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Low cost technique for vessel sizing
Clbriccd
Radilio/o,~~ ( 1999) 54, 6YY
Correspondence titters we prtb/ished ot the discretiorr of the Editor. Opirtior~~ expressed b.v corre,sporrdertts ore wt oecessorily those of rhe Editor. Unduly long letters may be retrrmed to rhr ortthonrfor .shrwterlirlg Letten in resport.se to o paper rrroy be sent to the utrthor ofthe paper so thot the reply con be published in the sonte issue. Lxtters .shortld be tyvped dotrblr .spocrd and .shorrld he signed by cdl otrthors pcr.wr~cdl~. References should be given in the style .speciJied in the Instructions to Attthors ot the fmttt of rhe Jorrmol
LOW
COST
TECHNIQUE
FOR
VESSEL
SIZING
SIR - The practxality and low cost of the method of geometric calibration in angiography reported by Snow and Brnnrts [I ] is to be commended. However. as is well known. all calibration techniques which rely on distances between objects have a dependence upon the angle of the plane in which the objects lie relative to the image receptor. The 4% maximum error achieved in their validation. which is assumed to have been carried out with the calibration phantom surface parallel to the Image intensitier face. will only be achieved itr-riw if the wire movement (e.g. vessel) lies in a plane parallel to the image intensifier face. Since the error increases relatively slowly with orientation. reaching 4% at 16.3”. and IO% at 25.8”. this may not be a problem for general clinical use, but remains a factor to be aware of when discussing the accuracy of the technique. The sune factors apply equally to the more expensive markercatheter techniques. and therefore these comments ‘arc not to be taken as critical of this apparently simple and effective procedure. A. J. BRIITEN
The echogenic material does tend to collect in the region of the renal papillae but may also be seen in the calyces and renal pelvis, as well as in the ureter and bladder 131. There is a difference in distribution of echogenic material in the transient form when compared IO the ‘bright’ medulla that is seen in nephrocalcinosis and other pathological conditions. In the transient form, echogenicity extends further into the renal sinus and this appearance is likely to relate in part to material within the calyces around the papillae and also echogenic material never fills the whole pyramid [3]. Transient RMH should not be confused with other causes of medullary pyramidal hyperechogenicity that usually occur later in infancy and the incidence is not affected by breast or bottle feeding or frusemide administration [2]. Transient RMH in neonates represents a spectrum of findings. On ultrasound examination. the presence of echogenic material may be widespread involving the kidneys and bladder. or may be focal within one kidney. Rarely. there may be associated renal dysfunction due to a combination of renal tubular blockage and ureteric obstruction secondruy to proteinaceous casts [3]. Transient RMH does have characteristic ultrasound appearances using high-frequency transducers and should be recognised as a normal finding. If clinical doubt persists then a repeat ultrasound examination IO- I4 days after birth will confirm resolution of the initial ultrasound appearances. Eostbounte District Hospital Kings Drive. Eostboume East Sussex, BN2l 2UD. U.K.
D. C. HOWLETT
References I Snow TM. Angioplasty.
Benneus Clirlicctl
M. A Low Cost Technique Radiolqq? lYY8:53:Y2Y-93
for
Vessel
Sizing
In
I.
References HYPERECHOIC
RENAL
PAPILLAE
IN NEONATES
SIK - I read with interest the recent paper on hyperechoic renal papillae in neonates [II and would like to make some further comment. The occurrence of renal medullury hyperechogenicity (RMH) after birth and its subsequent resolution is well described and is far more prevalent in healthy. term babies 12.31. The actiology of the echogenic debris remains unclear.
0009-9260/99/100699+0l
$12.00/O
I Nakamura M, Yokota K. Chan C er cl/. Hyperechoic renal papillae as a physiological tinding in neonates. C/in Rndiol lYYY;54:233-236. 2 Riebel TW. Abraham K. Warmer R. Muller R. Transient renal medullary hyperechogenicity in ultrasound studies of neonates: Is it a normal phenomena and what at the causes. J C/k U/trosourrd lY93:21:25-31. 3 Hewlett DC. Greenwood KL. Jarosz JM. MacDonald LM, Saunders AJS. The incidence of transient renal medullary hyperechogenicity in neonatal ultrasound examination. Br J Rodiol 1997~70: l40- 143.
0
1999 The Royal
College
of Radiologists
Radilio/o,~~ ( 1999) 54, 6YY
Correspondence titters we prtb/ished ot the discretiorr of the Editor. Opirtior~~ expressed b.v corre,sporrdertts ore wt oecessorily those of rhe Editor. Unduly long letters may be retrrmed to rhr ortthonrfor .shrwterlirlg Letten in resport.se to o paper rrroy be sent to the utrthor ofthe paper so thot the reply con be published in the sonte issue. Lxtters .shortld be tyvped dotrblr .spocrd and .shorrld he signed by cdl otrthors pcr.wr~cdl~. References should be given in the style .speciJied in the Instructions to Attthors ot the fmttt of rhe Jorrmol
LOW
COST
TECHNIQUE
FOR
VESSEL
SIZING
SIR - The practxality and low cost of the method of geometric calibration in angiography reported by Snow and Brnnrts [I ] is to be commended. However. as is well known. all calibration techniques which rely on distances between objects have a dependence upon the angle of the plane in which the objects lie relative to the image receptor. The 4% maximum error achieved in their validation. which is assumed to have been carried out with the calibration phantom surface parallel to the Image intensitier face. will only be achieved itr-riw if the wire movement (e.g. vessel) lies in a plane parallel to the image intensifier face. Since the error increases relatively slowly with orientation. reaching 4% at 16.3”. and IO% at 25.8”. this may not be a problem for general clinical use, but remains a factor to be aware of when discussing the accuracy of the technique. The sune factors apply equally to the more expensive markercatheter techniques. and therefore these comments ‘arc not to be taken as critical of this apparently simple and effective procedure. A. J. BRIITEN
The echogenic material does tend to collect in the region of the renal papillae but may also be seen in the calyces and renal pelvis, as well as in the ureter and bladder 131. There is a difference in distribution of echogenic material in the transient form when compared IO the ‘bright’ medulla that is seen in nephrocalcinosis and other pathological conditions. In the transient form, echogenicity extends further into the renal sinus and this appearance is likely to relate in part to material within the calyces around the papillae and also echogenic material never fills the whole pyramid [3]. Transient RMH should not be confused with other causes of medullary pyramidal hyperechogenicity that usually occur later in infancy and the incidence is not affected by breast or bottle feeding or frusemide administration [2]. Transient RMH in neonates represents a spectrum of findings. On ultrasound examination. the presence of echogenic material may be widespread involving the kidneys and bladder. or may be focal within one kidney. Rarely. there may be associated renal dysfunction due to a combination of renal tubular blockage and ureteric obstruction secondruy to proteinaceous casts [3]. Transient RMH does have characteristic ultrasound appearances using high-frequency transducers and should be recognised as a normal finding. If clinical doubt persists then a repeat ultrasound examination IO- I4 days after birth will confirm resolution of the initial ultrasound appearances. Eostbounte District Hospital Kings Drive. Eostboume East Sussex, BN2l 2UD. U.K.
D. C. HOWLETT
References I Snow TM. Angioplasty.
Benneus Clirlicctl
M. A Low Cost Technique Radiolqq? lYY8:53:Y2Y-93
for
Vessel
Sizing
In
I.
References HYPERECHOIC
RENAL
PAPILLAE
IN NEONATES
SIK - I read with interest the recent paper on hyperechoic renal papillae in neonates [II and would like to make some further comment. The occurrence of renal medullury hyperechogenicity (RMH) after birth and its subsequent resolution is well described and is far more prevalent in healthy. term babies 12.31. The actiology of the echogenic debris remains unclear.
0009-9260/99/100699+0l
$12.00/O
I Nakamura M, Yokota K. Chan C er cl/. Hyperechoic renal papillae as a physiological tinding in neonates. C/in Rndiol lYYY;54:233-236. 2 Riebel TW. Abraham K. Warmer R. Muller R. Transient renal medullary hyperechogenicity in ultrasound studies of neonates: Is it a normal phenomena and what at the causes. J C/k U/trosourrd lY93:21:25-31. 3 Hewlett DC. Greenwood KL. Jarosz JM. MacDonald LM, Saunders AJS. The incidence of transient renal medullary hyperechogenicity in neonatal ultrasound examination. Br J Rodiol 1997~70: l40- 143.
0
1999 The Royal
College
of Radiologists