrast media that cannot be explained by other means (e.g. osmolality, electrical charge). There are a number of properties of contrast media that relate to this tem (e.g. hydrophilicity/lipophilicity, protein-binding, histamine release). The hydrophilicity of a contrast medium is its preference for aqueous solvents, whereas its lipophilicity refers to its preference for fat-like (lipid) organic solvents such as the chemical solvent n-butanol. Since n-butanol does not mix with water, it is possible to assess the relative degree of lipophilicity by adding equal parts of water and n-butanol to a small quantity of contrast medium and shaking the mixture well, after which the solvents are allowed to separate into two layers and the amount of contrast medium dissolved in each layer is measured. The ratio of the amount in the lipid layer to the amount in the aqueous layer is termed the partition coefficient, which is therefore high for compounds of high lipophilicity and low for compounds of lower lipophilicity. Lipophilicity has been found to correlate roughly with the toxicity of ionic contrast media. Non-ionic contrast media seem to be too hydrophilic to make differences in the partition coefficient a critical issue. In this case properties other than lipophilicity (e.g. hydrogen bonding) are responsible for interactions with biological molecules and membranes. Protein-binding refers to the percentage of contrast medium which becomes bound to the plasma proteins in the blood stream. The cholegraphic media discussed in the previous chapter derive their ability to be excreted and concentrated in the bile, rather than to be rapidly eliminated by the kidneys, from their very high degree of protein-binding. In line with the above hypothesis, the cholegraphic agents (which are also ionic) have a rather higher chemotoxicity than the urographic contrast media.

24 Toxicity of media Major life threatening contrast reaction is rare
Non-ionic agents Severe 0.04% Very serious reactions 0.004% Deaths 0.001% Katayama et al, Radiology 1990

25 Toxicity of media Classification of adverse reactions
Idiosyncratic anaphylactoid reactions Not dose related Non-idiosyncratic chemotoxic reactions Dose dependent Molecular toxicity Physiological characteristics Mechanisms Chemotoxic Hyperosmolar

26 Idiosyncratic Not dose related
Mild Intermediate Severe Mild urticaria Extensive urticaria Cardiopulmonary collapse Angio-oedema Pulmonary oedema Bronchospasm Layngospasm Laryngospasm Hypotension

27 Non-idiosyncratic Dose dependent
Minor Intermediate Severe Tachy/brady Oliguria/anuria VT/VF Azotaemia MI Myocardial ischaemia Arrhythmia Bronchospasm

28 Adverse Drug Reactions - RCM
Ionic HOCM Patients Nonionic LOCM 169,284 Total No. 163,363 12.7% Total ADR 3.13% 0.22% Severe ADR 0.04% (1) Deaths Katayama et al, Radiology 1990

29 ADR - Symptoms Experienced
Ionic HOCM % Symptom Nonionic LOCM % 4.58 Nausea 1.04 2.29 Heat 0.92 2.97 Vomiting 0.45 3.16 Urticaria 0.47 1.12 Flushing 0.16 0.4 Venous pain 0.05 0.58 Coughing 0.15 0.17 Dyspnoea 0.04

30 Severe ADR to RCM Ionic HOCM ADR% Clinical history Non-ionic LOCM ADR%
0.18 No Hx of allergy 0.03 0.53 Hx of allergy 0.10 0.13 No previous ADR to RCM 0.73 Previous ADR to RCM 1.88 Asthma 0.23 0.49 Atopy 0.11 Heart disease 0.20 Renal disease 0.04 0.22 Diabetes 0.05

31 Iodinated Contrast Media: Adverse Reaction Summary, 1985–1999 Cochran et al. 2001
Year Ionic Nonionic Agent Unknown Overall Injection Adverse Reactions Injections Adverse Reactions Injections Adverse Reactions Injections Adverse Reactions Rate (%) NA , , NA , , NA , , NA , , NA , , NA , , NA , , NA , , NA , , , , , , , , , , , , NA NA Total 12, , , ,

32 Iodinated Contrast Media: Adverse Reaction Summary, 1985–1999 Cochran et al. 2001
Mild and moderate adverse events more common with ionic contrast material than with non-ionic Severe reactions are seen equally with ionic and non-ionic contrast material but differ in type: Ionic – allergic-like Non - ionic cario-pulmonary decompensation CONCLUSION: Mild and moderate adverse events are more common with ionic contrast material than with nonionic. Most reactions are allergic-like. Severe reactions are seen equally with ionic and nonionic contrast material but differ in type. The reactions were allergic-like in the ionic group but were predominantly attributable to cardiopulmonary decompensation in the nonionic group. Helical CT angiography may play a role in reactions.

33 Risk factors for adverse intravenous contrast media reactions
Previous reaction to CM – 5 x increased risk True allergies – 2 x Asthma – 6 x iso-, non-ionic, 10 x – HOCM Renal problems – risk proportional to the pre-existing impairment Metformin therapy Miscellaneous Risk Factors: Multiple myeloma and HOCM, B-blocker, sickle cell trait, pheochromocytoma and HOCM, thyroid cancer, cardiac status, anxiety, pregnancy Paraproteinemias, particularly multiple myeloma, are known to predispose patients to irreversible renal failure after high-osmolality contrast media (HOCM) administration due to tubular protein precipitation and aggregation; however, there is no data predicting risk with the use of low-osmolality or iso-osmolality agents. Age, apart from the general health of the patient, is not a major consideration in patient preparation [1]. In infants and neonates, contrast volume is an important consideration because of the low blood volume of the patient and the hypertonicity (and potentially detrimental cardiac effects) of even nonionic monomeric contrast media. Gender is not considered a major risk factor for IV contrast injection. Some retrospective case control studies suggest a statistically significant risk that the use of beta-adrenergic blocking agents lowers the threshold for and increases the severity of contrast reactions, and reduces the responsiveness of treatment of anaphylactoid reactions with epinephrine [9]. Others have suggested that sickle cell trait or disease increases the risk to patients; however, in neither case is there evidence of any clinically significant risk, particularly after the injection of low-osmolality contrast media (LOCM) [10]. Concomitant use of certain intra-arterial injections, such as papaverine, is believed to lead to precipitation of contrast media during arteriography. There have been reports of thrombus formation during angiography using nonionic as opposed to ionic agents. In both cases, there are in-vitro studies that suggest possible explanations. Some patients with pheochromocytoma develop an increase in serum catecholamine levels after the IV injection of HOCM. A subsequent study showed no elevation of catecholamine levels after the IV injection of nonionic contrast media [11]. Direct injection of either type of contrast medium into the adrenal or renal artery is to be avoided, however, as this may cause a hypertensive crisis. Some patients with hyperthyroidism or other thyroid disease (especially when present in those who live in iodine-deficient areas) may develop iodine-provoked delayed hyperthyroidism. This effect may appear 4 to 6 weeks after the IV contrast administration in some of these patients. This can occur after the administration of any iodinated contrast media. It is usually self-limited. Patients with carcinoma of the thyroid deserve special consideration before the IV or oral administration of iodinated contrast media (ionic or nonionic). Uptake of I-131 in the thyroid becomes moderately decreased to about 50% at one week after iodinated contrast injection but seems to become normal within a few weeks. Therefore, if systemic radioactive iodine therapy is part of planned treatment, a pretherapy diagnostic study of the patient using an iodinated radiographic contrast medium (intravascular or oral) may be contraindicated; consultation with the ordering clinician prior to contrast administration is recommended in these patients.

34 Previous reaction to CM
Exact nature of ADR Agent used Re-examine need for RCM study Risk/benefit ratio Alternative - non-contrast, USS, MRI If RCM necessary Use different RCM LOCM / iso-osmolar CM Prophlactic steroids - no conclusive evidence

35 Other known allergies - Atopy and CM
Increased risk – 2 x Confirm previous type of allergic reaction Re-examine need for RCM study Risk/benefit ratio Alternative - non-contrast, USS, MRI If RCM necessary Use different RCM LOCM / iso-osmolar CM

36 Asthma and CM  Risk severe ADR Confirm diagnosis
LOCM x6, HOCM x10 Confirm diagnosis Determine if well controlled Defer if exacerbation or poor control Rx as per previous reaction

37 Metformin therapy Excreted exclusively via kidneys
Can cause/exacerbate lactic acidosis Normal Cr range of eGFR – don’t stop If out of range consult stopping for 48 hrs with referring clinic Standards for intravascular contrast agent administration to adult patients. RCR 2010

38 Risk factors for adverse intravenous contrast media reactions
Use a non-ionic low or iso-osmolar agent Maintain close medical supervision Leave the cannula in place and observe the patient for 30 minutes Be ready to treat promptly any adverse reaction and ensure that emergency drugs and equipment are available Standards for intravascular contrast agent administration to adult patients. RCR 2010


40 MCQ

41 MCQ

42 MCQ

43 MCQ

44 MCQ

45 Incidence 3-5% inpatients develop ARF No strict definition of CMN
25-100% increase in 24-72hr (50% seems best) Occurs in % with normal renal function Risk factors Renal impairment (creat>140, GFR<70ml/min) DM Volume depletion Heart failure High doses, repeated doses AGE NSAIDS, gentamicin, chemotherapeutic agents (eg cisplatin) Mild/mod renal impairment: 5-10% CMN +DM : 10-40% Severe renal impairment: 50%

46 Renal processing of contrast
>99% excreted by kidneys Half life (with normal function) : approx 2 hours Freely filtered, osmotic force results in diuresis Concentration in urine x that of plasma Elimination by intestine and biliary tree may increase But accumulation also occurs with normal function Plasma concentration: bi-exponential decay curve Mixing of contrast into interstitial space (after 2 hours); as excreted in normal function Inhibition of Na and water reabsorption in proximal tubule Increased flow rates Increased perfusion of distal portion of loop Decrease in GFR (tubuloglomerular feedback- TGF)

47 Pathophysiology Incompletely understood Animal studies
Transient increase in renal perfusion Abrupt prolonged decrease Seems 2 main mechanisms Hypoperfusion Contrast and osmotic stress Endothelin, prostoglandins, NO reduced: vasoconstriction High osmolar : TGF response; vasoconstriction afferent arterioles Decrease in GFR, increase in renal vascular resistance Cannot be only mechanism as failure of vasodilators Direct toxicity to tubular cells Cytotoxic reactive oxygen species Rationale for anti-oxidant (N-acetyl cysteine) Structural effects: vacuolization proximal tubules, DNA fragmentation, necrosis of thick ascending limb of L of H Long term affects unknown (glomerulosclerosis?)

48 Diagnosis CMN Ischaemic ATN Atheroembolic disease
Form of ATN Differential; Ischaemic ATN Atheroembolic disease GFR ideal, but difficult Mild proteinuria and oliguria may occur Contrast media can affect protein assays Granular casts (muddy brown) Persistent nephrogram Most resolve in 1-2 weeks, peak creat at 3-5 days Recent study 1826 patients coronary angiography 14% CMN, mortality 7% Odds ratio for mortality of approx. 5

49 Prevention of CMN Volume expansion Isotonic saline best
Solomon et al. 0.45% saline 12 hrs before and after (1. + frusemide) (1. + manitol) Advantage in group 1 and 3 same. Frusemide group worse Isotonic saline best Sodium bicarbonate may be better than NaCl N-acetylcysteine Conflicting reports Meta analysis shows mixed benefits 600mg BD day before and day of contrast Others suggested; ANP, dopamine NSAIDS; discontinue 24hr before and after

50 Ultrasound CM & CEUS Alters echo amplitude in ultrasonography
Changes in absorption, reflection & refraction Encapsulated microbubbles <10µm diameter Confined to vascular space Increase echo strength up to 300 fold Can use targeting ligands to bind to endothelial receptors (integrins & growth facor receptors) enableing microbubble complex to accumultae in area of interest. Can derive measures of tumor blood flow and blood volume by employing high mechanical index ultrasonography to destroy micro bubbles in a given region and then determining the rate at which they reappear; a process termed replenishment kinetics Increased sensitivity of TRUSS guided prostate biopsy (38-54% vs %) Eg: Levovist, Sonovist Complications very rare

51 MRI Contrast Media Gadolinium (paramagnetic agent)
T1 - This tissue-specific time constant for protons, is a measure of the time taken to realign with the external magnetic field. Gadolinium decreases T1 relaxation time. Enhanced tissues and fluids appear extremely bright on T1-weighted images. Provides high sensitivity for detection of vascular tissues (e.g. tumors). Dynamic Contrast Enhanced MRI more sensitive than T2W images for prostate cancer localization (50% vs 21%; p = 0.006) and similarly specific (85% vs 81%; p = 0.593). Jackson et. al B J Radiol. 2009

52 Complications Minimal nephrotoxicity Allergy rare
Nephrogenic systemic fibrosis Severe delayed fibrotic reaction of tissues (from day of exposure up to 2-3 months) Can be progressive & fatal in around 5% Starts with red, itchy painful swelling on limbs progressing to muscle weakness and contractures. Risk with GFR <60 (Highest if <30) Not reported GRF >60 RCR 2007

53 Lymphotropic Superparamagnetic Nanoparticles
Particles are taken up by macrophages of the reticuloendothelial system and accumulate in lymph nodes. Passive, cell-specific targeting of the iron oxide nanoparticles to lymph nodes. Differential cellular content of benign versus malignantly infiltrated nodes make this method suitable for cancer staging. Lymphotropic nanoparticle enhanced MRI, differences in benign versus malignant infiltration of lymph nodes can be visualised, which adds accuracy to standard MRI beyond criteria based solely upon the size and shape of lymph nodes. LN staging CaP Sens 91% vs 35%, Spec 98% vs 90% - compared to standard MRI Mukesh et al NEJM, June 2003

54 Mechanism of action of lymphotropic superparamagnetic nanoparticles
Mouli, S. K. et al. (2010) Lymphotropic nanoparticle enhanced MRI for the staging of genitourinary tumors Nat. Rev. Urol. doi: /nrurol

55 PET Detects pairs of gamma rays emitted indirectly by positron (anti-particle of electron) emitting radionucleotide. Combined with CT or MRI. Carbon-11, Nitrogen-13, Fluorine-18 attached to glucose, water or a specific ligand. Commonest agent: Fluorine 18 fluorodeoxyglucose (FDG)

56 X-Rays - the unknown quantity
Wilhelm Conrad Roentgen 1896 Electromagnetic radiation Photon energies between -rays and UV radiation Basis for medical use Differential attenuation of x-rays interacting with tissues Transmitted x-ray ‘flux’ depends on attenuation of beam along path Superimposed shadow of internal anatomy X-ray sensitive detector captures transmitted fraction X-rays converted to visible projection image


58 X-Ray Production Conversion of kinetic energy attained by electrons accelerated under a potential difference X-ray generator Provides voltage to energise tube X-ray tube Environment = vacuum Cathode - filament Separate filament circuit Anode - tungsten target Collimators - define x-ray beam shape incident on patient

59 X-Ray Production Rotating Anode X-ray generator: A = Anode C = Cathode
E = Envelope (Vacuum) R = Rotor S = Stator windings T = Target W = X-ray window

60 X-Ray Production Cathode filament X-ray generator Anode
Filament circuit activated Intense heating Thermionic emission  electrons released X-ray generator Applies high voltage to cathode & anode Electrons accelerated to +ve anode Anode Highly energised electrons interact with target Target = tungsten - high atomic no. & high Tm (3653 K) Interactions  x-ray photon generation Bremsstrahlung effect = braking radiation Deceleration of electrons due to +ve nucleus Kinetic energy lost  converted to UV x-ray photons Characteristic radiation - displaced orbital electron

61 Bremsstrahlung This is radiation given off by the electrons as they are scattered by the strong electric field near the nuclei Electron ‘braked’ by positive charge of nucleus. As brakes looses energy emitted as X-ray photon.

62 Characteristic radiation

63 Output of typical X-ray tube
f the electron has enough energy it can knock an orbital electron out of the inner electron shell of a metal atom, and as a result electrons from higher energy levels then fill up the vacancy and X-ray photons are emitted. This process produces an emission spectrum of X-rays at a few discrete frequencies, sometimes referred to as the spectral lines. The spectral lines generated depend on the target (anode) element used and thus are called characteristic lines. Usually these are transitions from upper shells into K shell (called K lines), into L shell (called L lines) and so on

64 Characteristic radiation varies with type of anode

65 X-Ray Interactions Relative transparency of body to x-rays Attenuation
Removal of x-rays by absorption & scattering Attenuation by patient volume  pattern detected Mechanisms Photoelectric absorption Compton scatter Rayleigh scatter Pair production Combine to attenuate incident photon beam Removal of photons as beam passes through matter

66 X-Ray Detection Film - analogue Photostimulable luminescence
Silver bromide Pattern of X-ray beam incident on film Lots of photons opaque silver specks = black Fixation - unaffected silver bromide crystals removed Photostimulable luminescence Photostimulable storage phosphor Analogue to digital conversion Digital signal converted to output e.g. video Rapid sampling of digital image matrix  real time imaging Photostimulated luminescence (PSL) is the release of stored energy within a phosphor by stimulation with visible light, to produce a luminescent signal.

67 Digital Radiography Flat Panel Detectors (FPD) in place of X-ray film (Two types) Indirect FPD's – Amorphous silicone (a-Si) is the most frequent type of FPD sold in the medical imaging industry today. Combining a-Si detectors with a scintillator in the detector’s outer layer, which is made from Cesium Iodide, or Gadolinium Oxysulfide, converts X-ray to light. Because the X-ray energy is converted to light, the a-Si detector is considered an indirect image capture technology. Direct FPD's – Amorphous selenium (a-Se) are known as “direct” detectors because X-ray photons are converted directly to charge.

68 EMQ

69 Principle of IVU To obtain clinically useful information about the upper tract & related structures Adequate dose of contrast Radiograph Control Nephrogram Pyelocalyceal phase Sequence to assess dynamics of urine formation & propulsion Adequate distention of opacified collecting system Tomography Use of oblique, prone, upright positions Minimise risk to patient How to - viva question Metformin and - viva question

70 How to perform IVU?

71 How to perform IVU? Bolus dose eg. 50ml Omnipaque (350mg/ml)
Additional films: inspiratory/expiratory, tomography, prone, delayed Tomography at 9cm means F2 located 9cm from loin skin - therefore 9cm = upper pole, 11cm lower pole Prone films – contrast heavy, therefore tends to pool in kidney when supine; prone more readily identifies level of obstruction

72 Principle of Retrograde
Detailed image of upper tract anatomy & pathology Not functional - independent of renal function 5 to 7ch ureteric catheter 5-10 ml warm omnipaque - use minimum Strength mg/ml Avoid obscuring subtle details Slow injection - avoid high pressure Overdistention Rupture Backflow - pain, obscures findings

73 Indications for Retrograde
Non-visualisation of upper tract on IVU Inconclusive or suspicious IVU / CT Incomplete IVU Previous RCM adverse reaction Part of other procedure PCNL Pyeloplasty URS

74 Principle of DSA Indications for angiography
Investigation renovascular hypertension Trauma - view to embolise Transplant Pre-op donors Post – occlusion / stenosis anastamosis, acute thrombosis Suspected renal artery disease Vascular anatomy - complex surgery MR angiography and CT angiography superseding in certain situations The DSA image is produced by electronically subtracting images without contrast media from images after contrast media injection. The result of this subtraction process is the visualisation of contrast filled vessels which are free from the distraction of overlying structures.

75 Principle of DSA Digital subtraction Technique
Seldinger - needle, wire, catheter Aortogram  locate renal artery L1/L2 screen Mask image Contrast - fast infusion - 10mls in1.5 secs Images – 4 per sec for 2 sec, then 2 per sec for 6 sec Digital subtraction Optimises images Enhances electronically the contrast Minimum contrast,  dose 30-50% Removes background Fluoroscopy and ct and mri

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