Imaging in Urology (part 2)


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A Broad Idea About Imaging Procedures Taking Place in the Practice of Urology.

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Imaging in Urology (part 2)

  1. 1. Ultrasonography is a versatile and relatively inexpensive imaging modality that has the unique feature of being the only imaging modality to provide real-time evaluation of urologic organs and structures without the need for ionizing radiation. • All ultrasound imaging is the result of the interaction of sound waves with tissues and structures within the human body. • Ultrasound waves are produced by applying short bursts of alternating electrical current to a series of crystals housed in the transducer.
  2. 2. • A portion of the wave is reflected toward the transducer. The transducer then serves as a receiver and “listens” for the returning sound wave reconverting the mechanical to electrical energy & subsequently to an image. • The reflected waves gives the image of the tissue including the shape & density. • Because ultrasound waves are transmitted and received at frequent intervals, the images can be rapidly reconstructed and refreshed, providing a real-time image.
  3. 3. • The resolution of an ultrasound image refers to the ability to discriminate two objects in close proximity to one another. • Axial Resolution The ability to identify as separate two objects in the direction of the traveling sound wave & directly proportional with the wave’s frequency. • Lateral Resolution The ability to identify separately objects that are equidistant from the transducer & depends on the ultrasound beam focus.
  4. 4. • As sound waves transit tissues, energy is lost or attenuated by reflection, scattering, Interference, or absorption. • Reflection is the key physical phenomenon that allows information to return to the transducer as mechanical energy for • The amount of the reflected waves (Subsequently the image resolution) depends mainly on the impendence of two adjacent tissues. • Impendence is the property influenced by the density & stiffness of tissues The liver is used as a landmark for echogenicity. Darker structures are hypoechoic (High water content), brighter structures are hyperechoic (Less water content), Structures with similar echogenecity are Isoechoic, & structures with no echogenecity (e.g. Simple Cysts) are anechoic.
  5. 5. • The interaction of ultrasound waves with tissues may produce images that do not reflect the true underlying anatomy “artifacts.” although which may be misleading, it also may assist the diagnosis (e.g. acoustical shadows in stone diseases, or comet tail appearance on reverberation of waves through gas containing structures e.g. colon)
  6. 6. • Grey-Scale Ultrasound • Doppler Ultrasound • Spatial Compounding • Harmonic Scanning • Contrast media in US • 3-Dimentional Scanning
  7. 7. • Grey-Scale Ultrasound • Gray-scale B-mode ultrasonography is the most commonly employed mode of ultrasound. This pulsed-wave technique produces real-time two-dimensional images consisting of shades of gray. • Evaluation of gray-scale imaging requires the ability to recognize normal patterns of echogenicity from anatomic structures. Variations from these expected patterns of echogenicity indicate disorders of anatomy or physiology.
  8. 8. • Doppler Ultrasound • The Doppler ultrasound mode depends on the physical principle of frequency shift when sound waves strike a moving object. • The basic principle of Doppler ultrasound is that sound waves of a certain frequency will be shifted or changed on the basis of the direction and velocity of the moving object, as well as the angle of insonation. • Color Doppler ultrasonography allows for evaluation of the velocity and direction of motion. A color map may be applied to direction with the most common assignation of the color blue to motion away from the transducer and red for motion toward the transducer.
  9. 9. • Three Dimensional Scanning Three-dimensional (3-D) scanning has been used extensively in obstetrics and gynecology but so far has limited application in urology. 3-D scanning produces a composite of images (data set),which can then be manipulated to generate additional views of the anatomy in question.
  10. 10. • Contrast media in US Microbubbles (In special contrast media) are distributed in the vascular system and create strong echoes with harmonics when struck by sound waves. The bubbles themselves are rapidly degraded by their interaction with the sound waves. US with contrast media is useful in detection of areas with increased vasculature
  11. 11. • Renal Ultrasound Indications 1. 2. 3. 4. Assessment of renal and perirenal masses Assessment of the dilated upper urinary tract Assessment of flank pain during pregnancy Evaluation of hematuria in patients who are not candidates for conventional radiology 5. Assessment of the effects of voiding on the upper urinary tract 6. Evaluation for and monitoring of urinary stones 7. Intraoperative renal parenchyma and vascular imaging for ablation of renal masses 8. Percutaneous access to the renal collecting system 9. Guidance for transcutaneous renal biopsies, cyst aspiration, or ablation of renal masses 10. Postoperative evaluation of patients after renal and ureteral surgery 11. Postoperative evaluation of renal transplant patients
  12. 12. • Renal Ultrasound Normal Findings 1. 2. 3. Hypoechoic renal cortex Hyperechoic central hilum Parenchymal thickness more than 7 mm
  13. 13. • Renal Ultrasound Limitations 1. 2. 3. Obesity Intestinal gases Physical deformity • NB: • Ureter. US has limited usefulness in most ureteral disorders but for a few instances. • Dilated ureters may be seen, ureteroceles demonstrated within the bladder, and small calculi may be imaged, especially in the pelvic ureter. • Color-flow demonstration of asymmetric jets of urine from the ureteral orifices in the bladder often indicates the presence of uretral obstruction.
  14. 14. • Pelvic Ultrasound Indications 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Measurement of bladder volume or postvoiding residual urine Assessment of prostate size and morphology Demonstration of secondary signs of bladder outlet obstruction Evaluate bladder wall configuration and thickness Evaluation of hematuria of lower urinary tract origin The detection of ureteroceles Assessment for ureteral obstruction Detection of perivesical fluid collections Evaluation of clot retention Confirmation of catheter position Removal of retained catheter Guidance of suprapubic tube placement To establish bladder volume before flow rate determination.
  15. 15. • Pelvic Ultrasound Normal Findings
  16. 16. • Pelvic Ultrasound Examples
  17. 17. • Pelvic Ultrasound Limitations 1. 2. Empty Bladder (Although Prostate volume can be determined with empty bladder) Lack of PVRU determination in clot retention, obesity, ascites, bladder diverticulae, or peri-vesical collection.
  18. 18. • Scrotal Ultrasound Indications 1. 2. 3. 4. 5. 6. Assessment of scrotal and testicular mass Assessment of scrotal and testicular pain (Absence of testicular blood flow indicates tortion) Evaluation of scrotal trauma Evaluation of infertility Follow-up of scrotal surgery Evaluation of the empty or abnormal scrotum
  19. 19. • Scrotal Ultrasound Examples
  20. 20. • Ultrasound of penis & Urethra Indications 1. 2. 3. 4. 5. 6. Evaluation of erectile dysfunction Documentation of fibrosis of the corpora cavernosa Localization of foreign body Evaluation of urethral stricture Evaluation of urethral diverticulum Assessment of penile trauma or pain
  21. 21. • Trans-Rectal Ultrasound Indications • TRUS should not be used as a routine investigation 1. 2. 3. Palpable prostatic nodule on DRE Elevated levels of PSA To guide prostatic needle biopsy (in case of PSA ≥ 10) • TRUS is the main investigation to evaluate the prostate relative to carcinoma, although it may also be used to evaluate the benign prostate with regard to size and to look for abnormalities in cases of ejaculatory dysfunction • However, No Ultrasonographic findings to differentiate benign from malignant prostatic changes.
  22. 22. Radionuclide imaging is the procedure of choice to evaluate renal perfusion, obstruction and function. It is sensitive to changes that induce focal or global changes in kidney function. Scintigraphy is a non-invasive diagnostic meathod, it does not damage the kidney, has no toxicity, results in minimal absorbed radiation, and is free from allergic reactions. Technetium 99m-diethylene triamine pentaacetic acid (99m Tc-DTPA) is primarily a glomerular filtration agent
  23. 23. • Technetium 99m-diethylene triamine pentaacetic acid (99m TcDTPA) is the most useful for evaluation of obstruction & function. • Technetium 99m-dimercapt succinic acid (99m Tc-DMSA) localizes to the renal cortex therefore it is most useful for identifying cortical defects and ectopic or abhorrent kidneys. • Technetium 99m-mercaptoacetyl triglycine ( 99m Tc-MAG3) is an excellent agent for imaging due to its photon emission, 6-hour halflife, and ease of preparation. It is limited in measurement of GFR due to being bound to plasma proteins, but is of choice in renal insufficiency.
  24. 24. Flow phase shows renal uptake, back-ground clearance, and abnormal vascular lesions, which may indicate A-V malformations, tumors, or active bleeding. Renal phase Execratory phase The most sensitive indicator of renal dysfunction. The indicator phase of System Obstruction. A diuretic (usually furosemide 0.5 mg/kg) is administered when maximum col -lecting system activity is visualized. The T-1/2 is the time it takes for collecting system activity to decrease by 50% from that at the time of diuretic administration.
  25. 25. 1. Assessment of renal function & split renal functions for taking the decision of nephrectomy. 2. Evaluation of transplant failure including obstruction, extravasation, stenosis of arterial anastomosis. 3. Questionable or intermittent obstruction. (esp. UPJ Obstruction) 4. Evaluate for small urine leaks not detected by contrast studies. The only Contraindication for Radioneucleotide administration is pregnancy.
  26. 26. Normal Renal Scan
  27. 27. CT has become one of the most integral parts of urologic practice, and the CT urogram (CTU) has replaced IVU as the imaging modality of choice in modern urology The basis for CT imaging is the attenuation of x-ray photons as they pass through the patient. Tomography is an imaging method that produces 3-D images of internal structures by recording the passage of x-rays as they pass through different body tissues.
  28. 28. • A collimated x-ray beam is generated on one side of the patient, and the amount of transmitted radiation is measured by a detector placed on the opposite side of the x-ray beam. • These measurements are then repeated systematically, while a series of exposures from different projections is made as the x-ray beam rotates around the patient. The result is production of a 3-D image of internal structures in the human body. • Complex computer algorithms allow reconstruction of CT data into many forms, including different planes, such as coronal and sagittal.
  29. 29. • An abdominal CT starts at the diaphragm and ends at the iliac crest. The pelvic CT begins at the iliac crest and terminates at the pubis symphysis. • Intravenous contrast may be required for better delineation of soft tissue. Oral contrast is not commonly used in urology but may be helpful in certain cases to differentiate bowel from lymph nodes, scar, or tumor • Attenuation values are expressed in Hounsfield units (HU). The HU scale or attenuation value is based on a reference scale where air is assigned a value of −1000 HU and dense bone is assigned the value of +1000 HU. Water is assigned 0 HU.
  30. 30. 1. Renal Masses 2. Urolithiasis 3. Hydronephrosis 4. Prinephric Collections (abscess, urinoma, and hematoma) 5. Trauma : detecting the effect of renal trauma (vascular injury, extravasation from vascular system or urinary tract, urinoma formation, and impaired renal viability) 6. Retroperitoneal masses. 7. Retroperitoneal fibrosis.
  31. 31. • Urolithiasis • As time progresses, the CT is replacing the IVU as a main line of investigations of Urolithiasis • Almost all renal and ureteral stones can be detected on helical CT scan. • In the work-up of Urolithiasis the sensitivity of Non-Contrast CT is 96% - 100% and specificity 92% - 100%. • Stones in the distal ureter can be difficult to differentiate between pelvic calcifications, (Confirmed by presence of backpressure changes)
  32. 32. • Cysts & Masses • When the unenhanced CT images of a renal mass are compared with the enhanced images obtained in the cor tical medullar y or nephrogenic phase: 1. An increase in HU (measured in the area of the renal mass) by 15 to 20 HU confirms the presence of a solid enhancing mass, which is usually renal cancer. 2. The presence of fat, which should enhance less than 10 diagnostic for angiomyolipoma. 3. A hyperdense cyst shows no change in density between the postcontrast and delayed-phase images HU, is
  33. 33. • Hematuria • With MDCT it is possible to perform a comprehensive evaluation of the patient with one single examination, & so being one of the most important studies in diagnosing gross & microscopic hematuria. • As the most important cause of hematuria is urothelial tumours.
  34. 34. Normal PelviAbdominal C.T
  35. 35. Normal Pelvi-Abdominal C.T
  36. 36. C.T of Left Lower Ureteric Stone
  37. 37. C.T of Left Lower Ureteric Stone
  38. 38. Normal C.T with Contrast
  39. 39. Normal C.T with Contrast
  40. 40. C.T with Contrast – Right Renal Cell Carcinoma
  41. 41. MRI is increasingly being applied to the genitourinary system due to the excellent contrast resolution of soft tissue, without the need for contrast in many situations. MRI is used when patients cannot be given iodinated contrast (e.g. impaired renal functions, or contrast allergy) and when tissue findings in the urinary system cannot be resolved using CT or ultrasonography.
  42. 42. The patient is placed on a gantry that passes through the bore of the magnet. When exposed to a magnet field of sufficient strength, the free water protons in the patient orient themselves along the magnetic field’s z-axis. This is the head-to-toe axis, straight through the bore of the magnet. A radiofrequency (RF) antenna or “coil” is placed over the body part to be imaged. It is the coil that transmits the RF pulses through the patient. When the RF pulse stops, protons release their energy, which is detected and processed to obtain the magnetic resonance image according to the absorption & release of the magnetic energy by the soft tissues.
  43. 43. 1. Evaluation of solid or cystic renal masses. 2. Staging of renal malignancy. 3. Evaluation of venous structures. 4. Determination of vena cava involvement by renal cell carcinoma. 5. Characterization of adrenal pathology.
  44. 44. 1. 2. 3. 4. 5. 6. 7. Difficulty with breath holding. Severe claustrophobia. Pacemakers. Retained magnetic foreign bodies, cochlear implants. neurovascular aneurysm clips. Cardiac defibrillators. Urolithiasis because stones do not have signal characteristics that allow them to be detected.
  45. 45. There is No Safe Dose of Radiation Patients  Limit axial imaging studies to the anatomic area of interest  Substitute imaging studies not requiring ionizing radiation when feasible. Medical Personnel  Limiting the time of exposure  Maximizing the distance from the radiation source  Shielding